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Background: The war against multidrug-resistant bacteria is challenging and of global concern. Hospitals are increasingly plagued by resistant gram negative pathogens. Bacteria of the family Enterobacteriaceae such as Escherichia coli and Klebsiella pneumoniae are part of the normal human intestinal flora but are also often responsible for community- and healthcare-associated infections. These bacteria are prone to acquiring resistance genes.Methods: Rectal swabs/swabs from the peri-anal area of the patients who were admitted in the Intensive Care Unit (ICU) of the accident and emergency department of this teaching hospital. Swabs were collected first on day 1 of admission, then day 4, and thereafter weekly during the period of stay in the ICU. All the swabs were immediately inoculated into trypticase soy broth with one 10μg meropenem disc and were incubated overnight at 35±2ºC, ambient air. Next day, the broth was vortexed, and then sub-cultured onto a MacConkey agar plate. On the third day, MacConkey agar plates were examined for lactose fermenting (pink-coloured) colonies. The representative isolated colonies were subjected to conventional antimicrobial susceptibility testing by the Kirby Bauer Disc diffusion method following the CLSI guidelines to know the susceptibility to carbapenem and other antimicrobial agents. Carbapenemase production was done by a Modified Hodge Test (MHT) and Imipenem-EDTA test.Results: Out of 89 patients, carbapenem resistant Klebsiella pneumoniae and E. coli isolates were recovered from 35 (39.3%) patients i.e. Klebsiella pneumoniae isolates from fifteen patients and carbapenem resistant E. coli isolates from twenty patients. Prevalence of carbapenemase producing isolates was found to be 1.42%. Conclusions: Surveillance for CRE can definitely help reduce rates of healthcare associated infections.
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Background: Carbapenems have the broadest activity spectra of any β-lactam antibiotic and are often the most appropriate agents for use in the treatment of infections caused by multi resistant gram negative bacteria. The recent worldwide emergence and dissemination of carbapenemase-producing Gram negative rods that are resistant to carbapenems is a significant concern with respect to patient care and infection control strategies. Hence this study was undertaken to study the magnitude of carbapenem resistance among routine clinical isolates of family Enterobacteriaceae so as to guide the clinicians in selection of appropriate antimicrobial chemotherapies and infection control measures.Methods: The present study was conducted in the Department of Microbiology over a period 18 months from January 2017 to July 2018. All the clinical isolates of Enterobacteriaceae were screened for carbapenem resistance as per CLSI guidelines. Such strains were then subjected to phenotypic confirmation of carbapenemase production by the Modified Hodge test. All isolates that gave a positive screening test were further evaluated for metallo-β-lactamase production. The technique used was the Combined Disk Test using a combination of Imipenem and Imipenem-EDTA.Results: Out of the 400 total clinical isolates of Enterobacteriaceae isolated in the laboratory,57 were found to be Meropenem resistant (14.25%) and were labelled 'Carbapenem resistant Enterobacteriaceae" or CRE. Modified Hodge test (MHT) performed on the 57 carbapenem resistant isolates showed 41 (71.93%) isolates to be carbapenemase enzyme producers. Combined disc test (CDT) conducted on the 57 isolates of CRE detected Metallo-β-lactamase (MBL) enzyme production in 39 isolates (68.42%).Conclusions: Since there is a high prevalence of carbapenemase resistance in our setting hence we need to be cautious with the indiscriminate use of broad spectrum antimicrobials, more so, the carbapenems.
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Non Fermenter Gram negative bacilli (NFGNB) has emerged as important hospital pathogens they are more significant as they are found to be multi drug resistant. Resistance to carbapenems is common among NFGNB. AIMS & OBJECTIVES: To isolate & identify NFGNB from various clinical samples and to detect resistance to carbapenem in isolates resistant to Imipenem. MATERIAL & METHOD: NFGNB isolated from various samples were speciated using standard tests. Isolates resistant to Imipenem were subjected to detection of MBLs(Metallo-β-lactmase) and Amp-C. RESULTS: Out of 1566 samples received, NFGNB were 200. Among them 112 were Pseudomonas aeruginosa from which 31 were found to be resistant to Imipenem, of which 3 were MBLproducer by Modified Hodge test while 4 were MBLproducer by EDTAdisc synergy test. Out of 200 NFGNB 71 were Acinetobacter baumanii, of which 23 were found to be resistant to Imipenem, of which 6 were MBLproducer by Modified Hodge test, while 4 were seen to be MBL producer by EDTAdisc synergy test. Nineteen isolates of Acinetobacter baumanii were found to be resistant to cefoxitin of which 6 were found to be Amp-C producer by Amp-c disc test. None of the Pseudomonas aeruginosa were Amp-C producer. Other NFGNB isolated were either sensitive to Imipenem or if resistant were not MBLor Amp-C producer.
