Genotyping and molecular characterization of clinical Acinetobacter baumannii isolates from a single hospital in Southwestern Iran

Molecular epidemiology and molecular typing methods of Acinetobacter baumannii: An updated review

The aim of this study was to go through the molecular methods used for typing of carbapenem-resistant Acientobacter baumannii (CRAB) isolates for investigating the molecular epidemiology all over the world. Multiple typing techniques are required to understand the source and nature of outbreaks caused by Acientobacter baumannii (A. baumannii) and acquired resistance to antimicrobials. Nowadays, there is gradual shift from traditional typing methods to modern molecular methods to study molecular epidemiology and infection control. Molecular typing of A. baumannii strains has been revolutionized significantly in the last 2 decades. A few sequencing-based techniques have been proven as a breakthrough and opened new prospects, which have not been achieved by the traditional methods. In this review, discussed different pre-existing and recently used typing methods to explore the molecular epidemiology of A. baumannii pertaining in context with human infections.

High frequency of carbapenemase in extensively drug-resistant Acinetobacter baumannii isolates in central Iran

OBJECTIVES

We assessed the frequency of occurrence for infections caused by wild-type A. baumannii, multidrug-resistant (MDR) or XDR A. baumannii, and CRAB. We detected different antibiotic resistance genes in the genomes of infectious A. baumannii strains from central Iran.

METHODS

This study investigated 546 clinical patient samples for the presence of A. baumannii by using conventional culture methods and PCR. Antibiotic resistance profiles, and the phenotypic and genotypic characteristics of various antibiotic genes were analyzed.

RESULTS

Out of 546 samples, 87 (15.9%) A. baumannii isolates were obtained using culture and all culture positive samples were also positive by PCR. The most effective antibiotics were polymyxin B (n = 84 strains) (96.6% susceptibility), colistin (n = 81) (93.1%), and ampicillin/sulbactam (n = 18) (20.7%). All clinical A. baumannii isolates were ESBL-positive. The number of CRAB was 84 (96.5%). All CRAB isolates were both MDR and XDR. Of all CRAB isolates, 78 out of 84 (92.4%) produced metallo-β-lactamase (MBL) by phenotypic diagnosis. The most abundant genes were blaPER (32/87; 36.7%), blaTEM (29/87; 33.3%), blaVEB (26/87; 29.8%) for ESBL and Ambler class D β -lactamases included blaOXA-23 (69/84; 82.1%), blaOXA-24 (46/84; 54.7%), MBLs included blaVIM (51/84; 60.7%), and blaIMP (28/84; 33.3%) for carbapenemase.

CONCLUSION

High frequencies of XDR A. baumannii and CRAB (96.5%) were detected in central Iran. Quick and accurate diagnosis, appropriate isolation of patients colonized or infected by CRAB isolates, application of accurate and effective infection control policies and programs, and appropriate preventive measures are deemed helpful in preventing the further spread of these resistant and clinically highly relevant strains.

Antimicrobial resistance and biofilm formation capacity among Acinetobacter baumannii strains isolated from patients with burns and ventilator-associated pneumonia

BACKGROUND

Acinetobacter baumannii is a pathogen responsible for nosocomial infections, especially in patients with burns and ventilator-associated pneumonia (VAP). The aims of this study was to compare the biofilm formation capacity, antimicrobial resistance patterns and molecular typing based on PFGE (Pulsed-Field Gel Electrophoresis) in A. baumannii isolated from burn and VAP patients.

MATERIALS AND METHODS

A total of 50 A. baumannii isolates were obtained from burn and VAP patients. In this study, we assessed antimicrobial susceptibility, biofilm formation capacity, PFGE fingerprinting, and the distribution of biofilm-related genes (csuD, csuE, ptk, ataA, and ompA).

RESULTS

Overall, 74% of the strains were multidrug resistant (MDR), and 26% were extensively drug-resistant (XDR). Regarding biofilm formation capacity, 52%, 36%, and 12% of the isolates were strong, moderate, and weak biofilm producers. Strong biofilm formation capacity significantly correlated with XDR phenotype (12/13, 92.3%). All the isolates harbored at least one biofilm-related gene. The most prevalent gene was csuD (98%), followed by ptk (90%), ataA (88%), ompA (86%), and csuE (86%). Harboring all the biofilm-related genes was significantly associated with XDR phenotype. Finally, PFGE clustering revealed 6 clusters, among which cluster No. 2 showed a significant correlation with strong biofilm formation and XDR phenotype.

CONCLUSION

Our findings revealed the variable distribution of biofilm-related genes among MDR and XDR A. baumannii isolates from burn and VAP patients. A significant correlation was found between strong biofilm formation capacity and XDR phenotype. Finally, our results suggested that XDR phenotype was predominant among strong-biofilm producer A. baumannii in our region.

