Meropenem in combination with baicalein exhibits synergism against extensively drug resistant and pan-drug-resistant Acinetobacter baumannii clinical isolates in vitro.

Several studies have demonstrated that the effectiveness of carbapenems against drug-resistant Acinetobacter baumannii infections has been decreasing. Combination therapy with two or more drugs is currently under investigation to overcome the emerging resistance against carbapenems. In this study, we tested the possible synergistic interactions of a potent antibacterial flavonoid, baicalein, with meropenem to illustrate this duo's antibacterial and antibiofilm effects on 15 extensively drug resistant or pan-drug-resistant (XDR/PDR) A. baumannii clinical isolates in vitro. Isolates included in the study were identified with MALDI-TOF MS, and antibiotic resistance patterns were studied according to EUCAST protocols. Carbapenem resistance was confirmed with the modified Hodge test, and resistance genes were also analyzed with genotypical methods. Then, checkerboard and time-kill assays were performed to analyze antibacterial synergism. Additionally, a biofilm inhibition assay was performed for screening the antibiofilm activity. To provide structural and mechanistic insights into baicalein action, protein-ligand docking, and interaction profiling calculations were conducted. Our study shed light on the remarkable potential of the baicalein-meropenem combination, since either synergistic or additive antibacterial activity was observed against every XDR/PDR A. baumannii strain in question. Furthermore, the baicalein-meropenem combination displayed significantly better antibiofilm activity in contrast to standalone use. In silico studies predicted that these positive effects arose from inhibition by baicalein of A. baumannii beta-lactamases and/or penicillin-binding proteins. Overall, our findings highlight the prospective potential benefits of baicalein in combination with meropenem for the treatment of carbapenem-resistant A. baumannii infections.

[Relationship of Hypervirulent Capsular Genotypes of Klebsiella pneumoniae with Antibiotic Susceptibility and Beta-Lactamase Genes]. / Klebsiella pneumoniae Hipervirülan Kapsül Genotiplerinin Antibiyotik Duyarliligi ve Beta-Laktamaz Genleri ile Iliskisi.

Klebsiella pneumoniae which is a causative agent of nosocomial infections, is protected from phagocytosis and the lethal effect of serum bactericidal proteins owing to its capsular polysaccharides (CPS). The important leading problem in treating infections caused by this bacterium that successfully develops antimicrobial resistance, especially via mobile genetic elements, is that it acquires beta-lactamase genes, which are responsible for the resistance against beta-lactam antibiotics. Due to the increase in studies targeting capsular polysaccharides in developing strategies for vaccination and treatment, we aimed to investigate the possible relationship of the capsular genotypes of K.pneumoniae isolates obtained from various clinical specimens with antibiotic susceptibility and beta-lactamase genes. In K.pneumoniae clinical isolates; K1, K2, K5, K20, K54 and K57, which are known as hypervirulent capsular types, were investigated by polymerase chain reaction (PCR) method. In isolates whose capsular genotypes were determined, antibiotic susceptibility was examined by Kirby-Bauer disc diffusion method. Colistin resistance was investigated by the broth microdilution method. Carbapenem resistance was confirmed with the carbapenem inactivation test. The beta-lactamase genes blaCTX-M1, blaCTX-M2, blaCTX-M9, blaCTX-M8/25, blaKPC, blaNDM-1, and blaOXA-48-like were investigated by using PCR. Of the 38 K.pneumoniae isolates whose capsular genotypes were determined, 15 (39.5%), 12 (31.6%), seven (18.4%), two (5.3%), one (2.6%) and one (2.6%) were K5-CPS, K2-CPS, K20-CPS, K1-CPS, K54-CPS and K57-CPS genotypes, respectively. blaOXA-48-like, blaNDM-1, and blaCTX-M1 were detected in 68.4, 10.5, and 7.9%, whereas coexistence of blaOXA-48-like with blaNDM-1, and blaOXA-48-like with blaCTX-M1 were determined in 7.9, and 5.3% of the isolates, respectively. The relationship of the blaCTX-M1 gene, detected only in three K20-CPS isolates, was found to be statistically significant with this genotype. In addition, of the blaNDM-1-positive four isolates, three were K5-CPS, and one was K2-CPS, while blaOXA-48-like was similarly detected mostly in K5-CPS and K2-CPS (10 and 9 isolates, respectively). Except for the two isolates that were resistant to colistin, one K1-CPS and the other K5-CPS, the highest resistance was detected against cefotaxime (36/38) and the lowest resistance was detected against gentamicin (23/38) as a result of antibiotic susceptibility tests. The resistance relationship of K5-CPS isolates with amoxicillin/clavulanate, piperacillin/tazobactam, cefoxitin and ertapenem and the susceptibility relationship of K20-CPs isolates with amoxicillin/clavulanate, piperacillin/tazobactam, imipenem, tetracycline and trimethoprim/sulfamethoxazole were found as statistically significant. Our study is the first to investigate the relationship between K.pneumoniae capsular genotypes and beta-lactamase genes in Turkey. As a result, it is believed that this research will contribute to the determination of vaccine and treatment options by providing data to wider and regional studies that will examine other capsule genotypes and antibiotic resistance genes to clarify the importance of the capsule in virulence.