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Objective To analyze the resistance genes of carbapenem resistant Enterohacteriaceae (CRE) from Zhongnan Hospital of Wuhan University,so as to provide evidence for CRE infection.Methods WHONET 5.6 software was used to analyze the resistance of carbapenem resistant Enterobacteriaceae isolated.Phenotype screening of 53 CRE strains taken with the modified Hodge test by three drug susceptibility slip to imipenem,meropenem and ertapenem,and analysed resistance gene analysis of 31 CRE strains phenotype screening.Results In 53 CRE strains,34 strains of Klebsiella pneumoniae,ac counting for 64.15 ％,12 strains of Escherichia coli,accounting for 22.64 ％,7 strains of Enterobacter cloacae accounted for 13.21％,and there were 31 strains of Hodge test positive strains,accounting for 58.49％ (31/53).The Hodge test results of three kinds of drug sensitive paper of imipenem,meropenem and ertapenem were consistent.In 31 strains of CRE,29 strains of blaKPC gone were amplified,accounting for 93.55 ％,9 strains of blaNDM gene.accounting for 29.03 ％,contained simaltaneous and two genes of blaKPC and blaNDM were 8 strains,accounting for 25.81 ％,the resistance genes of BlaIMP,blaOXA,and blaVIM were not amplified.Conclusion Resistance to carbapenems was mainly due to the production of KPC and NDM in Enterobacteriaceae of 31 strains.The CRE was detected in the Intensive Care Unit and Respiratory ward for mainly Klebsiella pneumoniae,and the main genotype was KPC.The CRE was detected in the Cadre ward mainly Escherich ia coli,and the drug resistant genotype was mainly a mixed type of KPC and NDM.
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Objective To explore clinical distribution characteristics of carbapenem-resistant Klebsiella pneumoniae (CRKP), analyze enzyme production of strains and verify the in vitro antimicrobial activity of tigecycline.Methods Antimicrobial susceptibility testing results of 53 strains of CRKP isolated from clinical specimens of patients in a hospital from January to December 2015 were analyzed, carbapenemase production of target strains was detected by modified Hodge test, metallo-β-lactamase was detected by EDTA synergy test, minimum inhibitory concentration(MIC) of tigecycline susceptibility testing result detected by instrument was confirmed by MIC test strip(MTS method).Results 53 CRKP strains were mainly isolated from patients in intensive care unit (n=14, 26.42％) and burn unit(n=13, 24.53％);sputum(n=23, 43.40％) and wound secretion(n=15, 28.30％) were the main specimen sources;isolation rate of CRKB was highest in the elderly≥60 years old, 35 strains(66.04％)of CRKP were isolated.CRKP was most sensitive to tigecycline(96.2％).The modified Hodge test showed that 48 strains(90.6％) produced carbapenemases and 15 strains produced metallo-β-lactamase.MICs of tigecycline-resistant strains detected by instrument were all confirmed as susceptibility by MTS.Conclusion CRKP mainly produce carbapenems in this hospital, some strains can produce two types of different β-lactamases;antimicrobial susceptibility testing showed that tigecycline has good antimicrobial activity against CRKP, tigecycline-resistant strains detected by instrument must be confirmed by MTS method.
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Objective To discuss the application value of modified Hodge test(MHT) for screening carbapenemase-producing Enterobacteriaceae.Methods The 24 Enterobacteriaceae reduced susceptibility to carbapenems were detected by MHT.At the same time,polymerase chain reaction(PCR) was used to detect carbapenemase genes of KPC,NDM,IMP,SIM and VIM.PCR products were sequenced and the results were compared with the sequences of Gen Bank database.Comprehensive analysis the application value of MHT and PCR to detect carbapenemase.Results Among these 24 strains,13 stains appeared to produce carbapenemase by MHT,5 positive strains were found to carry carbapenemase genes by PCR.By comparing with the sequences of Gen Bank database 1 strain were confirmed to KPC-2 and 4 strains were confirmed to IMP-4.We found that 4 strains of Enterobacteriaceae,detected carbapenemase by MHT and PCR at the same time.9 strains of MHT were positive,but we couldn′t detect the carbapenemase genes.1 strain of MHT was negative,but carbapenemase gene was found in the strain.Conclusion The value of MHT to screen carbapenemase-producing Enterobacteriaceae is necessary to further study.
