Molecular Detection and Antibiotyping of Multidrug-Resistant Salmonella Isolated from Houseflies in a Fish Market

Abstract

Houseflies (<i>Musca domestica</i>) are well-known mechanical vectors for spreading multidrug-resistant bacteria. Fish sold in open markets are exposed to houseflies. The present study investigated the prevalence and antibiotypes of multidrug-resistant (MDR) <i>Salmonella</i> spp. in houseflies captured from a fish market. Direct interviews with fish vendors and consumers were also performed to draw their perceptions about the role of flies in spreading antibiotic-resistant bacteria. A total of 60 houseflies were captured from a local fish market in Bangladesh. The presence of <i>Salmonella</i> spp. was confirmed using PCR method. Antibiogram was determined by the disk diffusion method, followed by the detection of <i>tetA</i>, <i>tetB,</i> and <i>qnrA</i> resistance genes by PCR. From the interview, it was found that most of the consumers and vendors were not aware of antibiotic resistance, but reported that flies can carry pathogens. <i>Salmonella</i> spp. were identified from the surface of 34 (56.7%) houseflies, of which 31 (91.2%) were found to be MDR. This study revealed 25 antibiotypes among the isolated <i>Salmonella</i> spp. All tested isolates were found to be resistant to tetracycline. <i>tetA</i> and <i>tetB</i> were detected in 100% and 47.1% of the isolates, respectively. Among the 10 isolates phenotypically found resistant to ciprofloxacin, six (60%) were found to be positive for <i>qnrA</i> gene. As far as we know, this is the first study from Bangladesh to report and describe the molecular detection of multidrug-resistant <i>Salmonella</i> spp. in houseflies in a fish market facility. The occurrence of a high level of MDR <i>Salmonella</i> in houseflies in the fish market is of great public health concerns.