Effects of Atmospheric Plasma Corona Discharge on Agrobacterium tumefaciens Survival

Soil-borne pathogenic microorganisms are known to cause extensive crop losses. Agrobacterium tumefaciens, a member of the Proteobacteria, causes the neoplastic crown gall disease in plants. Plant protection is mainly based on toxic chemicals that are harmful to the environment. The use of cold atmospheric-pressure plasma is an attractive method for microbial eradication. Its antimicrobial mechanism includes the formation of large quantities of reactive oxygen species (ROS). The advantages of eradicating bacteria using cold plasma are not needed for chemicals, short treatment, and environmental temperatures. This study examined the impact of plasma corona discharge exposure on A. tumefaciens viability, membrane permeability, relative cell size, and ROS formation. The results showed that 90 s of plasma exposure led to a reduction by four orders of magnitude when the initial concentration was 1 × 107 CFU/mL and in a dry environment. When the initial concentration was 1 × 106 CFU/mL, 45 s of exposure resulted in total bacterial eradication. In a liquid environment, in an initial concentration of 2.02 × 106 CFU/mL, there was no complete bacterial eradication even at the most prolonged examined exposure (90 s). The influence of plasma treatment on the membrane permeability of A. tumefaciens, and their possible recovery, were analyzed using flow cytometer analysis using propidium iodide (PI). When the plasma-treated bacteria were suspended in Luria–Bertani (LB) (rich medium), the PI-positive count of the plasma-treated bacteria after two hours was 12 ± 3.9%. At the 24th hour, this percentage was only 1.74 ± 0.6%, as the control (0.7 ± 0.1%). These results may indicate the repair of the plasma-treated bacteria that were suspended in LB. At the 24th hour, the relative cell size of the treated bacteria shifted to the right, to ~3 × 104 forward side scatter (FSC), about 0.5-fold higher than the untreated cells. Measurement of the ROS showed that the intracellular fluorescence of the 90-s plasma-treated cells led to significant fluorescence formation of 32 relative fluorescence units (RFU)/cell (9 × 104 fold, compared to the nontreated cells). This study showed that cold plasma is a useful method for A. tumefaciens eradication. The eradication mechanism involves ROS generation, membrane permeability, and changes in cell size.

Efficacy of Ceftazidime-Avibactam Versus Polymyxin B and Risk Factors Affecting Clinical Outcomes in Patients With Carbapenem-Resistant Klebsiella pneumoniae Infections a Retrospective Study

Background: The worldwide outbreak of carbapenem-resistant Klebsiella pneumoniae (CRKP) has become an urgent public health problem. High mortality and lack of effective treatments further pose new challenges to control this infection. However, studies about the evaluation of available antibiotics for CRKP infection are limited. The present study aimed to compare the efficacy of polymyxin B versus ceftazidime-avibactam (CAZ/AVI) in Chinese patients with CRKP infections and to identify risk factors affecting 7-day bacterial eradication and 28-day all-cause mortality.Methods: From January 8, 2018, to July 6, 2020, a total of 115 adult CRKP infected patients from two tertiary teaching hospitals in Shanghai, China were enrolled based on the inclusion and exclusion criteria. By reviewing electronic medical records of these patients, demographic and clinical data were extracted. The selected patients were divided into polymyxin B and CAZ/AVI groups according to primary antibiotic exposure to compare therapeutic effects. Binary logistic and cox’s regression analysis were performed to identify risk factors for 7-day bacterial eradication and all-cause mortality.Results: One hundred and five patients were treated with polymyxin B (67.8%) or CAZ/AVI (32.2%). Patients in the CAZ/AVI group had significantly lower rates of 28-day mortality (8.1 vs 29.5%, p = 0.013), higher microbiological eradication and 28-day clinical success. Multivariate analysis showed that Charlson comorbidity index (≥3) and prior antibiotic use within 90 days were independent risk factors for poor microbiological eradication. Cox’s regression analysis indicated that the length of hospitalization after CRKP infection and baseline creatinine clearance negatively affected 28-day mortality.Conclusion: CAZ/AVI was more effective than polymyxin B and appeared to be a promising drug for CRKP infection, especially for critically ill patients.

Biofilm: An emergent form of bacterial life-a review

Biofilm formation is a method for bacteria to adapt for its survival, to put it another way, it act as a shield and prevents bacterial eradication. Microbial biofilms are one of the major reasons for progession of periradicular pathology. The article aims to concise and stratify the literature about, various factors that leads to biofilm formation their adaptation mechanisms, biofilms role in progression of peri-radicular infections, models developed to create biofilms, observation techniques of endodontic biofilms, and the effects of root canal irrigants and medicaments as well as lasers on endodontic biofilms.

Evaluation of Acute Renal Failure After Acinetobacter Baumannii-based Ventilator-associated Event: A Retrospective Cohort Study

Background: Ventilator-associated event (VAE) is the major complication caused mechanical ventilation (MV). We aimed to evaluate whether acute renal failure (ARF) has developed in patients who had been followed-up due to diagnosis of VAE with Acinetobacter baumannii (AcB), and whether renal replacement therapy (RRT) was used, and its relationship with mortality in patients who developed colistin during their treatment.Methods: Retrospective evaluation of the hospital electronic information system records of 2,622 patients were conducted in three years. Patients who had AcB-related VAE and underwent parental colistin treatment were evaluated according to age, gender, diagnosis for intensive care unit (ICU) administration, Acute Physiology and Chronic Health Evaluation (APACHE) II score, colistin dose and treatment duration, requirement for additional antibiotics, total time required for MV, total duration of ICU stay, presence of septic shock, requirement for percutaneous dilatation tracheostomy (PDT), ARF staging according to Kidney Disease Improving Global Outcomes criteria, requirement for RRT and mortality.Results: Total number of VAE cases was 85 (3.19%). AcB-related VAE was detected in 28 patients (32.9%). Bacterial eradication was achieved in 14 patients (50%), clinical response was received in 14 patients (50%), mean colistin dose was 298.2±85.5 mg/day, mean duration of colistin treatment was 14.3±8.6 days. ARF was detected as Stage-I in eight patients (28.6%), Stage-II in four (14.3%) and Stage-III in eight patients (28.6%). There was no difference between patients in need of RRT and those who did not, in terms of age, gender and body mass index. APACHE II score, bacterial eradication, presence of septic shock, clinical response to therapy, daily dose of colistin, duration of colistin treatment, MV duration, PDT requirement and time were similar in groups receiving RRT or not.Conclusion: Colistin treatment of AcB-related VAE caused ARF in 71.5% of the patients and led to serious conditions in 25% of patients requiring RRT.

Streptococcus pyogenes M1T1 Variants Induce an Inflammatory Neutrophil Phenotype Including Activation of Inflammatory Caspases

Invasive infections due to group A Streptococcus (GAS) advance rapidly causing tissue degradation and unregulated inflammation. Neutrophils are the primary immune cells that respond to GAS. The neutrophil response to GAS was characterised in response to two M1T1 isolates; 5448 and animal passaged variant 5448AP. Co-incubation of neutrophils with 5448AP resulted in proliferation of GAS and lowered the production of reactive oxygen species when compared with 5448. Infection with both strains invoked neutrophil death, however apoptosis was reduced in response to 5448AP. Both strains induced neutrophil caspase-1 and caspase-4 expression in vitro, with inflammatory caspase activation detected in vitro and in vivo. GAS infections involving strains such as 5448AP that promote an inflammatory neutrophil phenotype may contribute to increased inflammation yet ineffective bacterial eradication, contributing to the severity of invasive GAS infections.