Genotypes, virulence factors and antimicrobial resistance genes of
Staphylococcus aureus isolated in bovine subclinical mastitis from Eastern China
Javed Memon§, Yongchun Yang§,
Jam Kashifa, Muhammad Yaqoob, Rehana Buriroa,
Jamila Soomroa, Wang Liping and Fan Hongjie*
College of Veterinary Medicine, Nanjing
Agricultural University, Nanjing 210095, P.R China; aThese
authors are also affiliated with Sindh Agriculture University,
Tandojam 70060, Pakistan Corresponding author: fhj@njau.edu.cn
Abstract
This study was carried out to determine the
genotypes, virulence factors and antimicrobial resistance traits of 34
Staphylococcus aureus isolated from
subclinical mastitis in Eastern China. Minimal inhibitory concentration (MIC)
results showed resistance to erythromycin in all isolates. A high frequency of
Methicillin resistant S. aureus (MRSA;
29%) was observed and these isolates were also highly resistant to penicillin,
oxacillin, oxytetracycline and chloramphenicol than methicillin sensitive
S. aureus (MSSA) isolates. Thirteen
pathogenic factors and seven resistance genes including
mecA and blaZ gene were
checked through PCR. The spaX gene was
found in all isolates, whereas cna,
spaIg,
nuc, clfA,
fnbpB,
hlA, hlB and
seA were present in 35, 79, 85, 59,
35, 85, 71 and 38% isolates, respectively. Nine isolates carried a group of 8
different virulence genes. Moreover, macrolide resistance genes
ermB and
ermC were present in all isolates. High resistance rate against
methicillin was found but no isolate was positive for
mecA gene, whereas blaZ
and tetK were detected in 82 and 56%
isolates, respectively. Genes; fnbpA,
seB,
seC,seD, dfrK and
tetM were not found in any isolate. The statistical association between
phenotypic resistance and virulence genes showed,
clfA,
fnbpB, hlB and seA, were
potentially associated with penicillin G, ciprofloxacin, methicillin,
chloramphenicol, trimethoprim and oxytetracycline resistance (P≤0.05). REP-PCR
based genotyping showed seven distinct genotypes (A-G) prevalent in this region.
This study reports the presence of multidrug resistant
S. aureus in sub-clinical mastitis which were also highly virulent
that could be a major obstacle in the treatment of mastitis in this region of
China.
Key words:
Genotyping, SCM, Staphylococcus aureus, Virulence and resistance genes