RETROSPECTIVE STUDIES
Review of Enterococci Isolated from Canine and Feline Urine Specimens from 2006 to 2011 Kate S. KuKanich, PhD, DVM, DACVIM (Small Animal Internal Medicine), Brian V. Lubbers, PhD, DVM, DACVCP
ABSTRACT Canine and feline urine culture reports and medical records were reviewed at a veterinary teaching hospital from 2006 to 2011 for enterococcal growth, coinfections, antimicrobial resistance, urine sediment findings, clinical signs, and concurrent conditions. Of all of the urine specimens with significantly defined colony-forming units/mL, Enterococcus (E.) faecalis was the only enterococci isolated from cats and predominated (77.4%) in dogs followed by E. faecium (12.9%), E. durans (3.2%), and other Enterococcus spp. (6.5%). The majority of specimens with significant enterococcal growth resulted in complicated urinary tract infections in 83.9% of dogs and 81.8% of cats. Specimens with only enterococcal growth were more common than those mixed with other bacterial species. Cocci were observed in urine sediments of 8 out of 8 cats and 21 out of 25 dogs with available concurrent urinalyses. Pyuria was noted in 5 out of 8 feline and 15 out of 25 canine urine sediments, and pyuria in dogs was associated with growth of only enterococci on aerobic urine culture. Multidrug resistance was identified in 6 out of 11 cats and 7 out of 31 dogs, and E. faecium isolates from dogs were 4.53 more likely to be multidrug resistant than E. faecalis. (J Am Anim Hosp Assoc 2015; 51:148–154. DOI 10.5326/JAAHA-MS-6070)
Introduction
therapeutic strategies for veterinary patients with positive entero-
Enterococci are gram-positive commensal bacteria in the gastro-
coccal cultures remain undefined, including what patients require
intestinal tract of mammals. Enterococci can also act as opportunistic pathogens causing substantial systemic disease, and this genus is now labeled as a leading cause of hospital-acquired infections in human healthcare.1 Despite the clinical prevalence and vast amount of published information regarding enterococci in human healthcare, the prevalence, clinical significance, and optimal management of enterococcal infections in veterinary patients have not been fully investigated.
therapy and what antibiotics are most likely to be effective. Circumstances when enterococcal growth from a canine or feline urine specimen should be classified as asymptomatic colonization are currently undefined in the veterinary literature. Determining if factors such as enterococcal species isolated and sediment changes (e.g., hematuria, pyuria) are associated with presence of clinical signs of a UTI may help define asymptomatic colonization with enterococci versus true UTI and to clarify veterinarians’ understanding and management of enterococcal UTIs.
In veterinary medicine, urine cultures with enterococcal
The primary goals of this study were to determine the
growth are seen routinely, representing 8.5–24% of positive canine
proportion of aerobic urine cultures from dogs and cats analyzed
urine cultures and 5–27% of positive feline urine cultures.2–7
between 2006 and 2011 at the Kansas State University Veterinary
Management of enterococcal urinary tract infections (UTIs) can be
Health Center that were positive for growth of enterococci and of
challenging and is frequently complicated by the presence of mixed
those that yielded significant bacteriuria to determine if associa-
and complicated infections and multidrug resistance.7–9 Optimal
tions existed between the presence of clinical signs or urine
From the Department of Clinical Sciences (K.K.) and Kansas State
CFU, colony-forming units; CI, confidence interval; CLSI, Clinical and
Veterinary Diagnostic Laboratory (B.L.), College of Veterinary Medicine, Kansas State University, Manhattan, KS.
Laboratory Standards Institute; E., Enterococcus; MDR, multidrug resistance/resistant; MIC, mean inhibitory concentration; UTI, urinary
Correspondence:
[email protected] (K.K.)
