The potential of therapeutic hyperthermia to eradicate Staphylococcus aureus bacteria; an in vitro study.

Staphylococcus aureus is one of the most common infectious agents, causing morbidity and mortality worldwide. Most pathogenic bacteria are classified in the group of mesophilic bacteria and the optimal growth temperature of these bacteria changes between 33 and 41 °C. Increased temperature can inhibit bacterial growth and mobility, which in turn, can trigger autolysis and cause cell wall damage. Hyperthermia treatment is defined as a heat-mediated treatment method applied using temperatures higher than body temperature. Nowadays, this treatment method is used especially in the treatment of tumours. Hyperthermia treatment is divided into two groups: mild hyperthermia and ablative or high-temperature hyperthermia. Mild hyperthermia is a therapeutic technique in which tumour tissue is heated above body temperature to produce a physiological or biological effect but is often not aimed at directly causing significant cell death. The goal of this method is to achieve temperatures of 40-45 °C in human tissues for up to 2 h. Hyperthermia can be used in the treatment of infections caused by such bacterial pathogens. In addition, using hyperthermia in combination with antimicrobial drugs may result in synergistic effects and reduce resistance issues. In our study, we used two different temperature levels (37 °C and 45 °C). We assessed growth inhibition, some virulence factors, alteration colony morphologies, and antimicrobial susceptibility for several antibiotics with three methods (Kirby-Bauer, E-test and broth microdilution) under hyperthermia. In the study, we observed that hyperthermia affected the urease enzyme, antibiotic sensitivity levels showed synergy with hyperthermia, and changes occurred in colony diameters and affected bacterial growth. We hypothesise that hyperthermia might be a new therapeutic option for infectious diseases as a sole agent or in combination with different antimicrobials.

Inhibition of swarming motility using in vitro hyperthermia.

Hyperthermia is a therapeutic technique in which body tissue is exposed to temperatures in the region of 40-45 °C to induce a physiological or biological effect. Swarming motility is an important virulence factor for Proteus mirabilis and Pseudomonas aeruginosa and swarming phenomenon is a coordinated multicellular movement of differentiated bacterial population over semi-solid surfaces. In this study, we aimed to investigate the inhibitory effect of hyperthermia on bacterial swarming motility using a modified thermobiogram method and show the potential of this thermal method to treat bacterial infections. Ten P. mirabilis and 10 P. aeruginosa clinical isolates were included in the study. Sheep blood agar (SBA) plates were prepared and inoculated with bacterial suspensions of clinical isolates. Inoculated SBA plates were incubated inside 2 different incubators; at 37 °C and 45 °C for 20 h. The diameter of bacterial growing zones (swarming diameters) were measured every 2 h and noted. Finally, Gram stains of the isolates were prepared for microscopic examination. Wilcoxon signed-rank test was used to compare the swarming inhibition rates of the isolates incubated at 37 °C and 45 °C. Regarding P. mirabilis species, a significant difference was found between two different temperatures (P = 0.0078). So, a temperature at the level of hyperthermia significantly inhibited the swarming motility of P. mirabilis isolates. In addition, transformation to coccus form was observed at 45 °C. We speculate that these findings might be useful for employing thermal therapies including hyperthermia method to treat infectious diseases caused by swarming bacterial pathogens in the future.

Investigation of an outbreak of Elizabethkingia meningoseptica on a pediatric intensive care unit.

Objective: This paper reports an Elizabethkingia meningoseptica outbreak on a pediatric intensive care unit with emphasis on investigation of outbreak source, infection control interventions, patient characteristics and comparative antimicrobial susceptibility results. Methods: This was an ambidirectional cohort study conducted in a university hospital 20-bed pediatric intensive care unit. Patient ages ranged from 4 to 11 months, with a median age of 9 months. 83% of the patients had severe underlying conditions. Samples from staff and environmental surfaces were obtained to identify a common source of infection. Antimicrobial susceptibility tests of isolated bacteria were done using the disk diffusion method and the Vitek®2 automated system. Results: Environmental surveillance revealed contamination of the water reservoirs of two different mechanical ventilators. In-vitro antimicrobial susceptibility testing results with two different methods (Vitek®2 and disk diffusion) were coherent for most of the investigated antibiotics, but without coherence for ciprofloxacin and levofloxacin. Resistance was found to the relatively new antibiotics ceftaroline and ceftazidime-avibactam. Conclusions: E. meningoseptica is a significant cause of nosocomial infections, with high mortality especially in children. Investigation of the outbreak source and continuation of intensive infection control precautions are vital to handle E. meningoseptica outbreaks in PICUs. Using quinolones according to testing results of automated AST systems may lead to inadequate treatment and foster the selection of resistant strains.

Investigation of heteroresistant vancomycin intermediate Staphylococcus aureus among MRSA isolates.

INTRODUCTION: Heteroresistant vancomycin intermediate Staphylococcus aureus (hVISA) testing is recommended when therapeutic failure is suspected in the clinics. In our research, we aimed to investigate the prevalence of hVISA among methicilline-resistant S. aureus (MRSA) isolates in our university hospital and compared three methods for detection of hVISA. METHODOLOGY: One hundred MRSA clinical isolates were collected in our medical microbiology laboratory between 01.04.2018 and 01.10.2019. For screening of hVISA, we used two screening agar plates and used one commercial medium; brain heart infusion agar (BHI) plates containing 4 µg/mL vancomycin and 16 g/Lt casein (BHIA-VC; Satola's test), BHI agar plates containing 4 µg/mLvancomycin (BHIAV), and commercially obtained vancomycin resistant Enterococci (VRE) agar for detetection of hVISA. Colonies which could grow on plates were counted manually at 24th and 48th hours. RESULTS: Among 100 MRSA isolates, 43 (43%) were found as hVISA using Satola's test. BHIAV and VRE agar screening test results were found 70% and 4%, respectively. Finally, at the step, MIC values of 20 (47%) hVISA isolates reduced to 2 µg/mL after sub culturing for the gradient test. CONCLUSIONS: We found higher rates of hVISA comparing other studies in Turkey. Both VRE agar and BHIAV screening test failed to detect hVISA properly. Meropenem in combination with vancomycin inhibited the growth of 90% hVISA isolates in our study.

Investigation of bacteremia after debonding procedures.

OBJECTIVE: The purpose of this study is to investigate the effect of debonding procedures after completion of orthodontic treatments on bacteremia. MATERIALS AND METHODS: Twenty-eight patients who were treated with fixed orthodontic treatment at the Faculty of Dentistry's Department of Orthodontics at Gaziantep University and who had an indication of debonding were selected for this study, and blood samples were taken from these patients at different times and examined for bacteremia. Blood culture samples were taken from the antecubital veins of the patients prior to debonding (T0), immediately after removing the bracket (T1), and immediately after cleaning the composite residues and plaque deposits on the enamel surface (T2). The blood samples were then inoculated in blood culture bottles and investigated for bacterial growth. RESULTS: The results showed that there was no bacterial growth in the blood samples taken at T0 and T1, whereas 10 of the blood culture samples taken at T2 showed bacterial growth including the following bacteria; Streptococcus viridans, Streptococcus mitis, Streptococcus parasanguinis, Streptococcus salivarius, Streptococcus oralis, Staphylococcus aureus, Actinomyces oris, Actinomyces naeslundii and Klebsiella pneumoniae. CONCLUSION: It was concluded that patients in the risk group could develop bacteremia during debonding procedures. The presence of these bacteria in sterile blood suggested the possibility of bacterial endocarditis.