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BACKGROUND: Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae are resistant to most β-lactam antibiotics except carbapenems. In recent years, infrequently isolated Enterobacteriaceae that produce carbapenemase pose a serious threat in the selection of appropriate therapeutic antibiotics. The rapid detection method of carbapenemase-producing Enterobacteriaceae (CPE) is necessary to prevent the spread of CPE into healthcare facilities. METHODS: One hundred clinical Enterobacteriaceae isolates (Klebsiella pneumoniae 40, Escherichia coli 40, others 20) showing susceptibility to carbapenems and positivity in the CLSI ESBL phenotypic test from November 2015 to March 2016 and 59 stocked Enterobacteriaceae isolates harboring resistance genes producing carbapenemase (K. pneumoniae 56, Enterobacter cloacae 2, E. coli 1; types of CPE: KPC 36, GES 12, NDM 6, VIM 2, OXA 2, IMP 1) were subjected to the RAPIDEC CARBA NP test (bioMérieux, France) and CPE phenotypic test using the modified Hodge test (MHT) and carbapenemase inhibition test. RESULTS: All of the 100 Enterobacteriaceae isolates with carbapenem susceptibility and ESBL positivity were negative on the RAPIDEC CARBA NP test and CPE phenotypic test. Of 59 stock CPE isolates, 53 and 42 showed positive results to the RAPIDEC CARBA NP test and MHT, respectively. The sensitivity and specificity of the RAPIDEC CARBA NP test for detecting CPE were 89.8% and 100%, respectively. CONCLUSION: The RAPIDEC CARBA NP test is simple and produces a result within 3 hr. In conclusion, the test is a useful screen for detecting CPE because it shows high sensitivity and specificity for CPE detection.
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Anti-Bacterial Agents , Carbapenems , Delivery of Health Care , Enterobacter cloacae , Enterobacteriaceae , Escherichia coli , Methods , Pneumonia , Sensitivity and SpecificityABSTRACT
BACKGROUND: We evaluated the carbapenem inactivation method (CIM) compared with the modified Hodge test (MHT) for the detection of carbapenemase-producing Gram-negative bacilli. METHODS: A total of 61 isolates of carbapenemase-producing Enterobacteriaceae (CPE: 14 KPC, 7 GES-5, 8 NDM-1, 9 VIM-2, 9 IMP-1, and 14 OXA-48-like), 34 isolates of metallo-β-lactamase (MBL)-producing Pseudomonas spp. (14 VIM-2 and 20 IMP-6), and 70 carbapenem-nonsusceptible carbapenemase-negative isolates were included. The CIM and MHT were performed for all of the isolates. To perform the CIM, a meropenem disk was incubated with a suspension of the isolate to be tested and then on Mueller-Hinton agar with the Escherichia coli ATCC 29522 strains. The absence of an inhibition zone indicates presence of a carbapenemase. The presence of a clearing zone indicates lack of a carbapenemase. RESULTS: The total sensitivity and specificity of CIM (96% sensitivity and 100% specificity) in carbapenem-nonsusceptible Enterobacteriaceae and Pseudomonas spp. were better than those of the MHT (77% sensitivity and 94% specificity). The interpretation of CIM results was easy, with no or 20 mm inhibition zones indicating negative carbapenemase activity. CONCLUSION: The CIM had excellent sensitivity and specificity for detection of CPE and MBL-producing Pseudomonas spp., and a positive result was easily determined, unlike the MHT.
