Susceptibility Pattern and Distribution of Oxacillinases and bla PER-1 Genes among Multidrug Resistant Acinetobacter baumannii in a Teaching Hospital in Iran

Oxa-376 and Oxa-530 variants of β-lactamase: computational study uncovers potential therapeutic targets of Acinetobacter baumannii

Antimicrobial resistance is a major global health crisis, resulting in thousands of deaths each year. Antibiotics' effectiveness against microorganisms deteriorates over time as multidrug resistance (MDR) develops, which is exacerbated by irregular antibiotic use, poor disease management, and the evasive nature of bacteria. The World Health Organization has recognized multidrug resistance as a critical public health concern, and Acinetobacter baumannii has been at the center of attention due to its ability to develop multidrug resistance (MDR). It generally produces carbapenem-hydrolyzing oxacillinase, which has been identified as the primary source of beta-lactam resistance in MDR bacteria. Recently, point mutations in A. baumannii have been identified as a key factor of multidrug resistance, making them a prime concern for researchers. The goal of the current work was to establish a unique way of finding multidrug-resistant variants and identify the most damaging mutations in the existing databases. We characterized the deleterious variants of oxacillinases using several computational tools. Following a thorough analysis, Oxa-376 and Oxa-530 were found to be more damaging when compared with the wild-type Oxa-51. The mutants' 3D structures were then prepared and refined with RaptorX, GalaxyRefine, and SAVES servers. Our research incorporates seven antimicrobial agents to illustrate the resistance capability of the variants of oxacillinase by evaluating binding affinity in Autodock-vina and Schrodinger software. RMSD, RMSF, Radius of gyration analysis, the solvent-accessible surface area (SASA), hydrogen bonding analysis and MM-GBSA from Molecular Dynamics Simulation revealed the dynamic nature and stability of wild-type and Oxa-376 and Oxa-530 variants. Our findings will benefit researchers looking for the deleterious mutations of Acinetobacter baumannii and new therapeutics to combat those variants. However, further studies are necessary to evaluate the mechanism of hydrolyzing activity and antibiotic resistance of these variants.

Determining novel therapeutic targets of Acinetobacter baumannii. Deleterious variants, causing antibiotic resistance, were identified by molecular docking and molecular dynamics simulation suggesting new therapeutic targets Oxa-376 and Oxa-530.

Multidrug Resistant Acinetobacter baumannii Biofilms: Evaluation of Phenotypic-Genotypic Association and Susceptibility to Cinnamic and Gallic Acids

Acinetobacter baumannii armed with multidrug resistance (MDR) and biofilm-forming ability is increasingly recognized as an alarming pathogen. A deeper comprehension of the correlation between these two armories is required in circumventing its infections. This study examined the biofilm-forming ability of the isolates by crystal violet staining and the antibiotic susceptibility by broth microdilution method. The genetic basis of the MDR and biofilm-forming phenotypes was screened by polymerase chain reaction. The antimicrobial activities of cinnamic and gallic acids against planktonic cells and biofilms of A. baumannii were investigated, and the findings were confirmed with scanning electron microscopy (SEM). Among 90 A. baumannii isolates, 69 (76.6%) were MDR, and all were biofilm formers; they were classified into weak (12.2%), moderate (53.3%), and strong (34.5%) biofilm formers. Our results underlined a significant association between MDR and enhanced biofilm formation. Genotypically, the presence of bla_VIM and bla_OXA–23 genes along with biofilm-related genes (ompA, bap, and csuE) was statistically associated with the biofilm-forming abilities. Impressively, both gallic and cinnamic acids could significantly reduce the MDR A. baumannii biofilms with variable degrees dependent on the phenotype–genotype characteristics of the tested isolates. The current findings may possess future therapeutic impact through augmenting antimicrobial arsenal against life-threatening infections with MDR A. baumannii biofilms.

Prevalence and molecular epidemiology of carbapenem-resistant Gram-negative bacilli and their resistance determinants in the Eastern Mediterranean Region over the last decade

Carbapenem resistance in Enterobacteriaceae, Acinetobacter baumannii and Pseudomonas aeruginosa is increasing worldwide, which has led the World Health Organization (WHO) to list these bacteria in the critical priority pathogens group. Infections by such pathogens pose a serious threat to hospitalised patients and are associated with clinical and economic consequences. What worsens the case is the weak pipeline of available antimicrobial agents to treat such infections and the absence of new drugs. The aim of this review was to shed light on all studies tackling carbapenem resistance in Enterobacteriaceae, A. baumannii and P. aeruginosa in the Eastern Mediterranean region, with indication for each country, description of studies timeline, prevalence of carbapenem resistance, and carbapenem resistance-encoding genes detected in these countries.

Detection of multidrug resistant environmental isolates of acinetobacter and Stenotrophomonas maltophilia: a possible threat for community acquired infections?

