The effect of type II toxin-antitoxin systems on methicillinresistant Staphylococcus aureus persister cell formation and antibiotic tolerance

Persister cells are defi ned as a subpopulation of bacteria in a dormant state with the ability to reduce bacterial metabolism and they are involved in antibiotic tolerance. Toxin-antitoxin (TA) systems have been previously suggested as important players in persistence. Therefore, this study aimed to study the involvement of TA systems in persister cell formation in methicillin-resistant Staphylococcus aureus following antibiotic exposure. Using TADB and RASTA database, two type II TA systems including MazF/MazE and RelE/RelB were predicted in S. aureus. The presence of these TA genes was determined in 5 methicillin-resistant S. aureus isolates and the standard strain S. aureus subsp. aureus N315 using PCR method. To induce persistence, isolates were exposed to lethal doses of ciprofl oxacin and the expression of the studied TA system genes was measured after 5 h using Real-Time PCR. According to our results, all the studied isolates harbored the TA system genes. S. aureus was highly capable of persister cell formation following exposure to sub-MIC of ciprofl oxacin and RT-qPCR showed a signifi cant increase in the expression of the MazEF and RelBE loci, indicating their potential role in antibiotic tolerance. Considering the importance of antibiotic tolerance, further studies on persister cell formation and TA systems involved in this phenomenon are required to effi ciently target these systems

Erratum to: Nanoparticles Impact the Expression of the Genes Involved in Biofilm Formation in S. aureus, a Model Antimicrobial-Resistant Species

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Evaluation of Modified Hodge Test as a Non-molecular Assay for Accurate Detection of KPC-producing Klebsiella pneumoniae

Klebsiella pneumoniae carbapenemase (KPC) have become a major therapeutic challenge because of its increasingly fast dissemination throughout the world. Accurate detection of KPC is essential for optimal treatment. The Clinical and Laboratory Standards Institutes (CLSI) for fast detection of KPC producers currently recommend Modified Hodge Test (MHT) and Carba NP test. MHT can directly detect carbapenemase production in Enterobacteriaceae isolates. The current study was conducted to evaluate the capacity of MHT with two carbapenem disks for accurate detection of KPC. MHT was performed according to guidelines of CLSI to identify isolates with carbapenem resistance. In doing so, two substrates of MHT were assigned into two groups for examination: meropenem and ertapenem groups. A total of 96 non-repetitive clinical isolates of Klebsiella pneumoniae were tested. The presence of the blaKPC gene in each MHT-positive isolate was examined by PCR. A total of 54 isolates exhibited reduced susceptibility or resistance to carbapenems. Sensitivity of MHT with two carbapenem disks was similar. Specificity of the MHT with meropenem disk was 64 and with ertapenem disk was 53. Detection of KPC by MHT with meropenem disk was found to be more effective than with ertapenem disk. Based on our results, the presence of KPC does not in itself influence the categorization of resistance. Therefore, the use of MHT with ertapenem disk for the rapid detection of KPC among K. pneumoniae for infection control should not be recommended. © 2018 Atossa Ghasemnejad et al

An overview of case reports and case series of pulmonary actinomycosis mimicking lung cancer: a scoping review

BackgroundPulmonary actinomycosis (PA) is a rare type of Actinomyces infection that can be challenging to diagnose since it often mimics lung cancer.MethodsPublished case reports and case series of PA in patients with suspicion of lung cancer were considered, and data were extracted by a structured search through PubMed/Medline.ResultsAfter analyzing Medline, 31 studies were reviewed, from which 48 cases were extracted. Europe had the highest prevalence of reported cases with 45.1%, followed by Asia (32.2%), America (19.3%), and Africa (3.2%). The average age of patients was 58.9 years, and 75% of all patients were above 50 years old. Male patients (70%) were predominantly affected by PA. The overall mortality rate was 6.25%. In only eight cases, the causative agent was reported, and Actinomyces odontolyticus was the most common isolated pathogen with three cases. Based on histopathological examination, 75% of the cases were diagnosed, and the lobectomy was performed in 10 cases, the most common surgical intervention. In 50% of the cases, the selective antibiotics were intravenous and oral penicillin, followed by amoxicillin (29.1%), amoxicillin-clavulanic acid, ampicillin, levofloxacin, and doxycycline.ConclusionThe non-specific symptoms resemble lung cancer, leading to confusion between PA and cancer in imaging scans. Radiological techniques are helpful but have limitations that can lead to unnecessary surgeries when confusing PA with lung cancer. Therefore, it is important to raise awareness about the signs and symptoms of PA and lung cancer to prevent undesirable complications and ensure appropriate treatment measures are taken

Biofilm formation in clinical isolates of nosocomial Acinetobacter baumannii and its relationship with multidrug resistance

