abkBA toxin-antitoxin system may act as antipersister modules in Acinetobacter baumannii clinical isolates.

Aim: Persistence cells comprise a subpopulation of bacteria that is resistant to treatment. In this study, the role of the toxin-antitoxin (TA) system in the formation of persistence cells of Acinetobacter baumannii isolates was investigated. Methods: After confirming all isolates, TA systems abkBA, mqsRA and higBA were identified. Persister cells were confirmed using the standard method. Real-time PCR was used to compare the expression of TA systems in isolates in persistence and normal states. Results: The abkAB system was present in all isolates; 4% of isolates formed persister cells. The expression level of the abkB gene in persistent isolates showed a sevenfold increase compared with nonpersistent isolates. Conclusion: The abkBA system is proposed as an antipersistence target in A. baumannii isolates.

In Vitro and In Silico Investigation of some Type II TA Genes in H. Pylori.

BACKGROUND: In addition to antibiotic resistance, the entry of Helicobacter pylori into the persistence phase leads to recurrent and chronic infections, as well as the development of antibiotic resistance in persister cells. METHODS: In this study, after genetic confirmation of H. pylori in 20 biopsy specimens, the prevalence of the type II TA systems mazEF, relEB, yafQ/dinJ was investigated. Also, the most common system observed in the study in terms of structure, evolution, and molecular interaction was evaluated by bioinformatics tools. RESULTS: The results of the PCR test on 20 biopsy samples were positive for ureA and glmM genes. Moreover, yafQ/ dinJ was the only module positive in half of the samples (10 samples) in the PCR technique. The toxin residues and their interactions with the cognate antitoxin residues are revealed by docking analysis results. Furthermore, the multiple sequence alignment (MSA) of the YafQ toxin showed that this toxin has a low polymorphism among H. pylori species. The evolutionary study showed that the yafQ toxin had the highest sequence similarity among the bacteria Helicobacter cetorm (60% similarity) and Muricauda olearia (57.35 % similarity). CONCLUSIONS: Collectively, the data of the present study indicate that the YafQ/DinJ is the dominant type II TA system and has the highest frequency among the studied systems in H. pylori, and further studies are required to elucidate its exact role in this bacterium.

Effect of Chlorhexidine (CHX) and Hydrogen Peroxide (H2O2) on the Biofilm Formation of Enterococcus faecalis.

BACKGROUND: Biofilm makes bacteria resistant to antimicrobial agents and facilitates the transmission of infectious diseases in hospitals. Disinfectant compounds are frequently used to control surface contamination. This study was designed to investigate the effect of chlorhexidine (CHX) and hydrogen peroxide (H2O2) on biofilm formation of Enterococcus faecalis. METHODS: This study was performed on 40 E. faecalis clinical isolates. After the determination of MIC, the effect of different concentrations of CHX and H2O2 on the biofilm formation was evaluated. Also, the relative expression level of the studied biofilm genes, following exposure to sublethal concentration of CHX and H2O2, was assessed using quantitative reverse transcription PCR (qRT-PCR). RESULTS: The frequency of the asa1, efaA, epaI, and esp biofilm genes were 80%, 92.5%, 100%, and 75%, respectively. Various concentrations of CHX increased the biofilm mass in E. faecalis. Also, the combination of CHX and H2O2 at sub-minimal inhibitory concentrations, significantly elevated the expression of asa1, epaI, and esp genes. CONCLUSIONS: The results of this study showed that the improper use of disinfectants can increase the ability of biofilm formation in E. faecalis and may cause selective pressure leading to the emergence of biocide-resistant microorganisms.

Inhibitory Effects of Lactococcus lactis and its Supernatant on Listeria monocytogenes.

