Characterization of Verona Integron-Encoded Metallo-β-Lactamase-Type Carbapenemase-Producing Escherichia coli Isolates Collected over a 16-Year Period in Bolzano (Northern Italy)

Multidrug-resistant Escherichia coli, particularly carbapenemase producers, are a major source of concern. This study aims to investigate the long-term epidemiology of Verona integron-encoded metallo-β-lactamase (VIM)-producing E. coli in the health district of Bolzano, Northern Italy, by examining the phenotypic and genotypic characteristics of 26 isolates obtained during 2005-2020. Isolates were identified with matrix-assisted laser desorption/ionization time-of-flight, susceptibility testing was by Vitek 2, Sensititre, and Etest; carbapenemase activity was confirmed by Etest and Carbapenemase Inactivation Method (CIM) test; and the VIM-antigen was identified by the NG-Test CARBA 5. Genome sequencing was performed on an Illumina MiSeq platform. Carbapenem minimum inhibitory concentrations varied across methodologies, and overall category agreement between phenotypic methods was low. All 23 sequenced isolates contained blaVIM-1. Eleven (47.8%) isolates belonged to the clonal lineage ST131, with fimH30 being the most common subclone. In Bolzano ST131-fimH30 was present as early as 2005. While the ST131 clonal lineage predominated for the first 10 years, various clonal lineages were present, especially in subsequent years, indicating the concurrent circulation of multiple clonal lineages. Future efforts should focus on the implementation of surveillance methods, including genomic analysis, as well as the use of updated infection control strategies and antibiotic stewardship programs to prevent the spread of these carbapenem-resistant strains.

Development of a novel loop-mediated isothermal amplification assay for ß-lactamase gene identification using clinical isolates of Gram-negative bacteria

Rapid evaluation of antimicrobial susceptibility is important in the treatment of nosocomial infections by Gram-negative bacteria, which increasingly carry carbapenemases and metallo-β-lactamases. We developed loop-mediated isothermal amplification (LAMP)-based assays for four β-lactamase genes (bla _KPC, bla _NDM-1, bla _IMP-1 group, and bla _VIM). The assays were evaluated using eight reference bacterial strains (Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter bereziniae) harboring six β-lactamase genes. A total of 55 Gram-negative bacterial strains, including 47 clinical P. aeruginosa isolates, fully characterized by next-generation sequencing (NGS), were used to evaluate the LAMP assays. The results were compared to those of conventional PCR. The LAMP assays were able to detect as few as 10 to 100 copies of a gene, compared to 10 to 10⁴ copies for conventional PCR. The LAMP assay detected four β-lactamase genes with a sensitivity similar to that using purified DNA as the template in DNA-spiked urine, sputum, and blood specimens. By contrast, the sensitivity of PCR was 1- to 100-fold lower with DNA-spiked clinical specimens. Therefore, the LAMP assays were proved to be an appropriate tool for the detection of four β-lactamases.

Genotypic Characterization of Carbapenem-Resistant Klebsiella pneumoniae Isolated from an Egyptian University Hospital

Globally, Klebsiella pneumoniae (K. pneumoniae) has been identified as a serious source of infections. The objectives of our study were to investigate the prevalence of multidrug-resistant (MDR) K. pneumoniae in Tanta University Hospitals, Gharbia Governorate, Egypt; characterize their carbapenem resistance profiles; and identify their different capsular serotypes. We identified and isolated 160 (32%) K. pneumoniae from 500 different clinical samples, performed antimicrobial susceptibility testing, and then used multiplex PCR to detect carbapenemase genes and capsular serotypes K1, K2, K3, K5, K20, K54, and K57. We detected phenotypic carbapenem resistance in 31.3% (50/160) of the isolates; however, molecular assays revealed that 38.75% (62/160) of isolates were carrying carbapenemase-encoding genes. Generally, blaOXA-48 was the prevalent gene (15.5%), followed by blaVIM (15%), blaIMP (7.5%), blaKPC (4%), and blaNDM (3.8%). BlaVIM and blaOXA-48 correlated with phenotypic resistance in 91.67% and 88% of the isolates that harbored them, respectively. Capsular typing showed that the most prevalent pathotype was K1 (30.6%), followed by K57 (24.2%), K54 (19.35%), K20 (9.67%), and K2 (6.45%). A critical risk to community health is posed by the high incidence of multidrug-resistant (MDR) virulent K. pneumoniae isolates from our hospital, and our study examines this pathogen's public health and epidemiological risks.

