Downloaded from http://emj.bmj.com/ on January 30, 2015 - Published by group.bmj.com
EMJ Online First, published on December 31, 2014 as 10.1136/emermed-2013-203373 Original article
Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus among skin and soft tissue infections in an emergency department in Guyana Adeline Dozois,1 Isaac Thomsen,2 Natalia Jimenez-Truque,2 Nicole Soper,3 Alexis Pearson,3 Pheona Mohamed-Rambaran,3 Kristen B Dettorre,4 C Buddy Creech,2 Seth W Wright4 1
Vanderbilt University School of Medicine, Nashville, Tennessee, USA 2 Division of Pediatric Infectious Diseases, Department of Pediatrics, Vanderbilt University, Nashville, Tennessee, USA 3 Department of Laboratory Services, Georgetown Public Hospital Corporation, Georgetown, Guyana 4 Division of International Health, Department of Emergency Medicine, Vanderbilt University, Nashville, Tennessee, USA Correspondence to Adeline Dozois, Vanderbilt University School of Medicine, 2137 Fairfax Ave #13, Nashville, TN 37212, USA; [email protected] Received 31 October 2013 Revised 9 October 2014 Accepted 11 December 2014
ABSTRACT Objective The characteristics of staphylococcal skin and soft tissue infections (SSTIs) are poorly understood in northern South America and the Caribbean. The objectives of this study were to determine the frequency of methicillin resistance among Staphylococcus aureus isolates in an emergency department (ED) in Guyana and to identify specific molecular characteristics of these methicillin-resistant Staphylococcus aureus (MRSA) strains. Methods This was a cross-sectional study conducted at the main teaching hospital in Georgetown, Guyana. Eligible subjects included patients of all ages with SSTIs with obtainable purulent material. Purulent material was cultured, and S. aureus isolates were evaluated for antibiotic susceptibilities by disc diffusion. Molecular characterisation of MRSA isolates included identification of SCCmec type, assignment of genetic relatedness by rep-PCR and determination of the presence of two exotoxins, Panton-Valentine Leukocidin (PVL) and LukAB. Results Eighty-five samples were collected; of these, 47 grew S. aureus. 24 of the 47 S. aureus samples were MRSA (51%; 95% CI 37% to 65%), representing 28% of all samples. All MRSA isolates were SCCmec type IV, PVL positive, LukAB positive and were highly related to the current epidemic clone in the USA, USA300. Conclusions Here, we demonstrate a clinically significant proportion of methicillin resistance in SSTIassociated staphylococcal isolates. Guyanese isolates were highly related to the most common communityassociated strain seen in the USA, USA300. These results have important implications for empiric antibiotic therapy and infection control policies in Guyana and similar settings.
INTRODUCTION
To cite: Dozois A, Thomsen I, JimenezTruque N, et al. Emerg Med J Published Online First: [please include Day Month Year] doi:10.1136/emermed2013-203373
Staphylococcus aureus poses a significant threat to the health of both children and adults, causing a variety of diseases ranging from mild skin and soft tissue infections (SSTI) to more severe conditions such as endocarditis, necrotising pneumonia and sepsis.1 Methicillin-resistant Staphylococcus aureus (MRSA), which was initially found exclusively in the healthcare setting, is of particular concern. No longer solely a nosocomial pathogen, MRSA infections are increasingly common in individuals with no recent history of hospitalisation, particularly in North America.1 2 These community-associated MRSA
Key messages What is already known on this subject? ▸ Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of skin and soft tissue infections throughout the world. ▸ Though once considered a nosocomial pathogen, MRSA has increasingly been recognised as an important cause of infections in outpatient population, including individuals presenting to emergency departments. ▸ Little is known about the relative frequency of methicillin resistance among S. aureus isolates in Northern South America. What this study adds? ▸ Our study demonstrates a clinically significant proportion of methicillin resistance in skin and soft tissue infection-associated staphylococcal isolates in an emergency department in Northern South America. ▸ All the MRSA isolated in this study were highly related to the USA300 strain, which is currently the most common epidemic clone in the USA.
(CA-MRSA) strains are clinically and microbiologically distinct from previous iterations of MRSA, with distinct molecular and clinical characteristics that vary in infectivity, virulence and antibiotic susceptibility.1 2 In the USA, CA-MRSA strains typically possess the mecA gene in an SCCmec IV cassette; they typically harbour the genes encoding Panton-Valentine Leukocidin (PVL) and belong to the USA300 pulsed-field gel electrophoresis (PFGE) type.2–4 Though MRSA has been well studied in North America, considerably less is known about the epidemiology of CA-MRSA in South America and the Caribbean.4 5 No studies from South America or the Caribbean have examined the proportion of methicillin resistance and molecular characteristics of MRSA in emergency department (ED) patients with purulent SSTIs.4 5 Guyana is a South American country, bordered by Brazil, Venezuela and Suriname, with geographic and economic ties to the Caribbean region. An increased understanding of the prevalence and molecular characteristics
Dozois A, et al. Emerg Med J 2014;0:1–4. doi:10.1136/emermed-2013-203373
Copyright Article author (or their employer) 2014. Produced by BMJ Publishing Group Ltd under licence.