The Distribution of Cytotoxic Necrotizing Factors (CNF-1, CNF-2, CNF-3) and Cytolethal Distending Toxins (CDT-1, CDT-2, CDT-3, CDT-4) in Escherichia coli Isolates Isolated from Extraintestinal Infections and the Determination of their Phylogenetic Relationship by PFGE.

Backgrounds: Diagnostic markers of extraintestinal infection in Escherichia coli (E. coli) remain unclear in the literature. Extraintestinal pathogenic E. coli (ExPEC) is differentiated from other E. coli isolates in terms of virulence factors, such as host cell adhesion, invasion, cytotoxic necrotizing factor (CNF (cnf1-cnf3)) and cytolethal distending toxin (CDT (cdt1-cdt4) that are responsible for cell death. We aimed to investigate the frequency of CNF-CDT and the relationship between the clinical diagnosis and genotypes in E. coli isolates with different clinical origins. Methods: A total of 646 E. coli isolates (obtained from 645 patients) isolated from different infection sites other than the intestine were evaluated in aspects of the CNF, CDT virulence genes, phylogenetic grouping, and phylogenetic relationship by using PCR and PFGE. Results: At least one virulence gene was present in 156 (24%) of the 646 ExPEC isolates. We detected cnf1, cnf2, and cnf3, in 78, 12, and 20 ExPEC isolates, respectively. Also, cdt1, cdt2, cdt3, and cdt4 genes were present in 20, 4, 4, and 4 isolates, respectively. Some isolates harbored more than one gene, being cnf1-cnf3 (n = 6), cnf1-cdt1 (n = 4), and cdt1-cdt4 (n = 4). These 156 isolates were distributed into 106 large clusters by PFGE. Virulent ExPEC is primarily related to groups B2 (60%) and D (32%). Conclusion: To our knowledge, this study demonstrated the presence of cnf2, cnf3, cdt1, cdt2, cdt3, and cdt4 genes for the first time in the literature for Turkey. The widespread presence of the CNF gene in E. coli helps distinguish ExPEC from commensal isolates.

NDM-1 and rmtC-Producing Klebsiella pneumoniae Isolates in Turkey.