Acinetobacter spp. and Stenotrophomonas maltophilia are bacteria commonly associated with infections at the clinical settings. Reports of infections caused by environmental isolates are rare. Therefore, this study focused on determination of the antibiotic resistance patterns, antibiotic resistance genes, efflux pumps and virulence signatures of Acinetobacter spp. and S. maltophilia recovered from river water, plant rhizosphere and river sediment samples. The isolates were identified and confirmed using biochemical tests and PCR. The antimicrobial resistance profiles of the isolates were determined using Kirby Bauer disk diffusion assay and presence of antibiotic resistance and virulence genes were detected using PCR. S. maltophilia was more frequent in plant rhizosphere and sediment samples than the water samples. Acinetobacter spp. were mostly resistant to trimethoprim-sulfamethoxazole (96% of isolates), followed by polymyxin b (86%), cefixime (54%), colistin (42%), ampicillin (35%) and meropenem (19%). The S. maltophilia isolates displayed total resistance (100%) to trimethoprim- sulfamethoxazole, meropenem, imipenem, ampicillin and cefixime, while 80% of the isolates were resistant to ceftazidime. Acinetobacter spp. contained different antibiotic resistance genes such as sul1 (24% of isolates), sul2 (29%), blaOXA 23/51 (21%) and blaTEM (29%), while S. maltophilia harbored sul1 (8%) and blaTEM (20%). Additionally, efflux pump genes were present in all S. maltophilia isolates. The presence of multidrug resistant Acinetobacter spp. and Stenotrophomonas maltophilia in surface water raises concerns for community-acquired infections as this water is directly been used by the community for various purposes. Therefore, there is the need to institute measures aimed at reducing the risks of these infections and the resulting burden this may have on the health care system within the study area.

Evaluation of type II Toxin-Antitoxin Systems, Antibiotic Resistance Profiles, and Biofilm Quorum Sensing Genes in Acinetobacter Baumannii Isolates in Iraq

BACKGROUND

Bacterial Toxin-Antitoxin (TAs) systems are extensive two-component elements in the bacterial genome, which are involved in many key biological functions, including growth arrest, survival, biofilm formation, plasmid maintenance, defense against phages, persistence, and virulence.

AIM

This study aimed to assess the molecular determinants involved in TAs, biofilm quorum sensing, and antibiotic resistance profiles in Acinetobacter baumannii isolated from Baghdad's hospitals in Iraq.

METHODS

A total of 127 A. baumannii isolates were collected from 2160 different clinical samples. The antimicrobial susceptibility test was performed using the disk diffusion test. All isolates were characterized for molecular determinants involved in TAs and biofilm formation using the wellknown PCR-based sequencing assay.

RESULTS

A high multi-drug resistant (MDR) (96.06%; 122/127) and imipenem resistance (84.25%; 107/127) rates were observed from A.baumannii isolates. Results showed the presence of rhlIR gene in three isolates (2.36%), and lasIR gene appeared in two isolates (1.57%) isolates, whilst, mazEF, ccdAB, and relBE genes have not been detected among any of the isolates.

CONCLUSION

A high MDR and imipenem resistance rates within a low prevalence of rhlIR, and lasIR genes could be found in clinical A. baumannii isolates from some of the Iraqi hospitals.

Antibiotic resistance pattern of Acinetobacter baumannii from burns patients: increase in prevalence of bla OXA-24-like and bla OXA-58-like genes

BACKGROUND AND OBJECTIVES

Notwithstanding the increased prevalence of Acinetobacter baumannii drug-resistant isolates, treatment options are progressively limiting. This study aims to provide a recent report on antibiotic susceptibility in burn wound isolates of A. baumannii, and the importance of OXA beta-lactamases in carbapenem resistance.

MATERIALS AND METHODS

The susceptibility levels to different antimicrobial categories were determined among 84 A. baumannii isolates from burn wound infection between 2016 and 2018. Multiplex PCR was used to detect OXA beta-lactamases genes, including bla _OXA-51, bla _OXA-23, bla _OXA-24 and bla _OXA-58. ISAba-1 association with bla _OXA-51, bla _OXA-23 and bla _OXA-58 was detected by PCR mapping.

RESULTS

All the isolates were determined as multidrug-resistant (MDR) and 69% as extensively drug-resistant (XDR). Different carbapenems MIC ranges (MIC₅₀ and MIC₉₀) were observed among the isolates harboring bla _OXA-like genes and isolates with the OXA-24-like enzyme showed higher carbapenems MIC ranges. The prevalence of bla _OXA-51-like, bla _OXA-23-like, bla _OXA-24-like and bla _OXA-58-like were 100%, 53.57%, 41.66% and 30.95%, respectively. ISAba-1 insertion sequence was found to be upstream to bla _OXA-23-like and bla _OXA-58-like genes in 23 out of 45 (71.1%) bla _OXA-23-like-positive and 4 out of 23 (15.3) bla _OXA-58-like-positive isolates, respectively.

