Characterization of Staphylococcus aureus strains isolated from bovine milk in Hungary

Abstract

Staphylococcus aureus is a major foodborne pathogen due to its capability to produce a wide range of heat-stable enterotoxins. The primary purpose of this research was to characterize S. aureus isolates recovered from mammary quarter milk of mastitic cows and from bulk tank milk produced on Hungarian dairy farms of different sizes. Macrorestriction analysis of chromosomal DNA from S. aureus isolates was performed using the restriction enzyme SmaI followed by pulsed-field gel electrophoresis (PFGE). The prevalence rates of nine S. aureus enterotoxin genes (sea, seb, sec, sed, see, seg, seh, sei, and sej) and of the toxic shock syndrome toxin 1 gene (tst) were determined by multiplex polymerase chain reaction (PCR). The bulk tank milks of 14 out of 20 farms were contaminated with S. aureus at levels of up to 6.0 × 10 3 CFU/ml. Farm size had no significant effect (P N 0.05) on the S. aureus counts in bulk milk. The prevalence rates of penicillin resistance were 88.9% and 20.0% among the S. aureus recovered from mastitic quarter milk and bulk tank milk, respectively. After phenotypic characterization, a total of 59 S. aureus isolates were selected for genotyping. PFGE analysis revealed 22 distinct pulsotypes, including 14 main types and 8 subtypes, at a similarity level of 86%. Only one or two main types were observed on each of the farms tested, indicating a lack of genetic diversity among S. aureus isolates within farms, and there were only two pulsotypes which occurred on more than one farm. The PFGE patterns showed genetic relatedness between the S. aureus strains recovered from quarter milk and bulk milk on two large farms, implying that on farms having a high number of mastitic cows, S. aureus from infected udders may contaminate bulk milk and, subsequently, raw milk products. Sixteen (27.1%) of the S. aureus isolates tested by multiplex PCR were found to be positive for enterotoxin genes, with 15 of them carrying just one gene and one strain carrying two genes (seg and sei). The most commonly detected toxin genes were seb, sea, and sec, whereas none of our isolates possessed the see, seh, sej, or tst genes. On 75% of the dairy farms surveyed, no enterotoxigenic staphylococci were recovered from either mastitic quarter milk or bulk tank milk.

Antibiograms, toxin profiling and molecular typing of Staphylococcus aureus isolates from two tertiary hospitals in Jordan

“…Further, Demir et al [44] reported that 65.8% of the clinical isolates exhibited at least one toxin gene. However, these results appeared to be completely different from results reported by Peles et al [45] who reported that only 15% of S. aureus isolated from milk samples in Hungary harbored at least one toxin gene indicating the low prevalence of toxin genes in non-pathogenic S. aureus isolated from milk samples. However, the results appeared different from those reported by Naffa et al [23] who showed that only 23% of the clinical isolates exhibited at least one toxin gene.…”

“…The pattern distribution was changed upon digestion with CfoI enzyme where more than half of the isolates belonged to three genotypes D, C and F with 64, 45 …”

Occurrence and antibiotic resistance of enterotoxigenic Staphylococcus aureus in raw ovine and caprine milk in Greece

“…In other studies, however, the seb gene was detected in S. aureus isolates from milk and dairy products at various frequencies (Jørgensen et al 2005;Zouharova and Rysanek 2008). The fact that seb was the most commonly detected SE genotype in isolates from OM in our study is in agreement with the findings of previous studies (Arcuri et al 2010;Peles et al 2007).…”

Determination of antibiotics sensitivity profiles of bacteria isolated from raw milk

“…The foremost global public concern and health hazard related with antibiotic residues is the development of the antimicrobial resistant bacterial strains of animal origin and its consequential effect on human health (Threlfall, 2002;Aarestrup, 2006) regarding the efficacy of antimicrobial therapy (Casadevall, 1996). According to Prescott and Baggot (1993), microbial resistance to aminoglycosides, particularly Streptomycin, Neomycin, and Kanamycin is very common and pathogens present in the milk mainly S. aureus, E. coli O157:H7 and L. monocytogenes may easily develop antimicrobial resistance (Seeliger and Jones, 1986;Peles et al, 2007). Isolates of S. aureus are frequently resistant to methicillin and essentially all other β-lactam antibiotics.…”