Imipenem-resistant Isolates Research Articles

Antibiotic Resistance Pattern of Pseudomonas aeruginosa Isolated from Clinical Specimens from a Tertiary Care Centre in Central Kerala with Special Reference to Carbapenemase Detection

Pseudomonas aeruginosa is inherently resistant to many drugs. It is now an emerging opportunistic pathogen of clinical relevance. The emergence of carbapenemases is another major concern. Initiation of appropriate therapy is of paramount importance thus highlighting the need of active surveillance for newer emerging resistance trends for better infection control. To study the resistance pattern of P. aeruginosa isolates obtained from lab specimens and to determine the production of ESBL and Carbapenemase among them. A hospital-based cross-sectional study was carried out in the Department of Microbiology, Government medical college Thrissur, among P. aeruginosa isolates obtained from lab specimens, from January 2018 – December 2018. 162 isolates were studied. Antimicrobial susceptibility testing was done by Kirby – Bauer disc diffusion method, extended-spectrum beta-lactamase (ESBL) production was confirmed by and phenotypic confirmatory disc diffusion test. Carbapenemase detection was done using the modified carbapenemase inactivation (mCIM) method. The obtained data was analysed. Among 162 isolates 83% were non-multidrug-resistant (MDR) strains and 17% were MDR strains. 22% of ceftazidime resistant isolates were ESBL producers. 6.2% isolates were resistant to imipenem. Among the imipenem resistant isolates, Carbapenemase production was seen in 30% isolates by mCIM test. According to our study, the most effective antibiotic against P. aeruginosa were imipenem and cefoperazone/sulbactam showing resistance in 6.3% and 6.9% isolates respectively. The diversity of antibiotic resistance mechanisms and the emergence of carbapenem resistance is a threat that limits treatment choices. This suggests the need for ongoing antimicrobial susceptibility studies in the future.

Emergence of OXA-833 in Proteus Species at a Tertiary Care Hospital in Dhaka, Bangladesh.

Context:Proteus species are liable for multitude of infections and associated with resistance to routinely used antibiotics even to reserve drugs such as carbapenems.Aims:The aim of this study was to detect the presence of MBL producers, including blaOXA-833 gene in Proteus spp. along with their antibiotic resistance pattern.Settings and Design:This cross-sectional study was conducted in the Department of Microbiology of a tertiary care hospital of Bangladesh during July 2018 to June 2019.Subjects and Methods:Proteus spp. was isolated from a total of 500 samples. Antibiotic susceptibility was performed by disk-diffusion technique. Minimum inhibitory concentration (MIC) of imipenem was determined by agar dilution method. Carbapenemase producers were phenotypically detected by double disc synergy (DDS) test, combined disc (CD) assay, and modified Hodge test (MHT). Carbapenemase genes (blaKPC, blaVIM, blaIMP, blaNDM-1, blaOXA-23, blaOXA-48-like/blaOXA-833, and blaOXA-58) among imipenem-resistant Proteus spp. were detected by polymerase chain reaction (PCR). Sequencing was performed to differentiate OXA-833 from OXA-48-like gene by capillary method, and the nucleotide sequence of OXA-833 has been deposited to GenBank.Results:Ten (25%) imipenem-resistant isolates were detected during disk-diffusion technique, among them 60%, 70%, 50% carbapenemase producers were detected by DDS test, CD assay, MHT, respectively, and 70% by PCR. A significant increase in MIC was found between 8 and ≥128 μg/ml to imipenem. PCR revealed that 40% imipenem-resistant isolates were positive for blaNDM-1 and blaVIM followed by 20% for blaOXA-48-like/blaOXA-833 and blaOXA-23, respectively. Sequencing of blaOXA-48-like gene established the OXA-833 variant of class D carbapenemase encoding gene.Conclusion:The results of this study showed the presence of high proportion of carbapenemase enzyme-producing Proteus spp. in Bangladesh. blaOXA-833 is emerging in Bangladesh.

