Molecular Characterization of Methicillin-Resistant Staphylococcus aureus Strains Isolated from Patients with Hospital Readmissions
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Saleh Eghbaria, Kathy Schnitser, Nada Danial-Farran, Yoram Keness and Naiel Bisharat J. Clin. Microbiol. 2014, 52(4):1256. DOI: 10.1128/JCM.03449-13. Published Ahead of Print 29 January 2014.
Molecular Characterization of Methicillin-Resistant Staphylococcus aureus Strains Isolated from Patients with Hospital Readmissions Saleh Eghbaria,a Kathy Schnitser,a Nada Danial-Farran,b Yoram Keness,c,d Naiel Bisharata,d Department of Medicine D, Emek Medical Center, Afula, Israela; Institute of Genetics, Emek Medical Center, Afula, Israelb; Microbiology Laboratory, Emek Medical Center, Afula, Israelc; The Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israeld
M
ethicillin-resistant Staphylococcus aureus (MRSA) is one of the most important bacterial pathogens causing hospitalacquired infections and in recent years has become a serious cause of community-onset infections as well (1). While it has been shown that patients colonized with MRSA continue to carry MRSA for months and even years after the initial acquisition (2– 4), it is unclear whether colonized patients continue to harbor the same MRSA strain or acquire a different one during subsequent readmissions. We undertook to characterize MRSA strains isolated from patients found to be MRSA carriers at both index admission and subsequent admissions, in an effort to study the dynamics of strain shifting during hospital readmissions. The study was carried out at Emek Medical Center, a 550-bed community teaching hospital in northern Israel serving a population of some 600,000 inhabitants. The hospital’s MRSA screening policy recommends that the following categories of patients be screened for MRSA upon admission: patients with a known history of MRSA colonization or infection, patients admitted from long-term-care facilities (LTCFs) or other hospitals, patients receiving long-term hemodialysis, patients readmitted to the hospital within 3 months of discharge, patients who underwent a major operative procedure in the previous month, all patients admitted to the intensive care unit, and patients with pressure sores or permanent tracheostomy living at home. The following data were recorded from the medical records of every patient identified as an MRSA carrier at index admission from 2010 to 2012: number of admissions, number of strains isolated during each admission, body sites sampled, whether colonized patients received eradication therapy, and antimicrobial susceptibility patterns. Culture specimens were collected from the anterior nares and perineum. Microbiology analysis was carried out as previously described (5). Eradication therapy for MRSA included twice-daily application of nasal mupirocin ointment to the anterior nares and daily body wash with chlorhexidine, both for 5 days, with follow-up cultures on day 6. Molecular characterization included screening for the presence of the Panton-Valentine leukocidin (PVL) genes, multilocus sequence typing (MLST), and staphylococcal cassette chromosome mec (SCCmec) and spa typing, as previously described (6–9). Allele types and resulting sequence types (STs) and allocation of MLST clonal complex (MLST CC) were assigned at the S. aureus MLST database via the
