False Positive Phenotypic Detection of Metallo-Beta-Lactamases in Acinetobacter Baumannii

Bedenić, Branka; Ladavac, Ranko; Vranić-Ladavac, Mirna; Barišić, Nada; Karčić, Natalie; Sreter, Katherina Bernadette; Mihaljević, Slobodan; Bielen, Luka; Car, Haris; Beader, Nataša

doi:10.20471/acc.2019.58.01.15

Cited by 9 publications

(8 citation statements)

References 25 publications

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“…Although previous studies had reported on effectiveness of EDTA to inhibit metallo β-lactamase enzymes [41,42], still there is paucity of data on its capability to interact with bla KPC . However, we should put in consideration that EDTA itself effect membrane permeabilization particularly in non-fermenting bacilli and restore activity of carbapenem leading to false interpretation of CDT [43,44]. Additionally, CPO having bla VIM or bla NDM had shown statistically significant difference with MHT.…”

Section: Discussionmentioning

confidence: 96%

Insights on the performance of phenotypic tests versus genotypic tests for the detection of carbapenemase-producing Gram-negative bacilli in resource-limited settings

et al. 2022

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Background: Carbapenemase-producing Gram-negative (CPGN) bacteria impose life-threatening infections with limited treatment options. Rigor and rapid detection of CPGN-associated infections is usually associated with proper treatment and better disease prognosis. Accordingly, this study aimed at evaluating the phenotypic methods versus genotypic methods used for the detection of such pathogens and determining their sensitivity/specificity values. Methods: A total of 71 CPGN bacilli (30 Enterobacterales and 41 non-glucose-fermenting bacilli) were tested for the carbapenemase production by the major phenotypic approaches including, the modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), combined disk test by EDTA (CDT) and blue-carba test (BCT). The obtained results were statistically analyzed and correlated to the obtained resistant genotypes that were determined by using polymerase chain reactions (PCR) for the detection of the major carbapenemase-encoding genes covering the three classes (Class A, B, and D) of carbapenemases. Results: In comparison to PCR, the overall sensitivity/specificity values for detection of carbapenemase-producing organism were 65.62%/100% for MHT, 68.65%/100% for mCIM, 55.22%/100% for CDT and 89.55%/75% for BCT. The sensitivity/specificity values for carbapenemase-producing Enterobacterales were, 74%100% for MHT, 51.72%/ 100% for mCIM, 62.07%/100% for CDT and 82.75%/100% for BCT. The sensitivity/specificity values for carbapenemase-producing non-glucose fermenting bacilli were, 62.16%/100% for MHT, 81.57%/100% for mCIM, 50/100% for CDT and 94.74%/66.66% for BCT. Considering these findings, BCT possess a relatively high performance for the efficient and rapid detection of carbapenemase producing isolates. Statistical analysis showed significant association (p < 0.05) between blaNDM and/or blaVIM genotypes with MHT/CDT; blaKPC/blaGIM genotypes with CDT and blaGIM genotype with BCT. Conclusion: The current study provides an update on the performance of the phenotypic tests which are varied depending on the tested bacterial genera and the type of the carbapenemase. The overall sensitivity/specificity values for detection of CPO were 65.62%/100% for MHT, 68.65%/100% for mCIM, 55.22%/100% for CDT and 89.55%/75% for BCT. Based on its respective diagnostic efficiency and rapid turnaround time, BCT is more likely to be recommended in a resource-limited settings particularly, when molecular tests are not available.

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Section: Discussionmentioning

confidence: 96%

Insights on the performance of phenotypic tests versus genotypic tests for the detection of carbapenemase-producing Gram-negative bacilli in resource-limited settings

et al. 2022

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“…However, PCR for common MBLs in K. pneumoniae was negative. False positive phenotypic testing for MBLs was previously reported in A. baumannii [ 18 , 19 ]. The explanation is that in the presence of EDTA oxacillinases are converted to less active state leading to an augmentation of the inhibition zone around the carbapenem disks.…”

Section: Discussionmentioning

confidence: 97%

Diffusion of OXA-48 carbapenemase among urinary isolates of Klebsiella pneumoniae in non-hospitalized elderly patients

