Phenotypic and molecular characterization of clinical isolates of Acinetobacter baumannii isolated from Delhi, India

Dramatic increase in antimicrobial resistance in ESKAPE clinical isolates over the 2010-2020 decade in India

RATIONALE AND OBJECTIVES

ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) constitute a threat to humans worldwide. India is now the most populous country. The goal was to investigate the evolution of the rates of antimicrobial resistance in ESKAPE pathogens across India over the 2010-20 decade.

METHODS

The data (89 studies) were retrieved from the Medline PubMed repository using specific keywords.

RESULTS

The study of 20 177 ESKAPE isolates showed that A. baumannii isolates were the most represented (35.9%, n = 7238), followed by P. aeruginosa (25.3%, n = 5113), K. pneumoniae (19.5%, n = 3934), S. aureus (16.3%, n = 3286), E. faecium (2.6%, n = 517) and Enterobacter spp. (0.4%, n = 89). A notable increase in the resistance rates to antimicrobial agents occurred over the 2010-20 decade. The most important levels of resistance were observed in 2016-20 for A. baumannii (90% of resistance to the amoxicillin-clavulanate combination) and K. pneumoniae (81.6% of resistance to gentamycin). The rise in β-lactamase activities was correlated with an increase in the positivity of Gram-negative isolates for β-lactamase genes.

CONCLUSIONS

This review highlighted that, in contrast to developed countries that kept resistance levels under control, a considerable increase in resistance to various classes of antibiotics occurred in ESKAPE pathogens in India over the 2010-2020 decade.

Pathogen Burden Among ICU Patients in a Tertiary Care Hospital in Hail Saudi Arabia with Particular Reference to β-Lactamases Profile

Purpose

Ventilator-associated pneumonia (VAP) is associated with a higher mortality risk for critical patients in the intensive care unit (ICU). Several strategies, including using β-lactam antibiotics, have been employed to prevent VAP in the ICU. However, the lack of a gold-standard method for VAP diagnosis and a rise in antibiotic-resistant microorganisms have posed challenges in managing VAP. The present study is designed to identify, characterize, and perform antimicrobial susceptibility of the microorganisms from different clinical types of infections in ICU patients with emphasis on VAP patients to understand the frequency of the latter, among others.

Patients and Methods

A 1-year prospective study was carried out on patients in the ICU unit at a tertiary care hospital, Hail, Saudi Arabia.

Results

A total of 591 clinically suspected hospital-acquired infections (HAI) were investigated, and a total of 163 bacterial isolates were obtained from different clinical specimens with a high proportion of bacteria found associated with VAP (70, 43%), followed by CAUTI (39, 24%), CLABSI (25, 15%), and SSI (14, 8.6%). Klebsiella pneumoniae was the most common isolate 39 (24%), followed by Acinetobacter baumannii 35 (21.5%), Pseudomonas aeruginosa 25 (15.3%), and Proteus spp 23 (14%). Among the highly prevalent bacterial isolates, extended-spectrum beta-lactamase was predominant 42 (42.4%).

Conclusion

Proper use of antibiotics, continuous monitoring of drug sensitivity patterns, and taking all precautionary measures to prevent beta-lactamase-producing organisms in clinical settings are crucial and significant factors in fending off life-threatening infections for a better outcome.

Genotypic Patterns of Multidrug-Resistant Acinetobacter baumannii: A Systematic Review

Acinetobacter baumannii (A. baumannii) is one of the most common bacteria in nosocomial infections. Inappropriate usage of antibiotics has led to expanding emergence resistance to A. baumannii as a multidrug-resistant (MDR) strain. Empirical antibiotic therapy is necessary to evaluate the resistant gene pattern of MDR A. baumannii. For this purpose, the present study evaluated the resistance genes pattern of MDR A. baumannii collected from hospitalized patients using a genotypic diagnostic technique. To find evidence related to the study objectives, databases were searched such as Google Scholar, Web of Science, Science Direct, PubMed, and Scopus from 2000 to 2022, with specified keywords in the title and text of the articles. Articles were included based on inclusion and exclusion criteria. The mentioned database displayed 284 articles. After screening, 65 eligible articles were included. The results showed that various b-lactamases genes, aminoglycoside-modifying enzymes (AMEs) genes, and pump-expressing genes are resistance gene patterns in MDR A. baumannii isolates. MDR A. baumannii has significantly become resistant to b-lactams, carbapenems, and aminoglycosides.

Prevalence of classes 1 and 2 integrons in multidrug-resistant Acinetobacter baumanni isolates recovered from some aquatic environment in South Africa

The emergence of antibiotic-resistance genes (ARGs) by means of integrons in multidrug-resistant Acinetobacter baumannii (MDR A. baumannii) has become a significant challenge in the management of infections from this pathogen. In this paper, we report on the variable region of class 1 and 2 integrons observed in MDR A. baumanni isolates recovered from rivers in the Eastern Cape Province, South Africa. Class 1 and 2 integrons with their variable regions were evaluated with polymerase chain reaction techniques followed by sequencing. Antibiotic sensitivity testing, checkerboard assay, time-kill independent assay, and Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction (ERIC-PCR) were carried out using standard microbiological techniques. A total of fifty-six (56) isolates were examined, among which 45 (79%) tested positive for class 1 integron, and 7 (12.3%) had class 2 integron. None was found to be class 3 integron positive among the isolates. The variable region contained aadA1, aadA5, and aadA2 genes, which confer resistance against streptomycin and spectinomycin, aac(6')-Ib against amikacin/ tobramycin and dfrA17 genes against trimethoprim. The minimum inhibitory concentrations of the antimicrobials for one of the tested organisms were resistant against meropenem, colistin sodium methanesulfonate, tetracycline, ceftazidime, and ciprofloxacin (16, > 16, > 8, > 256, and 128 ug/mL respectively). The impact of colistin combined with quinolones (ciprofloxacin), with the FICIs (0.31) indicated synergistic effects against MDR A baumanni. However, when colistin was combined with meropenem and ceftazidime, additive effects with fractional inhibitory concentration (FIC) index ranging from 0.52 to 1 were observed. No antagonistic effect was evaluated among the examined isolates. ERIC-PCR analyses of A. baumanni isolates revealed significant genetic diversity, suggesting various sources of environmental contamination. We conclude that A. baumanni harbouring class 1 integrons in aquatic milieus are a significant source of ARGs and can transmit these elements to other organisms and consequently to man with significant public health implications.

