Biodiversity and Enterotoxigenic Potential of Staphylococci Isolated from Raw and Spontaneously Fermented Camel Milk

Patrick Njage

doi:10.9734/bmrj/2013/2896

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.

Highlights

S. aureus belonging to CPS is implicated in the aetiology of a series of infections in both man and animals whereas coagulase negative staphylococci (CNS) have been assumed to be rarely pathogenic [1]
S. epidermidis accounted for 43 % of the coagulase negative staphylococci (CNS)
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

Summary

Introduction

S. aureus belonging to CPS is implicated in the aetiology of a series of infections in both man and animals whereas CNS have been assumed to be rarely pathogenic [1]. S. aureus produces several virulence factors such as exoproteins and various cell surface proteins that contribute to the pathogenicity of this organism most of which have been well characterized (2). The detection of SEs facilitates monitoring of outbreaks and enterotoxigenicity of strains. This is most often based on molecular biological techniques (4) rather than immunological tools [1]. Little attention has been paid to the toxigenic potential of CNS though some investigators emphasize that they could produce toxic shock syndrome toxin alone or in combination with staphylococcal enterotoxins [5,6,7]. The important role of CNS as pathogens has been recognized only recently, and specific factors involved in pathogenesis are under exploration [8,5,9]. Modern species identification is another prerequisite for such attempts in CNS and it relies mostly on the 16S rRNA gene, rpoB, groEL, hsp, femA, tuf, gap, sodA, rpoB, dnaJ, and kat genes [10,11,12]

Methods

Results

Conclusion