Antimicrobial Resistance Mechanisms and Genetic Diversity of Multidrug-Resistant Acinetobacter baumannii Isolated from a Teaching Hospital in Malaysia

Acinetobacter baumannii: insights towards a comprehensive approach for the prevention of outbreaks in health-care facilities

Acinetobacter baumannii is known to be an opportunistic pathogen frequently responsible for outbreaks in health-care facilities, particularly in Intensive Care Units (ICU). It can easily survive in the hospital setting for long periods and can be transmitted throughout the hospital in a variety of ways, explored in this review. It can also easily acquire antibiotic resistance determinants rendering several antibiotic drugs useless. In 2019, the US Centre for Disease Control (CDC) considered the organism as an urgent threat. The aim of this review was to raise the awareness of the medical community about the relevance of this pathogen and discuss how it may impact seriously the healthcare institutions particularly in the aftermath of the recent COVID-19 pandemic. PubMed was searched, and articles that met inclusion criteria were reviewed. We conclude by the need to raise awareness to this pathogen's relevance and to encourage the implementation of preventive measures in order to mitigate its consequences namely the triage of specific high-risk patients.

Molecular and genetic characterization of emerging carbapenemase-producing Acinetobacter baumannii strains from patients and hospital environments in Bangladesh

Background

Carbapenemase-producing multidrug-resistant (MDR) Acinetobacter baumannii is a global health care problem. MDR A. baumannii has emerged as an important nosocomial pathogen, costing many lives worldwide including Bangladesh.

Aim

To investigate the detailed molecular epidemiology of carbapenem-resistant A. baumannii (CRAB) both from patients and the hospital environment, to shed light on genetic characteristics and transmission dynamics.

Methods

A set of 49 clinical A. baumannii strains collected during early 2015 was received from the clinical microbiology laboratory of Dhaka Medical College Hospital (DMCH) in Bangladesh. Additionaly, 100 environmental samples were also collected from the hospital surfaces of Dhaka Medical College Hospital and analyzed for carbapenamase-producing A. baumannii. CRAB were identified by culture on selective plates, biochemical testing and MALDI-TOF. All isolates were characterized by susceptibility testing, realtime-PCRs, conventional PCR, MLST and sequencing.

Findings

Clinical A. baumannii were resistant to ciprofloxacin (100%), imipenem (91.8%), meropenem (91.8%), gentamicin (91.8%), amikacin (87.7%), and trimethoprim-sulfamethoxazole (61.2%). The majority (59%) of the isolates were MDR. All environmental A. baumannii (n=10) were resistant to imipenem, meropenem, gentamicin, amikacin, and ciprofloxacin. Strains carried the following antibiotic resistant genes; bla_OXA-23,bla_OXA-58,bla_PER-7,qnrB1, qnrC1, aac(6′)1b-cr and armA. A total of 36 different clones were identified by rep-PCR and common clonal clusters were found both in patients and hospital environments. MLST analysis revealed different sequence types (ST2, ST10, ST149, ST575, ST1063 and ST1065). In clinical and environmental settings. A. baumannii ST2 dominated in both clinical and environmental settings. Both clinical and environmental A. baumannii strains with known STs carried several biofilm-related genes; bap, csuE, and pgaB.

Conclusion

Widespread dissemination of MDR A. baumannii in the DMC hospital of Bangladesh is a serious problem.

Phage Revolution Against Multidrug-Resistant Clinical Pathogens in Southeast Asia

Southeast Asia (SEA) can be considered a hotspot of antimicrobial resistance (AMR) worldwide. As recent surveillance efforts in the region reported the emergence of multidrug-resistant (MDR) pathogens, the pursuit of therapeutic alternatives against AMR becomes a matter of utmost importance. Phage therapy, or the use of bacterial viruses called bacteriophages to kill bacterial pathogens, is among the standout therapeutic prospects. This narrative review highlights the current understanding of phages and strategies for a phage revolution in SEA. We define phage revolution as the radical use of phage therapy in infectious disease treatment against MDR infections, considering the scientific and regulatory standpoints of the region. We present a three-phase strategy to encourage a phage revolution in the SEA clinical setting, which involves: (1) enhancing phage discovery and characterization efforts, (2) creating and implementing laboratory protocols and clinical guidelines for the evaluation of phage activity, and (3) adapting regulatory standards for therapeutic phage formulations. We hope that this review will open avenues for scientific and policy-based discussions on phage therapy in SEA and eventually lead the way to its fullest potential in countering the threat of MDR pathogens in the region and worldwide.