Molecular Characterization and Antibiogram of Acinetobacter baumannii Clinical Isolates Recovered from the Patients with Ventilator-Associated Pneumonia

A 2-year prospective study carried out on ventilator-associated pneumonia (VAP) patients in the intensive care unit at a tertiary care hospital, Hail, Kingdom of Saudi Arabia (KSA), revealed a high prevalence of extremely drug-resistant (XDR) Acinetobacter baumannii. About a 9% increase in the incidence rate of A. baumannii occurred in the VAP patients between 2019 and 2020 (21.4% to 30.7%). In 2019, the isolates were positive for IMP-1 and VIM-2 (31.1% and 25.7%, respectively) as detected by PCR. In comparison, a higher proportion of isolates produced NDM-1 in 2020. Here, we observed a high proportion of resistant ICU isolates towards the most common antibiotics in use. Colistin sensitivity dropped to 91.4% in the year 2020 as compared to 2019 (100%). Thus, the finding of this study has a highly significant clinical implementation in the clinical management strategies for VAP patients. Furthermore, strict implementation of antibiotic stewardship policies, regular surveillance programs for antimicrobial resistance monitoring, and screening for genes encoding drug resistance phenotypes have become imperative.

Molecular typing and antibiotic resistance patterns among clinical isolates of Acinetobacter baumannii recovered from burn patients in Tehran, Iran

Acinetobacter baumannii (A. baumannii) is now considered a highly resistant pathogen to various types of antibiotics. Therefore, tracking the source of its prevalence and continuous control is crucial. This study aimed to determine antibiotic resistance and perform various molecular typing methods on clinical isolates of A. baumannii isolated from hospitalized burn patients in Shahid Motahari Burn Hospital, Tehran, Iran. Hospital isolates were confirmed by phenotypic and molecular methods. Then the sensitivity to different antibiotics was determined using the minimum inhibitory concentration (MIC) method. In order to perform molecular typing, three-locus dual assay multiplex polymerase chain reaction (PCR), multiple-locus variable-number tandem repeat analysis (MLVA), and multilocus sequence typing (MLST) methods were used. Among the 60 isolates collected, the frequencies of multidrug-resistant (MDR) and extensively drug-resistant (XDR) isolates were 90 and 10%, respectively. The most effective antibiotics were colistin with 100% and tigecycline with 83.33% sensitivity. Isolates were 100% resistant to piperacillin/tazobactam and cephalosporins, and 68.3% were resistant to carbapenem. The results of multiplex PCR showed five groups that international clone I (IC I) and IC II were the most common. The MLVA method identified 34 MLVA types (MTs), 5 clusters, and 25 singletons. Multilocus sequence typing results for tigecycline-resistant isolates showed seven different sequence types (STs). Increasing antibiotic resistance in A. baumannii isolates requires careful management to control and prevent the occurrence of the pre-antibiotic era. The results of this study confirm that the population structure of A. baumannii isolates has a high diversity. More extensive studies are needed in Iran to better understand the epidemiology of A. baumannii.

Multidrug-resistant Acinetobacter baumannii infections: looming threat in the Indian clinical setting

INTRODUCTION

The recent increase in multidrug-resistant strains of A. baumannii has increased the incidences of ventilator-associated pneumoniae, catheter-associated urinary tract infections, and central line-associated blood stream infections, together increasing hospital stay, treatment cost, and mortality. Resistance genes blaOXA and blaNDM are dominant in India. Carbapenem-resistant A. baumannii (CRAB) International clone-2 (IC-2) are rising in India. High dependency on carbapenems and last-resort combination of tigecycline and polymyxins have aggravated outcomes. Despite nursing barriers, ward closure, environmental disinfections etc for detecting and controlling transmission, MDR isolates and CRAB nosocomial outbreaks continue. Treatment cost overruns by AMR adversely affect 80% of Indians without insurance cover.

AREA COVERED

This narrative review will cover epidemiology, resistance pattern, genetic diversity, device-related infection, cost, and mortality due to multidrug-resistant and CRAB in India. A comprehensive literature search in PubMed and Google Scholar using appropriate keywords at different time points yielded relevant articles.

EXPERT OPINION

It is challenging to enforce policies to control MDR A. baumannii in India. Government and hospitals should enforce stringent infection control measures, surveillance, and antimicrobial stewardship to prevent further spread and emergence of more virulent and resistant strains. Knowledge on antibiotic resistance mechanisms can help design novel antibiotics that can evade, resistance.

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.

Carbapenem resistance in Acinetobacter baumannii clinical isolates from northwest Iran: high prevalence of OXA genes in sync

Background and Objectives

Carbapenem treatment for Acinetobacter baumannii infections presently faces threats owing to the production of several types of carbapenemase enzymes, prevalence of which varies among different countries. We explored the current trend of antibiotic resistance in A. baumannii clinical isolates from North West Iran, sought the mechanism of carbapenem resistance and addressed the sequence type groups in carbapenem resistant A. baumannii (CRAB).

