Risk Factors Associated with Human Brucellosis: A Systematic Review and Meta-Analysis.

Background: Brucellosis is a zoonosis disease that can affect humans and a wide range of domestic and wild animals. Susceptibility to brucellosis in humans can be related to various factors, such as nutritional and occupational factors. This study evaluated factors related to brucellosis and identified influential risk factors for human infection. Methods: We performed a systematic literature review and meta-analysis of studies in PubMed, Web of Science, and Scopus. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to measure the strength of the association between some potential factors and the risk of brucellosis. Results: From 277 initial studies, 19 case-control studies were included in this review. Significant risk factors for brucellosis included occupation (OR 3.31, 95% CI 1.68-6.55), having aborted animals (OR 4.16, 95% CI 2.03-8.50), consumption of meat (OR 2.17, 95% CI 1.44-3.36), unpasteurized milk (OR 3.86, 95% CI 1.81-8.23), and raw cheese (OR 4.20, 95% CI 1.63-10.85). Conclusion: The results of this study advance the understanding of the etiology of brucellosis. In this meta-analysis, we found the association of different environmental factors with the risk of brucellosis. Additional high-quality prospective studies are needed to determine whether these factors cause brucellosis and to identify other factors.

Prevalence of Mycobacterium kansasii in clinical and environmental isolates, a systematic review and meta-analysis.

Background: Mycobacterium kansasii infection is one of the most common causes of non-tuberculosis mycobacterial (NTM) disease worldwide. However, accurate information on the global prevalence of this bacterium is lacking. Therefore, this study was conducted to investigate the prevalence of M. kansasii in clinical and environmental isolates. Methods: Databases, including PubMed, Scopus, and the Web of Science, were utilized to gather articles on the prevalence of M. kansasii in clinical and environmental isolates. The collected data were analyzed using Comprehensive Meta-Analysis software. Results: A total of 118 and 16 studies met the inclusion criteria and were used to analyze the prevalence of M. kansasii in clinical and environmental isolates, respectively. The prevalence of M. kansasii in NTM and environmental isolates were 9.4 and 5.8%, respectively. Subsequent analysis showed an increasing prevalence of M. kansasii over the years. Additionally, the results indicated a significant difference in the prevalence of this bacteria among different regions. Conclusion: The relatively high prevalence of M. kansasii among NTM isolates suggests the need for further implementation of infection control strategies. It is also important to establish appropriate diagnostic criteria and management guidelines for screening this microorganism in environmental samples in order to prevent its spread, given its high prevalence in environmental isolates.

Prevalence of colistin resistance in clinical isolates of Acinetobacter baumannii: a systematic review and meta-analysis.

INTRODUCTION: The development of colistin resistance in Acinetobacter baumannii during treatment has been identified in certain patients, often leading to prolonged or recurrent infections. As colistin, is the last line of therapy for A. baumannii infections that are resistant to almost all other antibiotics, colistin-resistant A. baumannii strains currently represent a significant public health threat, particularly in healthcare settings where there is significant selective pressure. AIM: The aim of this study was to comprehensively determine the prevalence of colistin resistance in A. baumannii from clinical samples. Regional differences in these rates were also investigated using subgroup analyses. METHOD: The comprehensive search was conducted using "Acinetobacter baumannii", "Colistin resistant" and all relevant keywords. A systematic literature search was performed after searching in PubMed, Embase, Web of Science, and Scopus databases up to April 25, 2023. Statistical analysis was performed using Stata software version 17 and sources of heterogeneity were evaluated using I2. The potential for publication bias was explored using Egger's tests. A total of 30,307 articles were retrieved. After a thorough evaluation, 734 studies were finally eligible for inclusion in the present systematic review and meta-analysis. RESULT: According to the results, the prevalence of resistance to colistin among A. baumannii isolates was 4% (95% CI 3-5%), which has increased significantly from 2% before 2011 to 5% after 2012. South America had the highest resistance rate to this antibiotic. The broth microdilution method had the highest level of resistance, while the agar dilution showed the lowest level. CONCLUSIONS: This meta-analysis found a low prevalence of colistin resistance among A. baumannii isolates responsible for infections worldwide from 2000 to 2023. However, there is a high prevalence of colistin-resistant isolates in certain countries. This implies an urgent public health threat, as colistin is one of the last antibiotics available for the treatment of infections caused by XDR strains of A. baumannii.

Prevalence of antibiotic resistance in clinical isolates of Mycobacterium kansasii: a systematic review and meta-analysis.