1
Downloaded from http://emj.bmj.com/ on January 30, 2015 - Published by group.bmj.com
Original article of MRSA in this setting could improve the regional understanding of MRSA epidemiology and improve local and regional management of S. aureus infections. The objectives of this study were to determine the frequency of methicillin resistance among S. aureus isolates in ED of the primary teaching hospital in Georgetown, Guyana, and to identify specific molecular characteristics of these MRSA strains.
METHODS Study setting and design We conducted a cross-sectional study of patients presenting to ED of Georgetown Public Hospital Corporation (GPHC) in Georgetown, Guyana. In Guyana, the majority of residents are concentrated in the capital city of Georgetown and the nearby coastal regions, whereas the inland jungle and savannah regions are sparsely populated. GPHC is a public hospital that serves as the tertiary care referral centre for the nation. ED has an annual volume of approximately 90 000 patients and is staffed by emergency medicine residents and medical officers. GPHC has the only public ED within the city of Georgetown; healthcare is free at both GPHC and other public facilities in Guyana.
Selection of participants Patients of all ages with an SSTI caused by a cutaneous abscess or an infected wound were considered eligible. All subjects were required to have purulent material obtainable from SSTI to be included for participation. Subjects were enrolled during an 8-week period from May to July 2012. Due to available resources, exclusion criteria included prisoners, those without capacity to give consent and minors without a parent or guardian present. Subjects were enrolled on a convenience basis when an investigator was available. Two investigators were typically available in overlapping 8 h shifts covering the hours of 09:00 to 22:00, 7 days per week.
Methods and measurements: We recorded the age, sex, history of recent antibiotic use (within 1 month), history of recent hospitalisation (within 1 month) and history of diabetes mellitus for each subject. A sample of purulent material was collected on a Culturette swab with liquid Amies media (BD, Franklin Lakes, New Jersey, USA) and cultured in the GPHC microbiology laboratory to detect S. aureus. Cultures positive for S. aureus were tested for resistance to methicillin, trimethoprim/sulfamethoxazole, clindamycin and tetracyclines by disc diffusion. A pure culture isolate of each S. aureus sample was shipped to Vanderbilt University for confirmation of methicillin
resistance and subsequent molecular characterisation. Confirmation of methicillin resistance and assignment of SCCmec type was performed by ccr and mec complex typing. Purified genomic DNA (Promega, Madison, Wisconsin, USA) was used as the template for PCR detection of genes encoding the PVL and LukAB exotoxins. Repetitive element, sequencebased PCR using the DiversiLab System (bioMérieux, Durham, North Carolina, USA) was used to determine genetic relatedness between strains. MRSA isolates were defined as CA-MRSA or HA-MRSA based upon PCR and repetitive element sequencebased PCR characteristics.
Analysis Proportion and prevalence data were expressed using descriptive statistics. 95% CIs were calculated using the modified Wald method with GraphPad Prism (GraphPad Software, La Jolla, California, USA) software.
RESULTS Eighty-nine patients meeting inclusion and exclusion criteria were approached for enrolment. Of these, four refused consent. Purulent samples were obtained from the remaining 85 patients. Table 1 describes baseline subject characteristics. Of the 85 samples, 47 (55%) grew S. aureus (figure 1). Also, 24 of the 47 S. aureus isolates were MRSA (51%, 95% CI 37% to 65%), giving an overall prevalence of 28% (95% CI 20% to 39%). All MRSA isolates were susceptible to tetracycline and trimethoprim/sulfamethoxazole and 22/24 (88%) were susceptible to clindamycin. All MRSA isolates possessed SCCmec IV and all contained the genes encoding PVL. All strains also harboured the LukAB genes. Repetitive element sequence-based PCR revealed two distinct clonal populations, both of which were highly related to the USA300 PFGE type. These findings suggest that all MRSA isolates in this study shared molecular characteristics consistent with the current epidemic clone of CA-MRSA in the USA.
DISCUSSION Community-acquired infections remain the leading cause of death in most developing countries, and appropriate initial
Table 1 Subject characteristics Staphylococcus aureus cultured (n=47)
Characteristic
All subjects (n=85)
MSSA (n=23)
MRSA (n=24)
Age (mean [range] years) Male sex, no. (%) History of diabetes mellitus, no. (%) Antibiotic use (1 month), no. (%) Recent hospitalisation (1 month), no. (%)
33 54 20 29 12
21 15 (65%) 5 (22%) 4 (17%) 2 (9%)
24 15 (63%) 4 (17%) 10 (42%) 2 (8%)
[1–79] (64%) (24%) (34%) (14%)
MRSA, methicillin-resistant Staphylococcus aureus; MSSA, methicillin-sensitive Staphylococcus aureus.