Materials and Methods

A. baumannii (n=112) isolates were recovered from various clinical specimens of patients admitted in internal, surgery, burn, infectious diseases and various ICUs wards. Genetically confirmed A. baumannii isolates were screened for carbapenem resistance by the Kirby-Bauer and E-test and the presence of bla _MBL, bla _OXA-like, ISAba1 genes by PCR. Sequence groups were identified by multiplex PCR.

Results

Multidrug-resistance (MDR) was a characteristic feature of all A. baumannii isolates. Frequency of oxacillinase genes in combination including bla _OXA-51-like/bla _OXA-23-like, bla _OXA-51-like/bla_{OXA-24/40-like}and bla _OXA-51-like/bla _OXA-23-like/bla _{OXA-24/40-like} was 82.1%, 36.6% and 25.8% respectively. Blending of oxacillinase and MBL genes was evident in eight bla _OXA-23-like positive and 7 bla _OXA-24-like positive isolates thereby depicting synchronous etiology of carbapenem resistance. Amongst CRAB isolates, 97.3% contained ISAba1 element and 50.9% belonged to the European clone II.

Conclusion

Synchronicity among bla _OXA-like with bla _MBL and ISAba1 gene was a hallmark of this investigation. Though origin or route of transmission was not elucidated in this study but co-existence among OXA and MBL producing genes is a therapeutic concern demanding strict surveillance strategies and control programs to halt the dissemination of these isolates in the hospital setting.

Antibiotic resistance assessment of Acinetobacter baumannii isolates from Tehran hospitals due to the presence of efflux pumps encoding genes (adeA and adeS genes) by molecular method

Objective

Acinetobacter baumannii (A. baumannii) has caused many problems in nosocomial infections. Efflux pumps are considered as one of the most important mechanisms of resistance in this bacterium and have the ability to excrete toxic substances such as antibiotics out of the cell.

Results

In this study, 60 isolates of A. baumannii were collected from patients in several hospitals in Tehran, Iran. After diagnosis using standard biochemical methods, the pattern of antibiotic susceptibility was determined using the disk diffusion method according to CLSI guidelines. The adeA and adeS genes were identified by PCR method. The highest resistance to Piperacillin and the lowest resistance to Gentamicin were observed (100% compared to 48.4%). 6.6% of the isolates had only adeA gene and adeS gene was observed in 8.4% of isolates and both genes were detected in 73.4% of the samples. Despite the high resistance of t A. baumannii o antibiotics and due to the high frequency of genes of adeA and adeS efflux pumps in A. baumannii isolates, it can be concluded that these efflux pumps may play an important role in resistance of this bacterium. By determining the pattern of antibiotic the resistance before treatment, the resistance of this pathogen can be prevented in societies.

Multidrug-resistant Acinetobacter baumannii outbreaks: a global problem in healthcare settings

INTRODUCTION

The increase in the prevalence of multidrug-resistant Acinetobacter baumannii infections in hospital settings has rapidly emerged worldwide as a serious health problem.

METHODS

This review synthetizes the epidemiology of multidrug-resistant A. baumannii, highlighting resistance mechanisms.

CONCLUSIONS

Understanding the genetic mechanisms of resistance as well as the associated risk factors is critical to develop and implement adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting.

Metallo-Beta-Lactamase-Producing Acinetobacter spp. from Clinical Isolates at a Tertiary Care Hospital in Ghana

Metallo-beta-lactamase-producing Acinetobacter spp. is a major challenge for therapeutic treatment of nosocomial infections. This study is aimed at determining the prevalence of MBL-producing Acinetobacter spp. among 87 clinical isolates of Acinetobacter spp. from the Korle-Bu Teaching Hospital, Accra, between August 2014 and July 2015. Acinetobacter spp. was identified by standard bacteriological method, and resistance to different antibiotics was assessed with the Kirby–Bauer disc diffusion method. Meropenem-resistant Acinetobacter isolates were screened for enzyme activity using the modified Hodge test (MHT) and combined disc test (CDT). Additionally, multiplex PCR was used to determine MBL genes presence (blaVIM_,blaIMP, and blaNDM). All Acinetobacter isolates showed high resistance to cefotaxime (90.8%), ceftazidime (75.9%), cotrimoxazole (70.1%), ciprofloxacin (64.4%), gentamicin (72.4%), levofloxacin (67.8%), and meropenem (59.8%). A total of 54 (62.1%) of Acinetobacter isolates were multidrug-resistant. Out of 52 (59.8%) meropenem-resistant Acinetobacter, 3 (5.8%) were carbapenemase producers by MHT, whilst, 23 (44.2%) were CDT positive. There was no significant difference between the resistance pattern of amikacin, ceftazidime, cotrimoxazole, ciprofloxacin, and meropenem amongst CDT-positive and CDT-negative isolates (p > 0.05). A total of 7/87 (8.1%) CDT-positive Acinetobacter isolates harboured blaNDM; of these, 4 (57.1%) were from wound swabs, urine (n = 2) (28.6%), and ear swab (n = 1) (14.3%). The study revealed that less than 9% of Acinetobacter spp. contained blaNDM encoding genes. Strict antibiotics usage plan and infection control measures are required to prevent the spread of these resistance genes.

