Molecular characterisation and control of Acinetobacter baumannii isolates resistant to multi-drugs emerging in inter-intensive care units

Characterization of class 1 integrons in metallo-β-lactamase-producing Acinetobacter baumannii isolates from hospital environment

BACKGROUND AND OBJECTIVE

The emergence and widespread dissemination of antibiotic resistance in A. baumannii, has become a globally challenge. The increasing hospital outbreaks by multi-drug resistant (MDR) A. baumannii strains, shows the necessity of continuous monitoring to find sources of resistant strains in hospitals. This study aimed to identify the presence of class 1 integrons and metallo-β-lactamase (MBL) related genes in A. baumannii isolates from hospital environment.

METHODS

In order to identify A. baumannii isolates, a total of 297 environmental samples were collected from burn wards and intensive care units (ICUs) of two university hospitals. Resistance to common antibiotics was studied by disk diffusion method and microbroth dilution assay was used to determine the minimum inhibitory concentrations (MICs) of imipenem, colistin and tigecycline. The A. baumannii isolates were studied by polymerase chain reaction (PCR) for the presence of class 1 integrons (intI1, intl CS) and metallo-β-lactamases (MBLs) (blaIMP, blaVIM, blaNDM) genes.

RESULTS

A. baumannii was identified in 68/297 (22.9%) of hospital environment. All A. baumannii strains were multidrug-resistant (MDR), but none of them were resistant to colistin, tigecycline and ampicillin-sulbactam. All (100%) and 38 (95.0%) of A. baumannii isolates from ICUs and burn wards were imipenem resistant respectively. Class 1 integrons was identified in 30/40 (75.0%) and 23/28 (82.1%) isolates from burn wards and ICUs respectively. Two different types of gene cassettes were identified, which included: arr-2, ereC, aadA1, cmlA5 and arr2, cmlA5. MBL genes including blaVIM and blaIMP were detected in 26/28 (92.8%), 27/28(96.4%) and 39/40 (97.5%) and 31/40 (77.5%) of the isolates from the ICUs and the burn wards respectively. None of the isolates contained the blaNDM-1 gene.

CONCLUSION

The findings of the present study showed that the isolation rate of MBL producing carbapenem-resistant A. baumannii (CRAB) was relatively high in the environmental surface of burn wards and ICUs, which can be considered as a potential source of outbreaks in hospitalized patients.

Genome sequences of bla NDM-1 producing Acinetobacter lactucae isolated from immunocompromised patients in India

Among the species within Acb-complex, Acinetobacter lactucae has not been frequently isolated from clinical settings, unlike Acinetobacter baumannii, which is an important nosocomial pathogen. We report the genomic sequences of A. lactucae strains (PKAL1732 and 1828C) harboring multiple-resistance determinants including metallo-β-lactamase (bla NDM-1) isolated from immunocompromised patients admitted to a referral hospital in India.

Does Emerging Carbapenem Resistance in Acinetobacter baumannii Increase the Case Fatality Rate? Systematic Review and Meta-Analysis

BACKGROUND

In the era of rising carbapenem resistance, we aimed to investigate the change in mortality rate and positivity of carbapenemase genes in Acinetobacter baumannii.

METHODS

Preferred Reporting Items for Systematic Review (PRISMA) guidelines were adopted in this systematic review. Our literature search included the Cochrane Library, Pubmed, Scopus, Web of Science, Medline, Tubitak TR Dizin, and Harman databases for studies dating back from 2003 to 2023 reporting bloodstream A. baumannii infections in Türkiye. A simple linear regression model was used to determine the association between resistance, mortality, and time.

RESULTS

A total of 1717 studies were identified through a literature search, and 21 articles were selected based on the availability of the data regarding mortality and resistance rate (four articles) or the molecular epidemiology of carbapenem-resistant A. baumannii (17 articles) in Türkiye. From 2007 to 2018, the carbapenem resistance rate increased (p = 0.025). The OXA-23 and OXA-58 positivities were inversely correlated (p = 0.025).

