Prevalence of bla NDM, bla PER, bla VEB, bla IMP, and bla VIM Genes among Acinetobacter baumannii Isolated from Two Hospitals of Tehran, Iran.
ABSTRACT: Background and Objectives. The aim of this study was to determine the frequency of bla NDM, bla PER, bla VEB, bla IMP, and bla VIM type genes among A. baumannii isolates from hospitalized patients in two hospitals in Tehran, Iran. Patients and Methods. Antibiotic susceptibility tests were performed by Kirby-Bauer disc diffusion and Broth microdilution methods. The frequency of MBL (metallo-beta-lactamase) and ESBL (extended-spectrum-beta-lactamase) producers was evaluated by CDDT. The ? -lactamases genes were detected by PCR and sequencing methods. Results. The resistance of A. baumannii isolates against tested antibiotics was as follows: 103 (95.4%) to ceftazidime, 108 (100%) to cefotaxime, 105 (95.7%) to cefepime, 99 (91.7%) to imipenem, 99 (91.7%) to meropenem, 87 (80.6%) to amikacin, 105 (97.2%) to piperacillin, 100 (92.6%) to ciprofloxacin, 103 (95.4%) to piperacillin/tazobactam, 44 (40.7%) to gentamicin, 106 (98.1%) to ampicillin/sulbactam, 106 (98.1%) to co-trimoxazole, 87 (80.6%) to tetracycline, and 1 (1.8%) to colistin. Using combined disk diffusion test, 91 (84.2%) and 86 (86.86%) were ESBL and MBL producers, respectively. The prevalence of bla PER-1, bla VEB-1, bla IMP-1, and bla VIM-1 genes was 71 (78.03%), 36 (39.5%), 3 (3.48%), and 15 (17.44%), respectively. Conclusions. The prevalence of ESBLs and MBLs-producing A. baumannii strains detected in this study is a major concern and highlights the need of infection control measures.
Project description:Background:Carbapenem resistance in Acinetobacter baumannii has become a major concern for treating physicians. The aim of this study was to investigate the prevalence of metallo ?-lactamase (MBL) genes (bla VIM , and bla IMP) among isolated multidrug-resistant A. baumannii . Methods:Fifty non-repetitive carbapenem-resistant A. baumannii isolates were collected. Antibiotic susceptibility was performed by disk diffusion method. MICs were determined by E test method. The resistant strains were tested for the production of carbapenemases by the Modified Hodge Test (MHT) followed by EDTA-disk synergy test was performed for metallo-?-lactamases (MBL) phenotypic detection. Detection of bla VIM , and bla IMP was performed by PCR followed by sequencing. Results:All isolates had a multidrug resistant profile, and were all resistant to all antibiotics including the carbapenems but remained susceptible to colistin. Among these isolates, Carbapenemase production was confirmed by the Modified Hodge test for 42 (84%) isolates. Phenotypic method showed the production of MBL in 15 (30%) isolates. PCR techniques revealed that out of 50 isolates, 13 (26%) were positive for bla VIM and all were negative for bla IMP . Conclusion:Our study concludes that the high prevalence of carbapenem resistant Acinetobacter species with MBL production is one of the main concerns in our country and this situation needs strict infection control measures.
Project description:Carbapenem-resistant Pseudomonas aeruginosa (CRPA) and Acinetobacter baumannii (CRAB) are the leading causes of nosocomial infections. A rapid and sensitive test to detect CRPA and CRAB is required for appropriate antibiotic treatment. We optimized a loop-mediated isothermal amplification (LAMP) assay to detect the presence of bla(VIM-2), bla(IMP-1), and bla(OXA-23), which are critical components for carbapenem resistance.Two sets of primers, inner and outer primers, were manually designed as previously described. The LAMP buffer was optimized (at 2mM MgSO₄) by testing different concentrations of MgSO₄. The optimal reaction temperature and incubation time were determined by using a gradient thermocycler. Then, the optimized bla(VIM-2), bla(IMP-1), and bla(OXA-23) LAMP reactions were evaluated by using 120 P. aeruginosa and 99 A. baumannii clinical isolates.Only one strain of the 100 CRPA isolates harbored bla(IMP-1), whereas none of them harbored bla(VIM-2). These results indicate that the acquisition of bla(VIM-2) or bla(IMP-1) may not play a major role in carbapenem resistance in Korea. Fifty two strains of the 75 CRAB isolates contained bla(OXA-23), but none contained bla(VIM-2) and bla(IMP-1) alleles.Our results demonstrate the usefulness of LAMP for the diagnosis of CRPA and CRAB.