Prevalence of Extended-Spectrum β-Lactamase Genes and Antibiotic Resistance Pattern in Clinical Isolates of Acinetobacter baumannii from Patients Hospitalized in Mashhad, Iran

Background: Carbapenem-resistant Acinetobacter baumannii strains are one of the most severe factors in hospital infection worldwide, in which the beta-lactamase enzyme is one of the main resistance mechanisms. Objectives: This study aimed to evaluate the presence of carbapenem-resistant beta-lactamase genes and determine antibiotic resistance patterns in the clinical isolates of A. baumannii from patients hospitalized in the Shahid Kamyab Hospital, Mashhad, Iran. Methods: Out of 286 collected isolates from patients hospitalized in Shahid Kamyab Hospital (from March 2017 to June 2017), 31 isolates were confirmed to be A. baumannii using biochemical tests. Antibiotic susceptibility testing was conducted using the disc diffusion method according to the CLSI standard protocols. The presence of beta-lactamase genes, namely blaVEB, blaPER, blaAmpC, blaVIM, blaIMP, blaSHV, and blaTEM, was detected using polymerase chain reaction. Results: In this study, 31 isolates were identified as Acinetobacter baumannii, all of which revealed high resistance to ceftazidime, cefixime, ceftriaxone, meropenem, imipenem, cefotaxime and cephalexin. In this case, the lowest resistance (19.35%) was observed against polymixin B. Moreover, blaAmpC, blaTEM, blaSHV, blaPER, and blaVIM were observed in 93.54% (29), 51.61% (16), 48.38% (15), 41.93% (13), and 77% (24) of the isolates, respectively. However, blaVEB and blaIMP were observed in none of the isolates. Conclusions: The results showed high carbapenem resistance and high frequency of beta-lactamase resistance genes among the clinical isolates of A. baumannii.

Antibacterial effects of Octenicept, and benzalkonium chloride on Acinetobacter baumannii strains isolated from clinical samples and determination of genetic diversity of isolates by RAPD-PCR method

BACKGROUND

Acinetobacter baumannii (A. baumannii) is among the important causes of nosocomial infections. Due to the emergence of antibiotic resistance, many problems have been raised in the successful treatment of patients infected by this bacterium with the subsequent mortality. Therefore, the present study was performed to evaluate the antibacterial effect of Octenicept (OCT), and Benzalkonium chloride (BZK) against A. baumannii strains isolated from clinical samples, and to determine the genetic diversity of strains by RAPD-PCR method.

METHODS

A total of 119 A. baumannii isolates were collected and confirmed by conventional culture and biochemical tests and PCR assay. Susceptibility of the isolates to antibiotics was evaluated by standard antibiotic susceptibility testing (AST). For antiseptics OCT and BZK, Minimum inhibitory concentration (MIC) was assessed by broth microdilution method. The prevalence of qacE and qacΔE1 genes related to antiseptics was estimated by PCR assay. Finally, genetic diversity of strains was determined by using RAPD-PCR.

RESULTS

All 119 suspected isolates were confirmed as A. baumannii using conventional microbiologic tests and PCR assay. The isolates were mostly originated from blood samples. In AST, the lowest resistance was seen for ciprofloxacin and gentamicin. For antiseptics, the MIC values were reported as 15.26 μg/ml for OCT and 640 μg/ml for BZK. The antiseptic genes of qacE and qacΔE1 were found to be present in 56 (47.05%) and 59 (49.57%) of isolates respectively. RAPD typing revealed great diversity among A. baumannii isolates, with 37 clusters in isolates from ICU, of which 32 clusters were single and 5 were multiple.

CONCLUSIONS

Considering the increase of resistance to antiseptics, it is of importance to monitor the susceptibility of A. baumannii to antiseptics and to promote antiseptic stewardship in hospitals. Furthermore, in this study great diversity was observed among A. baumannii isolates, which is important in understanding the molecular epidemiology of the outbreaks caused by this organism in the hospitals.

A Comprehensive Study of the Relationship between the Production of β-Lactamase Enzymes and Iron/Siderophore Uptake Regulatory Genes in Clinical Isolates of Acinetobacter baumannii

Background

The iron/siderophore uptake system (IUS) involved in the Acinetobacter baumannii pathogenicity. However, IUS's role in antibiotic resistance and the production of β-lactamase enzymes of A. baumannii are unclear. This study aimed to investigate the relationship between the production of β-lactamase enzymes and IUS regulatory genes in clinical isolates of A. baumannii. Methods. A. baumannii isolates were collected from clinical isolates using biochemical tests. The antibiotic resistance patterns and β-lactamase-producing strains were identified using the disk diffusion method (DDM). Also, IUS genes were detected by the polymerase chain reaction (PCR) method.

Results

Seventy-two (72) A. baumannii isolates were collected from a different clinical specimen. Gentamicin-resistant strains (43%) had the highest frequency, and aztreonam-resistant strains (12.5%) had the lowest frequency. Also, the distribution of AmpC and MBL producing isolates were 27.7% and 35%, respectively. Moreover, the frequencies of basD, bauA, pld, paaE, entA, feoB, hemO, and tonB genes were as follows: 12.5%, 15.2%, 11.1%, 15.2%, 19.4%, 16.6%, 23.6%, and 6.9%. Further, a strong correlation was observed between the abundance of β-lactamase-producing strains and IUS genes.

Conclusions

Based on our knowledge from this study, the association between β-lactamase production and IUS genes in A. baumannii plays an essential role in the emergence of drug-resistant strains.