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tract infection
Q 2015 by American Animal Hospital Association
Isolation of Enterococci from Urine Specimens
sediment findings (i.e., bacteriuria, pyuria) and various factors,
study as per the guidelines of the CLSI.12 Multidrug resistance
including species of enterococci isolated, number of bacterial
(MDR) was defined as resistance to three or more categories of
species isolated (Enterococcus only versus mixed Enterococcus
antimicrobial agents [i.e., b-lactams (excluding cephalosporins);
infections) and simple versus complicated infections. Another goal
fluoroquinolones; erythromycin; chloramphenicol; tetracyclines].
was to determine if an association existed between multidrug
Urinalyses performed at the Kansas State Veterinary Diag-
resistant isolates and enterococcal species. It was hypothesized that
nostic Laboratory within 24 hr of culture submission were reviewed
the presence of clinical signs consistent with lower urinary tract
to determine whether bacteria (cocci) or WBCs were identified in
disease would be associated with simple UTIs and that multidrug
urine sediment by trained laboratory technicians. For the purpose
resistant isolates would occur more commonly with Enterococcus
of this study, cocci were recorded as either present or not present
(E.) faecium than E. faecalis.
and pyuria was defined as .5 WBCs/high-power field.6 Medical records were analyzed to determine presence of clinical signs (e.g.,
Materials and Methods
pollakiuria, hematuria, stranguria) that would support a UTI and
This was a retrospective review of aerobic urine cultures and
for the presence of concurrent conditions or therapy that would
corresponding urinalyses submitted to the Kansas State Veterinary
suggest a complicated UTI. A simple, uncomplicated UTI was
Diagnostic Laboratory from canine and feline patients of the
defined as a sporadic bacterial infection of the urinary bladder in an
Kansas State University Veterinary Health Center between 2006
otherwise healthy individual with normal urinary tract anatomy
and 2011. Due to the retrospective nature of the study, urine
and function. A complicated UTI was defined as either the presence
specimen handling prior to delivery at the laboratory was not
of relevant comorbidities (e.g., diabetes mellitus, urinary or
standardized; however, hospital policy included submission of
reproductive tract conformational abnormalities) or 3 UTI/yr.9
urine samples immediately during daytime hours and, based on clinician preference, either having a student laboratory technician
Statistical Analysis
plate the sample after hours (7 days/wk) or refrigeration (,15 hr, 7
Absolute numbers and percentages of urine cultures with bacterial
days/wk) in a red top tube (i.e., no enrichment or medium)
growth, enterococcal growth, and significant enterococcal growth
overnight when the laboratory was closed with submission as early
were summarized as descriptive data, and 95% confidence intervals
as possible when the laboratory reopened.
(CIs) were calculatedc. A Fisher exact test and chi-square test were
Urine specimens submitted during that time period were
used to look for statistical associations, and significance was set at
initially plated on trypticase soy agar with 5% sheep blood and
P .05. The power of the study to detect differences was calculated
MacConkey agar using a 10 lL calibrated loop. Enrichment was
using an a level of 0.05 and the sample size available for each
also performed routinely at the laboratory; however, enriched
comparison. One urine culture/patient was included in the analysis
cultures were not included in the analyzed dataset for this study
for this study, and a urine culture was excluded from analysis if
due to the definition of significant bacteriuria. Cultures were
urine collection technique was not reported. Canine urine samples
incubated overnight (18–24 hr) at 378C in 5% CO2. Suspect
collected either by cystocentesis with 1000 colony-forming units
colonies were struck for isolation onto nonselective agar. Prior to
(CFU)/mL urine or by catheterization using sterile technique with
June 2010, isolates were identified using a combination of gram
10,000 CFU/mL urine and feline urine samples collected by either
staining, catalase, and traditional biochemical testing.10 After June
cystocentesis or catheterization using sterile technique with 1000
2010, isolates were identified using a computerized identification
CFU/mL urine were considered significant and representative of a
systema. Antimicrobial susceptibility was performed using micro-
true UTI and thus included in further analyses. Samples with
b
well dilution testing throughout the survey period, according to
enterococcal growth by enrichment only were not considered
published guidelines.11 During the study period, there were no
significant.13
revisions in the Clinical and Laboratory Standards Institute’s (CLSI’s) recommendations for testing methodology or interpreta-
Results
tions for enterococci.