Internet (www.mlst.net). spa types were assigned using StaphType software (version 1.4; Ridom GmbH, Wurzburg, Germany). Out of a total of 151,153 admissions to the hospital during the study period, around 10,000 patients were candidates for MRSA screening but only 8,481 patients were actually screened. The MRSA colonization rate averaged 5.8% during the study period. Of the 762 patients who underwent eradication therapy, 33 (4.3%) were identified as persistently colonized patients; 140 MRSA strains isolated from them were used for the study. The number of admissions ranged from 1 to 3 after index admission, with a mean intervening period between admissions of 34 days (range, 10 to 94 days). Eighteen patients (⬃55%) resided in 6 different LTCFs. The mean number of strains isolated from each patient was 4 with a range of 2 to 8 (Table 1). Seventeen of the 33 patients (51.2%) continued to harbor the same genotype, and 16 (48.5%) acquired MRSA with a different genotype. Twentyfive (76%) received eradication therapy, which was incomplete in 14 (56%) for various reasons: administration for less than 5 days, lack of adherence to chlorhexidine daily body wash, therapy not provided at every admission, and lack of follow-up. Sixteen of the 25 patients who received eradication therapy were recolonized with MRSA exhibiting a different genotype, and 9 were colonized with the same strain (Table 1). Among the 8 untreated patients, 6 continued to harbor MRSA with the same genotype and 2 were colonized with MRSA of a different genotype (Table 1, patients 15 and 25). Nine of the 18 patients living in LTCFs were recolonized with “new” MRSA strains; 7 received eradication therapy, and 2 did not (patients 15 and 25). The other 9 continued to harbor the same strain; 5 received incomplete therapy, and 4 were not treated. None of the patients suffered from an invasive MRSA infection during the study period. All strains were PVL negative, and the vast majority belonged to the MLST clonal
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Journal of Clinical Microbiology
Received 11 December 2013 Returned for modification 2 January 2014 Accepted 23 January 2014 Published ahead of print 29 January 2014 Editor: D. J. Diekema Address correspondence to Naiel Bisharat, [email protected]. Copyright © 2014, American Society for Microbiology. All Rights Reserved. doi:10.1128/JCM.03449-13
April 2014 Volume 52 Number 4
Downloaded from http://jcm.asm.org/ on March 31, 2014 by NATIONAL CHUNG HSING
It is unclear whether patients colonized with methicillin-resistant Staphylococcus aureus (MRSA) continue to harbor the same genotype during hospital readmissions. We characterized 140 MRSA strains isolated from 33 persistent MRSA carriers with hospital readmissions. Nearly half of the patients continued to harbor the same genotype, and the rest acquired different genotypes. Among 25 patients who received eradication therapy, 16 (64%) were colonized with MRSA strains exhibiting different genotypes from the preexisting one.
Characterization of MRSA from Readmitted Patients
TABLE 1 Clinical data and molecular characterization of MRSA strains from 33 persistently colonized patients No. of admissions
Residencea
Total no. of strains
No. of specimens per admission (1st/2nd/3rd/4th)b
MLST (CCc)d
spa typed
SCCmec typed
Eradication therapy
1 2 3 4 5 6 7 8 9 10 11
2 2 2 2 3 3 3 2 3 4 2
Home Home LTCF LTCF Home LTCF Home Home LTCF LTCF LTCF
2 3 4 4 5 6 3 4 5 5 3
1/1 2/1 2/2 2/2 2/1/2 2/2/2 1/1/1 2/2 1/2/2 1/1/1/2 1/2
ST5 (CC5) ST5 (CC5) ST228 (CC5)¡ST5 (CC5) ST5 (CC5) ST148 ST83 ST228 (CC5)¡ST273 ST45 (CC45) ST5 (CC5) ST22 (CC22) ST148
t002 t12282 t5172¡t002 t002 t002 t002 t2167¡t036 t065 t3376 t032 t002
II II I¡III II II II I IV II IV II
No No Yese No Yese Yese Yes Yes No Yese No
12 13 14 15 16 17 18 19 20 21
2 3 4 2 3 3 3 3 2 2
Home LTCF LTCF LTCF Home Home Home Home LTCF LTCF
2 3 8 2 4 4 6 6 6 6