INTRODUCTION: The prevalence of diseases caused by non-tuberculous mycobacteria (NTM), including M. kansasii, is increasing, necessitating further information to guide prevention, control, and treatment strategies. AREAS COVERED: A comprehensive analysis of articles published until February 2023 was conducted on PubMed, Web of Science, and Scopus databases to investigate antibiotic resistance in M. kansasii species. Stata software version 17 was employed for all analyses. EXPERT OPINION: A total of 1647 articles were obtained through database search. After removing duplicates and unrelated studies, 17 cross-sectional studies that examined the breakpoints proposed by CLSI were included. The rates of resistance of M. kansasii to various antibiotics were as follows: clarithromycin (0%), rifampin (1%), amikacin (0%), ciprofloxacin (14%), linezolid (0%), moxifloxacin (0%), rifabutin (1%), doxycycline (96%), and SXT (49%). Our findings underscore the importance of managing and monitoring the use of these antibiotics, as well as the need for further studies to elucidate the exact mechanism of M. kansasii resistance to these antibiotics.

Prevalence of Brucella endocarditis: A systematic review and meta-analysis.

Background: Endocarditis caused by Brucella infection is one of this infection's complications, including a high mortality rate. However, studies on the prevalence of this complication have been limited to some case reports. This study investigated the prevalence of Brucella endocarditis globally using a systematic review and meta-analysis. Methods: PubMed, Scopus, and Web of Science databases were searched using appropriate keywords until September 2022. All studies reporting the prevalence of endocarditis in patients with brucellosis were included in this current study. To investigate the pooled prevalence of Brucella endocarditis, random model was used in comprehensive meta-analysis software. Results: A total of 25 studies met the inclusion criteria and were included in the systematic review and meta-analysis. The prevalence of Brucella endocarditis was 1.3%, and the death rate was 26.5%. The results did not show a significant difference in the prevalence of this complication in different regions. Conclusion: According to this study's results, the prevalence of Brucella endocarditis is low, but it includes a large percentage of the deaths of affected patients. To complete our understanding of this complication and its management, more research should be done to investigate the effect of other factors, such as age and gender.

Prevalence of colistin resistance of Klebsiella pneumoniae isolates in Iran: a systematic review and meta-analysis.

OBJECTIVE: Klebsiella pneumoniae is a gram-negative pathogen common cause of nosocomial infections. Colistin is a last resort antibiotic to treat infections caused by K. pneumoniae. In recent years, the resistance rate to colistin has increased in K. pneumoniae. This study evaluated the prevalence of colistin resistance of K. pneumoniae isolates in Iran using a systematic review and meta-analysis. METHOD: A systematic search was performed for relevant articles until August 2021 in the following database: PubMed, Scopus, SID and Google Scholar. The pooled prevalence of colistin resistance in clinical K. pneumoniae isolates analyzed using Comprehensive Meta-Analysis Software (CMA). RESULTS: Finally, 19 articles with appropriate criteria were included in the meta-analysis. Our results showed 6.9% of the pooled prevalence of colistin resistance in clinical K. pneumoniae isolates in Iran. The results of subgroup analysis demonstrated increase resistance of colistin from 4.8%; (95% CI 1.5-13.9%) in 2013-2018 to 8.2%; (95% CI 3.4-18.6%), in 2019-2021. Also, the results of our study showed a strong association between the carbapenem producing K. pneumoniae and increased resistance to colistin. CONCLUSIONS: This study showed a high prevalence of colistin resistance in K. pneumoniae isolates. It is recommended that regular evaluation be performed to control colistin resistance.

Genotyping of Listeria monocytogenes isolates by high-resolution melting curve (HRM) analysis of tandem repeat locus.

Listeria monocytogenes is responsible for causing listeriosis, a type of food poisoning with high mortality. This bacterium is mainly transmitted to humans through the consumption of contaminated foods. Detection of L. monocytogenes through molecular methods is crucial for food safety and clinical diagnosis. Present techniques are characterized by low discrimination power and high cost, as well as being time-consuming and taking several days to give the final result. In our study, MLVA-HRM (Multiple-Locus Variable-number tandem repeats Analysis ‒ High-Resolution Melting) was investigated as an alternative method for a fast and precise method for the genotyping of L. monocytogenes isolates. Forty-eight isolates of L. monocytogenes obtained from the microbial bank of Department of Microbiology, Iran University of Medical Sciences, were typed by MLVA-HRM analysis using five Variable Numbers of Tandem Repeat (VNTR) loci. A total of 43 different types were obtained. This research demonstrated the usefulness of the MLVA-HRMA method and its ability to discriminate L. monocytogenes isolates. Since this method is easier and more efficient than existing methods, it can be widely used in food processing plants and diagnostic laboratories as a fast and accurate method.

