Susceptibility of canine and feline Escherichia coli and canine Staphylococcus intermedius isolates to fluoroquinolones

Methicillin-resistant staphylococci amongst veterinary personnel, personnel-owned pets, patients and the hospital environment of two small animal veterinary hospitals

This study investigated the transmission cycle of methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus pseudintermedius (MRSP) in small companion animal veterinary practice. Sampling was undertaken at two small animal veterinary hospitals in Sydney, Australia. Samples were collected from 46 veterinary personnel, 79 personnel-owned dogs and cats, 151 clinically normal canine hospital admissions and 25 environmental sites. Nasal swabs were collected from veterinary personnel. Nasal, oral and perineal swabs were collected from animals. Methicillin resistance was detected by growth on Brilliance^TM MRSA 2 Agar and confirmed by cefoxitin and oxacillin broth microdilution for S. aureus and S. pseudintermedius, respectively. MRSA and MRSP isolates were characterised using whole genome sequencing including mecA gene screening and multilocus sequence typing. MRSA was isolated from four (8%) veterinary personnel but no animals. MRSP was isolated from 11/151 (7%) of canine hospital admissions and 4/53 (8%) of personnel-owned dogs but no veterinary personnel or cats. No MRSA or MRSP was isolated from the environment. MRSP isolates were resistant to significantly more antimicrobial classes than MRSA. The main MRSP clone carried by canine patients (ST496) was distinct to that carried by personnel-owned dogs (ST64). One veterinary nurse, who carried Panton Valentine leucocidin-positive ST338 MRSA, also owned a ST749 MRSP-positive dog. Besides MRSP-positive dogs from the same household sharing the same clone of MRSP, MRSA and MRSP were not shared between humans, animals or environment. Therefore, in the non-outbreak setting of this study, there was limited MRS transmission between veterinary personnel, their pets, patients or the veterinary environment.

In vitro interaction of some drug combinations to inhibit rapidly growing mycobacteria isolates from cats and dogs and these isolates' susceptibility to cefovecin and clofazimine

OBJECTIVES

To investigate whether selected drug combinations used to treat rapidly growing mycobacteria (RGM) have drug-drug interactions that affect efficacy and to investigate each isolate's susceptibility to cefovecin and clofazimine, individually.

DESIGN

In vitro susceptibility testing of bacterial isolates.

METHODS

Initially, five feline isolates and one canine isolate from both Mycobacterium fortuitum and M. smegmatis clusters (n = 12) underwent microbroth susceptibility testing to individual drugs to establish minimum inhibitory concentrations (MIC) of cefovecin, ciprofloxacin, clarithromycin, clofazimine, doxycycline, enrofloxacin, trimethoprim and sulfanilamide (the latter two as a combination). Checkerboard assays were then performed for susceptible M. smegmatis isolates for the following combinations: clarithromycin (one isolate only) versus enrofloxacin, clarithromycin vs doxycycline, clarithromycin vs trimethoprim/sulfanilamide; enrofloxacin vs doxycycline (six isolates); enrofloxacin vs trimethoprim/sulfanilamide (six isolates). Susceptible M. fortuitum isolates were tested against enrofloxacin versus doxycycline (four isolates only).

RESULTS

All six M. fortuitum isolates were susceptible to enrofloxacin, but only four of six were susceptible to doxycycline. All six M. smegmatis isolates were susceptible to doxycycline, enrofloxacin and trimethoprim/sulfanilamide. A single isolate from the 12, a M. smegmatis isolate, was susceptible to clarithromycin. The fractional inhibitory concentration of each drug ranged from 0.64 to 1.84, indicating that neither synergism nor antagonism was evident. All 12 isolates were resistant to cefovecin. The clofazimine MIC50 to inhibit isolate growth was approximately 3.3 μg/mL for both strains.

CONCLUSION

Drugs commonly used for treatment of RGM, when tested as combinations, do not appear to antagonise one another in vitro. Cefovecin is not efficacious for treatment of RGM infections.

In vitro susceptibilities of feline and canine Escherichia coli and Pseudomonas spp. isolates to ticarcillin and ticarcillin-clavulanic acid

OBJECTIVES

To investigate in vitro susceptibilities of canine and feline Escherichia coli and canine Pseudomonas spp. isolates to ticarcillin and ticarcillin-clavulanic acid (T/C).

DESIGN

In vitro susceptibility testing of bacterial isolates collected from infections.

METHODS

We tested 148 (83 canine and 65 feline) E. coli and 61 canine Pseudomonas spp. isolates for susceptibility to T/C using both disc diffusion and Epsilometer tests (E-tests). Additionally, susceptibilities of 96 E. coli and 23 canine Pseudomonas spp. isolates were tested via disc diffusion to ticarcillin alone.

RESULTS

Of the E. coli isolates obtained from canine and feline urine, 92% by disc diffusion and 91% by E-tests were susceptible to T/C. Of the canine Pseudomonas isolates, 90% by disc diffusion and 82% by E-tests were susceptible to T/C. Of the Pseudomonas spp. isolates from the canine ear canal or tympanic bullae, 12% of isolates tested via disc diffusion and 23% via E-tests were found to be resistant to T/C. The 50% minimum inhibitory concentration of T/C for all feline E. coli isolates was significantly lower than that for all canine E. coli isolates (P = 0.0031). The addition of clavulanic acid significantly increased the efficacy of ticarcillin against E. coli (P< 0.0001), but had negligible effect against canine Pseudomonas spp. isolates.