Phenotypic and genotypic investigation of metallo-β-lactamases in Pseudomonas aeruginosa clinical isolates in Bushehr, Iran

Objectives

Production of metallo-β-lactamases (MBLs) is an important mechanism of resistance to carbapenems. This study aimed to detect the MBL-producing Pseudomonas aeruginosa clinical isolates and to investigate the presence of bla _VIM, bla _IMP, bla _SPM, bla _NDM, bla _GIM, bla _AIM, and bla _SIM genes in these isolates in Bushehr, Iran.

Materials and Methods

A total of 169 P. aeruginosa clinical isolates were collected from three hospitals in Bushehr. The modified carbapenem inactivation method (mCIM) was used for the phenotypic detection of carbapenemase production. A combination disk test (CDT) was performed for the phenotypic detection of MBL production. To investigate the presence of bla _VIM, bla _IMP, bla _SPM, bla _NDM, bla _GIM, bla _AIM, and bla _SIM genes, PCR and sequencing was carried out.

Results

Based on the results of mCIM, 40 (23.7%) of 169 isolates were carbapenemase producers. CDT revealed that 26 (15.4%) isolates were MBL producers. bla _IMP, bla _NDM, and bla _VIM genes were found in 18 (69.2%), 8 (30.8%), and 1 (3.8%) of the MBL-producing isolates, respectively. Coexistence of bla _IMP and bla _NDM was observed in 2 (7.7%) MBL-producing isolates. Among all 169 P. aeruginosa isolates, 23 (13.6%) harbored bla _NDM, 18 (10.6%) carried bla _IMP, and 1 (0.6%) carried the bla _VIM gene. bla _SPM, bla _GIM, bla _AIM, and bla _SIM were not found in the present study.

Conclusion

bla _NDM, bla _IMP, and bla _VIM genes were detected in this study, which could be a warning sign about the prevalence of these genes among P. aeruginosa clinical isolates in our region. Proper monitoring and detection of MBL-producing isolates are essential steps to prevent the spread of these isolates.

Association of Biofilm Inducer with bla VIM, bla IMP, and bla NDM in Pseudomonas aeruginosa Isolates

Pseudomonas aeruginosa (P. aeruginosa) is a ubiquitous opportunistic organism that is hard to treat. This study aimed to investigate the association of bla _VIM, bla _IMP, and bla _NDM prevalence with Cyclic di-GMP (c-di-GMP) in P. aeruginosa. To this end, 27 clinical isolates of P. aeruginosa were obtained from different hospitals in Baghdad, Iraq. The phenotypic detection of carbapenem and biofilm assays was performed by the M63 minimal medium, supplemented with glucose, magnesium sulfate. The polymerase chain reaction was utilized to detect carbapenem genes. The results showed that the isolates were highly resistant to Imipenem (37%) and Meropenem (63%). Imipenem (37%) and Meropenem (63%) demonstrated a moderate sensitivity against P. aeruginosa. The P. aeruginosa No.5 showed high resistance to carbapenem by bla _VIM ⁺, bla _IMP ⁺, and bla _NDM ⁺, followed by a robust biofilm confirmed with c-di-GMP levels and the twitching motility ability. Upon these findings, the use of antibiotics should be restricted to severe bacterial infections to avoid the rapid emergence of new resistant isolates, which leads to the hard treatment of infection with P. aeruginosa. It is highly recommended that these findings be notified for infectious control. Future studies can investigate the link between transferable resistant genes and c-di-GMP values.

Genetic diversity and molecular analysis of metallo beta lactamases among imipenem resistant clinical isolates of Pseudomonas aeruginosa from Peshawar, Pakistan

Objectives

Pseudomonas aeruginosa is an opportunistic pathogen with remarkable adaptation ability to thrive in diverse environmental conditions. This study aimed at phenotypic and molecular analysis of metallo beta lactamases (blaIMP, blaVIM, blaNDM-1 and blaSPM-1) and genetic diversity analysis among imipenem resistant clinical isolates of Pseudomonas aeruginosa.