Table 1 displays the breakdown of submitted urine cultures, urine
Information collected from culture reports included presence
cultures positive for any species of bacterial growth, urine cultures
and quantification of enterococcal growth, enterococcal species,
positive for enterococcal growth (including those with enrichment
susceptibility to antimicrobial agents, and coinfections with other
only), and urine cultures with significant enterococcal growth from
bacterial species. Susceptibilities to aminoglycosides, cephalospo-
urine collected by either cystocentesis or sterile catheterization in
rins, clindamycin, and trimethoprim-sulfa were not reported in this
specimens from dogs and cats. Over the study period, an average of
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and a simple versus complicated infection (P ¼ .454); however, an TABLE 1
additional 30 cases would have been necessary to provide a power
Number of Specimens Submitted for Urine Culture, Urine Cultures Positive for Bacterial Growth, Urine Cultures Positive for Enterococcal Growth, and Urine Cultures with Significant Urine Enterococcal Growth Collected by Cystocentesis or Sterile Catheterization from Dogs and Cats Between 2006 and 2011
of 80% to detect such an association.
Submissions Total submitted urine cultures
Canine
Feline
2184
1015
urinalyses available. Cocci were identified microscopically in all 8 urine sediments and 5 out of 8 had pyuria. No relationship was found between the presence of clinical signs and either presence or absence of pyuria (P ¼ .464); however, an additional 27 cases would have been necessary to provide a power of 80% to detect such an
Urine cultures positive for bacterial growth (any bacterial species)
745
195
Urine cultures positive for enterococcal growth
109
29
Urine cultures with significant enterococcal growth collected by cystocentesis or sterile catheterization
Of the 11 feline urine cultures analyzed, 8 had concurrent
association. The percent of feline urinary isolates resistant to tested antimicrobial agents is shown in Table 2. Of the feline enterococcal
31
11
urine isolates, antimicrobial resistance occurred most commonly with oxacillin [minimum inhibitory concentration (MIC) .4 lg/
15% of urine specimens with bacterial growth from 109 out of 745
mL for all 11 isolates] and enrofloxacin (7 out of 11 isolates). For
dogs (14.6%; 95% CI, 9.7–19.5) and 29 out of 195 cats (14.9%;
enrofloxacin testing of the remaining isolates, 2 had MICs 0.5 lg/
95% CI, 10–19.8%) had enterococcal growth. Roughly one-third of
mL and 2 had MICs of 1 lg/mL. Six feline isolates were classified as
those specimens [31 out of 109 dogs (28.4%; 95% CI, 14.6–42.2%)
MDR, with all six resistant to oxacillin. Four out of 6 isolates were
and 11 out of 29 cats (37.9%; 95% CI, 12.9–62.9%)] had significant
resistant to enrofloxacin, 4 out of 6 were resistant to erythromycin,
enterococcal bacteriuria to be defined as a urinary tract infection.
3 out of 6 were resistant to chloramphenicol, and 3 out of 6 were
Of the 29 feline urine cultures with enterococcal growth, 3
resistant to tetracycline.