Project description:In 2004 and 2005, 5 metallo-beta-lactamase (MBL)-positive Acinetobacter baumannii isolates were found in 2 Greek hospitals. Isolates were unrelated and carried blaVIM-1 in a class 1 integron; bla(OXA-51-) and bla(OXA-58-like) carbapenemase genes were also detected. VIM-1 MBL in Acinetobacter spp. causes concern, given the increasing resistance of this species.
Project description:During a survey conducted to evaluate the incidence of class B carbapenemase (metallo-beta-lactamase [MBL])-producing Pseudomonas aeruginosa strains from hospitals in Majorca, Spain, five clinical isolates showed a positive Etest MBL screening test result. In one of them, strain PA-SL2, the presence of a new bla(VIM) derivative (bla(VIM-13)) was detected by PCR amplification with bla(VIM-1)-specific primers followed by sequencing. The bla(VIM-13)-producing isolate showed resistance to all beta-lactams (except aztreonam), gentamicin, tobramycin, and ciprofloxacin. VIM-13 exhibited 93% and 88% amino acid sequence identities with VIM-1 and VIM-2, respectively. bla(VIM-13) was cloned in parallel with bla(VIM-1), and the resistance profile conferred was analyzed both in Escherichia coli and in P. aeruginosa backgrounds. Compared to VIM-1, VIM-13 conferred slightly higher levels of resistance to piperacillin and lower levels of resistance to ceftazidime and cefepime. VIM-13 and VIM-1 were purified in parallel as well, and their kinetic parameters were compared. The k(cat)/K(m) ratios for the antibiotics mentioned above were in good agreement with the MIC data. Furthermore, EDTA inhibited the activity of VIM-13 approximately 25 times less than it inhibited the activity of VIM-1. VIM-13 was harbored in a class 1 integron, along with a new variant (Ala108Thr) of the aminoglycoside-modifying enzyme encoding gene aacA4, which confers resistance to gentamicin and tobramycin. Finally, the VIM-13 integron was apparently located in the chromosome, since transformation and conjugation experiments consistently yielded negative results and the bla(VIM-13) probe hybridized only with the genomic DNA.
Project description:From January 2001 to December 2002, 587 strains of gram-negative bacterial isolates demonstrating resistance to ceftazidime and a combination of sulbactam and cefoperazone were subjected to a disk diffusion screening test using sodium mercaptoacetic acid; 431 strains (73.4%) appeared to produce metallo-beta-lactamase (MBL). Of these 431 strains, 357 were found by PCR to carry genes for IMP-1 type MBL (bla(IMP-1)), while only 7 and 67 strains carried the IMP-2 gene (bla(IMP-2)) and the VIM-2 gene (bla(VIM-2)), respectively. Neither VIM-1 nor SPM-1 type MBL genes were found among the strains tested. Of 431 strains, 427 carried the intI1 gene, and 4 strains carrying both the intI1 and intI3 genes were reidentified as Pseudomonas putida harboring bla(IMP-1). Of these four P. putida strains, three strains and one strain, respectively, were separately isolated from two hospitals located in the same prefecture, and the three strains showed very similar pulsed-field gel electrophoresis patterns. Of 357 bla(IMP-1) carriers, 116, 53, 51, 47, and 30 strains were identified as Pseudomonas aeruginosa, Alcaligenes xylosoxidans, P. putida/fluorescens, Serratia marcescens, and Acinetobacter baumannii, respectively. Four strains carrying bla(IMP-2) were reidentified as P. putida. Sixty-three P. aeruginosa strains and four P. putida strains carried bla(VIM-2). Of 427 intI1-positive strains, 180, 53, 51, 47, and 35 were identified as P. aeruginosa, A. xylosoxidans, P. putida/fluorescens, S. marcescens, and A. baumannii, respectively. In the present study, it was confirmed that strains carrying bla(IMP-1) with a class 1 integron are the most prevalent type in Japan, although several intI3 carriers have also been identified sporadically in this country.