CONCLUSION

Resistance to carbapenems as the last resort for treatment of A. baumannii infections is growing. This study, for the first time in Iran, has observed the increased frequency of bla _OXA-24-like and bla _OXA-58-like genes and found an association between ISAba-1 and bla _OXA-58-like gene, which signifies the possible risk of increased diversity in OXA beta-lactamases and growth in carbapenem resistance.

Understanding the Epidemiology of Multi-Drug Resistant Gram-Negative Bacilli in the Middle East Using a One Health Approach

In the last decade, extended-spectrum cephalosporin and carbapenem resistant Gram-negative bacilli (GNB) have been extensively reported in the literature as being disseminated in humans but also in animals and the environment. These resistant organisms often cause treatment challenges due to their wide spectrum of antibiotic resistance. With the emergence of colistin resistance in animals and its subsequent detection in humans, the situation has worsened. Several studies reported the transmission of resistant organisms from animals to humans. Studies from the middle east highlight the spread of resistant organisms in hospitals and to a lesser extent in livestock and the environment. In view of the recent socio-economical conflicts that these countries are facing in addition to the constant population mobilization; we attempt in this review to highlight the gaps of the prevalence of resistance, antibiotic consumption reports, infection control measures and other risk factors contributing in particular to the spread of resistance in these countries. In hospitals, carbapenemases producers appear to be dominant. In contrast, extended spectrum beta lactamases (ESBL) and colistin resistance are becoming a serious problem in animals. This is mainly due to the continuous use of colistin in veterinary medicine even though it is now abandoned in the human sphere. In the environment, despite the small number of reports, ESBL and carbapenemases producers were both detected. This highlights the importance of the latter as a bridge between humans and animals in the transmission chain. In this review, we note that in the majority of the Middle Eastern area, little is known about the level of antibiotic consumption especially in the community and animal farms. Furthermore, some countries are currently facing issues with immigrants, poverty and poor living conditions which has been imposed by the civil war crisis. This all greatly facilitates the dissemination of resistance in all environments. In the one health concept, this work re-emphasizes the need to have global intervention measures to avoid dissemination of antibiotic resistance in humans, animals and the environment in Middle Eastern countries.

Prevalence and Mechanisms of Carbapenem Resistance in Acinetobacter baumannii: A Comprehensive Systematic Review of Cross-Sectional Studies from Iran

Introduction: Carbapenem-resistant Acinetobacter baumannii (CRAB) is recognized to be among the most difficult antimicrobial-resistant gram-negative bacilli to control and treat. An understanding of the epidemiology of CRAB and the mechanisms of resistance to carbapenems is necessary to develop strategies to curtail their spread. Methods: Electronic databases were searched from January 1995 to December 2017 for all studies, which: (1) provide data on the frequency and antibiotic resistance profile of the isolated A. baumannii and (2) describe the mechanisms of carbapenem resistance in detail. Results: Sixty-eight studies were found referring to mechanisms of carbapenem resistance in clinical isolates of A. baumannii, and 56 studies were found referring to the frequency of CRAB. The pooled frequency of carbapenem resistance was 85.1% (95% confidence interval [CI]: 82.2-88.1) in 8,067 clinical isolates of A. baumannii. Resistances due to bla_OXA23 (55.3%), bla_OXA24 (41.4%), and bla_OXA58 (5.2%) genes were the most prevalent reported mechanisms of resistance to carbapenem, respectively. Conclusions: Our data warn that CRAB will rise if the current situation remains uncontrolled. Better control infection strategies and antibiotic managements, particularly in the health care systems, are needed to limit the spread of this pathogen.

The threat of carbapenem-resistant gram-negative bacteria in a Middle East region

Data on the status of carbapenem-resistant microorganisms in the Middle East countries are scarce. The aim of this review was to collect available data regarding resistance to carbapenems in a Middle East region. Available data regarding carbapenem-resistant isolates were considered for evaluation in this review. Biomedical electronic databases were systematically searched to find related articles. The key terms used were "carbapenem-resistant, resistant gram-negative bacilli, Enterobacteriaceae, fermenting and non-fermenting gram-negative bacilli, Pseudomonas, Acinetobacter, Klebsiella and Iran". After primary screening, 275 relevant articles were selected to be assessed thoroughly. Resistance rate to carbapenems was reported between 1% and 86% during years 2006-2018. Most of the carbapenem-resistant microorganisms were isolated from burn patients. Modified Hodge test was a commonly used phenotypic test. Only in few studies, genotypic assays were considered. Pattern of antibiotic use can affect emergence of resistant microorganisms. Rational use of drugs, and specifically, antibiotics is a challenging issue in developing countries. Mean number of drugs per prescription in these countries was higher than the World Health Organization standards. Overuse of antibiotics, especially injectable ones, and easy access to antibiotics without prescription is a warning alarm for future antibiotic resistance in developing countries. Establishing antimicrobial stewardship's programs is new in the hospitals. Unfortunately, rules and regulatory issues to restrict antibiotic access in community pharmacies and prescription by general physicians are limited.