1/1 1/2 2/2/2/2 1/1 2/1/1 1/1/2 2/2/2 2/2/2 3/3 3/3
ST868 ST5 (CC5) ST5 (CC5)¡ST7 ST15¡ST30 (CC30) ST5 (CC5) ST5 (CC5)¡ST8 (CC8) ST5 (CC5) ST5 (CC5) ST5 (CC5) ST5 (CC5)¡ST22 (C22)
t002 t067 t535¡t796 t084¡t037 t002 t002¡t052 t002¡t004 t001¡t002 t001 t002¡t032
II II II¡IV IV I I¡II I¡II I¡IV I I¡II
Yes Yese Yes No Yese Yes Yese Yes Yese Yes
22 23 24 25 26 27 28 29 30 31 32 33
2 2 3 4 3 3 3 2 2 2 3 3
Home LTCF Home LTCF Home LTCF LTCF LTCF LTCF Home LTCF Home
4 3 6 4 5 3 5 4 4 3 4 4
2/2 1/2 2/2/2 2/2 2/2/1 1/1/1 1/2/2 2/2 2/2 2/1 1/2/1 1/1/2
ST45 (CC45)¡ST8 (CC8) ST8 (CC8) ST5 (CC5)¡ST121 (CC121) ST8 (CC8)¡ST22 (C22) ST22 (CC22)¡ST7 ST8 (CC8) ST5 (CC5)¡ST8 (CC8) ST5 (CC5)¡ST22 (CC22) ST5 (CC5)¡ST121 (CC121) ST5 (CC5)¡ST30 (CC30) ST8 (CC8)¡ST22 (CC22) ST5 (CC5)¡ST33 (CC30)
t004¡t052 t064 t001¡t159 t051¡t002 t032¡t796 t1911 t010¡t189 t002¡t4896 t002¡t084 t002¡t377 t008¡t12282 t002¡t021
II¡I IV I¡IV I¡IV IV¡IV IV II¡ IV II¡III I¡II II¡I I¡IV II¡IV
Yes No Yese No Yes Yese Yese Yese Yes Yese Yese Yes
a
LTCF, long-term-care facility. The admission at which the genotype shift occurred is underlined. c CC, clonal complex. d Shift of MLST/clonal complex, spa type, or SCCmec type. e Incomplete eradication therapy. b
complex 5 (CC5) and spa clonal complex 002. These results are consistent with a recent report from Israel that characterized MRSA strains from other parts of the country (10). Nearly half of the 33 persistently colonized patients who had received eradication therapy eventually cleared their initial colonizing strain and acquired new MRSA genotypes, while the rest continued to harbor the same MRSA genotype. Failure of MRSA eradication and acquisition of new strains in these patients could be attributed to several factors; deficient eradication therapy, patient-to-patient cross-transmission, colonization of extranasal sites, and resistance to mupirocin (11–13). High-level resistance to mupirocin among MRSA strains from our region has been estimated to be 13.5% (Y. Keness, unpublished data), and among our cohort and subgroup of patients who received eradication therapy, it was 18.2% and 16%, respectively. It is reasonable to postulate that decolonization and subsequent colonization might have occurred. Unfortunately, the lack of follow-up specimens following eradication therapy in many of them precludes drawing robust conclusions. Given the observed deficiencies in eradication therapy, confirmed in our recent report showing the poor compliance of hos-
April 2014 Volume 52 Number 4
pital staff with MRSA surveillance guidelines (5), it is not surprising that 33 patients became persistent colonizers. Long-term persistence of specific MRSA genotypes among untreated MRSA carriers, for as long as 3 years, has been described elsewhere (14). However, the finding that nearly half of the patients in our cohort exhibited strain shifting during readmission is intriguing. This could be accounted for, in part, by reports on the dynamic nature of Staphylococcus aureus carriage in different settings showing that at the species level, long-term carriers did not carry the same genotypic profile consistently, with loss and acquisition of different genotypes over time (15–17). While our cohort is small, the molecular characterization of several MRSA strains from a single patient during multiple admissions over time provides important insights into the dynamics of MRSA colonization and strain shifting. REFERENCES 1. David MZ, Daum RS. 2010. Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic. Clin. Microbiol. Rev. 23:616 – 687. http://dx.doi.org /10.1128/CMR.00081-09. 2. Davis KA, Stewart JJ, Crouch HK, Florez CE, Hospenthal DR. 2004.