Project description:BACKGROUND:Carbapenem resistant Acinetobacter baumannii is an important nosocomial pathogen associated with a variety of infections. OBJECTIVES:The current study aimed to characterize the antimicrobial susceptibility, analyze the prevalence of oxacillinase and metallo-?-lactamase (MBL) genes and molecular typing of clinical isolates of A. baumannii. MATERIALS AND METHODS:A total of 124 non-repetitive isolates of A. baumannii were collected from various clinical specimens in two teaching hospitals in Ahvaz, south-west of Iran. Antimicrobial susceptibility test was carried out by disk diffusion method. The minimum inhibitory concentrations (MICs) of imipenem, meropenem, colistin and tigecycline were determined using E-test. To screen for MBL production, double disk synergy (DDs) test and MBL E-test were performed. The presence of bla OXA-23-like, bla OXA-24-like, bla OXA-51-like, bla OXA-58-like, bla VIM, bla IMP and bla SPM genes was assessed by polymerase chain reaction (PCR). To identify clonal relatedness, all isolates were subjected to repetitive sequence-based PCR (rep-PCR). RESULTS:Based on disk diffusion results, the highest rate of resistance was observed in rifampin (96.8%). Colistin and polymyxin-B were the most effective agents in vitro. According to the MIC results, the rate of resistance to imipenem, meropenem, colistin and tigecycline were 78.2%, 73.4%, 0.8% and 0, respectively. Metallo-?-lactamase production was positive in 42.3% and 79.4% of the isolates by DDs test and E-test, respectively. All isolates (100%) carried bla OXA-51-like gene. According to the results of multiplex PCR, bla OXA-23-like and bla OXA-24-like genes were detected in 85.6% and 6.2% of carbapenem resistant isolates, respectively. No bla OXA-58- like, bla VIM, bla IMP and bla SPM were detected. By rep-PCR, carbapenem resistant isolates were separated into six genotypes (A to F). Genotype A (30.9%) was the most prevalent (P value < 0.001). Genotypes B and C were found in 28.9% and 26.8% of the isolates, respectively. CONCLUSIONS:The rate of carbapenem resistant A. baumannii isolates were high in this study. Since, bla OXA-58-like or MBL genes were not detected, it seems that resistance to carbapenems is related to bla OXA-23-like and bla OXA-24-like. Moreover, bla OXA-23-like was the most prevalent oxacillinase (OXA) gene. Most of the isolates belonged to one of the four dominant genotypes indicating clonal dissemination in the hospitals under study. In order to control the spread of carbapenem-resistant A. baumannii, infection- control strategies are needed.
Project description:Acquired Metallo-?-Lactamases (MBLs) are emerging resistance determinants in Pseudomonas aeruginosa and other gram-negative bacteria.Using Combination Disk Diffusion test, it was found that among 83 imipenem non-susceptible P. aeruginosa strains, 48 (57.9%) were MBL producers. PCR and Sequencing methods proved that these isolates were positive for blaIMP-1 genes, whereas none were positive for bla(VIM) genes. The mortality rate due to MBL-producing Pseudomonas infection was 4 (8.3%) among the hospitalized patients. Therefore, identification of drug resistance patterns in P. aeruginosa and detection of MBLs producing isolates are of great importance in the prevention and control of infections.