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Agar , Enterobacteriaceae , Escherichia coli , Methods , Pseudomonas , Sensitivity and SpecificityABSTRACT
Background: Klebsiella pneumoniae carbapenemase (KPC) is one of the carbapenemases that can cause multi-antibiotics resistance in Acinetobacter baumannii. A simple phenotypic rapid and accurate test for the detection of A. baumannii - KPC-producer can be useful in treating related infections. The aim of this study was to determine the synergism effect of boronic acid (BA), as an inhibitor, and meropenem to confi rm modifi ed Hodge test (MHT) positive strains for KPC-production. Materials and Methods: Totally, 126 A. baumannii isolates were used as clinical strains. Imipenem resistant isolates were identifi ed by disk diffusion method according to the Clinical Laboratory Standards Institute recommendations. Presence of KPC in imipenem resistant isolates was determined using the MHT. In addition, we used BA as a KPC inhibitor for fi nal confi rmation of the species of interest. Additionally, we employed the use of synergism effect of meropenem and cloxacillin to detect false positive cases. Results: Of 126 strains, 108 were resistant to imipenem, for which 93 strains were MHT positive. Totally, 68 out of 93 MHT positive isolates had at least 5 mm enlargement of the diameter of the zone of growth inhibition between the meropenem alone and meropenem combined with BA. Of these 68 isolates, 8 had at least 5 mm enlargement of the diameter of the zone of growth inhibition with BA alone and in 60 strains it was observed by cloxacillin. Conclusion: Our study suggests that MHT alone cannot confi rm KPC-producer microorganisms and that it requires other complementary tests such as the usage of inhibitors.
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Background:Proteusis a common uropathogen causing urinary tract infections in catheterised patients and those with urinary tract abnormalities. It may also lead to pyelonephritis, renal stones & bacteraemia. Multidrug resistant Proteeae isolates are major problem in treating nosocomial infections. Beta lactamase production is being increasingly demonstrated in most of the Proteus species. Apart from ESBL, Carbapenemase production is also emerging, thereby limiting the treatment options. Aim: To isolate, speciate and study the antibiotic resistance pattern of the Proteeae isolates. To identify the extended spectrum beta lactamase andcarbapenemase producing strains of Proteeae isolates by employing phenotypic methods. Materials and Methods: A total of 145 isolates of Proteus species isolated from different clinical samples- urine, pus and sputum, were included in this study. Antibiotic sensitivity testing was performed by Kirby-Bauer disk diffusion method. Screening tests for ESBL &Carbapenemase production was confirmed by Disk diffusion method and Modified Hodge test respectively. Results: Out of the 145 Proteeae isolates, from various clinical samples 70 were from wound swabs, 62 from urine, and 13 from respiratory specimens. The species were identified as 64 P.mirabilis, 48 P.vulgaris, 19 M.morganii, 5 Prov.stuartii and 9 Prov.rettgeri.Different antibiotic resistance patterns were observed in different species. Providencia species showed resistance to most of the antibiotics than the Proteus species and M morganii. Of the total, 52 (36%) were ESBL producers. Among the ESBL producers 6 (11.5%) were Carbapenamase producers. Conclusion: The increasing incidence of multi drug resistant strains in Tribe Proteeae has made antimicrobial susceptibility testing more important. Avoidance of indiscriminate use of antibiotics is the first step in prevention of newly emerging drug resistant strains.
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Objective To study carbapenem-resistant genes in a Myroides odoratimimus strain and clinical therapy.Methods A strain of Myroides odoratimimus was isolated from nephrostomy drainage fluid of a patient with urinary tract infection in Xinhua Hospital in May 2013.MicroflexTM MALDI-TOF MS and 16S rDNA sequencing were performed for strain identification.Vitek-2 Compact combined with E-test method was used for antibiotic susceptibility test.Modified Hodge test and imipenem/imipenem-inhibitor (IP/IPI)E-test were performed for drug-resistant phenotype screening.Carbapenemase genes blaMUS-1,blaVIM-1,blaVIM-2,blaIMP-1,blaIMP-2,blaNDM-1,blaOXA-48 and blaGESwere amplified by PCR,and the positive products were sequenced and analyzed.Results The isolated strain was identified as Myroides odoratimimus.The strain was resistant to 17 antibacterial agents,and the minimum inhibitory concentration (MIC) of imipenem was ≥ 16 μg/mL,while it was sensitive to minocycline (MIC =0.38 μg/mL) and intermediate to meropenem (MIC =6 μg/mL).It was negative in modified Hodge test but positive in IP/IPI E-test (IP/IPI≥ 8).blaMUS-1 gene was detected by PCR,and further confirmed by sequencing.Meropenem combined with minocycline was effective for the patient.Conclusion Carbapenem-resistance in this Myroides odoratimimus strain may be related to blaMUS-1 gene,and appropriate therapy for its infection should be based on the result of antibiotic susceptibility test.
