ABSTRACT
Aims: To pheno- and genotypically characterise Staphylococcus aureus isolated from raw and fermented camel milk from Kenya and Somali for their antibiotic resistance. Methodology: Microdilution assays to determine minimal inhibitory concentrations (MICs) were done using to 20 different antibiotics. Further tests with selected antibiotics were done using disk diffusion test. Genotypic antibiotic resistance was tested using by microarray hybridization with selected isolates and consequent screening of antibiotic resistance genes by PCR. Results: Prevalence of antibiotic resistance among the 47 S. aureus tested were ampicillin 26% (12), gentamicin 26% (12), streptomycin 11% (5), tetracycline 13% (6), trimethoprim 6% (3) and fusidic acid 2% (1). Multi-resistance was detected with three isolates resistant to two antibiotics, six to three antibiotics and six to four or more antibiotics. Three multi-resistant S. aureus isolates were positive for the β-lactamase resistant genes (blaZ), the tetracycline resistance gene tet38 and the Panton-Valentine leukocidin gene pvl according to microarray hybridization assays. Two of the three isolates harbored additionally streptomycin resistance gene ant(6)-Ia. The tetracycline resistance gene tet(K) was also detected by microarray in four isolates. PCR detected tet(K) and blaZ in 2 and 7 additional isolates respectively. Conclusion: Controlled antibiotic therapy in camels should be introduced to prevent the increase of AB resistant bacteria for this and similar milk and hygienic situations in similar production environment. Detection of the Panton-Valentine leukocidin gene pvl by microarray hybridization calls for further research on possibility of community-acquired methicillin-resistant S. aureus (CA-MRSA) in the milk as CA-MRSA with high virulence potential has been associated with the gene lukF-PV (pvl).
ABSTRACT
Aims: To characterise the diversity, genotypic and phenotypic properties of coagulase negative and coagulase positive staphylococci from camel milk. Place and Duration of Study: Laboratory of Food Biotechnology, Department of Health Sciences and Technology (D-HEST), Swiss Federal Institute of Technology, Zurich, Switzerland, between July 2009 and June 2011. Methodology: Staphylococci isolated from 59 raw and spontaneously fermented camel milk (suusac) samples from Kenya and Somalia were identified, pheno- and genotypically characterized. Preliminary screening of colonies was done by catalase test, Gram staining reactions, clumping factor/protein A and microscopy. Further identification was done by 23S rDNA species PCR, thermostable nuclease gene (nuc) PCR and rep-PCR followed by staphylococcal genus ID32 Staph system and coagulase negative species specific PCR. PCR amplification of the genes encoding capsular polysaccharides cap5 and cap8, and staphylococcal enterotoxins SEA to SEE and SEG to SEJ was also carried out. Results: From a total of 235 BP medium isolates, staphylococci were 146 (62 %) of which, 66 (45 %) were Staphylococcus aureus. S. epidermidis accounted for 43 % of the coagulase negative staphylococci (CNS). The rest of the CNS were 25 % S. simulans, 16.3 % S. saprophyticus, 2.5 % S. haemolyticus, 2.5% S. hyicus, 2.5 % S. xylosus, 2.5 % S. lentus, 1.3 % S. carnosus and 1.3 % S. microti. Capsular polysaccharide gene cap5 was present in 15 % and cap8 in 23 % of the S. aureus isolates. Enterotoxin genes were detected in 47 % of the staphylococci with sej in 33 %, seb in 6 %, sed in 5 % and seg in 3 % of the isolates. Within the species enterotoxin genes were detected in 100 %, 64.7 %, 38.5 % and 22.7 % of the S. simulans, S. epidermidis, S. sapropyticus and S. aureus respectively. Conclusion: The diversity of CNS is remarkable and the prevalence of enterotoxin genes amongst CNS and CPS further informs generalizations for other milk and hygienic situations in similar production environment.