Antibiogram, Prevalence of OXA Carbapenemase Encoding Genes, and RAPD-Genotyping of Multidrug-Resistant Acinetobacter baumannii Incriminated in Hidden Community-Acquired Infections

Acinetobacter spp. has gained fame from their ability to resist difficult conditions and their constant development of antimicrobial resistance. This study aimed to investigate the prevalence, susceptibility testing, OXA carbapenemase-encoding genes, and RAPD-genotyping of multidrug resistant Acinetobacter baumannii incriminated in hidden community-acquired infections in Egypt. The antimicrobial susceptibility testing was assessed phenotypically using Kirby–Bauer disk diffusion method. Also, Modified-Hodge test (MHT) was carried out to detect the carbapenemases production. Multiplex-PCR was used to detect the carbapenemase-encoding genes. Furthermore, the genetic relationship among the isolated strains was investigated using RAPD fingerprinting. The bacteriological examination revealed that, out of 200 Gram-negative non-fermentative isolates, 44 (22%) were identified phenotypically and biochemically as Acinetobacter spp. and 23 (11.5%) were molecularly confirmed as A.baumannii. The retrieved A.baumannii strains were isolated from urine (69%), sputum (22%), and cerebrospinal fluid (csf) (9%). The isolated A. baumannii strains exhibited multidrug resistance and the production rates of carbapenemases were 56.5, 60.9, and 78.3% with meropenem, imipenem, and ertapenem disks, respectively. The bla_OXA-24-like genes were the most predominant among the tested strains (65.2%), followed by bla_OXA-23 (30.4%) and bla_OXA-58 (17.4%), in addition, the examined strains are harbored IMP, VIM, and NDM genes with prevalence of 60.9, 43.5, and 13%, respectively, while KPC and GES genes were not detected. RAPD-PCR revealed that the examined strains are clustered into 11 different genotypes at ≥90% similarity. Briefly, to the best of our knowledge, this study is the first report concerning community-associated A. baumannii infections in Egypt. The high prevalence of hidden multidrug-resistant (MDR) and extensively drug-resistant (XDR) A.baumannii strains associated with non-hospitalized patients raises an alarm for healthcare authorities to set strict standards to control the spread of such pathogens with high rates of morbidity and mortality.

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

ACINETOBACTER BAUMANNII

(A. baumannii) is a pathogen responsible for nosocomial infections among the hospitalized patients. The aim of this study was to investigate genotyping and molecular characterization and to examine the biofilm formation ability of A. baumannii isolates. In total, 70 A. baumannii isolates were collected from patients admitted to Imam Khomeini Hospital in Ahvaz, Southwestern Iran. Minimum inhibitory concentrations (MIC) test was performed using Vitek 2 system. The presence of genes encoding metallo-β-lactamases, oxacillinases, and integrase and the biofilm formation ability were then evaluated. Multiple locus variable-number tandem repeat (VNTR) analysis (MLVA) typing and multiplex PCR were performed to determine the genetic relationships. The blaOXA-23-like gene had the highest prevalence. The frequency of genes encoding blaSPM, blaIMP, and blaVIM among MDR A. baumannii isolates were 12 (17.1%), 18 (25.7%), and 22 (31.4%), respectively. Moreover, 46 isolates (75.4%) harbored class I integron and 10 isolates (16.39%) carried class II integron. The number of weak, moderate and strong biofilm-producing isolates were 3 (4.3%), 7 (10%), and 55 (78.5%), respectively. The results showed that 70 A. baumannii isolates were grouped into 12 distinct MLVA types with five clusters and four singleton genotypes. In addition, 25 (35.7%) isolates were assigned to international clone (IC) variants, 37 (52.8%) isolates belonged to group 1 (IC II), and 8  (11.4%) isolates belonged to group 2 (IC I). Our findings revealed that the population structure of the A. baumannii isolates was genetically diverse. More focus on genetic variation and antibiotic resistance of A. baumannii isolates are recommended.

Insights into the complete genomes of carbapenem-resistant Acinetobacter baumannii harbouring bla OXA-23, bla OXA-420 and bla NDM-1 genes using a hybrid-assembly approach

Carbapenem resistance in Acinetobacter baumannii is due to bla_OXA-23, which is endemic in India. Recently, the sporadic presence of bla_OXA-58 as well as the occurrence of dual carbapenemases were observed. The mobility as well as the dissemination of these resistance genes were mainly mediated by various mobile genetic elements. The present study was aimed at characterizing the genetic arrangement of bla_OXA-23, bla_NDM-1 and bla_OXA-58 identified in two complete genomes of carbapenem-resistant A. baumannii (CRAB). Complete genomes obtained using a hybrid-assembly approach revealed the accurate arrangement of Tn2006 with bla_OXA-23, ISAba125 with bla_NDM and ISAba3 with bla_OXA-58. In addition, the association of IntI1 integrase with the bla_CARB-2 gene and several virulence factors required for type-IV pili assembly, motility and biofilm formation have been identified. The current study provided deeper insight into the complete characterization of insertion sequences and transposons associated with the carbapenem-resistant genes using short reads of IonTorrent PGM and long reads of MinIon in A. baumannii.