Upstream region of OprD mutations in imipenem-resistant and imipenem-sensitive Pseudomonas isolates

The current study was aimed at investigating the prevalence of the mutations upstream of the oprD coding region and its promoters among imipenem-resistant and sensitive Pseudomonas aeruginosa isolated from educational hospitals in Yazd City, Iran. All isolates were identified by the conventional biochemical tests. Then, the antibiotic resistance of these isolates was determined using the disk diffusion method according to the CLSI guidelines. Also, the E.test was performed to determine the minimum inhibitory concentrations (MIC) of imipenem. The mutations of this gene were recognized by the amplification of this region and subsequently sequenced. Sequencing of the genomic region upstream of oprD these regions were done in the 29 clinical strains. Statistical analysis was done by the statistical software SPSS-18. Seventy (77.7%) of isolates had MIC ≥ 16 and were resistant to imipenem. Mutations of the upstream of the oprD gene and its promoters were seen in 25 (86.2%) isolates and 4 isolates had no mutation. One isolate had a base substitution A→Cat nt 25 in the coding region and this isolate had a point mutation leading to an amino acid change at positions 9 (I→L). Our study results indicated that none of the strains had mutation in Shine-Dalgarno and the point mutations were the most common mutations upstream of the oprD coding region among P. aeruginosa isolates. Mutations were observed in imipenem-resistant isolates and it seems this mechanism is effective in resistance of isolates to imipenem and this confirmed that the indiscriminate use of antibiotic should be controlled.

Characterization of Multidrug-Resistant Biofilm-Producing Escherichia coli and Klebsiella pneumoniae in Healthy Cattle and Cattle with Diarrhea

This study describes comparative occurrence and characterization of multidrug-resistant (MDR) Escherichia coli and Klebsiella pneumoniae (KP) in healthy cattle (HC) and cattle with diarrhea (DC) in India. During 2018-2020, 72 MDR isolates, including 35 E. coli (DC: 27; HC 8) and 37 K. pneumoniae (DC: 34; HC: 3), from 251 rectal swabs (DC: 219; HC: 32) were investigated for extended-spectrum beta-lactamase (ESBL), AmpC type β-lactamase and carbapenemase production, antimicrobial susceptibility profile, biofilm production, and efflux pump activity. Fifty-five MDR isolates were ESBL producers (ESBLPs) (DC: 50; HC: 5) and ESBLPs from DC were coresistant to multiple antibiotics. The blaCTX-M gene (50) was the most frequently detected β-lactamases followed by blaAmpC (22), blaTEM1 (13), blaCMY-6 (6), blaOXA1 (5), blaPER (2), blaDHA, and blaFOX and blaSHV12 (1 each). Plasmid-mediated quinolone resistance determinants qnrB, qnrS, qnrA, and qepA were detected in 18, 16, 2, and 3 isolates, respectively. Twenty three isolates revealed mutation in gyrA and parC genes. Tetracycline-resistance markers tetA, tetB, tetC, and tetE were detected in 33, 10, 3, and 2 isolates, respectively. Only one of the 41 imipenem-resistant isolates harbored blaNDM-5 and two were colistin-resistant. Altogether, 20 MDR isolates were strong biofilm producers and 19 harbored different virulence factors. This is the first ever report from India on the presence of MDR Enterobacteriaceae with resistance to even last-resort antimicrobials in the bovine diarrhea.

Antibiotic resistance heterogeneity and LasR diversity within Pseudomonas aeruginosa populations from pneumonia in intensive care unit patients

This study investigated within-host heterogeneity of 66 Pseudomonas aeruginosa populations from pneumonia in 51 critically ill ventilated patients by examining 30 colonies per bronchoalveolar lavage (BAL). Differences in antibiotic susceptibility and quorum-sensing (QS) phenotypes were observed between the members of 14 (21.2%) and 10 (15.2%) populations, respectively. A significant association was found between QS deficiency and ceftazidime resistance. QS deficiency was associated with various lasR modifications, and was observed in 25 of 51 (49.0%) patients, including seven patients who received ≤48 h of ventilation. This study confirms the need to examine diverse colonies when analysing BAL cultures, particularly in β-lactam-exposed patients, to avoid missing ceftazidime- or imipenem-resistant isolates.

