Tehran University Medical Journal

Background: Clindamycin is a suitable antibiotic for treatment of skin and soft tissue infections. Moreover, it can suppress toxin production in many pathogenic bacteria such as S. aureus. There are two mechanisms of resistance in this antibiotic. Constitutive resistance can be detected by standard disk diffusion method but in the case of inducible resistance, D-test should be carried out. The main aim of this study is to determine prevalence of clindamycin inducible resistance among methicillin resistant and susceptible isolates of S. aureus isolated from different clinical samples.

Methods: A total of 87 clinical isolates from clinical samples were collected. Methicillin resistance was determined using standard disk diffusion method. Subsequently, D-test was carried out according to CLSI guideline. Presence of the sea gene (enterotoxin A) was detected by PCR using specific primers.

Results: Out of 87 isolates, 18(20.7%) were clindamycin inducible resistant while constitutive resistance was detected among 21(24.1%) isolates. The 95% Confidence intervals for the proportion of inducible clindamycin resistance among clinical isolates of S. aureus was 12.2% to 29.2%. The inducible phenotype in MRSA isolates was more common than that of MSSA isolates (33.3% vs 5.1%).Significant differences were found between prevalence of inducible clindamycin resistance and type of infection (p=0.045). Importantly, there was a significant correlation between sea gene and the constitutive/inducible resistance (p<0.0001).

Conclusions: Due to the high prevalence of clindamycin inducible resistance among clinical isolates of S. aureus, we recommend D-test to avoid treatment failure.

Background: Staphylococcus aureus is a major foodborne pathogen throughout the world. Enterotoxins and toxic shock syndrome toxin-1 are important virulence factors and as pyrogenic toxin superantigens have profound effects on the ir host. Thus circulation of TSST1 producing S.aureus among people and food chain is a worrying issue. The present paper was conducted to study Prevalence of tst, entC, entA and entA/C genes in staphylococcus aureus strains isolated from different foods.
Methods: Over 1040 food samples have been analyzed differentially according to Iran national standard (number= 1194) for S.aureus identification. After DNA extraction, PCR reactions were carried out by reference strain as positive control, adequate primers.

Results: At present study, prevalence of foodstuffs contaminated by S.aureus isolates was about 9.5% (100 strains). Of 25% of isolates producing entC, 28% (seven strains) had tst gene at the same time and of 8% of isolates producing entA, 12.5% (one strain) were positive for tst genes simultaneously. Altogether of 9% isolates producing combination of entC and entA, 44.4% (four strains) were also producer of tst gene.

Conclusion: Prevalence of TSST1 producing strains in combination with enterotoxin genes is considerable especially with entC and A plus C. On the other hand, circulation of these isolates in humans, animals, foods and environment has hazardous effect for general public health.

Background: Staphylococcus aureus is a gram positive coccus which is able to cause different kinds of infection in certain condition. The function of this bacteria is to provide the conditions for the invasion of it to the host with the secretion of different sorts of toxins such as Staphylococcus aureus enterotoxin, including important virulence factors that super antigens are all factors digestive inconvenience. Staphylococcus aureus enterotoxin-secreting toxins such conditions provides invasion of host genes. There are different types of SE, but type A enterotoxin (SEA) and type B enterotoxin (SEB) are the most important types. Therefore, in this study, the prevalence of Staphylococcus aureus toxin-producing enterotoxin genes (SEB, SEA) in clinical strains isolated from patients in teaching hospitals of Shahrekord city, Iran, were studied.

Methods: This cross-sectional and descriptive study, which was conducted from May 2014 to December 2014. A hundred and ten isolates of Staphylococcus aureus from patients collected over a period of 8 months and were first identified using standard biochemical methods and laboratory. Using standard methods and laboratory tests were identified and compared with the antibiotic oxacillin minimum inhibitory concentration were determined by broth micro dilution, and then they were assessed by polymerase chain reaction (PCR) technique.

Results: The results indicated that, 110 samples of dairy products infected by Staphylococcus aureus were detected. Two cases (1.8%) of these infected samples were carrying both enterotoxin A and enterotoxin B genes. The frequencies of enterotoxin A genes were twenty-six cases (23/6%) and The frequencies of enterotoxin B genes were two cases (1/8%), respectively.

Conclusion: The detection of enterotoxin A and enterotoxin B genes, shows the most important role they have in bringing about superinfection. The detection of enterotoxin A and B genes, shows the most important role they have in bringing about superinfection. Enterotoxins SEA and SEB are heat stable; therefore heating has no effect on dairy products contaminated by enterotoxins and gastritis may occur in a short period of time. As PCR is a rapid, sensitive, specific and inexpensive method, we suggest that it can be replaced to traditionally assays for detecting Staphylococcus aureus enterotoxin.