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MJ. 2012. Molecular epidemiology of methicillin-resistant Staphylococcus aureus in Israel: dissemination of global clones and unique features. J. Clin. Microbiol. 50:134 –137. http://dx.doi.org/10.1128/JCM.05446-11. Mollema FP, Severin JA, Nouwen JL, Ott A, Verbrugh HA, Vos MC. 2010. Successful treatment for carriage of methicillin-resistant Staphylococcus aureus and importance of follow-up. Antimicrob. Agents Chemother. 54:4020 – 4025. http://dx.doi.org/10.1128/AAC.01240-09. Ammerlaan HS, Kluytmans JA, Wertheim HF, Nouwen JL, Bonten MJ. 2009. Eradication of methicillin-resistant Staphylococcus aureus carriage: a systematic review. Clin. Infect. Dis. 48:922–930. http://dx.doi.org/10.1086 /597291. Simor AE, Phillips E, McGeer A, Konvalinka A, Loeb M, Devlin HR, Kiss A. 2007. Randomized controlled trial of chlorhexidine gluconate for washing, intranasal mupirocin, and rifampin and doxycycline versus no treatment for the eradication of methicillin-resistant Staphylococcus aureus colonization. Clin. Infect. Dis. 44:178 –185. http://dx.doi.org/10.1086 /510392. Sanford MD, Widmer AF, Bale MJ, Jones RN, Wenzel RP. 1994. Efficient detection and long-term persistence of the carriage of methicillin-resistant Staphylococcus aureus. Clin. Infect. Dis. 19:1123–1128. http: //dx.doi.org/10.1093/clinids/19.6.1123. Miller R, Walker AS, Godwin H, Fung R, Votintseva A, Bowden R, Mant D, Peto TE, Crook DW, Knox K. 2014. Dynamics of acquisition and loss of carriage of Staphylococcus aureus strains in the community: the effect of clonal complex. J. Infect. http://dx.doi.org/10.1016/j.jinf.2013.12 .013. Bloemendaal AL, Fluit AC, Jansen WT, Vriens MR, Ferry T, Amorim JM, Pascual A, Stefani S, Papaparaskevas J, Borel Rinkes IH, Verhoef J. 2009. Colonization with multiple Staphylococcus aureus strains among patients in European intensive care units. Infect. Control Hosp. Epidemiol. 30:918 –920. http://dx.doi.org/10.1086/605640. Sakwinska O, Blanc DS, Lazor-Blanchet C, Moreillon M, Giddey M, Moreillon P. 2010. Ecological temporal stability of Staphylococcus aureus nasal carriage. J. Clin. Microbiol. 48:2724 –2728. http://dx.doi.org/10 .1128/JCM.02091-09.
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Methicillin-resistant Staphylococcus aureus (MRSA) nares colonization at hospital admission and its effect on subsequent MRSA infection. Clin. Infect. Dis. 39:776 –782. http://dx.doi.org/10.1086/422997. Huang SS, Hinrichsen VL, Datta R, Spurchise L, Miroshnik I, Nelson K, Platt R. 2011. Methicillin-resistant Staphylococcus aureus infection and hospitalization in high-risk patients in the year following detection. PLoS One 6:e24340. http://dx.doi.org/10.1371/journal.pone.0024340. Scanvic A, Denic L, Gaillon S, Giry P, Andremont A, Lucet JC. 2001. Duration of colonization by methicillin-resistant Staphylococcus aureus after hospital discharge and risk factors for prolonged carriage. Clin. Infect. Dis. 32:1393–1398. http://dx.doi.org/10.1086/320151. Zoabi M, Keness Y, Titler N, Bisharat N. 2011. Compliance of hospital staff with guidelines for the active surveillance of methicillin-resistant Staphylococcus aureus (MRSA) and its impact on rates of nosocomial MRSA bacteremia. Isr. Med. Assoc. J. 13:740 –744. http://www.ima.org.il /IMAJ/ViewArticle.aspx?aId⫽529. Said-Salim B, Mathema B, Braughton K, Davis S, Sinsimer D, Eisner W, Likhoshvay Y, Deleo FR, Kreiswirth BN. 2005. Differential distribution and expression of Panton-Valentine leucocidin among community-acquired methicillin-resistant Staphylococcus aureus strains. J. Clin. Microbiol. 43: 3373–3379. http://dx.doi.org/10.1128/JCM.43.7.3373-3379.2005. Enright MC, Day NP, Davies CE, Peacock SJ, Spratt BG. 2000. Multilocus sequence typing for characterization of methicillin-resistant and methicillin-susceptible clones of Staphylococcus aureus. J. Clin. Microbiol. 38:1008 –1015. http://jcm.asm.org/content/38/3/1008.long. Milheirico C, Oliveira DC, de Lencastre H. 2007. Update to the multiplex PCR strategy for assignment of mec element types in Staphylococcus aureus. Antimicrob. Agents Chemother. 51:3374 –3377. http://dx.doi.org /10.1128/AAC.00275-07. Milheirico C, Oliveira DC, de Lencastre H. 2007. Multiplex PCR strategy for subtyping the staphylococcal cassette chromosome mec type IV in methicillin-resistant Staphylococcus aureus: ‘SCCmec IV multiplex’. J. Antimicrob. Chemother. 60:42– 48. http://dx.doi.org/10.1093/jac/dkm112. Adler A, Chmelnitsky I, Shitrit P, Sprecher H, Navon-Venezia S, Embon A, Khabra E, Paitan Y, Keren L, Halperin E, Carmeli Y, Schwaber