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Objective To investigate the clinical distribution of carbapenem-resistant Enterobacteriaceae(CRE)strains separated in this hospital and the situation of its production of carbapenem enzyme.Methods The production of carbapenem enzyme by CRE strains was confirmed by using modified Hodge test,the situation of the production of metallo-beta-lactamases by CRE strains was screened by using imipenem-EDTA double-disk synergy test,and the clinical distribution of CRE strains was retrospectively ana-lysed.Results 37 strains of CRE isolated in this laboratory were screened by using instrument method and verified by using disk diffusion (K-B)method.It showed an increasing trend from 2012 to 2014 in the amount of CRE strains.In terms of bacterial spe-cies,K.pneumonia(1 6 strains)was the main kind of carbopenems-resistant strains,followed by E.coli(6 strains),Ser.marcescens(6 strains)and E.cloacae(4 strains).CRE strains were mainly isolated from geriatric ward and intensive care unit(ICU).Sputum,u-rine and blood specimen were key sources of CRE strains.Modified Hodge test confirmed that 36 strains of CRE were the strains that can produce carbapenemase,including 4 strains of K.pneumonia,3 strains of E.cloacae,and 1 strain of E.asburiae,and strains producing metallo-beta-lactamases were confirmed by using imipenem-EDTA double-disk synergy test.Conclusion Elderly patients with underlying diseases are susceptible population of CRE hospital infection and are primary preventive targets.The principal mechanism of carbapenem-resistant CRE strains in this hospital is the production of carbapenemase and production of metallo-β-lac-tamases in a small number of strains.
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To investigate the prevalence and gene types of KPC in Enterobacteriaceae strains isolated from 4 tertiary general hospitals in Hainan area ,a total 43 isolates which were resistant or intermediate to imipenem or ertapenem were collected from sterile sites between August 2012 and June 2013 from 4 tertiary general hospitals in Hainan area .Modified Hodge Tests (M HT ) were performed for KPC phenotype screening .PCR amplification and DNA sequence were performed to analyze the encoding genes of KPC .Results showed that in the 43 isolates ,21 strains were positive in M HT .PCR and DNA sequence analysis confirmed that 3 isolates produced KPC‐2 .It's suggested that there were the Enterobacteriaceae carrying KPC in Hain‐an area .The encoding genes were KPC‐2 .The KPC gene could be horizontally transmitted by plasmid among different groups of bacteria .It is important to control the transmission of these Enterobacteriaceae carrying KPC .
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Introducción: la producción de enzimas con actividad hidrolítica frente a carbapenémicos, denominadascarbapenemasas, es uno de los principales mecanismos de resistencia a carbapenémicos en Pseudomonas aeruginosa. El test de Hodge modificado es la prueba fenotípica más empleada para la detección de carbapenemasas; sin embargo, de acuerdo con el CLSI, este método sólo puede emplearse en Enterobacteriáceas ya que presenta limitaciones en Bacilos Gram negativos no fermentadorescomo Pseudomonas aeruginosa. Objetivo: evaluar la eficacia de variaciones del test de Hodge modificado para la detección de carbapenemasas en aislados de Pseudomonas aeruginosa. Materiales y métodos: se evaluó el desempeño del test 3D y tres variaciones del test de Hodge modificado, tomando como prueba de referencia la detección de los genes de las carbapenemasas KPC, VIM, IMP, NDM y OXA-48 mediante reacción en cadena de la polimerasa. Las variaciones consistieron en emplear: a) agar MacConkey en lugar de Mueller Hinton, b) Klebsiella pneumoniae ATCC 700603 como cepa indicadora sensible a carbapenémicos en lugar de Escherichia coli ATCC 29212 y c) las dos condiciones anteriores simultáneamente. Resultados: de los ensayos evaluados, la tercera variación, que empleó tanto agar MacConkey como la cepa indicadora de Klebsiella pneumoniaeATCC 700603, mostró los mejores valores de sensibilidad y especificidad para la detección de carbapenemasas en Pseudomonas aeruginosa (90,0% y 85,7%, respectivamente). Conclusiones: la implementación de las variaciones del test de Hodge modificado podría ser una alternativa económica y de fácil realización para la detección fenotípica de carbapenemasas en Pseudomonas aeruginosa en los laboratorios de Microbiología Clínica.