Methods

This study was conducted from May 2017 to June 2018. The study included 187 Pseudomonas aeruginosa isolates collected from different clinical specimens from Peshawar, Pakistan. The isolates were analyzed for resistance to imipenem. Combined disc test (CDT) was then performed for phenotypic detection of metallo beta lactamases among imipenem resistant isolates of Pseudomonas aeruginosa. Molecular detection of metallo beta lactamases genes i.e. blaIMP, blaVIM, blaNDM-1 and blaSPM-1 was analyzed through polymerase chain reaction. Genetic diversity was determined through RAPD-PCR.

Results

MBL production was observed in 76% (n=19) isolates. The occurrence of MBL genes blaIMP, blaNDM-1 and blaVIM was 68% (n=17), 48% (n=12), and 4% (n=1) respectively. The blaSPM-1 gene was not detected. High genetic diversity was observed in current study. Out of 182 isolates 171 isolates showed different RAPD profiles (93.95% polymorphism); 160 were unique RAPD strains and based on similarity coefficient ≥ 80%, 22 isolates were clustered into 11 distinct clones.

Conclusion

A high prevalence of blaIMP and blaNDM-1 among imipenem resistant isolates of Pseudomonas aeruginosa is alarming that calls for proper control and prevention strategies. RAPD technique was found to be a good genotyping technique when limited resources are available.

Design of Rapid Detection System for Five Major Carbapenemase Families (bla KPC, bla NDM, bla VIM, bla IMP and bla OXA-48-Like) by Colorimetric Loop-Mediated Isothermal Amplification

Purpose

Carbapenemase-producing Enterobacteriaceae (CPE) infection constitutes a public health threat. Timely and efficient diagnosis is of paramount importance for prompt and effective therapy. In order to quickly and comprehensively detect the five major families of carbapenemases (bla_KPC, bla_NDM, bla_VIM, bla_IMP, and bla_OXA-48-like), colorimetric loop-mediated isothermal amplification (LAMP) was employed.

Materials and Methods

Five sets of LAMP primers were designed, each of which can, respectively, amplify all the carbapenemase subtypes described in this work. Twenty whole genome sequencing-verified-“standard strains”, including 1 bla_NDM-1, 1 bla_NDM-5, 1 bla_NDM-6, 1 bla_NDM-7, 2 bla_IMP-4, 1 bla_IMP-8, 2 bla_KPC-2, 1 bla_KPC-3, 1 bla_KPC-4, 1 bla_KPC-5, 1 bla_KPC-6, 1 bla_KPC-7, 1 bla_OXA-48 and 1 bla_OXA-181 carrier, and 1 bla_VIM and bla_OXA-244, 1 bla_KPC-2 and bla_IMP-4, 1 bla_KPC-2 and bla_VIM-1 and 1 bla_KPC-2 and bla_NDM-1-co-carriers, were used to establish a 25-microliter visual LAMP reaction system (kept at 65°C for 30 minutes in water bath). Color change from bright pink to yellow indicated positive amplification. In addition, 126 pre-verified clinical carbapenem-resistant Enterobacteriaceae (CRE) isolates, including 65 CPE (23 bla_NDM, 2 bla_OXA-48-like, 1 bla_KPC and bla_VIM, 2 bla_IMP, and 37 bla_KPC carriers) and 61 non-CPE, were also detected.

Results

With the lowest detection limit of 10 colony forming units (CFU) per reaction for LAMP and 10³ CFU per reaction for PCR, the LAMP system demonstrated dramatically higher sensitivity while retaining the same specificity. Furthermore, we demonstrated concordant results between the two methods for the 126 clinical isolates.

Conclusion

Therefore, LAMP could be used for rapid identification of the five major carbapenemase gene families in routine clinical laboratories.