CONCLUSIONS

Despite the emergence of carbapenem resistance, mortality did not increase in parallel, which may be due to improved medical advancements or the fitness cost of bacteria upon prolonged antimicrobial exposure. Therefore, we suggest further global research with the foresight to assess clonal relatedness that might affect the carbapenem resistance rate.

Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii isolates in Turkiye: Systematic review

The World Health Organization has designated carbapenem-resistant Acinetobacter baumannii (CRAB) as a "critical" pathogen on the global priority list of antibiotic-resistant bacteria. This study aims to discuss the molecular epidemiology of CRAB isolates in Turkiye in the last 12 years and the prevalence of gene regions associated with resistance or pathogenesis using a systematic review method. Our study consists of a literature search, determination of eligibility and exclusion criteria, qualitative analysis of studies, data extraction, and statistical analysis. All studies were analyzed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Guidelines. The incidence rates of blaOXA-23, blaOXA-23-like, blaOXA-24/40, blaOXA-24/40-like, blaOXA-51, blaOXA-51-like, blaOXA-58, and blaOXA-58-like genes in CRAB strains were 76.4%, 68.6%, 1.2%, 3.4%, 97.0%, 98.6%, 8.4%, and 17.1%, respectively. It was determined that the prevalence of the blaOXA-23 and blaOXA-58 gene regions showed a statistically significant change over the years. Due to the high prevalence of A. baumannii strains carrying the blaOXA-23 variant, it is necessary to follow its geographical distribution and transposon and plasmid movements. Based on available data, molecular surveillance of CRAB strains should be standardized. In addition, sterilization and disinfection processes applied within the scope of an effective struggle against CRAB strains that can remain live on surfaces for a long time should be reviewed frequently.

Contamination of healthcare environment by carbapenem-resistant Acinetobacter baumannii

Acinetobacter baumannii is frequently found on floors, devices, and environmental sites in hospitals and can survive for prolonged periods and accumulate resistance determinants. The infection and presence of carbapenem-resistant A. baumannii (CRAB) in patients is associated with increased mortality, severe clinical outcomes, and longer lengths of stay at hospitals. This review addresses contamination by CRAB in corporal surfaces of patients and healthcare workers and environmental sites at healthcare-related settings. We summarized published data during the last decade on potential reservoirs for CRAB, including contamination frequency and the involved resistance mechanisms, and some measures associated with the elimination of CRAB from hospital surfaces.

Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii Blood Culture Isolates from Three Hospitals in Turkey

We aimed to investigate the clonal relationships, common sequence types, and carbapenemase genes in 177 non-repetitive blood culture isolates of Acinetobacter baumannii collected from patients at three university hospitals in Turkey in 2016. Molecular epidemiological characteristics of the isolates were examined using pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) (Pasteur scheme-cpn60, fusA, gltA, pyrG, recA, rplB, and rpoB). Multiplex PCR was used to investigate the carbapenemase genes, including bla_OXA-23-like, bla_OXA-24-like, bla_OXA-48-like, bla_OXA-58-like, bla_IMP, bla_VIM, and bla_NDM. PFGE genotyping yielded 92 pulsotypes with a clustering ratio of 69.7%. As per a ≥85% similarity coefficient, 159 (90.9%) isolates were found to be clonally related. The bla_OXA-23-like and bla_OXA-58-like genes were identified in 100% and 28.2% of the isolates, respectively. The bla_NDM gene was identified in two isolates. The MLST analysis included 54 isolates with different pulsotypes, and 29 sequence types (STs). Most of the isolates (n = 36) belonged to the clonal complex (CC)2, one isolate belonged to CC1, and one isolate belonged to CC164. Sixteen new STs (ST1235-ST1250) were identified. Identifying both global ST2 and a large number of new STs, revealed high genetic diversity in A. baumannii isolates in the study population.