Genotyping of Listeria monocytogenes isolates by high-resolution melting curve (HRM) analysis of tandem repeat locus

Abstract Listeria monocytogenes is responsible for causing listeriosis, a type of food poisoning with high mortality. This bacterium is mainly transmitted to humans through the consumption of contaminated foods. Detection of L. monocytogenes through molecular methods is crucial for food safety and clinical diagnosis. Present techniques are characterized by low discrimination power and high cost, as well as being time-consuming and taking several days to give the final result. In our study, MLVA-HRM (Multiple-Locus Variable-number tandem repeats Analysis ‒ High-Resolution Melting) was investigated as an alternative method for a fast and precise method for the genotyping of L. monocytogenes isolates. Forty-eight isolates of L. monocytogenes obtained from the microbial bank of Department of Microbiology, Iran University of Medical Sciences, were typed by MLVA-HRM analysis using five Variable Numbers of Tandem Repeat (VNTR) loci. A total of 43 different types were obtained. This research demonstrated the usefulness of the MLVA-HRMA method and its ability to discriminate L. monocytogenes isolates. Since this method is easier and more efficient than existing methods, it can be widely used in food processing plants and diagnostic laboratories as a fast and accurate method.

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.

Evaluation of gene expression and protein structural modeling involved in persister cell formation in Salmonella Typhimurium.

Persisters are phenotypic variants of the bacterial population that survive against lethal doses of bactericidal antibiotics.These phenotypes are created in numerous bacterial species, including those of clinical significance, such as Salmonella Typhimurium. Since persister cells are associated with the failure of antibiotic treatment and infection recurrence, it is crucial to identify the mechanisms that influence the formation of these cells. The aim of this study is to investigate the persister cell formation and expression analysis as well as to predict the 3D structure of the genes involved in the production of persister cells. The presence of persisters in S. Typhimurium was determined by time dependent killing of different types of bactericidal antibiotics and expression of genes associated with persister cell formation which was assessed five hours after the addition of antibiotics by the qRT-PCR. Indeed, the 3D structural model of the proteins studied was predicted by performing several computational methods of retrieved primary protein sequences. The results of the study showed that the S. Typhimurium produced high levels of persister cells in the exposure of bactericidal antibiotics. Furthermore, qRT-PCR resulted in the fact that the expression of related genes was different depending on the type of antibiotic. Overall, this study provides information on the creation of persister cells and the role of different genes in the formation of these cells and structure of proteins involved in the production of persister cells in S. Typhimurium.

Combination of Antibiotics-Nisin Reduces the Formation of Persister Cell in Listeria monocytogenes.

Persister cells are a subpopulation of bacteria with the ability of survival when exposed to lethal doses of antibiotics, and are responsible for antibiotic therapy failure and infection recurrences. In this study, we investigated persister cell formation and the role of nisin in combination with antibiotics in reducing persistence in Listeria monocytogenes. We also examined the expression of toxin-antitoxin (TA) systems in persister cells of L. monocytogenes to gain a better understanding of the effect of TA systems on persister cell formation. To induce persistence, L. monocytogenes were exposed to high doses of different antibiotics over a period of 24 hr, and the expression levels of TA system was genes were measured 5 hr after the addition of antibiotics by the quantitative reverse transcription-polymerase chain reaction (qRT-PCR) method. To investigate the effect of nisin, L. monocytogenes was exposed to a combination of nisin and antibiotics. According to our results, L. monocytogenes was highly capable of persister cell formation, and the combination of nisin and antibiotics resulted in reduced persistence. qRT-PCR results showed a significant increase in GNAT/RHH expression among the studied systems. Overall, our results demonstrated the potential of the combination of nisin and antibiotics in reducing persister cell formation, and emphasized the role of the GNAT/RHH system in bacterial persistence.

Evaluation of the genetic relatedness of Bacteroides fragilis isolates by TRs analysis.

OBJECTIVES: Human gastrointestinal tract harbors a variety of bacteria with vital roles in human health. Bacteroides fragilis is considered one of the dominant constituents of gut microflora which can act as an opportunistic pathogen leading to various diseases, including colon cancer, diarrhea, uterine and intrathecal abscesses, septicemia, and pelvic inflammation. In this study, multiple locus variable number of tandem repeats analysis (MLVA) was performed to genetically differentiate 50 B. fragilis isolates. MATERIALS AND METHODS: Eight suitable tandem repeats (TRs) were selected by bioinformatics tools and were then subjected to PCR amplification using specific primers. Finally, MLVA profiles were clustered using BioNumerics 7.6 software package. RESULTS: All VNTR loci were detected in all isolates using the PCR method. Overall, B. fragilis isolates were differentiated into 27 distinct MLVA types. The highest diversity index was allocated to TR1, TR2, TR5, TR6, and TR8; with this taken into account, strain type 14 was the most prevalent with 12 strains belonging to this type. Clustering revealed three major clusters of A, B, and C. With regards to the pathogenicity of B. fragilis and the outcomes of infections related to this microorganism, it is imperative to study this microorganism isolated from both patients and healthy individuals. CONCLUSION: This study aimed at evaluating the efficiency of MLVA for the genetic differentiation of B. fragilis. The results of this study indicate the promising efficiency of MLVA typing for cluster detection of this bacterium.