Occurrence of blaTEM and blaCTXM Genes and Biofilm-Forming Ability among Clinical Isolates of Pseudomonas aeruginosa and Acinetobacter baumannii in Yaoundé, Cameroon

Background: Pseudomonas aeruginosa (PSA) and Acinetobacter baumannii (ACB) are non-fermentative bacteria mostly associated with nosocomial infections in humans. Objective: This study aimed to determine the antimicrobial resistance profiles and virulence gene of PSA and ACB previously isolated from humans in selected health facilities in Yaoundé, Cameroon. Methods: A total of 77 and 27 presumptive PSA and ACB isolates, respectively, were collected from the Yaoundé teaching hospital. These isolates were previously isolated from various samples including pus, blood and broncho-alveolar lavage. The identities of the isolates were determined through polymerase chain reaction (PCR) amplification of PSA and ACB specific sequences. Antimicrobial susceptibility testing (AST) was performed using the Kirby–Bauer disc diffusion method. Phenotypical expression of AmpC β-lactamases (AmpC), extended spectrum β-lactamases (ESBLs) and metallo β-Lactamases (MBLs) were determined using the combined disc method. Bacterial genomes were screened for the presence of β-lactamases bla_TEM and bla_CTXM genes using specific PCR. The pathogenicity of PSA and ACB was assessed through amplification of the lasB, exoA, pslA and exoS as well as OmpA and csuE virulence genes, respectively. Results: Of the 77 presumptive PSA isolates, a large proportion (75 to 97.4%) were positively identified. All (100%) of the presumptive 27 ACB harbored the ACB-specific ITS gene fragment by PCR. Twenty five percent of the PSA isolates produced ESBLs phenotypically while more than 90% of these isolates were positive for the lasB, exoA, pslA and exoS genes. A large proportion (88%) of the ACB isolates harboured the OmpA and csuE genes. bla_TEM and bla_CTXM were detected in 17 and 4% of PSA, respectively, while a much higher proportion (70 and 29%) of the ACB isolates possessed these resistance determinants respectively. Conclusion: Our findings reveal the occurrence of both virulence and drug-resistant determinants in clinical PSA and ACB isolates from patients in health care settings in Yaoundé, Cameroon, thus suggesting their role in the pathological conditions in patients.

Phenotypic and Molecular Characterization of β-Lactamases among Enterobacterial Uropathogens in Southeastern Nigeria

Little is known about the molecular basis of antibiotic resistance among uropathogens in Southeast Nigeria. The aim of the study was to characterize enterobacterial uropathogens with respect to drug resistance. One hundred (100) enterobacterial uropathogens were studied. Their antibiotic susceptibility patterns were evaluated using disk diffusion, screened, and confirmed phenotypically for the presence of β-lactamases: ESBL, AmpC, carbapenemase, and MBLs. Screen positives were further tested for various β-lactamase genes by PCR. Our isolates showed variable resistance to most drugs tested. Out of the 58 ESBL screen positive E. coli, 35 were confirmed positive with PCR. The predominant ESBL gene was bla_TEM while bla_SPM was the most prevalent among MBL genes. Forty-six percentage of the screen positive Salmonella isolates coharbored bla_{TEM + SHV} genes. Nine of the 10 ESBL screen positive K. pneumoniae were phenotypically and PCR positive. Three isolates of K. pneumoniae were positive for MBL genes. All the 10 C. freundii were positive for ESBL genes. The study showed high prevalence of drug-resistant genes among the enterobacterial uropathogens. Majority of the uropathogens harbored >1 antibiotic-resistant gene, and the most predominant gene was ESBL (bla_TEM) followed by the MBL (SPM) gene.

Molecular characterization & epidemiology of carbapenem-resistant Acinetobacter baumannii collected across India

Background & objectives

Acinetobacter baumannii is an opportunistic pathogen responsible for causing nosocomial infections. A. baumannii develops resistance to various antimicrobial agents including carbapenems, thereby complicating the treatment. This study was performed to characterize the isolates for the presence of various β-lactamases encoding genes and to type the isolates to compare our clones with the existing international clones across five centres in India.

Methods

A total 75 non-repetitive clinical isolates of A. baumannii from five different centres were included in this study. All the isolates were confirmed as A. baumannii by bl a_OXA-51-likePCR. Multiplex PCR was performed to identify the presence of extended spectrum β-lactamases (ESBL) and carbapenemases. Multilocus sequence typing was performed to find the sequence type (ST) of the isolates. e-BURST analysis was done to assign each ST into respective clonal complex.

Results

bla_OXA-51-likewas present in all the 75 isolates. The predominant Class D carbapenemase was bla_OXA-23-likefollowed by Class B carbapenemase, bla_NDM-like. Class A carbapenemase was not observed. bla_PER-likewas the predominant extended spectrum β-lactamase. ST-848, ST-451 and ST-195 were the most common STs. Eight-novel STs were identified. e-BURST analysis showed that the 75 A. baumannii isolates were clustered into seven clonal complexes and four singletons, of which, clonal complex 208 was the largest.

Interpretation & conclusions

Most of the isolates were grouped under clonal complex 208 which belongs to the international clonal lineage 2. High occurrence of ST-848 carrying bla_OXA-23-likegene suggested that ST-848 could be an emerging lineage spreading carbapenem resistance in India.

Evaluation of synergistic effect of tazobactam with meropenem and ciprofloxacin against multi-drug resistant Acinetobacter baumannii isolated from burn patients in Tehran

Background:Acinetobacter baumannii is an increasingly important cause of nosocomial infections worldwide. In addition to the intrinsic resistance of Acinetobacter baumannii to many antibiotics, available treatment approaches with older antibiotics are significantly associated with an increase in multiresistant strains. The aim of this study was to evaluate the synergistic effect of tazobactam with meropenem and ciprofloxacin against carbapenems and drug resistant Acinetobacter baumannii isolated from burn patients in a tertiary burn center in Tehran.

Materials and methods: In this study, a total of 47 clinical isolates of A. baumannii were included from burn patients admitted to the Shahid Motahari Burns Hospital, Tehran, from June 2018 to August 2018. The disk diffusion method was used to determine resistance patterns. The synergistic effect of tazobactam with meropenem and ciprofloxacin was evaluated by determining the MIC. A PCR assay was performed to determine bla_OXA-40-like, bla_OXA-58-like and bla_OXA-24-like.