2
Figure 1 Patient recruitment diagram. MRSA, methicillin-resistant Staphylococcus aureus. MSSA, methicillin-sensitive Staphylococcus aureus. CoNS, coagulase-negative Staphylococcus. Dozois A, et al. Emerg Med J 2014;0:1–4. doi:10.1136/emermed-2013-203373
Downloaded from http://emj.bmj.com/ on January 30, 2015 - Published by group.bmj.com
Original article treatment is critical in reducing mortality and morbidity.6 Our findings suggest that patients with suspected staphylococcal infections may benefit from empiric antibiotic coverage for MRSA. We demonstrated that 51% of S. aureus isolates in Guyana were MRSA, representing 28% of all purulent SSTIs. These data clearly suggest that empiric antimicrobials should possess activity against MRSA, making the β-lactams such as cephalexin or penicillins poor choices in this region.1 While some antimicrobials, such as clindamycin, may not be readily available in low-income and middle-income countries, others, such as trimethoprim/sulfamethoxazole and doxycycline, are typically available; therefore, we suggest that empiric treatment of purulent SSTI in this region include one of these agents. To our knowledge, this is the first report of the prevalence and molecular characteristics of MRSA from purulent SSTIs in the region. The frequency of MRSA observed in Guyana is higher than what has been observed in nearby Caribbean countries. For instance, in a mixed inpatient/outpatient population in Trinidad, the proportion of MRSA increased from 12.5% in 1999 to 20.8% in 2004.7 More recently, a Jamaican study suggested that only 7% of S. aureus SSTI samples were MRSA.8 These studies are difficult to compare to ours as they included healthcare-associated infections, while ours was from an outpatient population. When compared with the rest of South America, data from this study are commensurate with the frequency of MRSA in the population.4 5 9 For instance, in a fourcountry survey from the Andes, 41% of all S. aureus samples were MRSA.9 Taken together, we can conclude that while the epidemiology of S. disease can vary by geographic region, MRSA is an important cause of staphylococcal abscesses in Guyana. The epidemiology of MRSA in EDs in the USA is better understood. A multihospital study of SSTIs in EDs in the USA demonstrated an overall MRSA prevalence of 59%, which represented 78% of S. aureus isolates.2 Both our overall prevalence (28%) and the proportion of MRSA among the S. aureus isolates (51%) were lower than that found in the multicentre study from the USA. Nevertheless, the proportions found in our study are similar to those seen in several sites in that study and the prevalence of resistant organisms is clinically significant.1 2 All MRSA samples in this study contained SCCmec IV and were PVL positive; moreover, these strains belonged to the USA300 pulsotype, consistent with CA-MRSA based on a genotypic definition.2 3 The lack of other HA-MRSA strain types in this study is typical for an outpatient population as HA-MRSA strains uncommonly cause infection in healthy individuals in the community.3 Two subjects reported hospitalisation within the previous month and would not meet the Centers for Disease Control and Prevention case definitions for community-associated MRSA.10 Whether the presence of hospitalised subjects in our population is reflective of the inherent difficulties of the current epidemiological definition or implies that CA-MRSA can be readily transmitted in the healthcare setting cannot be answered by this study; nevertheless, the homogeneity of infecting isolates is a critical finding as it suggests a sustainable reservoir of the organism in the community, likely maintained by frequent asymptomatic colonisation. Identifying the strains responsible for infection, particularly when CA-MRSA is suspected, can have important implications for both hospital and community control policies, as well as empiric antibiotic therapy.3 We found that all isolates in this community setting were highly related to the USA300 PFGE type. USA300 is the most common CA-MRSA strain in the USA and is the most common CA-MRSA strain in studies from South America.1–5 9 Given the speed by which USA300 CA-MRSA has Dozois A, et al. Emerg Med J 2014;0:1–4. doi:10.1136/emermed-2013-203373
spread in the USA, it is not surprising that Guyana and other parts of South America are also experiencing an increase in disease due to this strain. The high prevalence of the genes encoding PVL in these strains is thought to contribute to the increased virulence of USA300 isolates, though other virulence factors are also known to play an important role.2 4 All isolates in this study also possessed the genes for LukAB, a twocomponent exotoxin whose subunits are two of the most abundantly produced proteins in the staphylococcal secretome.11 To our knowledge, this is the first study to confirm the presence of this toxin in clinical isolates from South America.
LIMITATIONS As with any study, our research had limitations. First, subjects were enrolled in ED of the main tertiary care hospital in the capital city, thus it is unclear whether our results can be generalised to other ED or outpatient populations within Guyana. GPHC is the predominant institution within Georgetown and provides services for a diverse socioeconomic population. The majority of Guyana’s population resides in Georgetown and the demographically similar coastal regions. Thus, it is likely that our results are reflective of purulent SSTIs in the heavily populated sections of the country. It is unlikely that our results are fully generalisable to ED populations in other areas of South America or the Caribbean islands given the marked differences in MRSA prevalence between geographic regions.2 This is not a limitation per se as it is important to determine both local and regional prevalence. Second, this study focused only on purulent SSTIs. The prevalence of MRSA may not apply to invasive infections or non-purulent cellulitis. Our inclusion only of patients with purulent SSTIs makes this study similar to other ED studies conducted in the USA.2 Third, we identified antibiotic susceptibilities only for S. aureus isolates and not for gram-negative organisms; therefore, we cannot describe overall antibiotic susceptibilities for all purulent SSTI’s. However, the relative frequency of gram-negative infections was far less than either S. aureus or S. pyogenes. Fourth, data regarding the type of infection were not collected for all subjects, nor did we collect additional clinical characteristics such as fever or admission status. We did not collect this information because the study was to be a survey of the organisms present in ED, and we did not intend to correlate this information with the type of presentation or clinical outcomes. We included a convenience sample of patients presenting during daytime and evening hours. It is possible, though unlikely, that patients presenting during late night hours would have had different microbial findings. Subjects were recruited during a 2-month period, which may mask seasonal variability in MRSA infection rates. Given that Guyana is an equatorial country, seasonal differences are unlikely. Last, the study was limited to a relatively small sample size of 85 subjects and was not subject to a formal power analysis. CIs, while relatively wide, demonstrate that a clinically significant proportion of subjects were infected with MRSA. Moreover, formal hypotheses regarding the effect of gender, diabetes or antibiotic use on the frequency of MRSA could not be tested.