The expression of type II TA system genes following exposure to the sub-inhibitory concentration of gentamicin and acid stress in Brucella spp.

BACKGROUND: Brucellosis is one of the most common diseases that afflicts both humans and animals. Bacteria react to stress conditions using different mechanisms one of which is Toxin-Antitoxin (TA) systems. It is believed that the Toxin-Antitoxin (TA) systems have a key role in the chronicity of the disease. This study investigated the expression of TA system genes under acid and antibiotic stresses in Brucella spp. METHODS: Fifty Brucella isolates (17 isolated from animals and 31 isolated from human specimens, and two standard strains) were analyzed using PCR (using two pairs of primers). Then, to determine the effects of sub-MIC of gentamicin on bacterial survival and growth, colony forming unit was quantitated and turbidity was assessed following the treatment of Brucella spp, with ½ MIC of gentamicin at different time intervals. Furthermore, the colony forming unit of Brucella spp, was assessed under acid stress (pH = 5.5) compared to the control (pH = 7.6). Moreover, the expression of TA system genes in Brucella spp, was evaluated 1 h after treatment using qRT-PCR method. RESULTS: A total of 50 isolates, including 41 (82%) Brucella melitensis and 7 (14%) Brucella abortus with two standard strains Brucella melitensis (16 M) and Brucella abortus (B19) were investigated. Our results revealed the reduced growth of Brucella spp. in the presence of sub-MIC of gentamicin compared to the control. Furthermore, according to the results of qRT-PCR assay, gentamicin could increase the expression of TA system genes. Also, results of qRT-PCR showed that under acid stress, the expression of TA system gene COGT/COGAT decreased compared to the control. CONCLUSION: Although the exact role of the TA systems in response to stress is still unclear, our study provided information on the effect of the type II TA systems under the acid and antibiotic stress conditions. However, further studies are still required.

Persister cells formation and expression of type II Toxin-Antitoxin system genes in Brucella melitensis (16M) and Brucella abortus (B19).

BACKGROUND & OBJECTIVE: Persister cells are defined as a subpopulation of bacteria that are capable of reducing their metabolism and switching to dormancy in stress conditions. Persister cells formation has been attributed to numerous mechanisms, including stringent response and Toxin-Antitoxin (TA) systems. This study aimed to investigate the hypothetical role of TA systems in persister cells formation of Brucella strains by evaluating toxins of type II TA systems (RelE, Fic, Brn T, cogT) expression. METHODS: Brucella strains treated with a lethal dose of gentamicin and ampicillin and to determine the number of surviving cells, bacterial colonies were counted at different time intervals. The role of TA systems in persister cell formation was then determined by toxin expression levels using qRT- PCR method. RESULTS: Our results showed the viability of persister cells after 7 h. The results of relative qRT- PCR showed higher levels of toxin gene expression due to stress conditions, suggesting the possible role of TA systems in persister cells formation and antibiotics tolerance. CONCLUSION: The results of this study showed that considering the importance of persistence and the tolerance to antibiotics, further studies on persister cells formation and related genes such as the TA system genes in Brucella strains might help us to identify the precise mechanisms leading to persister cells formation.

Effects of sub-inhibitory concentrations of antibiotics and oxidative stress on the expression of type II toxin-antitoxin system genes in Klebsiella pneumoniae.

OBJECTIVES: Sub-inhibitory concentrations (sub-MICs) of antibiotics reflect the conditions that bacteria encounter in tissues and the natural environment. Sub-MICs of antibiotics can induce stress and alter the expression of different bacterial genes. Bacteria react to stress conditions using different mechanisms, one of which is the toxin-antitoxin (TA) system. This study investigated the expression of the TA system genes under oxidative and antibiotic stresses in Klebsiella pneumoniae (K. pneumoniae). METHODS: To determine the effects of sub-MICs of gentamicin, nalidixic acid, ceftazidime, and certain concentrations of H2O2 on bacterial survival and growth, colony forming units were quantitated and turbidity was assessed following the treatment of K. pneumoniae with ½ MICs of antibiotics and 5 mM H2O2 at different time intervals. The expression of TA system genes in K. pneumoniae was evaluated 1 h after treatment using the quantitative real-time PCR (qRT-PCR) method. RESULTS: The results revealed reduced K. pneumoniae growth in the presence of sub-MICs of antibiotics and 5 mM H2O2 compared to the control. Furthermore, according to the results of the qRT-PCR assay, only the presence of gentamicin could increase the expression of TA system genes. CONCLUSION: Although the exact role of the TA systems in response to stress is still unclear, this study provided information on the effect of the type II TA systems under oxidative and antibiotic stress conditions.