BACKGROUND: The resistance of aminoglycosides in strains that produce beta-lactamase can be developed through the multidrug resistant encoding genes carried by common plasmids. Recently, the association between 16S rRNA methyltransferase resistance and beta-lactamase enzymes carried by the same plasmids has drawn increased attention from researchers, particularly the association in aminoglycoside-resistant strains with a minimum inhibitory concentration (MIC) of ≥ 256 µg/mL. OBJECTIVES: We aimed to investigate the co-existence of 16S rRNA methyltransferase and beta-lactamase genes in multidrug resistant (MDR) Klebsiella pneumoniae strains isolated from clinical samples. METHODS: We determined the molecular mechanisms of aminoglycoside resistance and its relationship with resistance to carbapenem and beta-lactam group antibiotics in 40 extended-spectrum beta-lactamase (ESBL)-positive carbapenem- and aminoglycoside-resistant K. pneumoniae strains. Multidrug resistant K. pneumoniae was isolated from various clinical samples in the faculty of medicine of Cukurova University, Turkey. First, the resistance of aminoglycoside and beta-lactam antibiotics was phenotypically investigated using the Kirby-Bauer disk diffusion test, double disk synergy test, and modified Hodge test. The MIC values of aminoglycoside were determined using the agar dilution method. Polymerase chain reaction was performed to detect the carbapenemases, ESBL, and 16S rRNA methyltransferase genes. The results were confirmed by a sequence analysis. RESULTS: Twenty K. pneumoniae strains showed resistance to amikacin, and 40 were resistant to gentamicin. The MIC value was found to be > 512 µg/mL in five amikacin-resistant strains and > 128 µg/mL in 10 gentamicin-resistant isolates. The rmtC gene, a type of 16S rRNA methyltransferase, was amplified in four isolates (MIC amikacin: > 512 µg/mL, gentamicin: > 128 µg/mL). Of these four isolates, three had the blaNDM-1 gene and all contained at least one ESBL gene. CONCLUSIONS: This study demonstrated the co-existence of rmtC and blaNDM-1 genes for the first time in Turkey. The spread of this resistant type should be monitored and limited through molecular surveillance.

Detection of primary clarithromycin resistance of Helicobacter pylori and association between cagA (+) status and clinical outcome.

Helicobacter pylori was examined in 110 patients (82 (74.5) with gastritis, 18 (16.4) with duodenitis, six (5.5) with duodenal ulcer and gastroesophageal reflux, and four (3.6 %) with normal) with gastrointestinal problems living in rural area, no history of macrolide use, and detected by culture (71.8) or direct detection from gastric biopsies by PCR (82.7 %). Also, cagA gene was identified using PCR and was found positive in 68/91 (74.7 %) strains. The prevalence of clarithromycin-resistant H. pylori was investigated by two methods including PCR-RFLP (7.7 (A2142G 1.1 and A2143G 6.6 %)) and twofold agar dilution (8.9 %) to detect phenotypic and genotypic status simultaneously. Among all the H. pylori positive patients, eight (8.8 %) isolates were found to be resistant to clarithromycin by at least one of the AD and/or PCR-RFLP methods. H. pylori positive rates were significantly correlated with patients' sex, age, and endoscopic findings (p = 0.040, <0.001 and <0.001, respectively). There were no differences in gender or endoscopic findings related to cagA (+) and cagA (-) patients. The gene of cagA was not significantly helpful in predicting the clinical outcome of H. pylori infection alone. In conclusion, we revealed that there was a low prevalence of primer clarithromycin resistance in patients living in rural area with no history of macrolide use. The prevalence of mutant strains among the macrolide-resistant H. pylori varies even geographically between close provinces.

Prevalence and genotypes of Helicobacter pylori in gastric biopsy specimens from patients with gastroduodenal pathologies in the Cukurova Region of Turkey.

The effects of Helicobacter pylori genotypes on clinical prognosis in the Cukurova region of Turkey were investigated by PCR. The prevalence of type I strains carrying the s1c allele, unlike in neighboring regions and countries, was found to be significantly higher in patients with gastritis and/or gastric ulcers (P = 0.001), and that of type I strains carrying the s1a allele was found to be significantly higher in patients with duodenal ulcers (P < 0.001). The cagA gene was strongly associated with the more virulent vacA genotypes (P < 0.001).