Introduction: one of the most important mechanisms of carbapenem resistance in Pseudomonas aeruginosa is the production of carbapenem-hydrolyzing enzymes known as carbapenemases. The modified Hodge test is the most frequently used phenotypic screening test for carbapenemases. Nevertheless,CLSI recommends using modified Hodge test only in members of Enterobacteriaceae, sincethe test has demonstrated limitations in other Gram-negative bacilli and non-glucose-fermenters as Pseudomonas aeruginosa. Objective: To evaluate the performance of 3D test and three variations of modified Hodge test to detect carbapenemases in Pseudomonas aeruginosa isolates. Materials and methods: The efficacy of 3D test and three variations in modified Hodge test were evaluated taking polymerase chain reaction for carbapenemases KPC, VIM, IMP, NDM and OXA-48 as the gold standard. Variations consisted in using a) MacConckey agar instead of Mueller Hinton, b) Klebsiellapneumoniae ATCC 700603 as indicator carbapenem-sensitive strain instead of Escherichia coli ATCC 29212 and c) last two conditions simultaneously. Results: Of the variations tested, the third assay using both MacConckey agar and Klebsiella pneumoniae ATCC 700603 showed the best sensitivity and specificity (90.0% and 85.7%, respectively). Conclusions: The implementation of variations in modified Hodge test could be a cheap and easy to perform alternative for phenotypic carbapenemase detection in Pseudomonas aeruginosa in Clinical Microbiology laboratories.
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Humans , Carbapenems , Microbiology , Pseudomonas aeruginosaABSTRACT
BACKGROUND: We evaluated the combined use of the modified Hodge test (MHT) and carbapenemase inhibition test (CIT) using phenylboronic acid (PBA) and EDTA to detect carbapenemase-producing Enterobacteriaceae (CPE) and metallo-beta-lactamase (MBL)-producing Pseudomonas spp. METHODS: A total of 49 isolates of CPE (15 Klebsiella pneumoniae carbapenemase [KPC], 5 Guiana extended-spectrum beta-lactamase [GES]-5, 9 New Delhi metallo-beta-lactamase [NDM]-1, 5 Verona integron-encoded metallo-beta-lactamase [VIM]-2, 3 imipenem-hydrolyzing beta-lactamase [IMP], and 12 oxacillinase [OXA]-48-like), 25 isolates of MBL-producing Pseudomonas spp. (14 VIM-2 and 11 IMP), and 35 carbapenemase-negative controls were included. The MHT was performed for all isolates as recommended by the Clinical and Laboratory Standards Institute. Enhanced growth of the indicator strain was measured in mm with a ruler. The CIT was performed by directly dripping PBA and EDTA solutions onto carbapenem disks that were placed on Mueller-Hinton agar plates seeded with the test strain. RESULTS: Considering the results of the MHT with the ertapenem disk in Enterobacteriaceae and Pseudomonas spp., the CIT with the meropenem disk in Enterobacteriaceae, and the imipenem disk in Pseudomonas spp., three combined disk tests, namely MHT-positive plus PBA-positive, EDTA-positive, and MHT-positive plus PBA-negative plus EDTA-negative, had excellent sensitivity and specificity for the detection of KPC- (100% sensitivity and 100% specificity), MBL- (94% sensitivity and 100% specificity), and OXA-48-like-producing isolates (100% sensitivity and 100% specificity), respectively. CONCLUSIONS: Combined use of the MHT and CIT with PBA and EDTA, for the detection of CPE and MBL-producing Pseudomonas spp., is effective in detecting and characterizing carbapenemases in routine laboratories.