CONCLUSION

Ticarcillin-clavulanic acid has reasonable in vitro efficacy against canine and feline E. coli, and canine Pseudomonas spp. isolates. However, decisions to use this drug therapeutically must be made on prudent considerations to minimise selection for bacterial resistance.

The in vitro activity of 15 antimicrobial agents against bacterial isolates from dogs

The in vitro activity of 15 antimicrobial agents against clinical isolates of Staphylococcus pseudintermedius, Staphylococcus aureus, Escherichia coli, Pasteurella spp. and Streptococcus canis from dogs was investigated. For Staphylococcus spp., the highest frequency of resistance was observed for penicillin, followed by ampicillin, tetracycline and chloramphenicol. The highest frequency of resistance in E. coli isolates was recorded for tetracycline and streptomycin. Pasteurella spp. and S. canis had the highest resistance rate for tetracycline and chloramphenicol. Most isolates showed full susceptibility to low-level resistance to colistin, florfenicol and fluoroquinolones. Further studies using larger number of isolates from both healthy and diseased dogs would provide a broader picture of antimicrobial resistance at a national level and promote prudent use of antimicrobial agents in companion animals.

Anatomical distribution and genetic relatedness of antimicrobial-resistant Escherichia coli from healthy companion animals

AIMS

Escherichia coli have been targeted for studying antimicrobial resistance in companion animals because of opportunistic infections and as a surrogate for resistance patterns in zoonotic organisms. The aim of our study is to examine antimicrobial resistance in E. coli isolated from various anatomical sites on healthy dogs and cats and identify genetic relatedness.

METHODS AND RESULTS

From May to August, 2007, healthy companion animals (155 dogs and 121 cats) from three veterinary clinics in the Athens, GA, USA, were sampled. Escherichia coli was isolated from swabs of nasal, oral, rectal, abdomen and hindquarter areas. Antimicrobial susceptibility testing against 16 antimicrobials was performed using broth microdilution with the Sensititre™ system. Clonal types were determined by a standardized pulsed-field gel electrophoresis protocol. Although rectal swabs yielded the most E. coli (165/317; 52%) from dogs and cats, the organism was distributed evenly among the other body sites sampled. Escherichia coli isolates from both dogs and cats exhibited resistance to all antimicrobials tested with the exception of amikacin, cephalothin and kanamycin. Resistance to ampicillin was the most prevalent resistance phenotype detected (dogs, 33/199; 17%; and cats, 27/118; 23%). Among the resistant isolates, 21 resistance patterns were observed, where 18 patterns represented multidrug resistance (MDR; resistance ≥ 2 antimicrobial classes). Also among the resistant isolates, 33 unique clonal types were detected, where each clonal type contained isolates from various sampling sites. Similar resistance phenotypes were exhibited among clonal types, and three clonal types were from both dogs and cats.

CONCLUSIONS

Healthy companion animals can harbour antimicrobial-resistant E. coli on body sites that routinely come in contact with human handlers.

SIGNIFICANCE AND IMPACT OF THE STUDY

  This study is the first report that demonstrates a diverse antimicrobial-resistant E. coli population distributed over various sites of a companion animal's body, thereby suggesting potential transfer of resistant microflora to human hosts during contact.

Feline bacterial urinary tract infections: An update on an evolving clinical problem

Although feline urine is increasingly submitted for bacterial culture and susceptibility testing as part of a more general diagnostic work-up for a range of presentations in veterinary practice, bacterial urinary tract infections (UTIs) are relatively uncommon due to a variety of physical and immunological barriers to infection. Culture positive urine is most often obtained from older female cats and the clinical history may include hematuria, dysuria and pollakiuria, or the infection may be occult. Urinalysis usually reveals hematuria and pyuria, and Escherichia coli and Gram-positive cocci are cultured most frequently. Most feline UTIs can be successfully treated using oral amoxicillin or amoxicillin/clavulanic acid administered for at least 14days, but the prevalence of antimicrobial resistance amongst infecting bacterial species is a growing concern. There is currently no conclusive information on the safety and efficacy of alternative therapeutic agents for the treatment of feline UTIs.

Antimicrobial susceptibility of Staphylococci isolated from naturally occurring canine external ocular diseases

OBJECTIVE

The purpose of this study was to describe the species distribution and antimicrobial susceptibility patterns of Staphylococci isolated from naturally occurring canine ocular diseases. SAMPLES AND PROCEDURES: Samples obtained from 68 dogs with signs of external eye disease were processed for isolation of bacteria of the genus Staphylococcus sp. Isolates were identified by biochemical reactions and tested for susceptibility to 11 antimicrobials of six classes.

RESULTS

Forty (58.8%) samples yielded Staphylococcus sp. in pure culture. Coagulase-positive Staphylococci were most common and Staphylococcus intermedius was the most frequent (45%) species, followed by S. aureus (22.5%) and the coagulase-negative species S. epidermidis (20%), and S. simulans (12.5%). Resistance to at least one drug was observed in 92.5% of the isolates, and multidrug resistance was a common finding (72.5%). The most effective drugs against Staphylococcus strains isolated from extra-ocular canine ocular diseases were ceftiofur and cefalexin.

CONCLUSION

This study highlights the presence of Staphylococcus sp. genus in naturally occurring extra-ocular canine ocular disease and the emergence of resistant strains to common antimicrobial drugs. It also emphasizes the need for bacterial culture with species identification and susceptibility testing in order to choose the appropriate antimicrobial therapy.