Analysis of Resistance to Macrolide–Lincosamide–Streptogramin B Among mecA-Positive Staphylococcus Aureus Isolates

OBJECTIVES: Genetic determinants conferring resistance to macrolide, lincosamide, and streptogramin B (MLSB) via ribosomal modification such as, erm, msrA/B and ereA/B genes are distributed in bacteria. The main goals of this work were to evaluate the dissemination of MLSB resistance phenotypes and genotypes in methicillin-resistant Staphylococcus aureus (MRSA) isolates collected from clinical samples. METHODS: A total of 106 MRSA isolates were studied. Isolates were recovered from 3 hospitals in Tehran between May 2016 to July 2017. The prevalence of MLSB-resistant strains were determined by D-test, and then M-PCR was performed to identify genes encoding resistance to macrolides, lincosamides, and streptogramins in the tested isolates. RESULTS: The frequency of constitutive resistance MLSB, inducible resistance MLSB and MSB resistance were 56.2%, 22.9%, and 16.6%, respectively. Of 11 isolates with the inducible resistance MLSB phenotype, ermC, ermB, ermA and ereA were positive in 81.8%, 63.6%, 54.5% and 18.2% of these isolates, respectively. In isolates with the constitutive resistance MLSB phenotype, the prevalence of ermA, ermB, ermC, msrA, msrB, ereA and ereB were 25.9%, 18.5%, 44.4%, 0.0%, 0.0%, 11.1% and 0.0%, respectively. CONCLUSION: Clindamycin is commonly administered in severe MRSA infections depending upon the antimicrobial susceptibility findings. This study showed that the D-test should be used as an obligatory method in routine disk diffusion assay to detect inducible clindamycin resistance in MRSA so that effective antibiotic treatment can be provided.

The Effect of Lactobacillus acidophilus PTCC 1643 on Cultured Intestinal Epithelial Cells Infected with Salmonella enterica serovar Enteritidis

OBJECTIVES: Gastrointestinal disorders caused by Salmonella enterica serovar Enteritidis (SesE) are a significant health problem around the globe. Probiotic bacteria have been shown to have positive effects on the immune responses. Lactobacillus acidophilus was examined for its capability to influence the innate immune response of HT29 intestinal epithelial cells towards SesE. The purpose of this work was to assess the effect of L. acidophilus PTCC 1643 on cultured intestinal epithelial cells infected with SesE. METHODS: HT29 cells were cultured in Roswell Park Memorial Institute medium supplemented with 10% fetal bovine serum and 1% penicillin/streptomycin. The cells were treated with L. acidophilus PTCC 1643 after or before challenge with SesE. At 2 and 4 hours post-infection, we measured changes in the expression levels of TLR2 and TLR4 via real-time polymerase chain reaction. RESULTS: Treatment with L. acidophilus inhibited SesE-induced increases in TLR2 and TLR4 expression in the infected HT29 cells. Moreover, the expression of TLR2 and TLR4 in cells that were pretreated with L. acidophilus and then infected with SesE was significantly higher than that in cells infected with SesE without pretreatment. Taken together, the results indicated that L. acidophilus had an anti-inflammatory effect and modulated the innate immune response to SesE by influencing TLR2 and TLR4 expression. CONCLUSION: Our findings suggested that L. acidophilus PTCC 1643 was able to suppress inflammation caused by SesE infection in HT29 cells and reduce TLR2 and TLR4 expression. Additional in vivo and in vitro studies are required to further elucidate the mechanisms underlying this anti-inflammatory effect.

In vitro assessment of Tribulus terrestri aqueous extract and Benzoxacin fraction against Helicobacter pylori isolates from biopsy samples of Iranian patients

Helicobacter pylori [Hp] is related to gastritis, gastric ulcer, duodenal ulcer, and mucosal carcinoma. Emergence of multidrug resistant Hp strains encouraged researchers to find new effective drugs, especially medicinal herbs and plants which usually show fewer side effects. The aim of this study was an in vitro assessment of anti Hp activity of total extract of Tribulus terrestris [T. terrestris Benzoxacin], a local Iranian medicinal plant and its fraction Benzoxacin. Total aqueous extract of aerial parts of the plant was prepared and liquid extraction with petroleum ether was used to separate its components. LC/MS system proved the existence of Benzoxazine derivative in the water fraction and the third's fraction. Anti [Hp] effects of total extract and its third fraction were examined by cup plate method and using standard MacFarland. 50 biopsy samples of antrum were detected from patients who were endoscopic candidates in Milad and Fayazbakhsh hospitals of Tehran during 2011. All samples were isolated, diagnosed based on standard methods and biochemical tests and confirmed by PCR method for ureC gene, too. Different dilutions [250, 500,750 and 1000 mg/ml] of total extract were prepared. Clarythromycin [Cl[r]] E-test strips and an identified Hp OC1096 was used, simultaneously. Of 50 biopsy samples, 12 Hp strains were isolated. Rapid urease test were positive in all except one biopsy sample. Existence of ureC gene in all isolates was confirmed except for one strain by PCR. By cup plate method, resistance to concentrations of 1000 and 750mg/ml wase detected in 50% of Hp isolates and 66.6% of them were resistant to concentrations 250 and 500 mg/ml. Also, 83.3% of Hp strains were resistant to Benzoxacin fraction. Clarythromycin sensitivity was detected in 83% of Hp isolates, simultaneously. This study was done as a pilot study for in vitro evaluation of antibacterial effect of total extract of T. terrestris by cup plate method. Existence of high resistant rate [>/=50%] to different concentrations T. terrestris aqueous extract renders doing test on more Hp strains in future studies highly recommended. In contrast of the similarity of Benzoxazin structure to Ofloxacin, existence of 83.3% resistance among tested isolates showed no anti Hp effectiveness of this fraction