Phylodiversity of blaTEM and blaCTX-M genes of coliform isolates from ruminant mastitis in Plateau State Nigeria

Abstract

The study was conducted to determine the genetic characteristics, antibiotic susceptibility, and genetic relatedness of blaTEM-type and blaCTX-M-type ESBLs producing coliforms from ruminants suffering mastitis. In a cross sectional study, a total of 1052 milk samples were collected aseptically from ruminants across Plateau State, Nigeria. Bacterial culture and biotyping were performed according to standard guidelines. Phenotypic assay for ESBL production was carried out using the Brilliance ESBL Chromogenic Culture Medium (Oxoid, UK). Conventional PCR was used for amplification and detection of blaCTX-M, blaSHV, blaTEM genes as described previously. Sequencing reactions were also performed in the Master Cycler pro 384 (Eppendorf) using the ABI BigDye® Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems), following the protocols supplied by the manufacturer. Sequences obtained were aligned with sequences deposited in the GenBank using the Basic Local Alignment Search Tool (BLAST) and phylogentic analysis performed MEGA software version 10.1.8. Coliforms isolated from milk samples included Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Enterobacter aerogenes, and Serratia marcescens. 677 coliforms were isolated from the 1052 milk samples across Plateau State, where Escherichia coli had the highest prevalence of 44% while Serratia marcescens had the least with 1.8%. Plateau South had the highest prevalence of 82.3%, followed by Plateau North and Plateau Central with 72.9% and 20.5% prevalence respectively. E. aerogenes recorded the highest resistance (85.71%) against Gentamycin, followed by Serratia marcescens with an 81.82% resistance against Gentamycin. The blaCTX-M was more frequently isolated than blaTEM having 24.39 and 12.19% prevalence respectively. The high-level of phylodiversity observed among ruminants means that there is transfer coliform harboring the blaCTX-M and blaTEM genes which might have been transmitted from clones of varying origins. The relatedness of the genes among organisms in different animals from diverse geographical locations demand a quick intervention that would reduce mortality and morbidity of animals and zoonotic transmissions. Sustained hygienic standards of livestock housing, milking procedures and processes, culling of chronically affected livestock, regular laboratory screening of pastoralists for infections can serve as good interventions.