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Humans , Bacterial Proteins/antagonists & inhibitors , Boronic Acids/chemistry , Disk Diffusion Antimicrobial Tests/methods , Edetic Acid/chemistry , Enterobacteriaceae/drug effects , Enterobacteriaceae Infections/diagnosis , Pseudomonas/drug effects , Pseudomonas Infections/diagnosis , Sensitivity and Specificity , beta-Lactamases/chemistryABSTRACT
BACKGROUND: The modified Hodge test (MHT) was designed to detect carbapenemase-producing Enterobacteriaceae (CPE). This study evaluated variables to improve the performance of MHT. METHODS: Carbapenem-resistant Enterobacteriaceae isolated from November 2010 to March 2013 at the Asan Medical Center, were evaluated, including 33 metallo-beta-lactamase (MBL) producers and 103 non-CPEs. MHT was performed by using two carbapenem disks (ertapenem and meropenem; Becton Dickinson, USA), three media (Mueller-Hinton agar (MHA), MacConkey agar (MAC), and zinc-enriched MHA), and two inoculums (0.5-McFarland [McF] suspension and a 10-fold dilution of it.) PCR was performed to detect beta-lactamase genes of the MBL, AmpC, and CTX-M types. RESULTS: The sensitivity of MHT for detecting New Delhi metallo-beta-lactamase (NDM) producers was highest using ertapenem and 0.5-McF, 52.0% on MHA and 68.0% on MAC, respectively. NDM-producing Klebsiella pneumoniae (NDMKP) were detected with higher sensitivity on MAC (78.6%) vs. MHA (28.6%) (P=0.016), but VIM-producing Enterobacter, Citrobacter, and Serratia were detected with higher sensitivity on MHA (78.5%) vs. MAC (14.3%) (P=0.004). MBL producers were consistently identified with lower sensitivity using meropenem vs. ertapenem, 39.4% vs. 60.6% (P=0.0156), respectively. The effects of zinc and inoculum size were insignificant. Enterobacter aerogenes producing unspecified AmpC frequently demonstrated false positives, 66.7% with ertapenem and 22.2% with meropenem. CONCLUSIONS: The MHT should be adjusted for the local distribution of species and the carbapenemase type of MBL producers. MAC and ertapenem are preferable for assessing NDMKP, but MHA is better for VIM. Laboratory physicians should be aware of the limited sensitivity of MHT and its relatively high false-positive rate.
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Humans , Anti-Bacterial Agents/pharmacology , Carbapenems/pharmacology , DNA, Bacterial/genetics , Disk Diffusion Antimicrobial Tests , Drug Resistance, Bacterial , Enterobacteriaceae/drug effects , Enterobacteriaceae Infections/microbiology , Multiplex Polymerase Chain Reaction , Phenotype , beta-Lactamases/geneticsABSTRACT
Context: The modified Hodge test (MHT) is widely used as a screening test for the detection of carbapenemases in Gram‑negative bacteria. This test has several pitfalls in terms of validity and interpretation. Also the test has a very low sensitivity in detecting the New Delhi metallo‑β‑lactamase (NDM). Considering the degree of dissemination of the NDM and the growing pandemic of carbapenem resistance, a more accurate alternative test is needed at the earliest. Aims: The study intends to compare the performance of the MHT with the commercially available Neo‑Sensitabs ‑ Carbapenemases/ Metallo‑β‑Lactamase (MBL) Confirmative Identification pack to find out whether the latter could be an efficient alternative to the former. Settings and Design: A total of 105 isolates of Klebsiella pneumoniae resistant to imipenem and meropenem, collected prospectively over a period of 2 years were included in the study. Subjects and Methods: The study isolates were tested with the MHT, the Neo‑Sensitabs ‑ Carbapenemases/MBL Confirmative Identification pack and polymerase chain reaction (PCR) for detecting the blaNDM‑1 gene. Results: Among the 105 isolates, the MHT identified 100 isolates as carbapenemase producers. In the five isolates negative for the MHT, four were found to produce MBLs by the Neo‑Sensitabs. The Neo‑Sensitabs did not have any false negatives when compared against the PCR. Conclusions: The MHT can give false negative results, which lead to failure in detecting the carbapenemase producers. Also considering the other pitfalls of the MHT, the Neo‑Sensitabs ‑ Carbapenemases/MBL Confirmative Identification pack could be a more efficient alternative for detection of carbapenemase production in Gram‑negative bacteria.