Molecular characterization of carbapenemases of clinical Acinetobacter baumannii-calcoaceticus complex isolates from a University Hospital in Tunisia

The aim of this study was to identify the carbapenemases from clinical carbapenem-resistant Acinetobacter baumannii-calcoaceticus complex (CRABC) isolates and to assess their potential dissemination by conjugation and natural transformation. CRABC (n = 101) were collected consecutively from inpatients of the University Hospital of Monastir, Tunisia, from 2013 to 2016. Antimicrobial susceptibility was determined by the disk diffusion method and E-test. Carbapenemase-encoding genes were screened by PCR. Genotyping was performed by Pasteur MLST scheme. Isolates were resistant to all beta-lactams, fluoroquinolones and aminoglycosides while 80 and 90% were susceptible to tigecycline and colistin, respectively. Resistance and intermediate resistance to imipenem were 87 and 13%, respectively. The genes bla_OXA-24-like, bla_OXA-58-like, bla_OXA-143-like, bla_OXA-48-like, bla_VIM, bla_IMP, and bla_KPC were not found. The bla_OXA-51-like and bla_OXA-23-like genes were present in 100 and 82.17% isolates, respectively. One isolate (< 1%) carried bla_NDM-1 and bla_OXA-51-like and belonged to Sequence Type 85 (ST85). Absence of transconjugants suggests a chromosomal location of NDM-1 determinant. The bla_NDM-1 gene was inserted in a truncated form of Tn125, which may explain the absence of bla_NDM-1 carrier-transformants. To our knowledge, this is the first report of the finding of NDM-positive A. baumannii in Tunisian territory. The study shows that despite the low prevalence and potential spread of NDM-1 enzyme among CRABC, continuous regional antimicrobial resistance surveillance and improved infection control measures are required in Tunisia to prevent further dissemination.

Clonal diversity and detection of carbapenem resistance encoding genes among multidrug-resistant Acinetobacter baumannii isolates recovered from patients and environment in two intensive care units in a Moroccan hospital

Background

Carbapenem-resistant Acinetobacter baumannii has recently been defined by the World Health Organization as a critical pathogen. The aim of this study was to compare clonal diversity and carbapenemase-encoding genes of A. baumannii isolates collected from colonized or infected patients and hospital environment in two intensive care units (ICUs) in Morocco.

Methods

The patient and environmental sampling was carried out in the medical and surgical ICUs of Mohammed V Military teaching hospital from March to August 2015. All A. baumannii isolates recovered from clinical and environmental samples, were identified using routine microbiological techniques and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry. Antimicrobial susceptibility testing was performed using disc diffusion method. The carbapenemase-encoding genes were screened for by PCR. Clonal relatedness was analyzed by digestion of the DNA with low frequency restriction enzymes and pulsed field gel electrophoresis (PFGE) and the multi locus sequence typing (MLST) was performed on two selected isolates from two major pulsotypes.

Results

A total of 83 multidrug-resistant A. baumannii isolates were collected: 47 clinical isolates and 36 environmental isolates. All isolates were positive for the bla_OXA51-like and bla_OXA23-like genes. The coexistence of bla_NDM-1/bla_OXA-23-like and bla_{OXA 24-like}/bla_OXA-23-like were detected in 27 (32.5%) and 2 (2.4%) of A. baumannii isolates, respectively. The environmental samples and the fecally-colonized patients were significantly identified (p < 0.05) as the most common sites of isolation of NDM-1-harboring isolates. PFGE grouped all isolates into 9 distinct clusters with two major groups (0007 and 0008) containing up to 59% of the isolates. The pulsotype 0008 corresponds to sequence type (ST) 195 while pulsotype 0007 corresponds to ST 1089.The genetic similarity between the clinical and environmental isolates was observed in 80/83 = 96.4% of all isolates, belonging to 7 pulsotypes.

Conclusion

This study shows that the clonal spread of environmental A. baumannii isolates is related to that of clinical isolates recovered from colonized or infected patients, being both associated with a high prevalence of the bla_OXA23-like and bla_NDM-1genes. These findings emphasize the need for prioritizing the bio-cleaning of the hospital environment to control and prevent the dissemination of A. baumannii clonal lineages.

Electronic supplementary material

The online version of this article (10.1186/s13756-017-0262-4) contains supplementary material, which is available to authorized users.