Results: Antibiotic susceptibility testing revealed that all of the isolates were resistant to meropenem and ciprofloxacin. The MIC values decreased in the cases of combined use of ciprofloxacin and meropenem with tazobactam. The bla_OXA-24-like gene was the predominant carbapenemase gene (93.6%), followed by bla_OXA-40-like, which was detected in 48.9% of isolates. None of the A. baumannii isolates harbored the bla_OXA-58-like gene.

Conclusions: Based on in-vitro antimicrobial susceptibility in the current study, the MIC of tazobactam combined with meropenem or ciprofloxacin have been shown to be variable. Furthermore, the data acquired from such in vitro conditions should be confirmed by reliable results from sufficiently controlled clinical trials.

New Delhi metallo-β-lactamase-producing Acinetobacter isolates among late-onset VAP patients: multidrug-resistant pathogen and poor outcome

Background

Acinetobacter spp. are increasingly important microbes involved in late-onset ventilator-associated pneumonia (VAP).

Purpose

The aims of this study were to determine the prevalence of New Delhi metallo-β-lactamase (MβL) (blaNDM-1)-producing Acinetobacter spp. among late-onset VAP patients in different intensive care units (ICUs) of Menoufia and Kasr Al Ainy University Hospitals, to investigate the possible risk factors contributing to the acquisition of blaNDM-1-producing Acinetobacter infection, and to correlate between antimicrobial resistance pattern and therapeutic efficacy as well as clinical outcomes of these patients.

Materials and methods

Sixty-four Acinetobacter isolates were collected from mechanically ventilated patients with suspected late-onset VAP and subjected to antimicrobial susceptibility testing. The modified Hodge test (MHT) and combined disk tests (CDT) were applied for blaNDM-1 MβL detection. Acinetobacter isolates with phenotypically confirmed MβLs production were subjected to a PCR assay to verify the presence of blaNDM-1 gene. The most obvious risk factors for acquisition of carbapenem resistance in VAP patients and treatment outcomes were also analyzed.

Results

Out of 64 Acinetobacter isolates, 42 (65.6%) proved to be blaNDM-1 positive. The sensitivity and specificity of MHT were 52.38% and 41.67%, while for CDT they were 92.86% and 83.33%, respectively. Acinetobacter isolates showed high susceptibility to colistin (85.7%). The clinical response was better among VAP patients who received combined carbapenem plus colistin therapy than those who received colistin alone. Relapse of infection was detected in 12.5% (8/64) of VAP cases. The reported mortality reached 46.8% (30/64) of which 27 (64.3%) were infected with blaNDM-1-positive isolates. Prolonged duration of mechanical ventilation, longer hospital and ICU stays, and prior exposure to antibiotic therapy were by far the most important factors predisposing to carbapenem resistance among VAP patients.

Conclusion

A worldwide spread of Acinetobacter spp. expressing carbapenemases represents a significant threat to the medical community. The current study addressed the high prevalence of blaNDM-1-producing Acinetobacter isolates among late-onset VAP patients.

Synergistic activity of polymyxin B combined with vancomycin against carbapenem-resistant and polymyxin-resistant Acinetobacter baumannii: first in vitro study

PURPOSE

The effect of a combination of polymyxin B (PMB) and vancomycin (VAN) was assessed against six Acinetobacter baumannii clinical isolates belonging to six different clusters (three PMB-susceptible and three PMB-resistant).

METHODOLOGY

The synergistic effect of the PMB-VAN combination was determined with the checkerboard, time-kill, disk-diffusion and M.I.C.Evaluator assays. PMB-resistance was investigated with mcr-1 gene amplification and a mutant frequency assay.

RESULTS

In the checkerboard assay, all PMB-resistant isolates showed a synergistic effect. The time-kill assay demonstrated that the PMB-VAN combination had a bactericidal effect at 24 h against isolates with a high mutant rate for PMB, suggesting that this combination may block the hypermutation of some isolates. No antagonism was detected. All PMB-resistant isolates also showed synergism in the disk-diffusion test, and a significant decrease in VAN MICs in the M.I.C.Evaluator assay.

CONCLUSION

Our findings indicate that the PMB-VAN combination has a synergistic effect on A. baumannii, especially against PMB-resistant isolates.

Emergence and characterization of nosocomial multidrug-resistant and extensively drug-resistant Acinetobacter baumannii isolates in Tehran, Iran

RATIONALE

Acinetobacter baumannii is one of the antibiotic-resistant superbugs that threatens hospitalized patients. Emergence and spread of the multidrug-resistant (MDR) and extensively drug-resistant (XDR) clones cause erratic outbreaks following environmental contamination of hospital settings.

OBJECTIVE

The present study intended to characterize the antimicrobial resistant profiles and the genotypes of clinical and environmental isolates of A. baumannii as a result of dissemination of resistant strains.

METHODS

Clinical and environmental isolates of A. baumannii were obtained from patients, staff, and environment of an educational hospital in Tehran. Antimicrobial susceptibility testing was carried out using the disk diffusion and E-test methods. Multiplex PCR was performed for detection of OXA-type genes (bla_OXA-23-like, bla_OXA-24-like, bla_OXA-58-like, and bla_OXA-51-like). Genotypic relatedness of the isolates was achieved using repetitive extragenic palindromic element PCR (Rep-PCR) technique.

RESULTS

All the isolates were found to be susceptible to colistin and most of them (77%) were non-susceptible to tigecycline. A majority of the clinical and environmental isolates (97%) were considered as MDR strains and 41% as XDR. In multiplex detection, bla_OXA-23-like was found in 54% of the isolates, which was the most frequent OXA-type gene. In addition, the frequency of the carbapenem-resistant A. baumannii (CRAB) was observed to be high (96%). In addition, molecular typing showed different Rep patterns of clinical isolates and clonal spread of environmental isolates.