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Background & objectives: Carbapenemase-producing Enterobacteriaceae isolates have been increasingly identified worldwide. Though molecular data regarding New Delhi metallo-beta-lactamase-1 (NDM-1) producers are available, data regarding their rate of infection in a hospital setting and percentage among different clinical isolates are scarce. Hence, this study was undertaken to determine the occurrence of blaNDM-1 gene among clinical isolates of multidrug resistant Gram-negative bacilli (MDRGNB) in a tertiary care centre in Bangalore, Karnataka, India. Methods: A total of 74 MDRGNB isolates were studied. These were screened for MBL production by phenotypic assays such as double disk synergy test (DDST) and Modified Hodge’s test (MHT). PCR was performed for the molecular detection of the gene and antibiograms were confirmed by automated bacteriology system. Results: Of the 74 MDRGNB isolates, 34 were positive for blaNDM-1 gene. All isolates were resistant to aztreonam and two isolates were resistant to tigecycline. Complete resistance to the tested carbapenems was seen in 28 (82.35%) of the positive isolates whereas variable carbapenem resistance was seen in six (17.64%) of the positive clinical isolates. Of the total 34 PCR positive isolates, 33 (97.05%) NDM-1 producers were identified by DDST and 26 (76.47%) by MHT as producers of MBL. Interpretation & conclusions: A high percentage of plasmid encoded NDM was noted in MDRGNB. Phenotypic and molecular screening should be employed along with routine antimicrobial susceptibility testing to reflect the true number of metallo-beta-lactamase producers.
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In order to survey antibiotic resistance of clinical isolates carbapenem-resistant A cinetobacter baumannii in Meizhou and to investigate resistance mechanism and molecular epidemiological characteristics ,a total of 210 non-duplicated clinical isolates of carbapenem-resistant Acinetobacter baumannii from January 2012 to December 2012 were collected .The K-B disk diffusion method was applied for the drug-susceptibility test ,a modified Hodge test was used for the screening of carbapen-emase ,PCR was used to amplify carbapenemase genes (including IMP ,VIM ,OXA-23 ,OXA-24 ,OXA-51 and OXA-58) ,and the positive products were sequenced .Enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) was used for DNA typing and test of homology .Our results on the percentage of strains resistant for antibiotics tested were higher than 60% except for polymyxin B was 0 .48% .There were 163 positive strains by the modified Hodge test ,accounting for 77 .62% .OXA-51 gene was identified in 198 strains (94 .29% ) ,OXA-23 in 165 strains (78 .57% ) ,and VIM in 9 strains (4 .29% ) ,OXA-24 ,OXA-58 and IMP gene was not identified by PCR amplification .Seven genomic types were included in the 210 carbapenem-resistant Acinetobacter baumannii .The major prevalence types were Type A (97 strains) ,Type B (44 strains) and Type H (25 strains) . In conclusion ,multiple drug resistance of clinically isolated carbapenem-resistant A cinetobacter baumannii is a serious problem in Meizhou .Production of OXA-51 ,OXA-23 and IMP carbapenemases is an important mechanism of resistance to carbapenem antibiotics ,and there is prevalence of the same clones in these carbapenem-resistant strains .
ABSTRACT
OBJECTIVE: Enterobacteriaceae bacteria harboring Klebsiella pneumoniae carbapenemase are a serious worldwide threat. The molecular identification of these pathogens is not routine in Brazilian hospitals, and a rapid phenotypic screening test is desirable. This study aims to evaluate the modified Hodge test as a phenotypic screening test for Klebsiella pneumoniae carbapenemase. METHOD: From April 2009 to July 2011, all Enterobacteriaceae bacteria that were not susceptible to ertapenem according to Vitek2 analysis were analyzed with the modified Hodge test. All positive isolates and a random subset of negative isolates were also assayed for the presence of blaKPC. Isolates that were positive in modified Hodge tests were sub-classified as true-positives (E. coli touched the ertapenem disk) or inconclusive (distortion of the inhibition zone of E. coli, but growth did not reach the ertapenem disk). Negative results were defined as samples with no distortion of the inhibition zone around the ertapenem disk. RESULTS: Among the 1521 isolates of Enterobacteriaceae bacteria that were not susceptible to ertapenem, 30% were positive for blaKPC, and 35% were positive according to the modified Hodge test (81% specificity). Under the proposed sub-classification, true positives showed a 98% agreement with the blaKPC results. The negative predictive value of the modified Hodge test for detection was 100%. KPC producers showed high antimicrobial resistance rates, but 90% and 77% of these isolates were susceptible to aminoglycoside and tigecycline, respectively. CONCLUSION: Standardizing the modified Hodge test interpretation may improve the specificity of KPC detection. In this study, negative test results ruled out 100% of the isolates harboring Klebsiella pneumoniae carbapenemase 2. The test may therefore be regarded as a good epidemiological tool.