Multidrug-Resistant Gram-Negative Bacilli: Infection Control Implications

Antimicrobial resistance is a common iatrogenic complication of both modern life and medical care. Certain multidrug resistant and extensively drug resistant Gram-negative organisms pose the biggest challenges to health care today, predominantly owing to a lack of therapeutic options. Containing the spread of these organisms is challenging, and in reality, the application of multiple control measures during an evolving outbreak makes it difficult to measure the relative impact of each measure. This article reviews the usefulness of various infection control measures in containing the spread of multidrug-resistant Gram-negative bacilli.

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

Background

Acinetobacter has gained importance as a multi-drug resistant and hence a difficult to treat pathogen. This study was done to characterize our isolates with respect to drug resistance and presence of beta-lactamases which is a major mechanism of resistance and to type using RAPD and MLST so that comparison of our clones can be made with the existing international clones.

Methods

100 isolates recovered from clinical samples from two hospitals in Delhi were tested for their susceptibility against major groups of antimicrobials. The resistant isolates were screened and confirmed phenotypically for presence of ESBL, MBL and AmpC and MBLs also by PCR. The isolates were typed by RAPD and MLST.

Results

Out of the 100 isolates, 91, 78 and 2 % were MDR, XDR and PDR respectively. 97, 100 and 85 were screen positive for ESBL, AmpC and MBL respectively. Of these, 38.1 % were confirmed phenotypically to produce ESBL, 99 % produced AmpC and 29.4 % produced MBL comprising of GIM, VIM, SIM and IMP. MLST showed known STs 110, 188, 146, 69, 103, 108 and 194. Eight new STs were encountered. The RAPD showed a high degree of genetic variability among the isolates.

Conclusion

Majority of our isolates were MDR, producing one or more types of beta-lactamases. We encountered drug resistant international clones by MLST which are found in other continents there by confirming their spread to Indian sub continent. No data on ST types of other Indian isolates is available in the MLST database and hence comparison is not possible.

Multiple drug resistant carbapenemases producing Acinetobacter baumannii isolates harbours multiple R-plasmids

BACKGROUND & OBJECTIVES

The nosocomial human pathogen Acinetobacter baumannii has high propensity to develop resistance to antimicrobials and to become multidrug resistant (MDR), consequently complicating the treatment. This study was carried out to investigate the presence of resistant plasmids (R-plasmids) among the clinical isolates of A. baumannii. In addition, the study was performed to check the presence of common β-lactamases encoding genes on these plasmids.

METHODS

A total of 55 clinical isolates of A. baumannii were included in the study and all were subjected to plasmid DNA isolation, followed by PCR to check the presence of resistance gene determinants such as blaOXA-23, blaOXA-51, blaOXA-58 and blaIMP-1 on these plasmids that encode for oxacillinase (OXA) and metallo-β-lactamase (MBL) type of carbapenemases. Plasmid curing experiments were carried out on selected isolates using ethidium bromide and acridine orange as curing agents and the antibiotic resistance profiles were evaluated before and after curing.

RESULTS

All the isolates were identified as A. baumannii by 16SrDNA amplification and sequencing. Plasmid DNA isolated from these isolates showed the occurrence of multiple plasmids with size ranging from 500bp to ≥25 kb. The percentage of blaOXA-51 and blaOXA-23 on plasmids were found to be 78 and 42 per cent, respectively and 20 isolates (36%) carried blaIMP-1 gene on plasmids. Significant difference was observed in the antibiograms of plasmid cured isolates when compared to their parental ones. The clinical isolates became susceptible to more than two antibiotic classes after curing of plasmids indicating plasmid borne resistance.

INTERPRETATION & CONCLUSIONS

Our study determined the plasmid mediated resistance mechanisms and occurrence of different resistance genes on various plasmids isolated from MDR A. baumannii. The present findings showed the evidence for antibiotic resistance mediated through multiple plasmids in A. baumannii clinical isolates. This indicates towards a need for preventive measures to avert the dissemination of plasmid resistance determinants in clinical environments.