Updated information and services can be found at: http://jcm.asm.org/content/52/4/1256 These include: REFERENCES
CONTENT ALERTS
This article cites 17 articles, 13 of which can be accessed free at: http://jcm.asm.org/content/52/4/1256#ref-list-1 Receive: RSS Feeds, eTOCs, free email alerts (when new articles cite this article), more»
Information about commercial reprint orders: http://journals.asm.org/site/misc/reprints.xhtml To subscribe to to another ASM Journal go to: http://journals.asm.org/site/subscriptions/
Downloaded from http://jcm.asm.org/ on March 31, 2014 by NATIONAL CHUNG HSING
Saleh Eghbaria, Kathy Schnitser, Nada Danial-Farran, Yoram Keness and Naiel Bisharat J. Clin. Microbiol. 2014, 52(4):1256. DOI: 10.1128/JCM.03449-13. Published Ahead of Print 29 January 2014.
Molecular Characterization of Methicillin-Resistant Staphylococcus aureus Strains Isolated from Patients with Hospital Readmissions Saleh Eghbaria,a Kathy Schnitser,a Nada Danial-Farran,b Yoram Keness,c,d Naiel Bisharata,d Department of Medicine D, Emek Medical Center, Afula, Israela; Institute of Genetics, Emek Medical Center, Afula, Israelb; Microbiology Laboratory, Emek Medical Center, Afula, Israelc; The Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israeld
M
ethicillin-resistant Staphylococcus aureus (MRSA) is one of the most important bacterial pathogens causing hospitalacquired infections and in recent years has become a serious cause of community-onset infections as well (1). While it has been shown that patients colonized with MRSA continue to carry MRSA for months and even years after the initial acquisition (2– 4), it is unclear whether colonized patients continue to harbor the same MRSA strain or acquire a different one during subsequent readmissions. We undertook to characterize MRSA strains isolated from patients found to be MRSA carriers at both index admission and subsequent admissions, in an effort to study the dynamics of strain shifting during hospital readmissions. The study was carried out at Emek Medical Center, a 550-bed community teaching hospital in northern Israel serving a population of some 600,000 inhabitants. The hospital’s MRSA screening policy recommends that the following categories of patients be screened for MRSA upon admission: patients with a known history of MRSA colonization or infection, patients admitted from long-term-care facilities (LTCFs) or other hospitals, patients receiving long-term hemodialysis, patients readmitted to the hospital within 3 months of discharge, patients who underwent a major operative procedure in the previous month, all patients admitted to the intensive care unit, and patients with pressure sores or permanent tracheostomy living at home. The following data were recorded from the medical records of every patient identified as an MRSA carrier at index admission from 2010 to 2012: number of admissions, number of strains isolated during each admission, body sites sampled, whether colonized patients received eradication therapy, and antimicrobial susceptibility patterns. Culture specimens were collected from the anterior nares and perineum. Microbiology analysis was carried out as previously described (5). Eradication therapy for MRSA included twice-daily application of nasal mupirocin ointment to the anterior nares and daily body wash with chlorhexidine, both for 5 days, with follow-up cultures on day 6. Molecular characterization included screening for the presence of the Panton-Valentine leukocidin (PVL) genes, multilocus sequence typing (MLST), and staphylococcal cassette chromosome mec (SCCmec) and spa typing, as previously described (6–9). Allele types and resulting sequence types (STs) and allocation of MLST clonal complex (MLST CC) were assigned at the S. aureus MLST database via the