Emergence of Carbapenemase Encoding Genes in Proteus Species in Tertiary Care Hospital of Bangladesh

Along with different carbapenemase encoding genes, in recent year class D OXA enzymes are documented in Proteus spp which are not common in Enterobacteriaceae. The dissemination of plasmids, transposons and integrons among bacteria and species playing roles for this dissemination. So, this study was designed to observe the emergence and distribution of different classes of carbapenemase encoding genes among imipenem resistant Proteus spp. isolated from tertiary care hospital in Bangladesh. Total 15 imipenem resistant Proteus isolates were included in this study, which were collected from wound swab, pus, urine and blood samples. Identification was done by culture and biochemical test and antibiotic susceptibility test was done by disc diffusion method. MIC of imipenem (g/ml) was done among imipenem resistant P. mirabilis by agar dilution method. blaKPC, blaNDM-1, blaVIM, blaIMP, blaOXA-48 like, blaOXA-23 like, blaOXA-51 like, blaOXA-58 like carbapenemase encoding genes were detected among imipenem resistant Proteus spp. by PCR and sequencing of blaOXA-48 like, blaOXA-51 like gene done by capillary method to compare the sequences with the same gene, available in gene bank. Among 15 imipenem resistant isolates blaNDM-1 (26.67%), blaKPC (20%), blaVIM (20%), blaOXA-484 (20%) were predominant carbapenemase encoding genes followed by blaOXA-66(6.67%). This study finds that blaOXA-484 gene and blaOXA-66 class D carbapenemase encoding genes are emerging in Proteus spp. and may play a contributing factor in developing carbapenem resistance. Bangladesh Med J. 2020 May; 49(2) : 1-8

Retrospective study of incidence of metallo-β -lactamase-producing Non-fermenters in nosocomial infections of a tertiary care hospital, in Navi Mumbai

The growing increase in the rate of antibiotic resistance is a major cause for concern in both non-fermenting bacilli. β-lactams have been the mainstay of treatment for serious infections, and the most active of these are the carbapenems. Acquired metallo-β-lactamases (MBL) have recently emerged as one of the most worrisome resistance mechanisms owing to their capacity to hydrolyze all β-lactams, including carbapenems. We have undertaken this investigation to ascertain the incidence of MBL-producing non-fermenting bacilli, like Pseudomonas Spp. and Acinetobacter Spp.To determine the incidence of MBL in Nosocomial infections of non-fermenters and their clinical correlation.Screening of nosocomial isolates for multidrug resistance by antibiotic sensitivity tests as per CLSI guidelines as a reference.To perform phenotypic confirmatory test of potential MBL isolates by double disc synergy testClinical correlation with detection of these enzymes and the patients morbidity/mortality correlation with age, immunocompromised status and hospital stay.The study was conducted over a period of 12 months in a teaching hospital, in Navi Mumbai. Isolates included in the study were screened for imipenem resistance by conventional methods. The isolates that showed imipenem resistance were tested for MBL production by imipenem (IMP)-ethylene-diamine-tetra-acetic acid (EDTA) combined disc test. Imipenem-resistant non-MBL isolates also were tested for Modified Hodge test and AmpC β-lactamases production to detect other mechanisms of carbapenem resistance. Total number of isolates tested were 107.Out of 107, 29 (27.1%) were MBL producers and 78(72.9%) were non- MBL producers. Among both types of non-fermenters , 66(61.68%) were Pseudomonas aeruginosa and 41(32.23%) were of Acinetobacters. In the sex distribution, 65.5%were males and 34.5% were females.18.18% were MBL positive Pseudomonas and among Acinetobacter species 41.46% were MBL positive. Mean age of MBL producers was 34 years. Mean hospital stay was 28 days. Mortality rate was 51.7% in MBL producers. Mortality was higher in Acinetobacter MBL producers.when compared to Pseudomonas MBL producers.