were from the same patient but only the first culture from that
Of the feline specimens listed above, two cats (one 2 yr old
patient was included for analysis. Method of urine collection was
and one 7 yr old spayed female) had urine specimens with
unknown for 2 cultures, which were therefore excluded from further analysis. Of the 25 remaining cultures, 8 had 100,000 CFUs/mL urine (6 collected by cystocentesis and 2 collected by catheter), 3 had between 10,000 and 100,000 CFUs/mL urine (all 3 collected by cystocentesis), no cultures had between 1000 and 10,000 CFUs/mL urine, and 14 cultures had either ,1000 CFUs/ mL urine or nonnumeric descriptions of enterococcal growth. All 11 feline isolates included in further analysis were identified as E. faecalis, and 9 out of 11 infections were considered complicated UTIs. Concurrent conditions that contributed to complicated infections included: uroliths (one cat), cystostomy tube (one cat), urethral catheterization following urethral rupture
.100,000 CFU/mL E. faecalis growth and did not have any identified concurrent disease or predisposing factors. Both specimens were collected by cystocentesis. One was mixed with Escherichia coli, and one had enterococci alone. Both had many cocci on sediment exam; one had pyuria and one only had occasional WBCs. Owners of those cats reported inappropriate urinating around the house and malodorous urine as clinical signs. The E. faecalis isolate from one of these cats (the one with only enterococci) was MDR. Six canine patients had more than one urine sample culture positive for enterococcal growth, and only the first culture from each of these patients was considered for further analysis. Three canine urine specimens with .100,000 CFUs/mL were excluded
(one cat), spinal dysfunction (one cat), chronic kidney disease (six
because urine was collected by clean free catch. Four canine urine
cats), and hyperthyroidism (two cats). Three cats had more than
culture specimens had unreported collection technique and were
one concurrent disorder.
excluded as well. Of the remaining samples, 31 aerobic cultures of
Clinical signs consistent with lower urinary tract disease were
canine urine were included for further analysis. Of those, 14 had
observed in 5 out of 11 cats (45.5%). Eight specimens had E.
100,000 CFUs/mL urine (12 collected by cystocentesis, 2 collected
faecalis as the only bacterium isolated and three cultures had mixed
by sterile catheterization), 15 had between 10,000 and 100,000
bacterial growth (E. faecalis with one each of Enterobacter cloacae,
CFUs/mL urine (12 collected by cystocentesis, 3 collected by sterile
Pseudomonas aeruginosa, or Escherichia coli). Two-thirds of cats
catheterization), and 2 cultures had between 1000 and 10,000
with mixed bacterial cultures had clinical signs consistent with a
CFUs/mL urine (collected by cystocentesis).
UTI, whereas 4 out of 8 cats with only E. faecalis had clinical signs.
The 31 analyzed canine urine culture specimens were
No relationship was found between the presence of clinical signs
comprised of 24 E. faecalis, 4 E. faecium, 1 E. durans, and 2
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Isolation of Enterococci from Urine Specimens
TABLE 2 Number and Percent of Enterococcal Isolates from Feline and Canine Urine Specimens that were Resistant to Listed Antimicrobial Agents as Determined by Microwell Dilution Testing* Antimicrobial agent Resistance breakpoint (lg/mL)
Canine
Feline
E. faecalis n ¼ 24
E. faecium n ¼ 4
E. durans n ¼ 1
5 (20.8%)
3 (75%)
0 (0%)
0 (0%)
0 (0%)
5 (20.8%)
3 (75%)
0 (0%)
0 (0%)
1 (9.1%)
0 (0%)
0 (0%)
0 (0%)
0 (0%)
3 (27.3%)
10 (41.7%)
3 (75%)
0 (0%)
1 (50%)
7 (63.6%)
4 (16.7%)
2 (50%)
0 (0%)
1 (50%)
4 (36.4%)
5 (20.8%)
3 (75%)
0 (0%)
0 (0%)
1 (9.1%)
4 (100%)
1 (100%)
2 (100%)
5 (20.8%)
3 (75%)
0 (0%)
0 (0%)
1 (9.1%)
5 (20.8%)
3 (75%)
0 (0%)
0 (0%)
1 (9.1%)
5 (20.8%)
3 (75%)
0 (0%)
0 (0%)
1 (9.1%)
Uncharacterized Enterococcus spp. n ¼ 2
E. faecalis n ¼ 11
Amoxicillin trihydrate/clavulanate potassium 32/16 Ampicillin 16 Chloramphenicol 32 Enrofloxacin 2 Erythromycin 8 Imipenem 16 Oxacillin 4
24 (100%)
11 (100%)
Penicillin 16 Ticarcillin 128 Ticarcillin/clavulanate potassium 128/2
*Breakpoints for determination of resistance among isolates are provided.11 E., Enterococcus.