CONCLUSIONS In this study, CA-MRSA was the most common cause of purulent staphylococcal SSTI in patients presenting to a tertiary care ED in a developing country. Importantly, the characteristics of CA-MRSA in this region are highly related to the current epidemic clone in the USA. The frequency of MRSA in this population has implications for empiric treatment, infection control 3
Downloaded from http://emj.bmj.com/ on January 30, 2015 - Published by group.bmj.com
Original article strategies and antimicrobial monitoring policies in Guyana and similar settings.
2
Acknowledgements We thank the staff of GPHC and the Guyana National Reference Laboratory for their support with sample collection and processing. We would also like to thank Dr Nicolas Forget and Dr Ashley Brown for their assistance in establishing the study. Finally, would like to thank Shanik Fernando, Rosalynne Korman and Meaghan McArdle for their support throughout the study period.
3
Contributors AD, CBC and SWW conceived the study. AD, SWW, CBC, PM-R and KBD designed the trial. SWW obtained research funding. ARD, SWW, KBD and PM-R supervised the conduct of the trial and data collection. AD managed and analysed the data. BC and PM-R supervised the laboratory analysis. IT, NJ-T, NS and AP conducted laboratory analysis. AD drafted the manuscript, and all authors contributed substantially to its revision. AD and SWW take responsibility for the paper as a whole.
4
5
6 7 8
Competing interests None. Patient consent Obtained.
9
Ethics approval Vanderbilt University Institutional Review Board; Guyana Ministry of Health Institutional Review Board. Provenance and peer review Not commissioned; externally peer reviewed.
REFERENCES 1
4
Daum RS. Skin and soft-tissue infections caused by methicillin-resistant Staphylococcus aureus. N Engl J Med 2007;357:380–90.
10
11
Moran GJ, Krishnadasan A, Gorwitz RJ, et al. Methicillin-resistant S. aureus infections among patients in the emergency department. N Eng J Med 2006;355:666–74. Otter JA, French GL. Community-associated methicillin-resistant Staphylococcus aureus: the case for a genotypic definition. J Hosp Infect 2021;81:143–8. Rodriguez E, Seas C. The changing pattern of methicillin-resistant Staphylococcus aureus clones in Latin America: implications for clinical practice in the region. Braz J Infect Dis 2010:14(Suppl 2):S87–96. Mejia C, Zurita J, Guzman-Blanco M. Epidemiology and surveillance of methicillin-resistant Staphylococcus aureus in Latin America. Braz J Infect Dis 2010;14(Suppl 2):79–86. Okeke IN, Laxminarayan R, Bhutta ZA, et al. Antimicrobial resistance in developing countries. Part1: recent trends and current status. Lancet Infect Dis 2005;5:481–93. Orrett FA, Land M. Methicillin-resistant Staphylococcus aureus prevalence: current susceptibility patterns in Trinidad. BMC Infect Dis 2006;6:83. Nicholson AM, Thoms C, Wint H, et al. The detection of mupirocin resistance and the distribution of methicillin-resistant Staphylococcus aureus at the University Hospital of the West Indies, Jamaica. West Indian Med J 2010;59:509–13. Reyes J, Rincon S, Diaz L, et al. Dissemination of methicillin-resistant Staphylococcus aureus USA300 sequence type 9 lineage in Latin America. Clin Infect Dis 2009;49:1861–7. Buck JM, Como-Sbetti K, Harriman KH, et al. Community-associated Methicillin-resistant Staphylococcus aureus, Minnesota, 200–2004. Emerg Infect Dis 2005;11:1532–8. Dumont AL, Nygaard TK, Watkins RL, et al. Characterization of a new cytotoxin that contributes to Staphylococcus aureus pathogenesis. Mol Microbial 2011;79 (Suppl 3):814–25.
