MRSA ST88 isolated from pigs and humans in Nigeria

We determined the prevalence and genetic characteristics of methicillin resistant Staphylococcus aureus (MRSA) isolated from pigs and humans between September 2013 and February 2015 in Kogi State, Nigeria. A total of 680 nasal swabs were collected and analysed from pigs (n=425) and ‘pig-contact’ humans (n=55) on 35 farms, and ‘non pig-contact’ humans (n=200). MRSA was recovered from 20 (4.7%) pigs on 12 farms and 18 (7.0%) humans. Six (2.4%) of the human isolates were recovered from ‘pig-contact’ humans, of which only three were from farms also harbouring MRSA positive pigs. All 38 MRSA were resistant to β-lactams only, belonged to spa type t1603- sequence type (ST) 88, and mecA was associated with a SCCmec IVa element. Four isolates from a pig, a pig-contact human from the same farm, a pig-contact human from a different farm with no MRSA positive pigs, and a non pig-contact human were subjected to whole genome sequencing. Core genome SNP analysis revealed high genetic similarity between strains (3-11 SNP differences), despite the temporal (2 year gap) and geographic (165km) differences between isolates. To our knowledge, this is the first report of MRSA in pigs in Nigeria, which appear to be a CA-MRSA clone present in the human population.