uncharacterized Enterococcus spp. The majority (26 out of 31,
Enterobacter cloacae and 2 mixed with Escherichia coli), and 1 out of
83.8%) were considered complicated infections, including 10 dogs
8 contained an uncharacterized Enterococcus spp. mixed with a
with neurologic dysfunction; 4 dogs with diabetes mellitus; 4 dogs
Staphylococcus spp. No association was identified between either
with sphincter incontinence; 4 dogs receiving corticosteroid
the presence or absence of clinical signs and enterococcal species
therapy; 3 dogs having uroliths; 2 dogs with bladder neoplasia; 2
(P ¼ .394); however, an additional 134 cases would have been
dogs with recessed vulva; 2 dogs with indwelling urinary catheters;
necessary to provide a power of 80% to detect such an association.
1 dog with chronic kidney disease; and 1 dog with hyperadreno-
Similarly, no association was identified between presence or
corticism. Several dogs had more than one complicating concur-
absence of clinical signs and simple versus complicated infections
rent condition. Of the 31 culture specimens, 23 were enterococci-
(P ¼ .171); however, an additional 69 cases would have been
only specimens and 8 were specimens with enterococci mixed with
necessary to provide a power of 80% to detect such an association.
another bacterial species. Clinical signs consistent with lower
A concurrent urinalysis was available for 25 out of 31 canine
urinary tract disease were seen in 15 out of 31 dogs (48.4%) with
urine culture reports. Of those urinalyses, cocci were noted
enterococcal UTIs, including 3 out of 8 dogs with mixed bacterial
microscopically in 21 out of 25 urine sediments, and pyuria was
specimens and 12 out of 23 dogs with specimens growing only
documented in 15 out of 25. Presence of pyuria in canine urine
enterococci. Of the mixed bacterial specimens, 4 out of 8 contained
sediments was associated with growth of only Enterococcus (versus
E. faecalis (1 mixed with Klebsiella pneumoniae and 3 mixed with
mixed bacterial species) on aerobic urine culture (P ¼ .005). Of the
Escherichia coli), 3 out of 8 contained E. faecium (1 mixed with
15 canine patients with pyuria identified on urine sediment exam,
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100% had only an Enterococcus isolated from their urine.
or aggregation substance) may have provided more information
Identification of cocci on sediment exam was not significantly
regarding their pathogenicity; however, conclusive associations
associated with only Enterococcus infection versus mixed bacterial
between presence of virulence factors and uropathogenicity of
species (P ¼ .166); however, an additional 45 cases would have been
enterococci in dogs and cats have not yet been documented, this
necessary to provide a power of 80% to detect such an association.
testing is not routinely performed on aerobic urine cultures at the
Percent resistance of canine enterococcal isolates to tested
Kansas State Veterinary Diagnostic Laboratory, and those isolates
antimicrobial agents is also displayed in Table 2. Of the canine E.
were no longer available at the time this retrospective study was
faecalis isolates, antimicrobial resistance was most commonly seen
prepared.14 Presence of bacteriuria (cocci) and pyuria were
to oxacillin (MIC . 4 lg/mL for all 24 isolates) and to enrofloxacin
common in concurrent urine samples, giving support to entero-
(10 out of 24 isolates). For enrofloxacin testing of the 14 remaining
cocci causing infection and contributing to clinical signs; however,
E. faecalis isolates, 1 had a MIC of 0.5 lg/mL and 13 had a MIC of 1
it is possible that WBCs were present for other reasons (urinary
lg/mL. Seven canine isolates displayed MDR. E. faecium isolates (3
catheter, stones, etc.). Unfortunately, the small number of feline
out of 4) were 4.53 more likely to be MDR than E. faecalis isolates
urine specimens with enterococcal growth included in the current
(4 out of 24; P ¼ .038; 95% CI, 1.56–12.97).
analysis negatively affected the power, inhibiting the authors’ ability to make statistical conclusions about the relationships
Discussion
between various culture, sediment, and clinical findings.
