Prevalence and molecular characterization of colistin resistance in Pseudomonas aeruginosa isolates: insights from a study in Ardabil hospitals.

BACKGROUND: Pseudomonas aeruginosa is a common cause of nosocomial infections. However, the emergence of multidrug-resistant strains has complicated the treatment of P. aeruginosa infections. While polymyxins have been the mainstay for treatment, there is a global increase in resistance to these antibiotics. Therefore, our study aimed to determine the prevalence and molecular details of colistin resistance in P. aeruginosa clinical isolates collected between June 2019 and May 2023, as well as the genetic linkage of colistin-resistant P. aeruginosa isolates. RESULTS: The resistance rate to colistin was 9% (n = 18) among P. aeruginosa isolates. All 18 colistin-resistant isolates were biofilm producers and carried genes associated with biofilm formation. Furthermore, the presence of genes encoding efflux pumps, TCSs, and outer membrane porin was observed in all colistin-resistant P. aeruginosa strains, while the mcr-1 gene was not detected. Amino acid substitutions were identified only in the PmrB protein of multidrug- and colistin-resistant strains. The expression levels of mexA, mexC, mexE, mexY, phoP, and pmrA genes in the 18 colistin-resistant P. aeruginosa strains were as follows: 88.8%, 94.4%, 11.1%, 83.3%, 83.3%, and 38.8%, respectively. Additionally, down-regulation of the oprD gene was observed in 44.4% of colistin-resistant P. aeruginosa strains. CONCLUSION: This study reports the emergence of colistin resistance with various mechanisms among P. aeruginosa strains in Ardabil hospitals. We recommend avoiding unnecessary use of colistin to prevent potential future increases in colistin resistance.

Photocatalytic removal of Escherichia coli from aquatic solutions using synthesized ZnO nanoparticles: a kinetic study.

Development of effective and low-cost disinfection technology is needed to address the problems caused by an outbreak of harmful microorganisms. In this work, an effective photocatalytic removal of Gram-negative bacteria Escherichia coli from aqueous solution was reported by using ZnO nanoparticles under UV light irradiation. The effect of various parameters such as solution pH, ZnO dosage, contact time and initial E. coli concentration were investigated. Maximum photocatalytic disinfection was observed at neutral pH because of the reduced photocatalytic activity of ZnO at low and high pH values originated from either acidic/photochemical corrosion of the catalyst and/or surface passivation with Zn(OH)(2). As the ZnO dosage increased, the photocatalytic disappearance of E. coli was continuously enhanced, but was gradually decreased above 2 g/L of ZnO due to the increased blockage of the incident UV light used. The optimum ZnO dosage was determined as 1 g/L. Photocatalytic removal of E. coli decreased as initial E. coli concentration increased. Three kinetic models (zero-, first- and second-order equations) were used to correlate the experimental data and to determine the kinetic parameters.

Effect of Streptococcus mutans on the flexural strength of resin-based restorative materials.

BACKGROUND: There are a limited number of studies about the effects of microbial aging on the mechanical properties of restorative materials. Therefore, this study aimed to evaluate the effect of simulated aging with Streptococcus mutans on the flexural strength of different resin-based materials. MATERIALS AND METHODS: This experimental study was performed on the blocks of different types of restorative materials including composite resin, giomer, and a resin-modified glass ionomer (RMGI). Moreover, three types of aging, such as 30-day storage in distilled water, S. mutans, and germ-free culture medium, were used in this study. The three-point bending flexural strength of the specimens before and after aging was measured according to the International Organization for Standardization-4049 standard. Data were analyzed by two-way ANOVA and post hoc Tukey's tests. A P < 0.05 was considered statistically significant. RESULTS: Results showed that the 30-day aging with the S. mutans significantly reduced the flexural strength of all three types of materials (P = 0.00). In all restorative materials, storage in a bacteria-free culture medium acted the same as distilled water, and there was no significant difference between these two solutions in terms of the flexural strength of the material, compared to the before-aging strength (P > 0.05). Furthermore, no significant difference was observed between S. mutans-based aging and distilled water aging regarding RMGI (P = 0.75). CONCLUSION: It can be concluded that aging by S. mutans reduced the flexural strength in all three restorative materials.

Evaluating the efficiency of TaqMan real-time PCR and serological methods in the detection of Brucella spp. in clinical specimens collected from suspected patients in Ardabil, Iran.

BACKGROUND: This study aims to evaluate the efficiency of the TaqMan real-time PCR and serological methods in detecting Brucella spp. in clinical specimens that have been collected from suspected patients in Ardabil, Iran. METHODS: In this cross-sectional study, a total of 113 consecutive patients suspected of brucellosis who were referred to the three hospitals in Ardabil province were selected. In the first step, the diagnosis of brucellosis was performed by serological methods including the Rose Bengal slide agglutination test, Wright test, 2-ME test, and BrucellaCapt test. In the next step, TaqMan real-time PCR with primer and probe targeting the bcsp31 gene was used for the detection of Brucella spp. Specificity, sensitivity, and positive and negative predictive values of the TaqMan real-time PCR assay were calculated. RESULTS: Among 113 suspected patients with different clinical manifestations, the Rose Bengal slide agglutination test, Wright test, and 2-ME test were positive in 60 cases; however, the BrucellaCapt test titer was 1:160 for one patient. Six patients had high initial serum antibody titers; 2-ME titers of ≥1:640; STA titers of ≥1:1280; BrucellaCapt titers of ≥ 1:2560. Among positive cases, no correlation was observed among gender, age, and life (residence) in urban or rural areas. The TaqMan real-time PCR was positive in 35% of all 60 positive cases. The comparison of the results of the BrucellaCapt and TaqMan real-time PCR methods revealed that 19 out of 54 (35.2%) and 2 out of 6 (33.4%) BrucellaCapt positive cases with titers of >1:320 and ≤ 1:320 were positive, respectively. The sensitivities and specificities of the TaqMan real-time PCR assay were 49.1% and 100% respectively. CONCLUSION: The sensitivity of the TaqMan real-time PCR assay was low in the diagnosis of brucellosis, while the BrucellaCapt test turned out to be a very valuable, sensitive, and specific test for the diagnosis of brucellosis in suspected patients and, thus, can provide reliable results in medical laboratories.

Potent anti-cancer effects of less polar Curcumin analogues on gastric adenocarcinoma and esophageal squamous cell carcinoma cells.

Curcumin and its chalcone derivatives inhibit the growth of human cancer cells. It is reported that replacement of two OH groups in curcumin with less polar groups like methoxy increases its anti-proliferative activity. In this study, we explored benzylidine cyclohexanone derivatives with non-polar groups, to see if they possess increased anti-cancer activity. Novel 2,6-bis benzylidine cyclohexanone analogues of curcumin were synthesized, and their inhibitory effects on gastric adenocarcinoma (AGS) and esophageal squamous cell carcinoma (KYSE30) cancer cells were studied using an MTT assay. Cell apoptosis was detected by EB/AO staining, and cell cycle was analyzed by flow cytometry. Real-time PCR was performed for gene expression analysis. All synthesized analogues were cytotoxic toward gastric and esophageal cancer cells and showed lower IC50 values than curcumin. Treatment with 2,6-Bis-(3-methoxy-4-propoxy-benzylidene)-cyclohexanone (BM2) was 17 times more toxic than curcumin after 48 h incubation. All novel compounds were more effective than curcumin in apoptosis induction and cell cycle arrest at G1 phase. These results suggest that less polar analogues of curcumin have potent cytotoxicity in vitro. However, they need to be investigated further, especially with animal tumor models, to confirm their chemotherapeutic activity in vivo.