Dozois A, et al. Emerg Med J 2014;0:1–4. doi:10.1136/emermed-2013-203373
Downloaded from http://emj.bmj.com/ on January 30, 2015 - Published by group.bmj.com
Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus among skin and soft tissue infections in an emergency department in Guyana Adeline Dozois, Isaac Thomsen, Natalia Jimenez-Truque, Nicole Soper, Alexis Pearson, Pheona Mohamed-Rambaran, Kristen B Dettorre, C Buddy Creech and Seth W Wright Emerg Med J published online December 31, 2014
Updated information and services can be found at: http://emj.bmj.com/content/early/2014/12/31/emermed-2013-203373
These include:
References Email alerting service
Topic Collections
This article cites 11 articles, 1 of which you can access for free at: http://emj.bmj.com/content/early/2014/12/31/emermed-2013-203373 #BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Articles on similar topics can be found in the following collections Drugs: infectious diseases (260) Poisoning (242) Poisoning/Injestion (242)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
EMJ Online First, published on December 31, 2014 as 10.1136/emermed-2013-203373 Original article
Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus among skin and soft tissue infections in an emergency department in Guyana Adeline Dozois,1 Isaac Thomsen,2 Natalia Jimenez-Truque,2 Nicole Soper,3 Alexis Pearson,3 Pheona Mohamed-Rambaran,3 Kristen B Dettorre,4 C Buddy Creech,2 Seth W Wright4 1
Vanderbilt University School of Medicine, Nashville, Tennessee, USA 2 Division of Pediatric Infectious Diseases, Department of Pediatrics, Vanderbilt University, Nashville, Tennessee, USA 3 Department of Laboratory Services, Georgetown Public Hospital Corporation, Georgetown, Guyana 4 Division of International Health, Department of Emergency Medicine, Vanderbilt University, Nashville, Tennessee, USA Correspondence to Adeline Dozois, Vanderbilt University School of Medicine, 2137 Fairfax Ave #13, Nashville, TN 37212, USA; [email protected] Received 31 October 2013 Revised 9 October 2014 Accepted 11 December 2014
ABSTRACT Objective The characteristics of staphylococcal skin and soft tissue infections (SSTIs) are poorly understood in northern South America and the Caribbean. The objectives of this study were to determine the frequency of methicillin resistance among Staphylococcus aureus isolates in an emergency department (ED) in Guyana and to identify specific molecular characteristics of these methicillin-resistant Staphylococcus aureus (MRSA) strains. Methods This was a cross-sectional study conducted at the main teaching hospital in Georgetown, Guyana. Eligible subjects included patients of all ages with SSTIs with obtainable purulent material. Purulent material was cultured, and S. aureus isolates were evaluated for antibiotic susceptibilities by disc diffusion. Molecular characterisation of MRSA isolates included identification of SCCmec type, assignment of genetic relatedness by rep-PCR and determination of the presence of two exotoxins, Panton-Valentine Leukocidin (PVL) and LukAB. Results Eighty-five samples were collected; of these, 47 grew S. aureus. 24 of the 47 S. aureus samples were MRSA (51%; 95% CI 37% to 65%), representing 28% of all samples. All MRSA isolates were SCCmec type IV, PVL positive, LukAB positive and were highly related to the current epidemic clone in the USA, USA300. Conclusions Here, we demonstrate a clinically significant proportion of methicillin resistance in SSTIassociated staphylococcal isolates. Guyanese isolates were highly related to the most common communityassociated strain seen in the USA, USA300. These results have important implications for empiric antibiotic therapy and infection control policies in Guyana and similar settings.
INTRODUCTION
To cite: Dozois A, Thomsen I, JimenezTruque N, et al. Emerg Med J Published Online First: [please include Day Month Year] doi:10.1136/emermed2013-203373
Staphylococcus aureus poses a significant threat to the health of both children and adults, causing a variety of diseases ranging from mild skin and soft tissue infections (SSTI) to more severe conditions such as endocarditis, necrotising pneumonia and sepsis.1 Methicillin-resistant Staphylococcus aureus (MRSA), which was initially found exclusively in the healthcare setting, is of particular concern. No longer solely a nosocomial pathogen, MRSA infections are increasingly common in individuals with no recent history of hospitalisation, particularly in North America.1 2 These community-associated MRSA
Key messages What is already known on this subject? ▸ Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of skin and soft tissue infections throughout the world. ▸ Though once considered a nosocomial pathogen, MRSA has increasingly been recognised as an important cause of infections in outpatient population, including individuals presenting to emergency departments. ▸ Little is known about the relative frequency of methicillin resistance among S. aureus isolates in Northern South America. What this study adds? ▸ Our study demonstrates a clinically significant proportion of methicillin resistance in skin and soft tissue infection-associated staphylococcal isolates in an emergency department in Northern South America. ▸ All the MRSA isolated in this study were highly related to the USA300 strain, which is currently the most common epidemic clone in the USA.
(CA-MRSA) strains are clinically and microbiologically distinct from previous iterations of MRSA, with distinct molecular and clinical characteristics that vary in infectivity, virulence and antibiotic susceptibility.1 2 In the USA, CA-MRSA strains typically possess the mecA gene in an SCCmec IV cassette; they typically harbour the genes encoding Panton-Valentine Leukocidin (PVL) and belong to the USA300 pulsed-field gel electrophoresis (PFGE) type.2–4 Though MRSA has been well studied in North America, considerably less is known about the epidemiology of CA-MRSA in South America and the Caribbean.4 5 No studies from South America or the Caribbean have examined the proportion of methicillin resistance and molecular characteristics of MRSA in emergency department (ED) patients with purulent SSTIs.4 5 Guyana is a South American country, bordered by Brazil, Venezuela and Suriname, with geographic and economic ties to the Caribbean region. An increased understanding of the prevalence and molecular characteristics
Dozois A, et al. Emerg Med J 2014;0:1–4. doi:10.1136/emermed-2013-203373
Copyright Article author (or their employer) 2014. Produced by BMJ Publishing Group Ltd under licence.