Genotypic to Phenotypic Resistance Discrepancies Identified Involving β-Lactamase Genes, blaKPC, blaIMP, blaNDM-1, and blaVIM in Uropathogenic Klebsiella pneumoniae

Introduction

Klebsiella pneumoniae carbapenemase (KPC) belongs to the Group-A β-lactamases that incorporate serine at their active site and hydrolyze various penicillins, cephalosporins, and carbapenems. Metallo-beta-lactamases (MBLs) are group-B enzymes that contain one or two essential zinc ions in the active sites and hydrolyze almost all clinically available β-lactam antibiotics. Klebsiella pneumoniae remains the pathogen with the most antimicrobial resistance to KPC and MBLs.

Methods

This research investigated the blaKPC, and MBL genes, namely, blaIMP, blaVIM, and blaNDM-1 and their phenotypic resistance to K. pneumoniae isolated from urinary tract infections (UTI) in Bangladesh. Isolated UTI K. pneumoniae were identified by API-20E and 16s rDNA gene analysis. Their phenotypic antimicrobial resistance was examined by the Kirby-Bauer disc diffusion method, followed by minimal inhibitory concentration (MIC) determination. blaKPC, blaIMP, blaNDM-1, and blaVIM genes were evaluated by polymerase chain reactions (PCR) and confirmed by sequencing.

Results

Fifty-eight K. pneumoniae were identified from 142 acute UTI cases. Their phenotypic resistance to amoxycillin-clavulanic acid, cephalexin, cefuroxime, ceftriaxone, and imipenem were 98.3%, 100%, 96.5%, 91.4%, 75.1%, respectively. Over half (31/58) of the isolates contained either blaKPC or one of the MBL genes. Individual prevalence of blaKPC, blaIMP, blaNDM-1, and blaVIM were 15.5% (9), 10.3% (6), 22.4% (13), and 19% (11), respectively. Of these, eight isolates (25.8%, 8/31) were found to have two genes in four different combinations. The co-existence of the ESBL genes generated more resistance than each one individually. Some isolates appeared phenotypically susceptible to imipenem in the presence of blaKPC, blaIMP, blaVIM, and blaNDM-1 genes, singly or in combination.

Conclusion

The discrepancy of genotype and phenotype resistance has significant consequences for clinical bacteriology, precision in diagnosis, the prudent selection of antimicrobials, and rational prescribing. Heterogeneous phenotypes of antimicrobial susceptibility testing should be taken seriously to avoid inappropriate diagnostic and therapeutic decisions.

Detection of VIM-1, VIM-2 and IMP-1 metallo- β-lactamase genes in Klebsiella pneumoniae isolated from clinical samples in Sanandaj, Kurdistan, west of Iran

BACKGROUND AND OBJECTIVES

Klebsiella pneumoniae is an important cause of serious nosocomial infections among Gram-negative bacteria. The aim of this study was evaluating the prevalence of VIM-1, VIM-2, and IMP-1 metallo-β-lactamase genes in clinical specimens at two teaching hospitals in Sanandaj, Kurdistan west of Iran.

MATERIALS AND METHODS

Four hundred different clinical specimens were collected from hospitalized patients or referred to hospitals from May 2013 to March 2014 in Sanandaj, Kurdistan, Iran. MBLs - producing K. pneumoniae detected by Double Disk Synergy Test. The MBL positive isolates were examined for the presence of VIM-1, VIM-2 and IMP-1 genes using PCR technique.

RESULTS

Of four hundred clinical specimens, 114 K. pneumoniae isolates were identified. Twenty-eight (24.6%) isolates were resistant to imipenem and 15 strains (53.6%) were positive for MBL enzymes production. PCR results showed VIM-1 and IMP-1 genes frequencies are 4 (26.7%) and 1 (6.7%). Only one strain of K. pneumoniae was found to be MBL producer among the outpatients.

CONCLUSION

The study results exhibited a high level of resistance to most of the antibiotics tested and high prevalence of MBLs producing in K. pneumoniae at two hospitals. Thus, the infection control methods and the implementation of antibiotic agents should be taken into account.