Internet (www.mlst.net). spa types were assigned using StaphType software (version 1.4; Ridom GmbH, Wurzburg, Germany). Out of a total of 151,153 admissions to the hospital during the study period, around 10,000 patients were candidates for MRSA screening but only 8,481 patients were actually screened. The MRSA colonization rate averaged 5.8% during the study period. Of the 762 patients who underwent eradication therapy, 33 (4.3%) were identified as persistently colonized patients; 140 MRSA strains isolated from them were used for the study. The number of admissions ranged from 1 to 3 after index admission, with a mean intervening period between admissions of 34 days (range, 10 to 94 days). Eighteen patients (⬃55%) resided in 6 different LTCFs. The mean number of strains isolated from each patient was 4 with a range of 2 to 8 (Table 1). Seventeen of the 33 patients (51.2%) continued to harbor the same genotype, and 16 (48.5%) acquired MRSA with a different genotype. Twentyfive (76%) received eradication therapy, which was incomplete in 14 (56%) for various reasons: administration for less than 5 days, lack of adherence to chlorhexidine daily body wash, therapy not provided at every admission, and lack of follow-up. Sixteen of the 25 patients who received eradication therapy were recolonized with MRSA exhibiting a different genotype, and 9 were colonized with the same strain (Table 1). Among the 8 untreated patients, 6 continued to harbor MRSA with the same genotype and 2 were colonized with MRSA of a different genotype (Table 1, patients 15 and 25). Nine of the 18 patients living in LTCFs were recolonized with “new” MRSA strains; 7 received eradication therapy, and 2 did not (patients 15 and 25). The other 9 continued to harbor the same strain; 5 received incomplete therapy, and 4 were not treated. None of the patients suffered from an invasive MRSA infection during the study period. All strains were PVL negative, and the vast majority belonged to the MLST clonal
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jcm.asm.org
Journal of Clinical Microbiology
Received 11 December 2013 Returned for modification 2 January 2014 Accepted 23 January 2014 Published ahead of print 29 January 2014 Editor: D. J. Diekema Address correspondence to Naiel Bisharat, [email protected]. Copyright © 2014, American Society for Microbiology. All Rights Reserved. doi:10.1128/JCM.03449-13
April 2014 Volume 52 Number 4
Downloaded from http://jcm.asm.org/ on March 31, 2014 by NATIONAL CHUNG HSING
It is unclear whether patients colonized with methicillin-resistant Staphylococcus aureus (MRSA) continue to harbor the same genotype during hospital readmissions. We characterized 140 MRSA strains isolated from 33 persistent MRSA carriers with hospital readmissions. Nearly half of the patients continued to harbor the same genotype, and the rest acquired different genotypes. Among 25 patients who received eradication therapy, 16 (64%) were colonized with MRSA strains exhibiting different genotypes from the preexisting one.
Characterization of MRSA from Readmitted Patients
TABLE 1 Clinical data and molecular characterization of MRSA strains from 33 persistently colonized patients No. of admissions
Residencea
Total no. of strains
No. of specimens per admission (1st/2nd/3rd/4th)b
MLST (CCc)d
spa typed
SCCmec typed
Eradication therapy
1 2 3 4 5 6 7 8 9 10 11
2 2 2 2 3 3 3 2 3 4 2
Home Home LTCF LTCF Home LTCF Home Home LTCF LTCF LTCF
2 3 4 4 5 6 3 4 5 5 3
1/1 2/1 2/2 2/2 2/1/2 2/2/2 1/1/1 2/2 1/2/2 1/1/1/2 1/2
ST5 (CC5) ST5 (CC5) ST228 (CC5)¡ST5 (CC5) ST5 (CC5) ST148 ST83 ST228 (CC5)¡ST273 ST45 (CC45) ST5 (CC5) ST22 (CC22) ST148