The Role of Antibiotic Resistant A. baumannii in the Pathogenesis of Urinary Tract Infection and the Potential of Its Treatment with the Use of Bacteriophage Therapy

Acinetobacter baumannii are bacteria that belong to the critical priority group due to their carbapenems and third generation cephalosporins resistance, which are last-chance antibiotics. The growing multi-drug resistance and the ability of these bacteria to form biofilms makes it difficult to treat infections caused by this species, which often affects people with immunodeficiency or intensive care unit patients. In addition, most of the infections are associated with catheterization of patients. These bacteria are causative agents, inter alia, of urinary tract infections (UTI) which can cause serious medical and social problems, because of treatment difficulties as well as the possibility of recurrence and thus severely decrease patients' quality of life. Therefore, a promising alternative to standard antibiotic therapy can be bacteriophage therapy, which will generate lower costs and will be safer for the treated patients and has real potential to be much more effective. The aim of the review is to outline the important role of drug-resistant A. baumannii in the pathogenesis of UTI and highlight the potential for fighting these infections with bacteriophage therapy. Further studies on the use of bacteriophages in the treatment of UTIs in animal models may lead to the use of bacteriophage therapy in human urinary tract infections caused by A. baumannii in the future.

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.

Systematic surveillance and meta-analysis on the prevalence of metallo-β-lactamase producers among carbapenem resistant clinical isolates in Pakistan

BACKGROUND

Emergence of carbapenem resistance (CR) is a health concern of pertinent importance. Epidemiological surveillance of CR at global and indigenous level (Pakistan) can help to improve infection control and establish pharmacovigilance programs. This study evaluates the prevalence of clinically significant CR isolates, and its genetic variant distribution among geographical regions of Pakistan.

METHODS

A meta-analysis was conducted to present the current rate of CR infections and prevalence of Metallo-β-lactamases (MBLs). The proposed subject was researched using electronic databases to identify the available literature. Thereafter, relevant data was extracted and statistical analysis was performed using STATA version 14.

RESULTS

A total of 110 relevant studies were identified with 19 meeting the inclusion criteria for the meta-analysis of CR, while 22 for MBLs. Pooled rate for carbapenem resistance was determined to be 0.28 (95% CI: 0.26-0.31) with overall significant heterogeneity (I²=99.61%, P<0.001) and significant estimated score ES=0 (Z=22.65, P<0.001). In Pakistan, the pooled proportion of MBL producers was 0.34 (95% CI: 0.29-0.39) with overall heterogeneity significance (I²=99.62%, P<0.001) and significant ES=0 (Z=13.17, P<0.001).

CONCLUSION

Conclusively, diverse variants of carbapenemases (VIM, IMP, NDM, KPC, GIM) along with other β-lactamase variants (OXA, TEM, SHV, CTX-M) have been reported across the country. However, New Delhi Metallo-β-lactamase (NDM)-variants were reported in predominant literature. The prevalence of CR isolates in Pakistan is alarming, associated with MBL production primarily evident from the studies. The study emphasizes the need for regular surveillance, pharmacovigilance and antibiotic stewardship programs to ensure the availability of data to the authorities for preemptive measures of infection control.

In vitro antimicrobial photodynamic inactivation of multidrug-resistant Acinetobacter baumannii biofilm using Protoporphyrin IX and Methylene blue

BACKGROUND

Acinetobacter baumannii is a challenging pathogen due to the rapid development of antimicrobial resistance and biofilm formation. The objective of this study was to evaluate the effect of antimicrobial photodynamic inactivation against biofilms of multidrug-resistant A. baumannii isolated from clinical, abattoir and aquatic sources.

METHODS

The isolates were tested for susceptibility to imipenem, meropenem, tigecycline and colistin using autoSCAN-4 automated system and rechecked by the E-test. Methylene blue, Protoporphyrin IX, and a halogen lamp were used in the in vitro assay against biofilms of the isolates. The antimicrobial photodynamic inactivation was assessed by counting colony-forming units (CFU).

RESULTS

The isolates from abattoir and aquatic sources were resistant to carbapenems (>64 μg/mL) but susceptible to tigecycline (2 μg/mL) and colistin (Abattoir, 0.35 μg/mL and Aquatic, 0.24 μg/mL), whereas the clinical isolate was susceptible to only colistin (0.5 μg/mL) using the E-test. The log survival percentages of the control group at a concentration of 20 μM were 5 × 10^-6 % for Protoporphyrin IX and 2 × 10^-6 % for Methylene blue. Therefore, Methylene blue showed higher bacterial reduction of 7.0 log₁₀ colony forming units than 6.0 log₁₀ for Protoporphyrin IX. No significant difference was observed with respect to the origin of isolates and the minimum inhibitory concentrations.

CONCLUSION

The results indicate that antimicrobial photodynamic inactivation could be an alternative strategy for the control of infections caused by multi-drug resistant A. baumannii by significantly reducing biofilm growth at a sub-lethal concentrations.