1
Downloaded from http://emj.bmj.com/ on January 30, 2015 - Published by group.bmj.com
Original article of MRSA in this setting could improve the regional understanding of MRSA epidemiology and improve local and regional management of S. aureus infections. The objectives of this study were to determine the frequency of methicillin resistance among S. aureus isolates in ED of the primary teaching hospital in Georgetown, Guyana, and to identify specific molecular characteristics of these MRSA strains.
METHODS Study setting and design We conducted a cross-sectional study of patients presenting to ED of Georgetown Public Hospital Corporation (GPHC) in Georgetown, Guyana. In Guyana, the majority of residents are concentrated in the capital city of Georgetown and the nearby coastal regions, whereas the inland jungle and savannah regions are sparsely populated. GPHC is a public hospital that serves as the tertiary care referral centre for the nation. ED has an annual volume of approximately 90 000 patients and is staffed by emergency medicine residents and medical officers. GPHC has the only public ED within the city of Georgetown; healthcare is free at both GPHC and other public facilities in Guyana.
Selection of participants Patients of all ages with an SSTI caused by a cutaneous abscess or an infected wound were considered eligible. All subjects were required to have purulent material obtainable from SSTI to be included for participation. Subjects were enrolled during an 8-week period from May to July 2012. Due to available resources, exclusion criteria included prisoners, those without capacity to give consent and minors without a parent or guardian present. Subjects were enrolled on a convenience basis when an investigator was available. Two investigators were typically available in overlapping 8 h shifts covering the hours of 09:00 to 22:00, 7 days per week.
Methods and measurements: We recorded the age, sex, history of recent antibiotic use (within 1 month), history of recent hospitalisation (within 1 month) and history of diabetes mellitus for each subject. A sample of purulent material was collected on a Culturette swab with liquid Amies media (BD, Franklin Lakes, New Jersey, USA) and cultured in the GPHC microbiology laboratory to detect S. aureus. Cultures positive for S. aureus were tested for resistance to methicillin, trimethoprim/sulfamethoxazole, clindamycin and tetracyclines by disc diffusion. A pure culture isolate of each S. aureus sample was shipped to Vanderbilt University for confirmation of methicillin
resistance and subsequent molecular characterisation. Confirmation of methicillin resistance and assignment of SCCmec type was performed by ccr and mec complex typing. Purified genomic DNA (Promega, Madison, Wisconsin, USA) was used as the template for PCR detection of genes encoding the PVL and LukAB exotoxins. Repetitive element, sequencebased PCR using the DiversiLab System (bioMérieux, Durham, North Carolina, USA) was used to determine genetic relatedness between strains. MRSA isolates were defined as CA-MRSA or HA-MRSA based upon PCR and repetitive element sequencebased PCR characteristics.
Analysis Proportion and prevalence data were expressed using descriptive statistics. 95% CIs were calculated using the modified Wald method with GraphPad Prism (GraphPad Software, La Jolla, California, USA) software.
RESULTS Eighty-nine patients meeting inclusion and exclusion criteria were approached for enrolment. Of these, four refused consent. Purulent samples were obtained from the remaining 85 patients. Table 1 describes baseline subject characteristics. Of the 85 samples, 47 (55%) grew S. aureus (figure 1). Also, 24 of the 47 S. aureus isolates were MRSA (51%, 95% CI 37% to 65%), giving an overall prevalence of 28% (95% CI 20% to 39%). All MRSA isolates were susceptible to tetracycline and trimethoprim/sulfamethoxazole and 22/24 (88%) were susceptible to clindamycin. All MRSA isolates possessed SCCmec IV and all contained the genes encoding PVL. All strains also harboured the LukAB genes. Repetitive element sequence-based PCR revealed two distinct clonal populations, both of which were highly related to the USA300 PFGE type. These findings suggest that all MRSA isolates in this study shared molecular characteristics consistent with the current epidemic clone of CA-MRSA in the USA.
DISCUSSION Community-acquired infections remain the leading cause of death in most developing countries, and appropriate initial
Table 1 Subject characteristics Staphylococcus aureus cultured (n=47)
Characteristic
All subjects (n=85)
MSSA (n=23)
MRSA (n=24)
Age (mean [range] years) Male sex, no. (%) History of diabetes mellitus, no. (%) Antibiotic use (1 month), no. (%) Recent hospitalisation (1 month), no. (%)
33 54 20 29 12
21 15 (65%) 5 (22%) 4 (17%) 2 (9%)
24 15 (63%) 4 (17%) 10 (42%) 2 (8%)
[1–79] (64%) (24%) (34%) (14%)
MRSA, methicillin-resistant Staphylococcus aureus; MSSA, methicillin-sensitive Staphylococcus aureus.