Association of the genes encoding Metallo-β-Lactamase with the presence of integrons among multidrug-resistant clinical isolates of Acinetobacter baumannii

Background: Metallo-β-Lactamases (MBL) are usually encoded on the gene cassettes harboring integrons and disseminated easily among Acinetobacter baumannii isolates. This study was aimed to investigate the association of the genes encoding MBL with the presence of class 1 and 2 integrons among multidrug-resistant (MDR) A.baumannii isolates.

Methodology: A total of 85 non-duplicated A.baumannii isolates were collected and evaluated for the amplification of bla_OXA-51. The presence of genes encoding MBLs, including bla_IMP, bla_VIM, bla_SIM, bla_SPM, bla_GIM, bla_DIM and bla_NDM, as well as intI 1 and intI 2 was evaluated by PCR. Also, the production of MBLs was screened phenotypically by the combination of EDTA and meropenem.

Results: In this study, 77 out of 85 isolates were MDR. Also, 34 isolates had only intI 1, 10 had only intI 2 and 15 had both intI 1 and intI 2. The phenotypic detection of MBLs was found in 30 isolates, among which bla_VIM was as the most common the gene encoding MBL followed by bla_IMP, bla_SPM and bla_SIM. The gene cassettes analysis revealed that class 1 integron is often responsible for transferring the genes harboring MBLs.

Conclusion: The production of MBLs among A. baumannii strains is one of the main mechanisms of resistance to carbapenems. Therefore, the development of inexpensive screening methods for the phenotypic detection of MBLs in clinical laboratories settings is essential. Also, our data revealed that the class 1 integron is often responsible for the dissemination of the MBL genes among A. baumannii isolates.

Genetic Characterization of a bla VIM-24-Carrying IncP-7β Plasmid p1160-VIM and a bla VIM-4-Harboring Integrative and Conjugative Element Tn6413 From Clinical Pseudomonas aeruginosa

This study presents three novel integrons In1394, In1395, and In1443, three novel unit transposons Tn6392, Tn6393, and Tn6403, one novel conjugative element (ICE) Tn6413, and the first sequenced IncP-7 resistance plasmid p1160-VIM from clinical Pseudomonas aeruginosa. Detailed sequence comparison of p1160-VIM (carrying Tn6392 and Tn6393) and Tn6413 (carrying Tn6403) with related elements were performed. Tn6392, Tn6393, and Tn6403 were generated from integration of In1394 (carrying bla _VIM-24), In1395 and In1443 (carrying bla _VIM-4) into prototype Tn3-family unit transposons Tn5563, Tn1403, and Tn6346, respectively. To the best of our knowledge, this is the first report of a bla _VIM-24-carrying P. aeruginosa isolate.

Drug Resistance and Molecular Epidemiology of Carbapenem Resistant Gram-negative Bacilli Isolates

Objectives:

Detection and comparison of metallo-β-lactamase (MBL) production in clinical isolates by phenotypic and genotypic measures. The objective of this study is to evaluate clinical characteristics and risk factors in patients infected with MBLs.

Materials and Methods:

Study was conducted by the Department of Microbiology, Jawaharlal Nehru Medical College from February 2014 to December 2015. Bacterial culture, identification, and antibiotic susceptibility were carried out according to standard guidelines. MBL production was detected both phenotypically (Modified Hodge test [MHT], imipenem-ethylene diamine tetraacetic acid double disk potentiation test [IMP-EDTA DDPT], IMP-EDTA combined disk synergy test [IMP-EDTA CDST]), and genotypically (blaNDM-1, blaVIM and blaIMP).

Results:

Among 116 carbapenem-resistant Gram-negative Bacilli (CRGNB), Citrobacter species 28 (24.1%) was the most common pathogen. Phenotypically, MHT, IMP-EDTA DDPT, and IMP-EDTA CDST detected MBL production in 105 (90.5%), 96 (81%), and 87 (75%) CRGNB, respectively. BlaNDM-1 genes were detected in 6 6 (56.8%) isolates, however, very few blaVIM (16, 15.2%) and blaIMP (1, 1.2%) were identified. Considering polymerase chain reaction (PCR) as the gold standard, it was observed that IMP-EDTA CDST was most specific (78.3%) while MHT was most sensitive (97.4%). Results of blaNDM-1 gene by PCR were further confirmed by sequencing (Triyat genomics, Nagpur). All the 11 representative strains were confirmed to be NDM-1 gene. Major risk factors in patients infected with MBLs were in-dwelling devices (68%), prolonged hospital stay (72%) and prior antibiotic treatment (86%). However, on tracing their outcome, it was interesting to note that mortality was relatively low 5 (4.3%).

