NASAL CARRIAGE AND MOLECULAR CHARACTERIZATION OF STAPHYLOCOCCUS AUREUS IN PIGS AND OCCUPATIONALLY EXPOSED HUMANS IN JOS METROPOLIS, PLATEAU STATE, NIGERIA

NASAL CARRIAGE AND MOLECULAR CHARACTERIZATION OF STAPHYLOCOCCUS AUREUS IN PIGS AND OCCUPATIONALLY EXPOSED HUMANS IN JOS METROPOLIS, PLATEAU STATE, NIGERIA

Abstract:

Most staphylococci species are commensals andpathogenic bacteria that cause a wide variety of diseases in humans and animals with high impact on public health and the livestock industry. The aim of this study was to investigate the nasal carriage and antimicrobial resistance pattern of staphylococci speciesand to molecularly characterizeS. aureusin pigs and occupationally exposed humans from both pig farms and abattoir.A total of 300 pigs and 101 humans from both pig farms and abattoir in Jos metropolis were screened for nasal carriage ofcoagulase negative staphylococci species (CoNS) species, S. hyicus, S. intermedius andS. aureus. Risk factors associated with S. aureus carriage among occupationally exposed humans was also determined using a structured questionnaire. Fifty three (53/401) 13.2% out of the 401 isolates were CoNS, 4.9% (20/401) were S. hyicus and 4.2% (17/401) of the isolates were S. intermedius based on confirmatory test with microgen biochemical kit. Twenty nine of the isolates (29/401)7.2% were found to be S. aureusafter confirmatory test with microgen biochemical kit and MALDI-TOF technique. Eight different CoNS species were identified and they include; S. haemolyticus, S. simulans, S. chromogen, S. warneri, S. xylosus, S. epidermidis, S. schleiferi, S. hominis. 48.9% (44/90) of the CoNS, S. hyicus and S. intermedius isolates showed marked resistance to 3 or more of the 10 antibiotics tested. Six (6) of the seven(7)S. intermediusisolates that were phenotypically resistant to vancomycin had MIC valuesthat were resistant to the vancomycin when tested with Etest. The 29S. aureus isolates were subjected to antibioticsusceptibility testing.Three different multiplex PCRs were used to detect enterotoxin genes and staphylococcal protein A, mec A, scn, and pvl genes.Staphylococcal protein A (spa) typing was undertaken and DNA microarray analysis was also used to ix detect antibiotic resistance and virulence genes on the isolates. All the S. aureusisolates were resistant to at least one antibiotic and had multiple antibiotic resistance (M.A.R.I) value >0.2. The isolates were resistant to beta-lactams (cefoxitin, ceftarbiproleand ceftaroline), macrolides (erythromycin), aminoglycoside (gentamicin, kanamycin), mupirocin, linezolide. The microarray analysis of a subset of the methicillin susceptible Staphylococcus aureus (MSSA) isolates identified numerous virulence genes (ica, agr, pvl, enterotoxins, cap, chp, scn, sak, fnb) associated with pathogenesis which are commonly identified in isolates of human origin and sometimes in animal isolatesand antibiotic resistance genes(blaZ, ermA, msrA, tetK and cat-pC221). There was a positive correlation between the phenotypic and genotypic expression of antibiotic resistance. All the 29 S. aureusisolates carried spa A gene, 27 (93%) carried scn gene, 6 (21%) carried the pvl gene and other leukocidin genes (lukF, lukX and lukY) were also detected. The 29 S. aureus obtained from both pigs and in-contact humans belonged to five (5) clonal complexes (CCs); CC15, CC152, CC5, CC1 and CC8 and a cluster of spa type t5427, t5126 and t5576 could not be assigned to any CC-group. Among these genotypes, the genotype CC15 was the most prevalent genotype (44.8%). Three (3) accessory gene regulator (agr) (agr I, II, IV) allelic groups were identified among the S. aureus isolates. Among these, agr II was the most prevalent (87.5%).The capsule and biofilm associated genes detected include capsular polysaccharide synthesis enzymes (cap), surface protein involved in biofilm formation (bap) and intercellur adhesion protein (icaA, icaC and icaD). All the isolates either carried the capsular polysacharide gene; cap 5 orcap 8; 58% and 100% of the pig and human isolates carried cap 8 while 80% and 25% of the pig and human isolatescarried the cap 5 gene, icaA, icaC, icaD and the bap genes. Some of the virulence genes detected were haemolysin (hlg), staphylokinase (sak), and chemotaxis-inhibiting protein (chp) genes. x Carriage of hlaand hlbwas 100% and 75% for pigs and 25% each for humansrespectively while humans and pigs had 25%each and 75% each for the sakand chpgene, respectively. The genes encoding enterotoxins including classical enterotoxins were also observed as well as the genes for microbial surface components recognizing adhesive matrix molecules (MSCRAMM) genes. The results of the questionnaire showed that age, gender, occupation and work experience were not significantly (p>0.05) associated with carriage of S. aureus. However, medical related occupation of household members was a significant factor (p<0.5) for colonization with S. aureus. This study revealed the presence of MDRSA, MSSA and the absence of MRSA carriage among the study population, but revealed a diverse range of virulence and resistance determinants among the isolates

NASAL CARRIAGE AND MOLECULAR CHARACTERIZATION OF STAPHYLOCOCCUS AUREUS IN PIGS AND OCCUPATIONALLY EXPOSED HUMANS IN JOS METROPOLIS, PLATEAU STATE, NIGERIA