Carriage of antibiotic resistant bacteria in endangered and declining Australian pinniped pups

The rapid emergence of antimicrobial resistance (AMR) is a major concern for wildlife and ecosystem health globally. Genetic determinants of AMR have become indicators of anthropogenic pollution due to their greater association with humans and rarer presence in environments less affected by humans. The objective of this study was to determine the distribution and frequency of the class 1 integron, a genetic determinant of AMR, in both the faecal microbiome and in Escherichia coli isolated from neonates of three pinniped species. Australian sea lion ( Neophoca cinerea ), Australian fur seal ( Arctocephalus pusillus doriferus ) and long-nosed fur seal ( Arctocephalus forsteri ) pups from eight breeding colonies along the Southern Australian coast were sampled between 2016-2019. DNA from faecal samples ( n =309) and from E. coli ( n =795) isolated from 884 faecal samples were analysed for class 1 integrons using PCRs targeting the conserved integrase gene ( intI ) and the gene cassette array. Class 1 integrons were detected in A. p. doriferus and N. cinerea pups sampled at seven of the eight breeding colonies investigated in 4.85% of faecal samples ( n =15) and 4.52% of E. coli isolates ( n =36). Integrons were not detected in any A. forsteri samples. DNA sequencing of the class 1 integron gene cassette array identified diverse genes conferring resistance to four antibiotic classes. The relationship between class 1 integron carriage and the concentration of five trace elements and heavy metals was also investigated, finding no significant association. The results of this study add to the growing evidence of the extent to which antimicrobial resistant bacteria are polluting the marine environment. As AMR determinants are frequently associated with bacterial pathogens, their occurrence suggests that these pinniped species are vulnerable to potential health risks. The implications for individual and population health as a consequence of AMR carriage is a critical component of ongoing health investigations.

Abundance of Multiple-Antibiotic-Resistant Salmonella Strains in Fecal Samples of Rhinoceros unicornis of the Kaziranga National Park, India

Aims: This study was undertaken to assess the abundance of multiple-antibiotic-resistant (MAR) Salmonella strains in fecal samples of Rhinoceros unicornis of the Kaziranga National Park (KNP), India. Study Design: Antibiotic-resistance profile of the Salmonella isolates from fecal samples of rhinoceros was carried out by replica plating on Muller Hinton Agar (MHA) plates containing antibiotics. The presence of class 1 integrons in metallo-β-lactamase (MBL) producing Salmonella isolates was determined by multiplex PCR. Place and Duration of Study: The study was carried out on rhinos of KNP situated in the Golaghat district of Assam, India in April 2015. Methodology: Fresh rhino fecal samples (designated as 1R, 2R, 3R, 4R and 5R) were dilution plated onto MacConkey agar. Purified bacterial colonies were then streaked separately on bismuth sulphite (BS) agar plates. All black colonies which are characteric growth of Salmonella were selected and used to make master plates on Luria Agar. To determine the antibiotic-resistance profile of the isolates, master-plates of purified single colonies of Salmonella spp. were replicate-printed on plates containing antibiotics from the β-lactam, aminoglycoside, or quinolone groups. To detect the presence of an integron, a conserved segment polymerase chain reaction was used. Results: 97.6% of the Salmonella isolates tested were resistant to >1 antibiotics (multidrug resistant or MAR). A total of 100 isolates from two fecal samples, 4R and 5R, were found to be imipenem resistant; 52 of them tested positive for the presence of MBLs. Five of the twenty MBL producing strains contained class 1 integrons. Conclusion: Because Salmonella is usually spread by drinking contaminated water, it is likely that water bodies in KNP are contaminated with MAR Salmonella strains. In case of Salmonellosis outbreak among Indian one-horned rhinos, our antibiogram will assist the veterinarians to choose the appropriate regimen of antibiotics for the rhinos in the KNP.

Genetic Features of Plasmid- and Chromosome-Mediated mcr-1 in Escherichia coli Isolates From Animal Organs With Lesions

The genomic context of the mcr-1 gene in Escherichia coli from animal feces has been widely reported. However, less is known about the mcr-1-carrying plasmid characteristics and other functional regions of Escherichia coli isolates from animal organs with lesions. The present study investigated the antimicrobial resistance, population structure, and genetic features of mcr-1-positive Escherichia coli strains isolated from animal organs with lesions. The antimicrobial susceptibility testing indicated that 24 mcr-1-positive Escherichia coli isolates were resistant to at least three or all antimicrobial categories. MLST analysis suggested that the dominant clone complexes (CC) were mainly CC156, CC448, and CC10. In addition, ST10596, a newly discovered sequence type in swine, failed to be classified. Meanwhile, the mcr-1 gene located on the different plasmids was successfully transferred to the recipients, and whole-genome sequencing indicated the mcr-1 gene was embedded in mcr-1-pap2 cassette but not flanked by ISApl1. The mcr-1 gene is located on the chromosome and embedded in Tn6330. Furthermore, NDM-5 was found on the IncX3-type plasmid of J-8. The virB6 and traI gene of type IV secretion system (T4SS) were truncated by IS2 and IS100 and located on the IncX4- and the IncHI2/HI2A/N-type plasmids, respectively. The multidrug-resistant (MDR) region of IncHI2/HI2A/N-type plasmids contained two class 1 integrons (In0, In640) and four composite transposons (Tn4352, Tn6010, cn_4692_IS26, cn_6354_IS26). Overall, 24 mcr-1-positive Escherichia coli isolates in our study showed MDR, or even extensively drug resistant (XDR), and exhibited population diversity. The T4SS gene truncation by the insertion sequence may affect the efficiency of plasmid conjugative transfer. Furthermore, the class 1 integrons and composite transposons in the MDR region of IncHI2/HI2A/n-type plasmid contributed to the multireplicon plasmid formation, the acquisition, and transfer of antimicrobial resistance genes (ARGs).