Conclusion:

The present study shows a rising trend of blaNDM-1 in CRGNB, an ominous sign heralding the post antibiotic era. It is essential to assess the prevalence of various MBLs so that infection control measures can be reinforced. We recommend three phenotypic tests in tandem for the detection of MBL. While phenotypic tests are easy and cost-effective to perform, quick, effective molecular diagnostic techniques can tailor treatment guidelines to optimize patient's management.

blaVIM and blaIMP Genes Detection in Isolates of Carbapenem Resistant P. aeruginosa of Hospitalized Patients in Two Hospitals in Iran

BACKGROUND & OBJECTIVE

Beta-lactam antibiotics resistance specifically Imipenem and Meropenem, the last choices of treatment, causes fatal events in patients with P.aeruginosa infection. The aim of this study was to detect the VIM and IMP of metallo-beta-lactamase genes in 103 isolates of P. aeruginosa in two Iranian hospitals.

METHODS

In this study, we evaluated the susceptibility of P. aeruginosa to a range of β-lactam antibiotics using disk diffusion method as a standard biochemical test. Combined disk test of Imipenem (IMP) and Imipenem plus Ethylenediaminetetraacetic acid (EDTA) was performed as a phenotypic method to find metallo-beta-lactamase producing isolates.Using conventional PCR method; we evaluated VIM and IMP of metallo-beta-lactamase (MBL) genes in 103 isolates of P.aeruginosa.

RESULTS

Twenty six (25.2%) out of 103 isolates were resistant to Imipenem and 26 (25.2%) to Meropenem. Among 26 Imipenem and Meropenem-resistant strains (25.2%), 19 cases (73.0%) were MBL producing. Using PCR method, we detected the bla_VIM and bla_IMP genes in 6 (5.8%) and 2(1.9%) of 19 MBL producing isolates, respectively.

CONCLUSIONS

Evaluation of these carbepenemases genes improve epidemiologic researches and also, can be used as a diagnostic tool for discriminating between antibiotics resistant and sensitive strains of P.aeruginosa as well as follow-up the patients after treatment.

Comparative Evaluation of Multiplex PCR and Routine Laboratory Phenotypic Methods for Detection of Carbapenemases among Gram Negative Bacilli

BACKGROUND

Carbapenem resistant pathogens cause infections associated with significant morbidity and mortality.

OBJECTIVE

This study evaluates the use of Multiplex PCR for rapid detection of carbapenemase genes among carbapenem resistant Gram negative bacteria in comparison with the existing phenotypic methods like modified Hodge test (MHT), combined disc test (CDT) and automated methods.

MATERIAL AND METHODS

A total of 100 Carbapenem resistant clinical isolates, [Escherichia coli (25), Klebsiella pneumoniae (35) P. aeruginosa (18) and Acinetobacter baumannii (22)] were screened for the presence of carbapenemases (bla NDM-1, bla VIM , blaIMP and blaKPC genes) by phenotype methods such as the modified Hodge test (MHT) and combined disc test (CDT) and the molecular methods such as Multiplex PCR.

RESULTS

Seventy of the 100 isolates were MHT positive while, 65 isolates were positive by CDT. All the CDT positive isolates with EDTA and APB were Metallo betalactamase (MBL) and K. pneumoniae carbapenemase (KPC) producers respectively. bla NDM-1 was present as a lone gene in 44 isolates. In 14 isolates bla NDM-1 gene was present with blaKPC gene, and in one isolate bla NDM-1 gene was present with blaVIM , gene. Only one E. coli isolate had a lone blaKPC gene. We didn't find bla IMP gene in any of the isolates. Neither of the genes could be detected in 35 isolates.

CONCLUSION

Accurate detection of the genes related with carbapenemase production by Molecular methods like Multiplex PCR overcome the limitations of the phenotypic methods and Automated systems.