Corynebacterium species and Streptococcus species are the most commonly isolated bacteria from clinically ill pet...

To report the prevalence of bacterial isolates and associated antimicrobial susceptibility from samples obtained from clinically diseased pet guinea pigs (Cavia porcellus).

A retrospective, observational, quantitative study was performed to identify bacterial isolates of pet guinea pigs and antibiotic susceptibility. Medical records were reviewed for guinea pigs evaluated at a university teaching hospital between 2004 and 2023, from which aerobic or anaerobic bacterial cultures were obtained.

A total of 112 bacterial isolates were cultured from 63 guinea pigs. The most cultured sites included abscesses and the urinary tract. The 3 most prevalent bacterial genera isolated were Streptococcus (21 of 112 [19%]), Corynebacterium (19 of 112 [17%]), and Prevotella (11 of 112 [11%]). The most isolated species was Corynebacterium renale (12 of 112 [11%]). Corynebacterium spp accounted for 53% (10 of 19) of all urinary tract isolates. Susceptibility of Corynebacterium spp towards commonly used oral antibiotics was 94% for doxycycline, 82% for azithromycin, 71% for enrofloxacin, and 65% for trimethoprim-sulfamethoxazole (TMS). Among all urinary tract isolates, only 50% were susceptible to TMS, and 59% were susceptible to enrofloxacin. Among oral antibiotics used in guinea pigs, Streptococcus spp were all susceptible to TMS and azithromycin.

The 2 gram-positive bacterial genera Corynebacterium and Streptococcus were the most common isolates in this study, with C renale being the most common species overall and the predominant urinary tract isolate from the guinea pigs in this study.

Enrofloxacin and TMS are often prescribed empirically for urinary tract infections in guinea pigs, yet resistance may be high. Therefore, culture and susceptibility testing should be performed whenever feasible.