Molecular typing of methicillin and vancomycin-resistant Staphylococcus aureus isolated from clinical specimens by double locus sequence typing(DLST)method

Methicillin-resistant Staphylococcus aureus(MRSA)strains are the essential cause of infections in communities and hospitals.The present study was conducted to determine the molecular typing of MRSA,isolated from hospitalized patients,using the double-locus sequence typing(DLST).In total,280 S.aureus isolated from clinical specimens by phenotypic(catalase,coagulase,DNase,oxacillin,vancomycin screening agar and antibiotic disk diffusion),and molecular methods(PCR for determining the mecA,vanA and nuc genes).The DLST and sequencing was performed for MRSA containing mecA.Out of 280 specimens,confirmed as Staphylococcus aureus(S.aureus),123(43.9%)strains were MRSA.The highest resistance toward the erythromycin(15μg),followed by ciprofloxacin(5μg),clindamycin(2μg),tetracycline(30μg),gentamicin(10μg)and rifampicin(5μg),was 98.3%,97.5%,94.3%,90.2%,83.7%and 41.4%,respectively.Also,the least resistance(0%)was observed in each of teicoplanin(30μg),linzolide(30μg),and vancomycin(30μg).All(100%)of MRSA strains had the mecA,and none of them have had the vanA.The results of DLST showed that the most common sequence types were BPH 2003 and 0217.The DLST type 18-32 was a significant cluster of MRSA.By sequencing MRSA and comparing the dominant types via the DLST,it is possible to establish the etiology of the disease in a much shorter time,and prevent the complications of the disease.Therefore,the combination of partial sequences of clfB and spa can serve as useful genetic markers for MRSA typing.It concluded that the MRSA in our region was relatively high,but no vancomycin resistance was found.The majority of the MRSA DLST type was 18–32.

Identification of <i>Bifidobacterium animalis</i>, <i>Bifidobacterium adolescentis</i>and <i>Bifidobacterium bifidum</i>from Stool of Children and Detection of Their Antibacterial Properties

Introduction and Objective: The genus Bifidobacterium can generally be found in quantity in the habitats such as human and animal gastrointestinal tract, dental caries, vagina and oral cavity. The aim of this study was to isolate Bifidobacterium from stool and determine their inhibitory effect against some pathogens. Materials and Methods: 130 samples were collected by wet swabs and kept in sterile tubes containing MRS broth media. And Bifidobacterium isolated from stool was enriched in Man-Rogosa-Sharpe medium (MRS) broth and isolated by growing on MRS agar medium and characterized by phenotypic characteristics and PCR technique at genus and species levels. The antimicrobial substance was extracted from ethyl acetate solvent and the antimicrobial activity against some pathogenic bacteria, such as Salmonella typhi and Shigella sonnei, were investigated. Results: Eleven Bifidobacterium bifidum and four Bifidobacterium adolescentis, which were isolated from fresh stool, were identified by PCR. Antimicrobial substance from MRS broth medium was extracted. This antimicrobial compound showed a potent inhibitory activity against four tested bacteria. These bacteria produced acetic acid and lactic acid as inhibitory substances that were different from bacteriocins. Conclusion: Fresh stool may be used as a source of antimicrobial lactic acids bacteria, Bifidobacterium bifidum and adolescentis as two probiotics can establish themselves in gut and urogenital tract to prevent the human body from adverse effects of pathogens.

Virulence determinants and biofilm formation in clinical isolates of Enterococcus: A cross-sectional study

Objective:To evaluate the relationship between biofilm formation and incidence of virulence determinants in clinical isolates of Enterococcus.Methods:In this cross-sectional study,the clinical isolates of Enterococcus strains were collected from the university teaching hospitals in Ahvaz,Iran from June 2017 to June 2018.Then,the prevalence of Enterococcus species,antibiotic resistance,virulence factors,and biofilm-producing ability were determined.Results:Of the 119 tested isolates,17(14.3%)were Enterococcus faecalis,72(60.5%)were Enterococcus faecium and 30(25.2%)were other Enterococcus spp.Gelatinase was detected in 97(81.5%)isolates,enterococcal surface protein in 41(34.5%)isolates,serine protease in 39(32.8%)cases,accessory colonization factor in 111(93.3%)cases and pathogenicity islands in 17(14.3%)cases.The biofilm formation ability was observed in 75(63.0%)of all isolates and the association between the presence of enterococcal surface protein gene and biofilm formation was statistically significant.Higher resistance to vancomycin,gentamycin,and teicoplanin was indicated in Enterococcus faecium with 81.8%,58.4%,and 85.7%resistance rate,respectively.All Enterococcus faecalis isolates were sensitive to teicoplanin and vancomycin.Conclusions:The presence of antibiotic-resistance with several virulence factors in Enterococcus spp has become a concern.High prevalence of enterococcal surface protein gene among biofilm-producing isolates suggests a potential relation between biofilm formation and the enterococcal surface protein gene,and further studies are needed to identify the mechanism of biofilm inhibition.