Risk Factors and Drug Resistance of the MDR Acinetobacter Baumannii in Pneumonia Patients in ICU

OBJECTIVE

To investigate the risk factors and drug resistance of MDR Acinetobacter baumannii in pneumonia patients.

METHODS

From January 2013 to February 2016, 98 pneumonia patients with MDR Acinetobacter baumannii in our hospital ICU were selected as the observation group, and 49 pneumonia patients with not-MDR Acinetobacter baumannii in our hospital ICU were selected as the control group in accordance with the proportion of 2:1. Sputum samples were collected from the two groups for drug resistance, and the risk factors and prognosis of MDR Acinetobacter baumannii in pneumonia patients were given survey analysis.

RESULTS

The observation group was highly resistant to cefotaxime, piperacillin, imipenem, levofloxacin, gentamicin, tetracycline and ceftazidime, and was only sensitive to polymyxin. In addition to piperacillin, polymyxin B, the other antimicrobial drug resistance rates in the control group was significantly lower than in the observation group (P<0.05). Univariate analysis showed that diabetes, infection before hospitalization, admission 24h score of APACHE II and GCS scores, deep venous catheterization, and mechanical ventilation were related to the MDR Acinetobacter baumannii in pneumonia patients(P<0.05). Non conditional logistic regression analysis showed that diabetes mellitus, infection before hospitalization, admission 24h score of APACHE II and GCS scores were the independent risk factors for the MDR Acinetobacter baumannii in pneumonia patients(P<0.05).

CONCLUSION

MDR Acinetobacter baumannii in pneumonia patients in ICU is common, where diabetes infection before hospitalization, admission 24h score of APACHE II and GCS scores are the main risk factors, and the vast majority of the antibiotics are resistant to the MDR Acinetobacter baumannii that can lead to poorer prognosis and followed-up of patients with increased mortality.

Urinary tract colonization is enhanced by a plasmid that regulates uropathogenic Acinetobacter baumannii chromosomal genes

Multidrug resistant (MDR) Acinetobacter baumannii poses a growing threat to global health. Research on Acinetobacter pathogenesis has primarily focused on pneumonia and bloodstream infections, even though one in five A. baumannii strains are isolated from urinary sites. In this study, we highlight the role of A. baumannii as a uropathogen. We develop the first A. baumannii catheter-associated urinary tract infection (CAUTI) murine model using UPAB1, a recent MDR urinary isolate. UPAB1 carries the plasmid pAB5, a member of the family of large conjugative plasmids that represses the type VI secretion system (T6SS) in multiple Acinetobacter strains. pAB5 confers niche specificity, as its carriage improves UPAB1 survival in a CAUTI model and decreases virulence in a pneumonia model. Comparative proteomic and transcriptomic analyses show that pAB5 regulates the expression of multiple chromosomally-encoded virulence factors besides T6SS. Our results demonstrate that plasmids can impact bacterial infections by controlling the expression of chromosomal genes.

Acinetobacter baumannii is generally considered an opportunistic pathogen. Here, Di Venanzio et al. develop a mouse model of catheter-associated urinary tract infection and show that a plasmid confers niche specificity to an A. baumannii urinary isolate by regulating the expression of chromosomal genes.

Investigation of multidrug-resistant ST2 Acinetobacter baumannii isolated from Saint George hospital in Lebanon

BACKGROUND

Acinetobacter baumannii is an opportunistic pathogen causing various nosocomial infections. The spread of multidrug-resistant A. baumannii is a major public health problem. The aim of this study was to investigate the molecular epidemiology and the genetic support of multidrug-resistant A. baumannii isolates collected from Saint-Georges Hospital in Lebanon.

METHODS

Between January and August 2016, 31 A. baumannii isolates were collected from sputum samples of patients infected with ventilator-associated pneumonia (VAP) and treated with colistin-carbapenem combination therapy. Antibiotic susceptibility testing was performed using the disk diffusion method. Carbapenemases, extended spectrum β-lactamases encoding genes and mcr-1/2 genes were investigated by RT-PCR and standard PCR. The epidemiological relatedness of the strains was studied using MLST analysis.

RESULTS

Most of the isolates exhibited multidrug-resistant phenotypes. All the isolates were carbapenem-resistant and among them, 30 carried the class D carbapenemase bla_oxa-23 gene while one isolate carried bla_oxa-72 gene. MLST results revealed three sequence types, namely ST2, ST699, and ST627. Isolates having ST2 were the most prevalent clone (29/31, 93.5%).

CONCLUSIONS

This study shows a nosocomial spread of multidrug-resistant A. baumannii ST2 having bla_OXA-23 gene in Saint-George in Lebanon. Monitoring and control measures need to be adopted to avoid the spread of A. baumannii to patients.