AbstractObjectiveTo check biofilm formation by Acinetobacter baumannii (A. baumannii) clinical isolates and show their susceptibility to different antibiotics and investigate a possible link between establishment of biofilm and multidrug resistance.MethodsThis study was performed on clinical samples collected from patients with nosocomial infections in three hospitals of Tehran. Samples were initially screened by culture and biochemical tests for the presence of different species of Acinetobacter. Identifications were further confirmed by PCR assays. Their susceptibilities to 11 antibiotics of different classes were determined by disc diffusion method according to Clinical and Laboratory Standards Institute guidelines. The ability to produce biofilm was investigated using methods: culture on Congo red agar, microtiter plate, and test tube method.ResultsFrom the overall clinical samples, 156 specimens were confirmed to contain A. baumannii. The bacteria were highly resistant to most antibiotics except polymyxin B. Of these isolates, 10.26% were able to produce biofilms as shown on Congo red agar. However, the percentage of bacteria with positive biofilm in test tube, standard microtiter plate, and modified microtiter plate assays were 48.72%, 66.66%, and 73.72%, respectively. At least 92% of the biofilm forming isolates were multidrug resistant.ConclusionsSince most of the multidrug resistant strains produce biofilm, it seems necessary to provide continuous monitoring and determination of antibiotic susceptibility of clinical A. baumannii. This would help to select the most appropriate antibiotic for treatment

Nanoparticles Impact the Expression of the Genes Involved in Biofilm Formation in S. aureus, a Model Antimicrobial-Resistant Species

Background:     Infection with resistant bacteria are still reported in hospitals despite the routine cleaning of hospital surfaces. Presence of drug-resistant microbes in the on environment of hospitals and on medical equipment is indicative of the need for control measures which could impact the emergence of such microbes. In addition, biofilms are increasingly associated with human infections and it necessitates careful considerations on usage of a diverse range of medical devices, such as catheters, implants and pacemakers in hospitals.  Methods:      This study was designed to compare the effect of silver, ZnO nanoparticles and curcumin on drug-resistant Gram-positive and Gram-negative bacteria which were already isolated from different wards of the hospital. The MIC value were determined for silver, curcumin and ZnO nanoparticles. As the second step, the expression level of the genes involved in biofilm formation in S. aureus, including icaA, icaD, fnbA and fnbB, was studied to analyze the physiological reaction to controlled concentrations of such nanoparticles using RT-qPCR assessments. Results:     In this study, a total of 172 bacterial isolates were recovered from clinical and environmental samples (96 and 76 isolates, respectively). API-20 test revealed that these isolates belonged to 8 species. All antimicrobial resistant isolates were susceptible to the metal oxide nanoparticles. The results of q-PCR in this study showed that the expression of icaA and icaD genes in the presence of silver, curcumin and zinc nanoparticles were not significantly reduced compared to the control samples. But, exposure to nanoparticles reduced the expression of fnbA and fnbB genes from 0.46 to 0.06. Conclusion:  The results of our study showed that nanoparticles are highly effective on antibiotics- resistant isolates and these compounds can be used in the treatment of resistant bacteria. In addition, this study also demonstrates the promising potential of using nanoparticles as anti-biofilm formation agents

Effectiveness of photodynamic therapy on the treatment of chronic periodontitis: a systematic review during 2008–2023

ObjectiveThis study investigated the effect of photodynamic therapy on chronic periodontitis patients and then evaluated the microbial, immunological, periodontal, and clinical outcomes. The significant effects of photodynamic therapy obtained by in vitro and in vivo studies have made it a popular treatment for periodontal diseases in recent years. Photodynamic therapy is a novel bactericidal strategy that is stronger, faster, and less expensive than scaling and root planing.MethodThis study registered on PROSPERO (CRD42021267008) and retrieved fifty-three randomized controlled trials by searching nine databases (Medline, Embase, Scopus, Open Gray, Google Scholar, ProQuest, the Cochrane Library, Web of Science, and ClinicalTrials.gov) from 2008 to 2023. Of 721 records identified through database searches following title and full-text analysis, and excluding duplicate and irrelevant publications, 53 articles were included in this systematic review. Fifty of the 53 eligible studies fulfilled all the criteria in the Joanna Briggs Institute’s (JBI’s) Checklist for RCTs; the remaining articles met 9–12 criteria and were considered high quality.ResultsThe present study showed that photodynamic therapy in adjunct to scaling and root planing has the potential to improve periodontal parameters such as clinical attachment loss or gain, decrease in bleeding on probing, and probing pocket depth. In addition, photodynamic therapy decreases the rate of periodontal pathogens and inflammation markers, which, in turn, reduces the progression of periodontitis.ConclusionPhotodynamic therapy is considered a promising, adjunctive, and low-cost therapeutic method that is effective in tissue repair, reducing chronic periodontitis, reducing inflammation, and well-tolerated by patients

Prevalence of Methicillin-resistant (MRSA) gene in Staphylococcus aureus isolates expressing PantonValentin Leukocidin (pvl) gene recovered from clinical cases in Rasht hospitals