2
Figure 1 Patient recruitment diagram. MRSA, methicillin-resistant Staphylococcus aureus. MSSA, methicillin-sensitive Staphylococcus aureus. CoNS, coagulase-negative Staphylococcus. Dozois A, et al. Emerg Med J 2014;0:1–4. doi:10.1136/emermed-2013-203373
Downloaded from http://emj.bmj.com/ on January 30, 2015 - Published by group.bmj.com
Original article treatment is critical in reducing mortality and morbidity.6 Our findings suggest that patients with suspected staphylococcal infections may benefit from empiric antibiotic coverage for MRSA. We demonstrated that 51% of S. aureus isolates in Guyana were MRSA, representing 28% of all purulent SSTIs. These data clearly suggest that empiric antimicrobials should possess activity against MRSA, making the β-lactams such as cephalexin or penicillins poor choices in this region.1 While some antimicrobials, such as clindamycin, may not be readily available in low-income and middle-income countries, others, such as trimethoprim/sulfamethoxazole and doxycycline, are typically available; therefore, we suggest that empiric treatment of purulent SSTI in this region include one of these agents. To our knowledge, this is the first report of the prevalence and molecular characteristics of MRSA from purulent SSTIs in the region. The frequency of MRSA observed in Guyana is higher than what has been observed in nearby Caribbean countries. For instance, in a mixed inpatient/outpatient population in Trinidad, the proportion of MRSA increased from 12.5% in 1999 to 20.8% in 2004.7 More recently, a Jamaican study suggested that only 7% of S. aureus SSTI samples were MRSA.8 These studies are difficult to compare to ours as they included healthcare-associated infections, while ours was from an outpatient population. When compared with the rest of South America, data from this study are commensurate with the frequency of MRSA in the population.4 5 9 For instance, in a fourcountry survey from the Andes, 41% of all S. aureus samples were MRSA.9 Taken together, we can conclude that while the epidemiology of S. disease can vary by geographic region, MRSA is an important cause of staphylococcal abscesses in Guyana. The epidemiology of MRSA in EDs in the USA is better understood. A multihospital study of SSTIs in EDs in the USA demonstrated an overall MRSA prevalence of 59%, which represented 78% of S. aureus isolates.2 Both our overall prevalence (28%) and the proportion of MRSA among the S. aureus isolates (51%) were lower than that found in the multicentre study from the USA. Nevertheless, the proportions found in our study are similar to those seen in several sites in that study and the prevalence of resistant organisms is clinically significant.1 2 All MRSA samples in this study contained SCCmec IV and were PVL positive; moreover, these strains belonged to the USA300 pulsotype, consistent with CA-MRSA based on a genotypic definition.2 3 The lack of other HA-MRSA strain types in this study is typical for an outpatient population as HA-MRSA strains uncommonly cause infection in healthy individuals in the community.3 Two subjects reported hospitalisation within the previous month and would not meet the Centers for Disease Control and Prevention case definitions for community-associated MRSA.10 Whether the presence of hospitalised subjects in our population is reflective of the inherent difficulties of the current epidemiological definition or implies that CA-MRSA can be readily transmitted in the healthcare setting cannot be answered by this study; nevertheless, the homogeneity of infecting isolates is a critical finding as it suggests a sustainable reservoir of the organism in the community, likely maintained by frequent asymptomatic colonisation. Identifying the strains responsible for infection, particularly when CA-MRSA is suspected, can have important implications for both hospital and community control policies, as well as empiric antibiotic therapy.3 We found that all isolates in this community setting were highly related to the USA300 PFGE type. USA300 is the most common CA-MRSA strain in the USA and is the most common CA-MRSA strain in studies from South America.1–5 9 Given the speed by which USA300 CA-MRSA has Dozois A, et al. Emerg Med J 2014;0:1–4. doi:10.1136/emermed-2013-203373
spread in the USA, it is not surprising that Guyana and other parts of South America are also experiencing an increase in disease due to this strain. The high prevalence of the genes encoding PVL in these strains is thought to contribute to the increased virulence of USA300 isolates, though other virulence factors are also known to play an important role.2 4 All isolates in this study also possessed the genes for LukAB, a twocomponent exotoxin whose subunits are two of the most abundantly produced proteins in the staphylococcal secretome.11 To our knowledge, this is the first study to confirm the presence of this toxin in clinical isolates from South America.
LIMITATIONS As with any study, our research had limitations. First, subjects were enrolled in ED of the main tertiary care hospital in the capital city, thus it is unclear whether our results can be generalised to other ED or outpatient populations within Guyana. GPHC is the predominant institution within Georgetown and provides services for a diverse socioeconomic population. The majority of Guyana’s population resides in Georgetown and the demographically similar coastal regions. Thus, it is likely that our results are reflective of purulent SSTIs in the heavily populated sections of the country. It is unlikely that our results are fully generalisable to ED populations in other areas of South America or the Caribbean islands given the marked differences in MRSA prevalence between geographic regions.2 This is not a limitation per se as it is important to determine both local and regional prevalence. Second, this study focused only on purulent SSTIs. The prevalence of MRSA may not apply to invasive infections or non-purulent cellulitis. Our inclusion only of patients with purulent SSTIs makes this study similar to other ED studies conducted in the USA.2 Third, we identified antibiotic susceptibilities only for S. aureus isolates and not for gram-negative organisms; therefore, we cannot describe overall antibiotic susceptibilities for all purulent SSTI’s. However, the relative frequency of gram-negative infections was far less than either S. aureus or S. pyogenes. Fourth, data regarding the type of infection were not collected for all subjects, nor did we collect additional clinical characteristics such as fever or admission status. We did not collect this information because the study was to be a survey of the organisms present in ED, and we did not intend to correlate this information with the type of presentation or clinical outcomes. We included a convenience sample of patients presenting during daytime and evening hours. It is possible, though unlikely, that patients presenting during late night hours would have had different microbial findings. Subjects were recruited during a 2-month period, which may mask seasonal variability in MRSA infection rates. Given that Guyana is an equatorial country, seasonal differences are unlikely. Last, the study was limited to a relatively small sample size of 85 subjects and was not subject to a formal power analysis. CIs, while relatively wide, demonstrate that a clinically significant proportion of subjects were infected with MRSA. Moreover, formal hypotheses regarding the effect of gender, diabetes or antibiotic use on the frequency of MRSA could not be tested.