Molecular epidemiology and genetic characterisation of carbapenem-resistant Acinetobacter baumannii isolates from Guangdong Province, South China

OBJECTIVES

Carbapenem-resistant Acinetobacter baumannii (CRAB) has become a worldwide issue. This study aimed to characterise the epidemiology and genetic relationships of A. baumannii isolates in Guangdong Province, China.

METHODS

CRAB isolates were collected from five municipal hospitals from June-December 2017. The 16S-23S rRNA intergenic spacer region was used for confirmation of strain identity. Antimicrobial susceptibility testing and the CarbAcineto NP test were performed to analyse the resistance spectrum and carbapenemase production of the isolates. PCR-based assays were used to detect β-lactamase genes and related mobile genetic elements. Genetic diversity among the isolates was analysed by enterobacterial repetitive intergenic consensus (ERIC)-PCR, multilocus sequence typing (MLST) and multiplex PCR.

RESULTS

A total of 122 isolates were confirmed as A. baumannii; all were resistant to the tested antibiotics except for tigecycline and colistin. The CarbAcineto NP test showed that 93.4% of the isolates produced a carbapenemase. bla_OXA-23-like and extended-spectrum β-lactamase-encoding genes were found by PCR in 94.3% and 91.8% of the isolates, respectively. Furthermore, the genetic environment of bla_OXA-23-like was mainly associated with transposons Tn2008 (46.1%), Tn2006 (27.0%) and Tn2009 (20.9%). MLST identified six existing sequence types (STs) and three novel STs, of which ST195 (35.7%) and ST208 (32.1%) were the most common, belonging to clonal group 92 and European clone II.

CONCLUSION

This study suggests that co-production of β-lactamases was the major resistance mechanism of CRAB isolates. Dissemination of bla_OXA-23-like may be facilitated by transposable elements. ST195 and ST208 were the predominant epidemic types of A. baumannii in Guangdong Province.

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.

Acinetobacter spp. Infections in Malaysia: A Review of Antimicrobial Resistance Trends, Mechanisms and Epidemiology

Acinetobacter spp. are important nosocomial pathogens, in particular the Acinetobacter baumannii-calcoaceticus complex, which have become a global public health threat due to increasing resistance to carbapenems and almost all other antimicrobial compounds. High rates of resistance have been reported among countries in Southeast Asia, including Malaysia. In this review, we examine the antimicrobial resistance profiles of Acinetobacter spp. hospital isolates from Malaysia over a period of nearly three decades (1987–2016) with data obtained from various peer-reviewed publications as well as the Malaysian National Surveillance on Antibiotic Resistance (NSAR). NSAR data indicated that for most antimicrobial compounds, including carbapenems, the peak resistance rates were reached around 2008–2009 and thereafter, rates have remained fairly constant (e.g., 50–60% for carbapenems). Individual reports from various hospitals in Peninsular Malaysia do not always reflect the nationwide resistance rates and often showed higher rates of resistance. We also reviewed the epidemiology and mechanisms of resistance that have been investigated in Malaysian Acinetobacter spp. isolates, particularly carbapenem resistance and found that bla_OXA-23 is the most prevalent acquired carbapenemase-encoding gene. From the very few published reports and whole genome sequences that are available, most of the Acinetobacter spp. isolates from Malaysia belonged to the Global Clone 2 (GC2) CC92 group with ST195 being the predominant sequence type. The quality of data and analysis in the national surveillance reports could be improved and more molecular epidemiology and genomics studies need to be carried out for further in-depth understanding of Malaysian Acinetobacter spp. isolates.

Biology of Acinetobacter baumannii: Pathogenesis, Antibiotic Resistance Mechanisms, and Prospective Treatment Options

Acinetobacter baumannii is undoubtedly one of the most successful pathogens responsible for hospital-acquired nosocomial infections in the modern healthcare system. Due to the prevalence of infections and outbreaks caused by multi-drug resistant A. baumannii, few antibiotics are effective for treating infections caused by this pathogen. To overcome this problem, knowledge of the pathogenesis and antibiotic resistance mechanisms of A. baumannii is important. In this review, we summarize current studies on the virulence factors that contribute to A. baumannii pathogenesis, including porins, capsular polysaccharides, lipopolysaccharides, phospholipases, outer membrane vesicles, metal acquisition systems, and protein secretion systems. Mechanisms of antibiotic resistance of this organism, including acquirement of β-lactamases, up-regulation of multidrug efflux pumps, modification of aminoglycosides, permeability defects, and alteration of target sites, are also discussed. Lastly, novel prospective treatment options for infections caused by multi-drug resistant A. baumannii are summarized.