Background & Objective: Panton-Valentine Leukocidin (PVL) is associated with strains of Staphylococcus aureus that produce a high level of virulence which is characterized by skin abscesses and acute necrosis. Goals: The aim of this study was to investigate the prevalence of pvl gene and its relationship with Methicillin- resistant Staphylococcus aureus (MRSA) in isolated samples taken from hospitalized patients in Rasht, north of Iran. Materials & Methods: During a six-month treatment period, a total of 92 clinical isolates of Staphylococcus were obtained. Initial tests were performed using the Disk Diffusion Method and Methicillin resistance test determined by an Oxacillin disk. In order to elucidate the frequency detection of pvl gene, standard PCR was accomplished using specific primers and then pvl positive isolates were further analyzed for the presence of mecA gene by the use of specific primers in PCR. Result: In total, 18 isolates (19.56%) were shown to be positive in terms of their carrying the pvl gene among which, 15 isolates (83.33%) were MRSA, 3 (16.66%) were MSSA, and 8 (44.44%) were positive for mecA gene. Conclusion: Despite the existence of pvl genes in MRSA isolates, PVL toxin producing strains of Staphylococcus aureus are serious threats for health. So, it seems that achieving a rapid and repeatable method for medical center, will help the timely diagnosis and control of PVL- producing strains

Studying the Relationship between the Ability of Biofilm Formation and Antibiotic Resistance in Acinetobacter baumannii Clinical and Environmental Isolates in Tehran, 2015

Abstract Background: Acinetobacters are aerobic gram-negative bacteria which are distributed widespread in soil and water. The bacteria are isolated from cultured skin, mucous membranes, secretions and hospital environment. Acinetobacter baumannii, is a strain that more frequently isolated. Acinetobacter strains are often resistant against antimicrobial agents. Materials and Methods: The method of this study was based on field, observation and test. On August and October 2015, samples were isolated from the soil and water of the Sadeghieh Square river in Tehran, respectively, and were transferred to the laboratory in the ice pack. 50 baumannii samples were isolated by biochemical methods (TSI, SIM, OF and gram test). November 1394, 100 clinical samples were isolated from Imam Khomeini hospital by biochemical method, and in the culture media Mueller Hinton agar plates were transferred to the laboratory. Antibiogram test for 150 baumannii samples was performed. Biofilms formation of Acinetobacter baumannii environmental and clinical samples was investigated by Congo red agar and culture plate methods. Results: In all samples (clinical and soil), most of antibiotic resistance was 92% for imipenem and the resistance of water samples to imipenem was 99.9%. Biofilm formation by Congo red agar in water, soil, and clinical samles was resprctively 44%, 40% and 1%. All isolates were negative biofilm culture plate. Conclusion: Considering Acinetobacter baumannii resistance to antibiotics and the lack of biofilm formation of in clinical and environmental isolates, it was concluded that there wasn’t any relationship between antibiotic resistance and biofilm formation

An Investigation of the Presence of Oxacillinase genes (blaOXA-51 , bla OXA-23, blaOXA-58, bla OXA-24 ) in Acinetobacter baumannii Strains Isolated from Patients in Tehran Imam Khomeini Hospital and Shiraz Namazi Hospital, Iran

Background and Objectives: Acinetobacter baumannii is an opportunistic bacterium and a cause of infection in human. This bacterium has complicated the treatment process by becoming resistant to many antibiotics. One of the most important characteristics of this organism is resistance to carbapenems. There has been several reports regarding isolation of carbapenem resistance in A. baumannii in Iran. The aim of this study was to evaluate antibiotic resistance pattern and presence of oxacillinase in Acinetobacter baumannii isolated from clinical specimens. Methods: In this case cross-sectional study, a total of 140 isolates of Acinetobacter baumannii were collected from clinical specimens in Tehran Imam Khomeini Hospital and Shiraz Namazi Hospital, 2013-2014. The strains were identified using standard culturing, biochemical, and molecular methods. Antibiotic susceptibility test was performed by disk diffusion method against 12 different antibiotics, Then, multiplex PCR assay was used to detect the presence of 4 carbapenemase genes (blaOXA-23, 24, 51, 58). Results: Among the strains, a resistance above 80% was seen to imipenem, gentamicin, amikacin, co-trimoxazole, cefepime, ceftazidime, tetracycline, and rifampicin antibiotics. Also, the samples isolated from clinical specimens in Namazi Hospital of Shiraz city, showed higher resistance to tigecycline, ampicillin, sulbactam, and ciprofloxacin. The multiplex PCR technique showed that the presence of blaOXA-23, blaOXA-24, and blaOXA-58 genes were, respectively, 82.1%, 4.3%, and 0.7%. All 14 strains identified phenotypically, carried blaOXA-51 gene. Conclusion: According to the findings of this study, a resistance above 80% to the majority of antibiotics seen in our clinical isolates, emphasizes the necessity of using new drugs, such as tigecycline. Also, high presence (82.1%) of blaOXA-23 among the carbapenem resistant isolates of Acinetobacter baumannii emphasizes the importance of this gene in the induction of resistance