In both canine and feline patients of the authors’ veterinary
In dogs, clinical signs of lower urinary tract disease were
teaching hospital, approximately 15% of urine specimens submit-
observed in slightly fewer than 50% of all patients with a significant
ted for aerobic culture that were positive for bacterial growth
enterococcal UTI, and the majority of enterococcal UTIs were
identified enterococci, which is consistent with other prevalence
found in patients characterized as having complicated UTIs.
studies and underscores the relevance of this genus in UTI
Although no association could be identified between the presence
discussions.2–7 When considering quantitative urine culture in light
of clinical signs and simple versus complicated UTIs, the low
of urine collection method to classify UTIs as significant, E. faecalis
sample size limited the power to detect any association, and further
was the most commonly cultured enterococcal species from dogs
research with increased urine specimens would be more conclusive.
and cats in this study, followed by E. faecium. In contrast, another
A clinician may submit a urine culture from either a dog or cat
study performed at Michigan State University found that
without clinical signs of lower urinary tract disease if the clinician is
enterococcal UTIs in dogs were most commonly caused by E.
concerned about the consequences of failing to treat an overlooked
faecium (37%), followed by E. gallinarum (31%) and E. faecalis
UTI and/or if it is suspected that clinical signs may be present but
8
(20%). In that study, method of urine collection and quantifica-
not easily observed. Lack of clinical signs in some patients may be
tion of enterococci (CFU/mL) were not provided, making it
due to the opportunistic nature of this organism and raises the
unclear if isolates included in that study would have fit the criteria
question of colonization versus true infection. In human health-
for significant bacteriuria used in the present study. Other possible
care, most patients with asymptomatic enterococcal bacteriuria are
reasons for the discrepant percentage of species identified in the
believed to be colonized rather than infected and do not require
Michigan State study could include differences in geography, time
treatment.15 Elimination of predisposing factors, such as an
period (the Michigan State isolates were from 1996 to 1998),
indwelling urinary catheter, is recommended when possible and
methodology for species identification, or random error from low
may eliminate enterococcal bacteriuria.15 The Infectious Disease
sample sizes.
Society of America has concluded that asymptomatic bacteriuria in
The majority of feline urine specimens with significant
most human patients is not harmful, leading to current
enterococcal cultures originated from cats with concurrent disease;
recommendations that only pregnant women and individuals
however, two cats under the age of 10 yr had enterococcal UTIs
undergoing either prostate or invasive urogenital surgery should be
without evidence of either concurrent disease or predisposing
screened with urine culture when asymptomatic.16 In veterinary
factors. The ability to cause disease in otherwise healthy young or
medicine, the consequences of not treating patients with entero-
middle age cats supports enterococci being a true uropathogen
coccal bacteriuria have not been thoroughly evaluated, and
rather than solely an opportunistic organism. Nonetheless, it is
elimination of predisposing conditions is not always possible.
possible those cats may have had underlying conditions that were
Until prospective studies are available to determine risk of
not recognized. Further testing of those enterococcal isolates for
consequences (i.e., pyelonephritis, bacteremia) in veterinary
presence of virulence factors (such as extracellular surface protein
patients with enterococcal bacteriuria, global recommendations
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Isolation of Enterococci from Urine Specimens
cannot be made and therapeutic decisions continue to be made on
of 11 feline isolates) may also not clinically respond to enrofloxacin
an individual basis considering concurrent conditions and
because those would be in an intermediate susceptibility range.
perceived risk.
