Prevalence and Pattern of Antimicrobial Resistant Staphylococcus pseudintermedius, Escherichia coli, and Pseudomonas aeruginosa Infections in Dogs and Cats

Background and Objective: Antimicrobial resistance (AMR) in companion animals is increasingly a rising public and veterinary health concern. Of the most relevant bacterial pathogens found in dogs and cats, Staphylococcus pseudintermedius, Escherichia coli, and Pseudomonas aeruginosa have developed ever-increasing resistance to the most widely used antibiotics. All three opportunistic pathogens are commonly implicated in pyoderma, urinary tract infections (UTIs), and systemic infections, respectively, and their resistance patterns directly impact the outcome of therapy. This study aimed to determine the prevalence, antimicrobial susceptibility patterns, and resistance mechanisms of these three ubiquitous bacterial pathogens isolated from clinical cases in dogs and cats presenting to primary and referral veterinary hospitals over a defined six-month period. Methods: A total of ۳۶ clinical cases (۲۲ dogs and ۱۴ cats) were selected based on clinical suspicion of bacterial infection and access to comprehensive history. From these specimens, ۵۲ clinical specimens including wound swabs (n=۲۵), urine (n=۱۴), blood (n=۴), and ear discharges (n=۹) were collected under sterile aseptic conditions. Bacteriological culture methods were carried out on selective and non-selective media under routine bacteriological conditions. Bacteria were described by a combination of colony morphology, Gram stain, biochemical reactions (e.g., catalase, oxidase, indole), and finally established using species-specific PCR assays for ۱۶S rRNA genes if in doubt. Antimicrobial susceptibility was established by the Kirby-Bauer disk diffusion test on Mueller-Hinton agar, interpreted according to CLSI guidelines (۲۰۲۳). Results: ۳۸ of ۵۲ samples collected yielded heavy bacterial growth (۷۳%). Frequency of isolation was: S. pseudintermedius in ۱۵ cases (۴۱% of positive cultures), E. coli in ۱۳ cases (۳۶%), and P. aeruginosa in ۱۰ cases (۲۷%). To our surprise, ۴ cases (۱۱%) were instances of co-isolation of two different species. Resistance profiling revealed hair-raising trends: Methicillin-resistant S. pseudintermedius (MRSP) was detected in ۱۰ out of ۱۵ S. pseudintermedius isolates (۶۶%), as indicated by mecA gene presence. Extended-spectrum beta-lactamase (ESBL)–producing E. coli was detected in ۸ out of ۱۳ isolates (۶۱%), as indicated by cefotaxime inhibition tests. Fluoroquinolone-resistant P. aeruginosa was epidemic, with ۷۰% of isolates being resistant to 
ciprofloxacin. Multi-drug resistance (MDR; resistance to geq ۳ classes of antimicrobials) was found in ۲۲ of ۳۸ isolates (۵۸%) across all bacterial species. Resistance was most quantitatively common against beta-lactams (ampicillin, cefazolin), fluoroquinolones (ciprofloxacin), and macrolides 
(erythromycin), while aminoglycosides (amikacin) and oxazolidinones (linezolid) had significantly greater in vitro activity (resistance rates < ۲۰% for both). Conclusion: The results are in line with a high and alarming rate of antimicrobial-resistant pathogens in pet animals of this study population, particularly MRSP, ESBL-producing E. coli, and P. aeruginosa showing multidrug resistance.

کلیدواژه ها:

Antimicrobial Resistant ، Staphylococcus pseudintermedius ، Escherichia coli ، Pseudomonas aeruginosa ، Dogs ، Cats