Browsing by Author "Jovčić, Branko (57215743197)"

Purpose: The present study investigated the role of resistance-nodulation-cell division (RND) efflux pumps in tigecycline resistance of Acinetobacter baumannii clinical isolates recovered from three Western Balkan countries (Serbia, Bosnia and Herzegovina and Montenegro). Methods: A total of 37 A. baumannii isolates recovered from seven tertiary care hospitals in 2016 and 2022 were tested against tigecycline using broth microdilution method. Then, efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP) was used to determine the involvement of efflux pumps in tigecycline resistance. Molecular typing was performed by pulsed-field gel electrophoresis (PFGE) and multiplex PCR-based determination of clonal lineage. Regulators of efflux pumps were analyzed for amino acid substitutions, while reverse transcription-quantitative PCR (RT-qPCR) enabled quantification of RND efflux pumps expression. Results: All tested isolates were interpreted as resistant to tigecycline and showed reduced tigecycline minimum inhibitory concentration (MIC) values in the presence of CCCP. PFGE analysis showed significant diversity among isolates grouped in cluster I including IC2 (n = 32) and IC3 (n = 1) isolates, while cluster II was comprised of four IC1 isolates. The most prevalent substitutions in AdeR were V120I and A136V and in AdeS G186V and N268H (n = 33). The Q262R substitution was detected in AdeL proteins of IC1 isolates, whereas no alterations were observed within AdeN. The expression of the adeB, adeG, and adeJ genes in selected isolates was upregulated in five (1.16- to 3-fold), sixteen (1.35- to 2.82-fold), and twelve isolates (1.62- to 4-fold) compared to ATCC19606, respectively. Conclusion: This study revealed that overexpression of RND efflux pumps underlies tigecycline resistance in A. baumannii clinical isolates from the Western Balkans. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.

Background: Burkholderia cenocepacia is considered one of the most problematic cystic fibrosis (CF) pathogens. Colonization prevalence in the Serbian CF population is high and virtually exclusively limited to a single highly transmissible clone of B. cenocepacia ST856 which is positive for both the B. cepacia epidemic strain marker (BCESM) and cable pilin, and is closely related to the epidemic strain CZ1 (ST32). Methods: Biofilm formation for 182 isolates, and adhesion to components of the host extracellular matrix, proteolytic activity, mucoidy and motility of selected ST856 representatives, as well as B. cenocepacia ST858 and ST859, and B. stabilis ST857, novel STs isolated from Serbian CF patients, were investigated in this study. The presence of the cepI, cepR, fliG, llpE, wbiI, and bcscV genes was analyzed. Results: Biofilm-formation ability of analyzed strains was poor under standard laboratory conditions, but changed in stress conditions (cold stress) and conditions that mimic CF milieu (increased CO2). All strains expressed ability to bind to collagen and fibronectin albeit with different intensity. Representatives of ST856 exhibited gelatinase activity. ST858, ST859 and 9/11 of ST856 genotypes were positive for swimming and twitching motility whereas ST857 was non-motile. Mucoidy was demonstrated in all ST856 genotypes, ST857 was semi-mucoid, and ST858 and ST859 were non-mucoid. Molecular analysis for major virulence factors revealed that ST856 and ST857 carried the six analyzed genes, while ST858 and ST859 were negative for the llpE gene. Conclusion: Variations in virulence phenotypes in different genotypes of epidemic B. cenocepacia ST856 clone, in vitro, could be a consequence of diversification driven by pathoadaptation. Diversity of epidemic clone genotypes virulence, could be challenging for accurate diagnosis and treatment, as well as for infection control. © 2017 The Author(s).