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Molecular epidemiology of livestock-associated Methicillin resistant Staphylococcus aureus (LA-MRSA) and extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in pigs and exposed workers in Cameroon and South Africa.

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2017

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Abstract

Livestock-associated methicillin resistant Staphylococcus aureus (LA-MRSA) and extendedspectrum β-Lactamase (ESBL)-producing Enterobacteriaceae (ESBL-PE) are amongst the main resistant bacteria of serious public health concern worldwide. Between March and October 2016, MRSA and ESBL-PE were identified from 288 nasal and rectal pooled samples collected from 432 pigs as well as from nasal and hand swabs sampled from 82 humans in five abattoirs in both Cameroon and South Africa. Carriage, risk factors, antibiotic resistance profiles, genotypic characteristics and clonal relatedness of circulating MRSA and ESBL-PE in pigs and humans were investigated using various microbiological (selective agar, biochemical testing, VITEK 2 system) and molecular methods (REP-PCR, ERIC-PCR and whole genome sequencing) and compared with statistical tools. Of the 288 pooled samples, methicillin resistant staphylococci (MRS) were isolated from 108/144 (75%) and 102/144 (70%) of the pooled nasal and rectal samples, respectively. Only one (0.07%) and four (16.66%) MRSA were detected from pigs in Cameroon and South Africa, respectively. None of the workers were colonized by MRSA. Genome analysis revealed that all circulating MRSA isolates belonged to the clonal lineage ST398. ESBL-PE were isolated from 75% (108/144) and 71% (102/144) of the pooled nasal and rectal samples, respectively. ESBL-PE prevalence in animal samples from Cameroon was higher than for South Africa whereas human ESBL-PE carriage was observed in Cameroonian workers only. Some E. coli and K. pneumoniae isolates detected in humans were highly related to those isolated from pigs within and across countries. The circulating K. pneumoniae strains were dominated by the sequence types (ST) 14 and 39. The “high-risk” ST307 clone and two novel STs assigned ST2958 and ST2959 were also detected. LA-MRSA ST398 is already present in both Cameroon and South Africa and is probably underestimated in the absence of molecular epidemiological studies. The high prevalence of ESBL-PE in pigs in both countries as well as in humans in Cameroon highlights their active dissemination in the farm-to-plate continuum. LA-MRSA and ESBL-PE are serious food safety and public health threats requiring the urgent implementation of multi-sectorial, multi-faceted, and, sustainable interventions among all stakeholders involved in this continuum to contain their emergence and zoonotic transmission.

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Doctoral Degree. University of KwaZulu-Natal, Durban.

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