t002 t12282 t5172¡t002 t002 t002 t002 t2167¡t036 t065 t3376 t032 t002
II II I¡III II II II I IV II IV II
No No Yese No Yese Yese Yes Yes No Yese No
12 13 14 15 16 17 18 19 20 21
2 3 4 2 3 3 3 3 2 2
Home LTCF LTCF LTCF Home Home Home Home LTCF LTCF
2 3 8 2 4 4 6 6 6 6
1/1 1/2 2/2/2/2 1/1 2/1/1 1/1/2 2/2/2 2/2/2 3/3 3/3
ST868 ST5 (CC5) ST5 (CC5)¡ST7 ST15¡ST30 (CC30) ST5 (CC5) ST5 (CC5)¡ST8 (CC8) ST5 (CC5) ST5 (CC5) ST5 (CC5) ST5 (CC5)¡ST22 (C22)
t002 t067 t535¡t796 t084¡t037 t002 t002¡t052 t002¡t004 t001¡t002 t001 t002¡t032
II II II¡IV IV I I¡II I¡II I¡IV I I¡II
Yes Yese Yes No Yese Yes Yese Yes Yese Yes
22 23 24 25 26 27 28 29 30 31 32 33
2 2 3 4 3 3 3 2 2 2 3 3
Home LTCF Home LTCF Home LTCF LTCF LTCF LTCF Home LTCF Home
4 3 6 4 5 3 5 4 4 3 4 4
2/2 1/2 2/2/2 2/2 2/2/1 1/1/1 1/2/2 2/2 2/2 2/1 1/2/1 1/1/2
ST45 (CC45)¡ST8 (CC8) ST8 (CC8) ST5 (CC5)¡ST121 (CC121) ST8 (CC8)¡ST22 (C22) ST22 (CC22)¡ST7 ST8 (CC8) ST5 (CC5)¡ST8 (CC8) ST5 (CC5)¡ST22 (CC22) ST5 (CC5)¡ST121 (CC121) ST5 (CC5)¡ST30 (CC30) ST8 (CC8)¡ST22 (CC22) ST5 (CC5)¡ST33 (CC30)
t004¡t052 t064 t001¡t159 t051¡t002 t032¡t796 t1911 t010¡t189 t002¡t4896 t002¡t084 t002¡t377 t008¡t12282 t002¡t021
II¡I IV I¡IV I¡IV IV¡IV IV II¡ IV II¡III I¡II II¡I I¡IV II¡IV
Yes No Yese No Yes Yese Yese Yese Yes Yese Yese Yes
a
LTCF, long-term-care facility. The admission at which the genotype shift occurred is underlined. c CC, clonal complex. d Shift of MLST/clonal complex, spa type, or SCCmec type. e Incomplete eradication therapy. b
complex 5 (CC5) and spa clonal complex 002. These results are consistent with a recent report from Israel that characterized MRSA strains from other parts of the country (10). Nearly half of the 33 persistently colonized patients who had received eradication therapy eventually cleared their initial colonizing strain and acquired new MRSA genotypes, while the rest continued to harbor the same MRSA genotype. Failure of MRSA eradication and acquisition of new strains in these patients could be attributed to several factors; deficient eradication therapy, patient-to-patient cross-transmission, colonization of extranasal sites, and resistance to mupirocin (11–13). High-level resistance to mupirocin among MRSA strains from our region has been estimated to be 13.5% (Y. Keness, unpublished data), and among our cohort and subgroup of patients who received eradication therapy, it was 18.2% and 16%, respectively. It is reasonable to postulate that decolonization and subsequent colonization might have occurred. Unfortunately, the lack of follow-up specimens following eradication therapy in many of them precludes drawing robust conclusions. Given the observed deficiencies in eradication therapy, confirmed in our recent report showing the poor compliance of hos-
April 2014 Volume 52 Number 4
pital staff with MRSA surveillance guidelines (5), it is not surprising that 33 patients became persistent colonizers. Long-term persistence of specific MRSA genotypes among untreated MRSA carriers, for as long as 3 years, has been described elsewhere (14). However, the finding that nearly half of the patients in our cohort exhibited strain shifting during readmission is intriguing. This could be accounted for, in part, by reports on the dynamic nature of Staphylococcus aureus carriage in different settings showing that at the species level, long-term carriers did not carry the same genotypic profile consistently, with loss and acquisition of different genotypes over time (15–17). While our cohort is small, the molecular characterization of several MRSA strains from a single patient during multiple admissions over time provides important insights into the dynamics of MRSA colonization and strain shifting. REFERENCES 1. David MZ, Daum RS. 2010. Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic. Clin. Microbiol. Rev. 23:616 – 687. http://dx.doi.org /10.1128/CMR.00081-09. 2. Davis KA, Stewart JJ, Crouch HK, Florez CE, Hospenthal DR. 2004.
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