Phenotypic antimicrobial susceptibility of Escherichia coli isolated from bovine superficial cervical (prescapular) lymph nodes from market-derived bovine products in Semey, Kazakhstan

Аннотация

Background and Aim. Bovine lymph nodes are relevant to veterinary diagnostics and beef safety because bacteria within lymphatic tissue may evade carcass surface decontamination and enter the food chain. The aim of this study was to describe the phenotypic antimicrobial susceptibility profile of E. coli isolated from bovine superficial cervical (prescapular) lymph nodes collected from marketderived bovine products in Semey, Kazakhstan.
Materials and Methods. Thirty-two E. coli isolates recovered in autumn from bovine prescapular lymph nodes during pre-sale veterinary-sanitary inspection were tested by disk diffusion on MuellerHinton agar. Eighteen antimicrobial agents were evaluated. Finalsusceptible/intermediate/resistant (S/I/R) categories were determined using CLSI breakpoints where applicable, and Wilson 95% confidence intervals were calculated for susceptible proportions. Isolate-level MDR profiles were summarized from the available phenotypic susceptibility profiles.
Results. The highest susceptibility was observed for gentamicin and amikacin (32/32 each; 100%), followed by enrofloxacin and ceftriaxone (31/32 each; 97%), and ciprofloxacin, cefotaxime, and amoxicillin/clavulanate (30/32 each; 94%). High susceptibility was also observed for azithromycin and tetracycline (29/32 each; 91%), streptomycin (28/32; 88%), and kanamycin and neomycin (27/32 each; 84%). Lower susceptibility was observed for imipenem (18/32; 56%), amoxicillin (14/32; 44%), and doxycycline (4/32; 12%). The highest resistance rates were detected for benzylpenicillin (32/32; 100% R), tylosin (30/32; 94% R), doxycycline (15/32; 47% R), and amoxicillin (10/32; 31% R). Isolate-level analysis classified 17/32 isolates (53.1%) as MDR; the dominant resistant classes in MDR isolates were penicillins/beta-lactams, macrolides, and tetracyclines.
Conclusion. E. coli isolated from bovine prescapular lymph nodes showed a heterogeneous susceptibility profile. Gentamicin and amikacin showed complete in vitro susceptibility, and fluoroquinolones and third-generation cephalosporins retained high activity against most isolates. In contrast, benzylpenicillin and tylosin showed poor activity based ondescriptive phenotypic observations, whereas doxycycline and aminopenicillin-related agents showed mixed or reduced activity. MDR was detected in 17/32 isolates (53.1%), with isolate-level profiles dominated by combinations involving penicillins/beta-lactams, macrolides, and tetracyclines. These data support continued phenotypic surveillance of carcass-associated tissues and should be interpreted together with approved indications, food-animal regulations, and antimicrobial stewardship principles rather than as empirical treatment recommendations.