CONCLUSIONS In this study, CA-MRSA was the most common cause of purulent staphylococcal SSTI in patients presenting to a tertiary care ED in a developing country. Importantly, the characteristics of CA-MRSA in this region are highly related to the current epidemic clone in the USA. The frequency of MRSA in this population has implications for empiric treatment, infection control 3
Downloaded from http://emj.bmj.com/ on January 30, 2015 - Published by group.bmj.com
Original article strategies and antimicrobial monitoring policies in Guyana and similar settings.
2
Acknowledgements We thank the staff of GPHC and the Guyana National Reference Laboratory for their support with sample collection and processing. We would also like to thank Dr Nicolas Forget and Dr Ashley Brown for their assistance in establishing the study. Finally, would like to thank Shanik Fernando, Rosalynne Korman and Meaghan McArdle for their support throughout the study period.
3
Contributors AD, CBC and SWW conceived the study. AD, SWW, CBC, PM-R and KBD designed the trial. SWW obtained research funding. ARD, SWW, KBD and PM-R supervised the conduct of the trial and data collection. AD managed and analysed the data. BC and PM-R supervised the laboratory analysis. IT, NJ-T, NS and AP conducted laboratory analysis. AD drafted the manuscript, and all authors contributed substantially to its revision. AD and SWW take responsibility for the paper as a whole.
4
5
6 7 8
Competing interests None. Patient consent Obtained.
9
Ethics approval Vanderbilt University Institutional Review Board; Guyana Ministry of Health Institutional Review Board. Provenance and peer review Not commissioned; externally peer reviewed.
REFERENCES 1
4
Daum RS. Skin and soft-tissue infections caused by methicillin-resistant Staphylococcus aureus. N Engl J Med 2007;357:380–90.
10
11
Moran GJ, Krishnadasan A, Gorwitz RJ, et al. Methicillin-resistant S. aureus infections among patients in the emergency department. N Eng J Med 2006;355:666–74. Otter JA, French GL. Community-associated methicillin-resistant Staphylococcus aureus: the case for a genotypic definition. J Hosp Infect 2021;81:143–8. Rodriguez E, Seas C. The changing pattern of methicillin-resistant Staphylococcus aureus clones in Latin America: implications for clinical practice in the region. Braz J Infect Dis 2010:14(Suppl 2):S87–96. Mejia C, Zurita J, Guzman-Blanco M. Epidemiology and surveillance of methicillin-resistant Staphylococcus aureus in Latin America. Braz J Infect Dis 2010;14(Suppl 2):79–86. Okeke IN, Laxminarayan R, Bhutta ZA, et al. Antimicrobial resistance in developing countries. Part1: recent trends and current status. Lancet Infect Dis 2005;5:481–93. Orrett FA, Land M. Methicillin-resistant Staphylococcus aureus prevalence: current susceptibility patterns in Trinidad. BMC Infect Dis 2006;6:83. Nicholson AM, Thoms C, Wint H, et al. The detection of mupirocin resistance and the distribution of methicillin-resistant Staphylococcus aureus at the University Hospital of the West Indies, Jamaica. West Indian Med J 2010;59:509–13. Reyes J, Rincon S, Diaz L, et al. Dissemination of methicillin-resistant Staphylococcus aureus USA300 sequence type 9 lineage in Latin America. Clin Infect Dis 2009;49:1861–7. Buck JM, Como-Sbetti K, Harriman KH, et al. Community-associated Methicillin-resistant Staphylococcus aureus, Minnesota, 200–2004. Emerg Infect Dis 2005;11:1532–8. Dumont AL, Nygaard TK, Watkins RL, et al. Characterization of a new cytotoxin that contributes to Staphylococcus aureus pathogenesis. Mol Microbial 2011;79 (Suppl 3):814–25.
Dozois A, et al. Emerg Med J 2014;0:1–4. doi:10.1136/emermed-2013-203373
Downloaded from http://emj.bmj.com/ on January 30, 2015 - Published by group.bmj.com
Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus among skin and soft tissue infections in an emergency department in Guyana Adeline Dozois, Isaac Thomsen, Natalia Jimenez-Truque, Nicole Soper, Alexis Pearson, Pheona Mohamed-Rambaran, Kristen B Dettorre, C Buddy Creech and Seth W Wright Emerg Med J published online December 31, 2014
Updated information and services can be found at: http://emj.bmj.com/content/early/2014/12/31/emermed-2013-203373
These include:
References Email alerting service
Topic Collections
This article cites 11 articles, 1 of which you can access for free at: http://emj.bmj.com/content/early/2014/12/31/emermed-2013-203373 #BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Articles on similar topics can be found in the following collections Drugs: infectious diseases (260) Poisoning (242) Poisoning/Injestion (242)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