CONCLUSION

The present study highlights the circulation of drug-resistant A. baumannii strains in different wards of hospitals principally in intensive care unit (ICU) as a nosocomial pathogen due to unwise managements.

Synergy and mechanism of action of α-mangostin and ceftazidime against ceftazidime-resistant Acinetobacter baumannii

To address the resistance of Acinetobacter baumannii to β-lactam antibiotics, combination therapy between different antibiotic classes is increasingly used. The antibacterial activity of α-mangostin (AMT) alone or in combination with ceftazidime (CTZ) was investigated against ceftazidime-resistant A. baumannii DMST 45378 (CRAB). Initial screening showed that A. baumannii strains possessed AmpC β-lactamase (AmpC), extended-spectrum beta-lactamase (ESBL) and metallo-β-lactamases (MBL). Minimum inhibitory concentrations (MICs) of all test agents were >800 μg ml^-1 against CRAB. The combination of AMT/CTZ exhibited a fractional inhibitory concentration index (FICI) of <0·35 suggestive of synergy. Time-kill curves showed that the AMT/CTZ combination was significantly more efficient (P < 0·01) at reducing CRAB than the individual components. Structural analysis revealed that AMT/CTZ-treated cells exhibited increased cell volume, increased cytoplasmic and outer membrane permeability and a decrease in outer membrane peptidoglycan-associated protein (OMPG) bands. In addition, it was shown that Type IV β-lactamase was inhibited by AMT. The data suggest that AMT in combination with CTZ is synergistic and efficient against CRAB. The data also indicate that the AMT/CTZ combination may target multiple structures on the bacterial cell surface. This represents the first report of this effect on CRAB and could potentially be expanded into in vivo studies.

SIGNIFICANCE AND IMPACT OF THE STUDY

Significance and Impact of the Study: Acinetobacter baumannii strains cause serious infections, patient mortality, and have been reported to rise of multidrug resistance. This article represents the first report of using α-mangostin plus ceftazidime against these resistant strains and its mechanism of action. α-mangostin has no cytotoxic effects. Therefore, α-mangostin has strong potential for development as a useful, novel adjunct phytopharmaceutical to ceftazidime synergistically for the treatment of these strains. The synergy approach could potentially be a novel tool to combat the resistant strains.

Molecular Epidemiology of Carbapenem-Resistant Acinetobacter baumannii in a Tertiary Care Hospital in Egypt: Clonal Spread of blaOXA-23

Of great concern is the increased frequency of carbapenem-resistant Acinetobacter baumannii (CRAB) causing healthcare-associated infections. Different classes of β-lactamases are involved in this resistance through hydrolyzing carbapenems. Multilocus sequence typing (MLST) has been applied successfully for characterizing different varieties of bacterial pathogens epidemiologically. In the present study, we aimed to type and characterize the resistance profile of clinical isolates of CRAB causing healthcare-associated infections in patients admitted to Kasr Al-Aini hospital, using MLST, and compare with sequence types (STs) from other countries. A total of 50 isolates were collected from clinical samples (predominantly wound and blood), then identified by blaOXA-51-like gene PCR, and subjected to Oxford MLST scheme. The ST was designated according to PubMLST database, and e-BURST algorithm was used to assign clonal complexes. Four sets of multiplex PCR were performed to detect common carbapenem resistance genes. ST391 was the predominant ST detected in 17 cases, 70.5% of which harbored blaOXA-23 alone, both blaOXA-23 and blaKPC in 11.8%. Newly recognized 13 STs were submitted to the PubMLST database. Carbapenem resistance due to blaOXA-23 carbapenemase was detected in 36/50 (72%), followed by blaOXA-23 concomitant with blaKPC in 7/50 (14%), while blaNDM with blaOXA-58 in 3/50 (6%) and blaNDM alone in 1 case (2%). To conclude, this study demonstrates the propagation of highly resistant clone of STs 391 and 1151, carrying blaOXA-23 genes, with the first report of blaKPC in blaOXA carrying CRAB and the presence of new STs by performing the MLST technique in an Egyptian laboratory facility.

Molecular Study of Acinetobacter baumannii Isolates for Metallo-β-Lactamases and Extended-Spectrum-β-Lactamases Genes in Intensive Care Unit, Mansoura University Hospital, Egypt

Acinetobacter baumannii (A. baumannii) has been known as a causative pathogen of hospital acquired infections. The aim of this study is to examine the presence of A. baumannii among clinical isolates from intensive care unit (ICU) in Mansoura University Hospital (MUH), its antibiotic resistance pattern, and prevalence of antibiotic resistance genes metallo-β-lactamases (MBLs) and extended-spectrum-β-lactamases (ESBLs) among A. baumannii isolates. A. baumannii was identified by colony morphology, API 20E, and confirmed by detecting the bla OXA-51-like carbapenemase gene by PCR. Phenotypic expression of MBLs resistance was demonstrated by Combined Disk Test (CDT) in 273 isolates (97.5%) and of ESBLs was demonstrated by double disc synergy method (DDST) in 6 isolates (2.1%). MBLs genes were positive in 266 isolates (95%) and ESBLs genes were positive in 8 isolates (2.9%). The most frequent genes of MBLs studied genes were IMP (95.7%) followed by SIM and GIM (47.1% and 42.9%; resp.). For ESBL genes, the most frequent gene was TEM (2.9%). From this study, we conclude that multidrug resistant (MDR) A. baumannii with MBLs activity was the most common isolate. Careful monitoring for the presence of MDR A. baumannii among hospitalized patients is recommended to avoid wide dissemination of antibiotic resistance.