et al. 2022

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Background Recently, a dramatic increase of Klebsiella pneumoniae positive for OXA-48 β-lactamases was observed first in the hospital setting and later in the long-term care facilities (LTCFs) and community in the Zagreb County, particularly, in urinary isolates. The aim of the study was to analyse the epidemiology and the mechanisms of antibiotic resistance of OXA-48 carbapenemase producing K. pneumoniae strains isolated from urine of non-hospitalized elderly patients. Results The isolates were classified into two groups: one originated from the LTCFs and the other from the community. Extended-spectrum β-lactamases (ESBLs) were detected by double disk-synergy (DDST) and combined disk tests in 55% of the isolates (51/92). The ESBL-positive isolates exhibited resistance to expanded-spectrum cephalosporins (ESC) and in majority of cases to gentamicin. LTCFs isolates showed a significantly lower rate of additional ESBLs and consequential resistance to ESC and a lower gentamicin resistance rate compared to the community isolates, similarly to hospital isolates in Zagreb, pointing out to the possible transmission from hospitals.ESBL production was associated with group 1 of CTX-M or SHV-12 β-lactamases. Ertapenem resistance was transferable from only 12 isolates. blaOXA-48 genes were carried by IncL plasmid in 42 isolates. In addition IncFII and IncFIB were identified in 18 and 2 isolates, respectively. Two new sequence types were reported: ST4870 and ST4781. Conclusions This study showed eruptive and extensive diffusion of OXA-48 carbapenemase to LTCFs and community population in Zagreb County, particularly affecting patients with UTIs and urinary catheters. On the basis of susceptibility testing, β-lactamase production, conjugation experiments, MLST and plasmid characterization it can be concluded that there was horizontal gene transfer between unrelated isolates, responsible for epidemic spread of OXA-48 carbapenemase in the LTCFs and the community The rapid spread of OXA-48 producing K. pneumoniae points out to the shortcomings in the infection control measures.

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“…Moreover, MBL detection in Acinetobacter with EDTA can result in false positive tests. 48 Considering A. baumannii, ampicillin-sulbactam was the drug of choice with high susceptibility (64%) excluding polymyxins. The increased susceptibility of ampicillinsulbactam against A. baumannii is because sulbactam containing β-lactam drug is a good therapeutic agent against A. baumannii 49 as it inhibits penicillin-binding proteins (PBPs)-PBP1 and PBP3, with a very low frequency of resistance.…”

Section: Discussionmentioning

confidence: 99%

Characterisation of ESKAPE Pathogens with Special Reference to Multidrug Resistance and Biofilm Production in a Nepalese Hospital

Pandey¹,

Mishra²,

Shrestha³

2021

IDR

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Background “ESKAPE” is an acronym for a group of life-threatening nosocomial pathogens, viz, Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp. Global efforts on controlling multidrug-resistant (MDR) organisms have been hampered by their ability to escape antibacterial drugs. This study was undertaken to determine the prevalence of ESKAPE pathogens with prime focus on biofilm production and antibiotic resistance. Methods A total of 8756 clinical samples were processed for the isolation and identification of ESKAPE pathogens following standard microbiological procedures. These isolates were subjected to antimicrobial sensitivity test as per Clinical and Laboratory Standards Institute (CLSI) guidelines. Test for MDR, extended-spectrum β-lactamase (ESBL), metallo-β-lactamase (MBL), methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE) was done by the disk diffusion and E-test methods. In the case of VRE molecular detection was done for vanA and vanB genes. All the isolates were processed for biofilm detection by the tube adherence method. Results The percentage distribution of Enterococcus faecium was 5.5%, S. aureus 33.4%, K. pneumoniae 33.0%, A. baumannii 8.6%, P. aeruginosa 18.6%, and Enterobacter aerogenes 0.9%. MRSA was 57.6%, and vancomycin resistance among Enterococcus faecium was 20%. ESBL- and MBL-producing K. pneumoniae were 16.1%, and 8.1%, A. baumannii 10.3% each and P. aeruginosa 10.7% and 8.3%, respectively. A total of 42.3% of isolates were biofilm producers. Linezolid was the drug of choice for VRE. Ampicillin-sulbactam was most useful against A. baumannii apart from polymyxins, whereas piperacillin-tazobactam was effective against other Gram-negative bacteria. VanA gene was detected in all the VRE isolates. Conclusion This study estimates the burden of the ESKAPE organisms and their antimicrobial resistance pattern in a hospital setting. A high percentage of drug resistance and biofilm production was noted; hence antimicrobial resistance surveillance targeting ESKAPE pathogens should be incorporated in the infection control policy in Nepal.

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False Positive Phenotypic Detection of Metallo-Beta-Lactamases in Acinetobacter Baumannii

Cited by 9 publications

References 25 publications

Insights on the performance of phenotypic tests versus genotypic tests for the detection of carbapenemase-producing Gram-negative bacilli in resource-limited settings

Insights on the performance of phenotypic tests versus genotypic tests for the detection of carbapenemase-producing Gram-negative bacilli in resource-limited settings

Diffusion of OXA-48 carbapenemase among urinary isolates of Klebsiella pneumoniae in non-hospitalized elderly patients

Characterisation of ESKAPE Pathogens with Special Reference to Multidrug Resistance and Biofilm Production in a Nepalese Hospital

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