Serovar-Specific Antimicrobial Resistance and Virulence Profiles of Salmonella enterica From Poultry in Bangladesh.

Abstract

Salmonella enterica is a major foodborne pathogen that poses significant risks to public health and poultry production. This study aimed to investigate the distribution, serovar types, virulence genes, and antimicrobial resistance (AMR) profiles of S. enterica isolated from chickens in Bangladesh. A total of 250 samples from broiler (n = 100), layer (n = 100), and Sonali (n = 50) chickens were collected across four districts in Bangladesh and analyzed using polymerase chain reaction (PCR) and MALDI-TOF for identification and serotyping. The presence of virulence and AMR genes was assessed via PCR, while phenotypic resistance was determined using the disk diffusion method. In PCR, S. enterica was detected in 14.4% (36/250) of the samples, with significantly higher prevalence in layers compared with broilers and Sonali. Among the isolates, 61.1% (22/36) were identified as serovar Typhimurium, 27.8% (10/36) as Enteritidis, and 11.1% (4/36) remained untyped. All isolates harbored the invA, stn, sivH, and lpfA virulence genes, while hilA and spvC were detected in 97.2% and 63.9% of the isolates, respectively. High phenotypic resistance was observed to sulfamethoxazole (94.4%), sulfonamide (91.7%), nitrofurantoin (55.5%), and ampicillin (52.8%), with 86.1% of isolates classified as multidrug-resistant. Genotypically, resistance genes aadA2 and SUL1 were most common (94.4%), followed by bla(75%) and bla(52.8%), with variations across serovars and poultry types. These findings highlight the high burden of antimicrobial-resistant S. enterica serovars in Bangladeshi poultry and underscore the need for continuous surveillance and prudent antimicrobial use.