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.
Date
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.
Description
Doctoral Degree. University of KwaZulu-Natal, Durban.