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Open Access Research article

Diversity of antibiotic resistance genes and staphylococcal cassette chromosome mec elements in faecal isolates of coagulase-negative staphylococci from Nigeria

Luca Agostino Vitali1, Dezemona Petrelli2, Adebayo Lamikanra3, Manuela Prenna2 and Ezekiel Olugbenga Akinkunmi13*

Author Affiliations

1 School of Pharmacy, University of Camerino, Camerino, Italy

2 School of Biosciences and Biotechnology, University of Camerino, Camerino, Italy

3 Department of Pharmaceutics, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Nigeria

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BMC Microbiology 2014, 14:106  doi:10.1186/1471-2180-14-106

Published: 26 April 2014

Abstract

Background

Coagulase-negative staphylococci (CoNS) are opportunistic pathogens found as colonisers of the human gut. This study was carried out to examine the genetic resistance mechanisms in faecal isolates of CoNS. The study investigated 53 non-duplicate CoNS isolates obtained from the fresh stool samples of apparently healthy subjects in the community of Ile-Ife, South-Western Nigeria. Antibiotic susceptibility testing was assessed by the disc diffusion test while antibiotic resistance genes were analysed by PCR. mecA positive isolates were analysed by Staphylococcal Chromosome Cassette mec (SCCmec) and cassette chromosome recombinase (ccr) complex typing methods.

Results

Resistance genes were detected only in isolates that showed resistance by phenotypic screening. The aac(6′)–aph(2″) gene was detected in all the three isolates resistant to gentamicin. Four of the five erythromycin resistant isolates were positive for the ermC gene, the remaining isolate carried the msrA gene. The tetK gene was detected in 6 of the 7 tetracycline resistant isolates while 4 possessed the tetM gene. Three of the isolates (S. haemolyticus, S. xylosus and S. capitis) had both genes. Several SCCmec types were found: SCCmec I- ccrABβ2-α2 (4 isolates: 3 S. epidermidis, 1 S. warneri), SCCmecIVb- ccrABβ2-α3 (1 isolate: S. epidermidis), SCCmecIVd- ccrABβ2-α3 (8 isolates: 3 S. epidermidis, 2 S. xylosus, 1 S. saprophyticus, 1 S. warneri, 1 S. capitis), and untypable (2 isolates: S. epidermidis).

Conclusion

This genetic background could be a reservoir for interspecies gene transfer among CoNS and S. aureus in the intestinal tract.

Keywords:
Coagulase negative staphylococci; Methicillin resistance; Antibiotic resistance genes; Gastrointestinal tract