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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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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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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5. Bailiff NL, Nelson RW, Feldman EC, et al. Frequency and risk factors for urinary tract infection in cats with diabetes mellitus. J Vet Intern Med 2006;20:850–5. 6. Mayer-Roenne B, Goldstein RE, Erb HN. Urinary tract infections in cats with hyperthyroidism, diabetes mellitus and chronic kidney disease. J Fel Med Surg 2007;9:124–32. 7. Litster A, Moss SM, Honnery M, et al. Prevalence of bacterial species in cats with clinical signs of lower urinary tract disease: recognition of Staphylococcus felis as a possible feline urinary tract pathogen. Vet Microbiol 2007;121:182–8. 8. Simjee S, White DG, McDermott PF, et al. Characterization of Tn1546 in vancomycin-resistant Enterococcus faecium isolated from canine urinary tract infections: evidence of gene exchange between human and animal enterococci. J Clin Microbiol 2002;40:4659–65. 9. Weese JS, Blondeau JM, Boothe D, et al. Antimicrobial use guidelines for treatment of urinary tract disease in dogs and cats: antimicrobial guidelines working group of the international society for companion animal infectious diseases. Vet Med Int 2011;2011:263768. 10. Quinn PJ, Carter ME, Markey B, et al. Clinical veterinary microbiology. 9th ed. London (UK): Mosby; 1994.

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Review of enterococci isolated from canine and feline urine specimens from 2006 to 2011.

Canine and feline urine culture reports and medical records were reviewed at a veterinary teaching hospital from 2006 to 2011 for enterococcal growth,...
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