Significance and impact of the study: Houseflies (Musca domestica) are endophilic cosmopolitan pests of medical and veterinary importance. These are associated with regions of human activities such as food centres, butcher houses, animal farms and surrounding areas and create an annoyance to people, poultry and domestic farm animals. The present study reports that housefly samples collected from milk and meat outlets were positive for multidrug-resistant (MDR) E. coli and harbour bla CTX-M and bla TEM genes in plasmid along with other resistant genes for tetracyclines and quinolones. The presence of MDR genes in bacteria isolated from housefly samples is of serious concern from public health and food safety points of view. Investigation of genetic determinants of MDR in bacteria would be of great value for formulating and validating suitable control strategies to combat the spread of antimicrobial resistance.
Abstract
The emergence and spread of antimicrobial resistance have become a major global public health concern. A component of this problem is the spread of antibiotic-resistant bacteria. Flies move freely between habitats of food-producing animals and human beings and thus have great potential for dissemination of antimicrobial-resistant bacteria from a contaminated environment to milk and meat markets, posing potential hazards for consumers. During the present study, a total of 150 houseflies were captured from milk and meat shops located in Durg and Raipur city of Chhattisgarh, India. The Escherichia coli were isolated from houseflies and characterized on the basis of cultural and molecular tests. Further, the isolates were subjected to antimicrobial susceptibility testing against frequently used antibiotics using the disk diffusion method. The antibiotic resistance genes and int1 gene were detected using polymerase chain reaction (PCR). A total of 45 E. coli isolates were obtained from the fly samples with an overall prevalence rate of 30·0%. Antibiogram results confirmed that E. coli isolates were resistant to multiple antibiotics. Out of the (45) isolates of E. coli, 17 (37·8%) isolates were extended-spectrum beta-lactamase (ESBL) producer and multi-drug-resistant (MDR). Out of the ESBL and MDR E. coli isolates, bla CTX-M (24·4%), bla TEM (11·1%), tetA (28·8%), tetB (26·7%), gyrA (26·7%), parC (31. 1%) and int1 genes (15·5%) were detected but none of the isolates were found positive for bla SHV gene. Findings of the present study confirm that MDR E. coli are widely distributed in houseflies and play an important role in the transmission of antibiotic-resistant bacteria from contaminated environments to milk and meat shop environment.