Carbapenem-Resistant Acinetobacter baumannii and Enterobacteriaceae in South and Southeast Asia

Carbapenem-resistant Gram-negative bacteria, in particular the Acinetobacter baumannii-calcoaceticus complex and Enterobacteriaceae, are escalating global public health threats. We review the epidemiology and prevalence of these carbapenem-resistant Gram-negative bacteria among countries in South and Southeast Asia, where the rates of resistance are some of the highest in the world. These countries house more than a third of the world's population, and several are also major medical tourism destinations. There are significant data gaps, and the almost universal lack of comprehensive surveillance programs that include molecular epidemiologic testing has made it difficult to understand the origins and extent of the problem in depth. A complex combination of factors such as inappropriate prescription of antibiotics, overstretched health systems, and international travel (including the phenomenon of medical tourism) probably led to the rapid rise and spread of these bacteria in hospitals in South and Southeast Asia. In India, Pakistan, and Vietnam, carbapenem-resistant Enterobacteriaceae have also been found in the environment and community, likely as a consequence of poor environmental hygiene and sanitation. Considerable political will and effort, including from countries outside these regions, are vital in order to reduce the prevalence of such bacteria in South and Southeast Asia and prevent their global spread.

Carbapenem-Resistant Acinetobacter baumannii and Enterobacteriaceae in South and Southeast Asia

Carbapenem-resistant Gram-negative bacteria, in particular the Acinetobacter baumannii-calcoaceticus complex and Enterobacteriaceae, are escalating global public health threats. We review the epidemiology and prevalence of these carbapenem-resistant Gram-negative bacteria among countries in South and Southeast Asia, where the rates of resistance are some of the highest in the world. These countries house more than a third of the world's population, and several are also major medical tourism destinations. There are significant data gaps, and the almost universal lack of comprehensive surveillance programs that include molecular epidemiologic testing has made it difficult to understand the origins and extent of the problem in depth. A complex combination of factors such as inappropriate prescription of antibiotics, overstretched health systems, and international travel (including the phenomenon of medical tourism) probably led to the rapid rise and spread of these bacteria in hospitals in South and Southeast Asia. In India, Pakistan, and Vietnam, carbapenem-resistant Enterobacteriaceae have also been found in the environment and community, likely as a consequence of poor environmental hygiene and sanitation. Considerable political will and effort, including from countries outside these regions, are vital in order to reduce the prevalence of such bacteria in South and Southeast Asia and prevent their global spread.

High prevalence of extensively drug-resistant and metallo beta-lactamase-producing clinical Acinetobacter baumannii in Iran

Acinetobacter species particularly Acinetobacter baumannii (A. baumannii) have been widely reported as broad-spectrum antibiotic resistant pathogens. Expression of various types of metallo beta-lactamases (MBL), classified as Ambler class B, has been associated with carbapenem resistance. Here, we attempted to assess the frequency of extensively drug-resistant (XDR) and MBL-producing A. baumannii among clinical isolates. 86 clinical A. baumannii strains were collected from 2014 to 2015 and their susceptibility to meropenem (10 μg), imipenem (10 μg), azteronem (30 μg), pipracillin (100 μg) tazobactam (110 μg), tobramycin (10 μg), fosfomycin (200 μg), rifampicin (5 μg), colistin (10 μg), tigecycline (15 μg), sulbactam/ampicillin (10 μg + 10 μg) and polymixin B (300 U) was evaluated using disk diffusion method. The MBL-producing isolates were screened using combined disc diffusion method. Furthermore, the presence of blaVIM, blaIMP, blaSPM, blaGIM, blaSIM and blaNDM was detected by PCR. 34.9% of isolates were recovered from bronchoalveolar lavage (BAL). 81 (94.2%) and 62 (71.2%) isolates were multidrug resistance (MDR) and XDR, respectively. 44 (51.2%) and 65 (75.6%) isolates were MBL-producing strains with resistance to imipenem and meropenem, respectively. 2 (2.3%), 13 (15.1%), 2 (2.3%), 4 (4.7%) and 2 (2.3%) isolates carried blaVIM, blaIMP, blaSPM, blaGIM and blaSIM genes, respectively. Our data showed that the rate of XDR and MBL A. baumannii is on the rise.

Functional Characterization of AbeD, an RND-Type Membrane Transporter in Antimicrobial Resistance in Acinetobacter baumannii

Background

Acinetobacter baumannii is becoming an increasing menace in health care settings especially in the intensive care units due to its ability to withstand adverse environmental conditions and exhibit innate resistance to different classes of antibiotics. Here we describe the biological contributions of abeD, a novel membrane transporter in bacterial stress response and antimicrobial resistance in A. baumannii.

Results

The abeD mutant displayed ~ 3.37 fold decreased survival and >5-fold reduced growth in hostile osmotic (0.25 M; NaCl) and oxidative (2.631 μM–6.574 μM; H₂O₂) stress conditions respectively. The abeD inactivated cells displayed increased susceptibility to ceftriaxone, gentamicin, rifampicin and tobramycin (~ 4.0 fold). The mutant displayed increased sensitivity to the hospital-based disinfectant benzalkonium chloride (~3.18-fold). In Caenorhabditis elegans model, the abeD mutant exhibited (P<0.01) lower virulence capability. Binding of SoxR on the regulatory fragments of abeD provide strong evidence for the involvement of SoxR system in regulating the expression of abeD in A. baumannii.

Conclusion

This study demonstrates the contributions of membrane transporter AbeD in bacterial physiology, stress response and antimicrobial resistance in A. baumannii for the first time.