Background: Methicillin resistant Staphylococcus aureus (MRSA) are one of the most common and important pathogens, accounting for diverse nosocomial and community-acquired infections. The serious concern about these bacteria is the development of antibiotic resistance. Objectives: The present study was conducted to investigate the frequency of MRSA strains, their epidemiological and molecular relationships and antibiotic susceptibility patterns of isolated strains from university teaching hospitals of Tabriz, Northwestern Iran (during years 2014 and 2015). Methods: A total of 215 non-repetitive clinical isolates of S. aureus were identified using standard methods. The MRSA isolates were detected by the combination of phenotypic and genotypic methods. The presence of pvl gene and SCCmec types was determined by PCR and multiplex PCR, respectively. The MRSA isolates, in which the presence of mecA gene had been confirmed by PCR, were subjected to Rep-PCR analysis. Resistance to antibacterial agents was determined by disk diffusion, screening agar, and E-test methods. Results: All S. aureus isolates were positive for nuc gene and 87 (40.5%) of them revealed the presence of mecA gene, confirming them as MRSA. All isolates were found to be sensitive to linezolid and vancomycin. However, a reduced sensitivity of 3 MRSA isolates to vancomycin was observed (MIC = 6 µg/mL). SCCmec type III was the most prevalent (79.31%), followed by type IVd (13.80%) and type I (6.90%). The PVL occurrence was detected in 33 (15.35%) S. aureus isolates. The MRSA isolates could be divided to 2 main clusters, indicating the possible clonal relatedness of MRSA isolates. Conclusions: The MRSA isolates with SCCmec type III were the predominant MRSA strains in this area. The majority of MRSA isolates were MDR. Linezolid and vancomycin were found as suitable antibiotics for the treatment of MRSA. The results of typing methods indicated possible clonal relatedness among MRSA isolates. Therefore, routine infection control surveillance is necessary for the prevention of epidemic emergence.

Background: Resistance to macrolide, lincosamide, and streptogramin B (MLSB) antibiotics is mediated by erm and msrA genes in Staphylococcus aureus. The expression of these genes can lead to three phenotypes, namely constitutive resistance (cMLSB), inducible resistance (iMLSB), which are resistant to macrolide, lincosamide, and streptogramin B antibiotics, and MSB phenotype, which is resistant only to macrolide and streptogramin B. Inducible clindamycin resistance is an important concern because it is not detected in routine laboratory tests. Objectives: The aim of this study was to determine the frequency of MLSB phenotypes and genotypes among 215 clinical isolates of S. aureus and then, examine their resistance to antibacterial agents, which is recommended for methicillin-resistant S. aureus (MRSA) isolates. Methods: Two hundred and fifteen non-repetitive clinical isolates of S. aureus were collected. Resistance to antibacterial agents was determined by disk diffusion and E-test methods. Susceptibility to clindamycin and erythromycin was tested by D-test. All isolates were screened by PCR for the presence of nucA, mecA, ermA, ermB, ermC, and msrA genes. Results: The prevalence of iMLSB, cMLSB and MSB phenotypes among all the isolates was determined as 10.69%, 34.42%, and 0%, respectively. In our study, iMLSB was prevalent more in methicillin susceptible S. aureus (MSSA) (11.71%) than MRSA (9.19%) isolates (P = 0.557). In contrast, the rate of cMLSB was significantly higher in MRSA (79.31%) than MSSA (3.90%) isolates (P = 0.000). No MSB phenotype was detected in our study. The most prevalent genes were ermC and ermA with 39% and 21.5% frequencies, respectively. Six isolates showed D phenotype, while the PCR results of erm genes were negative. All 215 isolates of S. aureus were negative for the presence of ermB and msrA genes. Conclusions: The rate of iMLSB in S. aureus isolates is relatively high in the Northwest Iran. Since isolates with inducible resistance may mutate and change to constitutive resistance, to prevent clinical treatment failure, D-test should be performed along with routine antibiotic susceptibility tests. In this study, ermC gene was the predominant genetic determinant for the expression of MLSB resistance. This predominance is probably due to the spread of distinctive clones (which carry ermC gene) in our region.

BackgroundDiarrhea is the most frequent health problem among children in developing countries. Defining the etiology of acute diarrhea is critical to disease therapy and prevention. Some anaerobic bacteria such as Enterotoxigenic Bacteroides fragilis (ETBF) strains cause diarrheal disease by production of enterotoxin in children less than 5 years old.ObjectivesThis study aimed to evaluate the prevalence of ETBF among common bacteria and viruses causing diarrhea in children aged less than five years.Materials and MethodsOne hundred diarrheal stools were cultured for detection of aerobic and anaerobic pathogen bacteria by direct plating on selective media and antibiotic susceptibility tests were performed according to clinical and laboratory standards institute (CLSI) guidelines on isolates of ETBF. The enterotoxigenic gene among B. fragilis isolates was also investigated using the polymerase chain reaction (PCR) method. Detection of viral pathogens was carried out using the latex agglutination test.ResultsTen B. fragilis were isolated from 100 diarrheal fecal specimens. All isolates were susceptible to metronidazole, while 10% were susceptible to clindamycin. Four (40%) ETBF were isolated. Rotaviruses (57.2%) and adenoviruses (18.6%) were the most frequently detected etiological agents.ConclusionsETBF is one of the etiological agents that may cause diarrhea in children but it is not the commonest of them. Metronidazole is still an effective antibiotic against B. fragilis. Viruses are the most important etiological agents of diarrhea in children less than 5 years of age.