These results support the previous suggestion that enrofloxacin
The majority (72.7% of feline and 74.2% of canine cases) of
may have limited efficacy against enterococci.9 However, with the
urine specimens in the current study with significant enterococcal
retrospective nature of this review it was not possible to obtain a
growth were found to be Enterococcus-only specimens, rather than
full antibiotic history on these patients to determine if previous
mixed with other bacterial species. Similarly, a 2008 study reported
fluoroquinolone use could have influenced these results. Although
that 73.3% of canine urine samples that were positive for
E. faecium was rarely isolated in this study, E. faecium isolates
enterococcal growth had Enterococcus-only rather than mixed
showed a high proportion of antimicrobial resistance and were
bacterial species.2 In the current study, the presence of pyuria was
4.53 more likely than E. faecalis to be MDR. These findings
associated with Enterococcus-only UTIs in dogs. Presence of WBCs
emphasize the need for culture and susceptibility testing to assist in
in all dogs with an Enterococcus-only UTI supports the idea that
antimicrobial selection rather than choosing empirical therapy for
inflammation and true infection may have been caused by
enterococcal infections.
Enterococcus spp. Based on anecdotal evidence, it has been recommended that when enterococci are found in combination
Conclusion
with more pathogenic bacteria, such as Escherichia coli, the clinician
Enterococci were routinely isolated from the urine of dogs and cats
should select an antimicrobial agent that targets the more
in quantities sufficient to be defined as UTIs. E. faecalis was the
pathogenic organism because it is believe that the enterococcal
most common enterococcal species isolated from the urine of dogs
infection may resolve if the other organism is successfully
and cats, followed by E. faecium from dogs. Most urine specimens
eliminated.9 Prospective longitudinal research is needed to further
with enterococcal growth contained enterococci alone, rather than a
investigate this recommendation. Until available, the CFUs/mL
mixed bacterial population. Medical record review revealed that the
urine, enterococcal species and risk of ascending infection should
majority of patients whose urine grew significant quantities of
be considered when making therapeutic decisions, and therapy
enterococci had complicated UTIs and fewer than 50% showed
should be targeted towards both organisms whenever possible.
clinical signs of UTIs. E. faecium isolates had the highest
Interpreting enterococcal susceptibility is challenging because CLSI breakpoints specific to canine and feline enterococcal UTIs
proportion of antimicrobial resistance and were most likely to carry multidrug resistance.
are not available for any antimicrobial agent. Enterococci-specific breakpoints are available for ampicillin, penicillin, and erythromycin, but these are not canine, feline, or urinary specific.
11
The authors would like to thank Rob McGaughey, Tanya Purvis,
Similarly,
and Cassondra Sapata-Smith for their assistance with data
there are CLSI breakpoints for enrofloxacin that are canine and
collection. This study was supported in part by the Kansas State
UTI specific, but not specific for enterococci.
11
Until the CLSI is
University Developing Scholars Program.
able to provide more specific breakpoint recommendations, clinical laboratories use breakpoints suggested for other animal species or humans, other bacterial organisms (often Staphylococcus spp.), and often other body sites when interpreting enterococcal UTI isolates. That is a limitation for interpreting results of this study as well as interpreting clinical culture reports with enterococcal growth. From a list of commonly used antibiotics for UTIs (amoxicillin or ampicillin, amoxicillin trihydrate/clavulanate potassium, cephalosporins, fluoroquinolones, chloramphenicol, trimethoprim-sulfa), clinicians treating enterococcal UTIs are limited because cephalosporins and trimethoprim-sulfa are known to have little clinical efficacy for most enterococci infections.9,12,13 This study documented enterococcal resistance to enrofloxacin in E. faecalis (10 out of 24 canine isolates; 7 out of 11 feline isolates) and E. faecium (3 out of 4 canine isolates). The additional E. faecalis isolates with a MIC of 1 lg/mL (13 out of 24 canine isolates; 2 out
FOOTNOTES a b c
Omnilog Gen III; Biolog Inc., Hayward, CA Sensititre; Trek Diagnostic Systems, Cleveland, OH SigmaPlot 12; Systat Software Inc., San Jose, CA
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