Synanthropic rodents and shrews are reservoirs of zoonotic bacterial pathogens and act as sentinels for antimicrobial resistance spillover in the environment: A study from Puducherry, India

Abstract

Antimicrobial resistance (AMR) is a global public health concern and needs to be monitored for control. In this study, synanthropic rodents trapped from humans and animal habitats in Puducherry, India, were screened as sentinels for bacterial pathogens of public health importance and antimicrobial resistance spillover. From the trapped rodents and shrews (n = 100) pathogens viz., Staphylococcus sp, E. coli and Salmonella sp were isolated from oropharyngeal and rectal swabs on Mannitol salt, Mac Conkey and Xylose lysine deoxycholate media respectively. The AMR genes in these isolates were screened by PCR. A total of 76, S. aureus and 19, Staphylococcus non aureus were isolated. E. coli was isolated in 89 samples and among the Salmonella sp (n = 59), 16, were S. enteritidis and 29, were S. typhimurium. A total of 46 MRSA isolates with mec A (n = 40) and mec C (n = 6) were detected. Also, 36.84% and 5.3% Staphylococcus non aureus isolates were tested to have mec A and mec C genes. AMR genes encoding ESBL [bla_TEM in 21, bla_SHV in 45 and bla_CTX-M in 11] was tested positive in 77 E. coli isolates. Among, Salmonella isolates 44/45 were screened to have AMR genes [tet in 13, sul3 & sul4 in 20 and qnrA in 11]. Antibiotic sensitivity test confirmed the antimicrobial resistance. Isolation of pathogens of public health importance and demonstration of genetic elements conferring antimicrobial resistance in the synanthropic rodents confirms that they act as reservoirs and appropriate sentinels to monitor AMR spillover in the environment.

Keywords: AMR; Drug resistance; ESBL; MRSA; Rodents and shrews; Salmonella sp; Sentinels.

Fig. 1

The map representing the sites of rodents trapping in Puducherry. The red dot indicates the villages, where the rodents were trapped. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

A. Phenotypic confirmation of methicillin resistance (5 μg) in Staphylococcus aureus isolated from a shrew. The isolate was tested by PCR to harbour the AMR genes mec A and mec C. B. Demonstration of resistance to (a) Cefpodoxime (30 μg), (b) Cefotaxime + Clavulanic acid (30 μg), (c) Ceftazidime + Clavulanic acid (30 μg), (d) Ceftriaxone (30 μg), and (e) Aztreonam (30 μg) in E.coli, harbouring genetic elements (bla_TEM. bla_SHV and bla_CTX-M). C. A non typhoidal Salmonella isolate tested to harbour genetic elements such as tet, qnrA and sul genes, exhibiting complete resistance to antibiotics such as (a)Tetracycline, (b) Enrofloxacin, (c) Sulphamethoxazole + trimethoprim.