BACKGROUND: The application of biological compounds generated by lactic acid bacteria, especially Lactococcus lactis, is recently considered to be a natural preservative for improving quality and health of food. The purpose of this study is to investigate the inhibitory potential of L. lactis supernatant on the expression of inlA, plc, and hly genes related to L. monocytogenes virulence capacity. METHODS: L. lactis was cultured under anaerobic conditions for 16 - 18 hours. The supernatant and live bacteria were then separated by centrifuge. The antilisteria effects of L. lactis and supernatant were measured using the agar diffusion technique, and the effect on the expression of the virulence-related genes was calculated by real-time PCR. Also, the effects of live bacteria and its supernatant on the microbial count of milk and sausage infected by L. monocytogenes was evaluated by the colony count assay. RESULTS: After 24 hours, the highest non-growing hole diameter was obtained in the presence of acidic supernatant (pH = 3.5). The microbial count showed the inhibitory effect on the eighth day after incubation with L. lactis. qPCR data revealed a down-regulation of virulence-related genes of inlA (8 fold), hly (6 fold), and plc (1 fold) in L. monocytogenes after 24-hour incubation with the supernatant. CONCLUSIONS: Our findings showed that the supernatant of L. lactis has an effective inhibitory role in the growth of L. monocytogenes. In the presence of supernatant, among plc, inlA and hly genes, the expression of inlA and hly genes decreased after 2 hours, which could indicate the molecular inhibitory mechanism of L. lactis in L. monocytogenes.

Multiple-Locus Variable-Number Tandem-Repeat Analysis Genotyping of Brucella Isolates from Iran.

BACKGROUND: Brucellosis is considered a main health concern in humans and animals. Neither familiar molecular methods nor the classical biotyping techniques are acceptable for subtyping Brucella spp. Loci containing variable number tandem repeats (VNTRs) have recently demonstrated their practicality in typing isolates from human and animal origin despite the excessive genetic homogeneity in the genus Brucella. METHODS: The genotypic characteristics of sixty-six Brucella melitensis and thirty-four Brucella abortus isolates from veterinary samples and human brucellosis cases in Iran during 2014 - 2018. They were analyzed using multiple-locus variable-number tandem-repeat analysis (MLVA) which consisted of sixteen primer pairs and designed and classified as belonging to one of the three panels: panel 1 (MLVA-8: eight loci including Bruce06, Bruce08, Bruce11, Bruce12, Bruce42, Bruce43, Bruce45, and Bruce55), panel 2A (three loci including Bruce18, Bruce19, and Bruce21), and panel 2B (five loci including Bruce04, Bruce07, Bruce09, Bruce16, and Bruce30); MLVA-11 (panels 1 and 2A), and MLVA-16 (panels 1, 2A, and 2B) using BioNumerics software (Version 7.6). RESULTS: Using panel 1, 2A, and 2B (MLVA-16), 59 genotypes with a genetic similarity coefficient ranging from 91 to 100% were obtained from the 100 Brucella spp. isolates. For all isolates, only genotype 36 and genotype 26 were obtained using panels 1 and 2A, respectively. The B. abortus isolates showed variations at 9 different genotypes, while B. melitensis isolates have been dispersed in 50 different genotypes. Bruce16 and Bruce4 showed the highest discriminatory power. CONCLUSIONS: The MLVA-16 assay appeared to be a useful and important molecular genotyping tool that is capable of proving epidemiological linkages in outbreak and trace-back investigations and is helpful in improving the effectiveness of brucellosis control programs.

Evaluation of Fosfomycin Activity Against Extended Spectrum Beta Lactamase (ESBL) Producing Enterobacteriaceae Isolated from Three Centers of Tehran, Iran.

BACKGROUND: Rising rates of antimicrobial resistance among Enterobacteriaceae limit the use of reliably active forms of available drugs. The aim of this study was to investigate the prevalence of fosfomycin (US6794490B2) resistance gene among ESBL producing isolates in Iran. METHOD: We tested 355 isolates of Enterobacteriacea collected from various clinical samples including urine, wounds, blood and other sources during June 2016 to July 2017. Antibiotic sensitivity and Extended Spectrum Beta Lactamase (ESBL) production were tested using agar dilution method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. ESBL genes (blaTEM, bla SHV,bla CTX-M), plasmid-encoded fosfomycin resistance genes (fosA, fosB, fosA3 and fosC2) and chromosomal mutations (murA, glpT, uhpT) were detected by Polymerase Chain Reaction (PCR). RESULTS: In this study, 151 of the 355 isolates were ESBL-positive. blaCTX-M (77%) was the most common gene followed by blaSHV (70%) and blaTEM (58%), either alone or in combination. Eighty nine percent (132/151) of the ESBL-positive isolates were MDR. Antimicrobial susceptibility rates were higher for fosfomycin (92.8%) and imipenem (35.5%) among ESBL-positive isolates. None of the ESBL- positive isolates harbored any mutations or plasmid-mediated fosfomycin resistance determinants. CONCLUSION: In conclusion, fosfomycin showed good antimicrobial activity against multidrug resistance ESBL- positive Enterobacteriaceae.