Project description:The purpose of this study was to identify the genes coding for resistance to ceftazidime and imipenem and describe the molecular epidemiology of A. baumannii strains isolated from a clinical center in Colombia. Twenty isolates of imipenem-resistant A. baumannii from an equal number of patients with nosocomial infections were obtained. Primers were used to amplify genes bla IMP, bla VIM, bla OXA-23, bla OXA-24, bla OXA-58, bla OXA-51 and bla ADC-7. To detect insertion sequences ISAba1/bla OXA-23, ISAba1/bla OXA-51 and ISAba1/bla ADC-7, mapping by PCR using combinations of reverse primers ISAba1 and reverse primers of bla OXA-23, bla OXA-51 and bla ADC-7 were used. The amplification products were purified and cloned into PCR 2.1-TOPO vector and transformed into chemically competent Escherichia coli TOP10. These amplicons were then sequenced. PFGE was performed on DNA of A. baumannii isolates digested with ApaI. Results. The DNA profiles obtained included 9 clusters with, four 2-7 isolates per profile, and 5 single-isolate profiles. Of the 20 isolates resistant to imipenem, 15 carried bla OXA-23 gene, 4 contained ISAba1 upstream of bla OXA-51 gene, and 6 contained ISAba1 upstream of bla OXA-23 gene. Eighteen of these isolates carried the bla ADC-7 gene, with 9 of the isolates having ISAba1 located upstream of this gene. This is the first report of the ISAba1/ADC-7 associated with OXAs genes in A. baumannii isolates from Colombia.
Project description:Carbapenem resistance mediated by acquired carbapenemase genes has been increasingly reported, particularly for clinical isolates of Pseudomonas aeruginosa and Acinetobacter spp. Of 1,234 non-duplicate isolates of carbapenem-resistant Pseudomonas spp. and Acinetobacter spp. isolated at a tertiary-care hospital in Seoul, Korea, 211 (17%) were positive for metallo-beta-lactamase (MBL). Of these, 204 (96%) had either the bla(IMP-1) or bla(VIM-2) allele. In addition, seven Acinetobacter baumannii isolates were found to have a novel MBL gene, which was designated bla(SIM-1). The SIM-1 protein has a pI of 7.2, is a new member of subclass B1, and exhibits 64 to 69% identity with the IMP-type MBLs, which are its closest relatives. All SIM-1-producing isolates exhibited relatively low imipenem and meropenem MICs (8 to 16 microg/ml) and had a multidrug resistance phenotype. Expression of the cloned bla(SIM-1) gene in Escherichia coli revealed that the encoded enzyme is capable of hydrolyzing a broad array of beta-lactams, including penicillins, narrow- to expanded-spectrum cephalosporins, and carbapenems. The bla(SIM-1) gene was carried on a gene cassette inserted into a class 1 integron, which included three additional cassettes (arr-3, catB3, and aadA1). The strains were isolated from sputum and urine specimens from patients with pneumonia and urinary tract infections, respectively. All patients had various underlying diseases. Pulsed-field gel electrophoresis of SmaI-digested genomic DNAs showed that the strains belonged to two different clonal lineages, indicating that horizontal transfer of this gene had occurred and suggesting the possibility of further spread of resistance in the future.
Project description:The occurrence of carbapenem-resistant (CR) strains of Acinetobacter baumannii is reported to contribute to the severity of several nosocomial infections, especially in critically ill patients in intensive care units. The present study aims to determine the antibiotic susceptibility, clonality, and genetic mechanism of carbapenem resistance in twenty-eight Acinetobacter baumannii isolates from four hospitals in Washington DC. The antibiotic susceptibility of the isolates was determined by VITEK 2 analyses, while PCR was used to examine the presence of antibiotic-resistant genes and mobile genetic elements. Trilocus multiplex-PCR was used along with pulsed-field gel electrophoresis (PFGE) for strain typing and for accessing clonal relationships among the isolates. Antimicrobial susceptibility testing indicated that 46% of the isolates were carbapenem-resistant and possessed MDR and XDR phenotypes. PFGE clustered the 28 isolates into seven clonal (C1-C7) complexes based on >75% similarity cut-off. Thirty-six percent of the isolates belonged to international clone II, while 29% were assigned to Group 4 by trilocus multiplex-PCR. Although the bla OXA-51-like gene was found in all the isolates, only 36% were positive for the bla OXA-23-like gene. PCR analysis also found a metallo-?-lactamase (MBL) gene (bla VIM ) in 71% of the isolates. Of the 13 CR isolates, 8 were PCR positive for both bla VIM and bla OXA-23-like genes, while 5 harbored only bla VIM gene. This study revealed the emergence of VIM carbapenemase-producing A. baumannii isolates, which has not been previously reported in the United States.