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.

Comparative evaluation of phenotypic methods for detection of MBL producing Pseudomonas aeruginosa strains isolated from burn wound infections

Introduction: Pseudomonas aeruginosa is a notorious nosocomial pathogen with a resistant drug profile and a predominant isolate in burn wound infections. Recently Metallo beta lactamase (MBL) producing isolates have emerged particularly in P.aeruginosa leading to failure of therapy with carbapenems with increased mortality and morbidity in burn units. Objectives: To detect MBL production among the imipenem resistant isolates of P.aeruginosa by different phenotypic methods – Modified Hodge test (MHT), Combined disc test (CDT), Imipenem-EDTA Double disc synergy test (DDST) and MBL-E-test. Materials and Methods: A total of 108 clinical isolates of P.aeruginosa obtained in 189 pus samples collected from different burn wound sites, were subjected to antimicrobial susceptibility testing by modified Kirby-Bauer disc diffusion method. All the imipenem resistant isolates were further tested for MBL-production by MHT, CDT, DDST and MBL-E-test. Results: Out of 108 isolates of P.aeruginosa 26 (24.07%) ware imipenem resistant. Among 26 imipenem resistant isolates 16(61.54%) were detected as MBL producers by MBL-E-test, 15(57.69%) by DDST, 14(53.85%) by CDT and 11(42.31%) by MHT. Considering MBL-E-test as standard, maximum sensitivity was shown with DDST (93.75%) followed by CDT (87.5%) and MHT (68.75%). Conclusion: A comparative evaluation of MHT, CDT and DDST against MBL-E-test proved DDST to be most effective, with higher sensitivity and specificity. DDST is observed to be an economical feasible alternative compared to MBL-E-test as a regular screening test in MBL detection in critically ill. Keywords: Pseudomonas aeruginosa, Metallo beta lactamases (MBLs), Modified Hodge test (MHT), Combined disc test (CDT), Imipenem -EDTA Double disc synergy test (DDST), MBL-E-test.

Detection of metallobetalactamase producing imipenem resistant acinetobacter species in intensive care unit patient in a Tertiary Care Centre

Introduction: Metallobetalactamase producing Acinetobacter species has been reported to be an important cause of nosocomial infection and is a critical therapeutic problem worldwide, especially in the intensive care unit. Objectives: To determine the frequency of metallo‐β‐lactamases among imipenem‐resistant Acinetobacter species and to compare different phenotypic methods. Materials and Methods: 59 imipenem‐resistant Acinetobacter species isolated from various clinical samples were tested for metallo‐β‐lactamase production using different phenotypic methods. Minimal Inhibitory Concentratrion (MIC) to meropenem was determined by E test. Results: Of all the imipenem resistant isolates, 50.8% of Acinetobacter species were MBL producers. MIC of all those MBL producing isolates were ? 16?g/ml. Among the Acinetobacter species MBL production were detected in 30 isolates (50.8%) by E test, 29 isolates (49.2%) by CDT and in 15 isolates (25.4%) by DDST and DPT. The sensitivity and specificity of CDT, DDST and DPT compared to E test was 98%, 48.1%, 48.1% and 100%, respectively. Conclusion: Prevalence of MBL producing Acinetobacter species is being increasingly reported in ICU patients. The MIC of all the MBL producing isolates for meropenem were >16?g/ml (Resistant). E test and CDT were more reliable for MBL detection. CDT was cost effective, easy to perform and interpretation also straightforward. MBL producing isolates were multidrug resistant making therapeutic choices limited. Continuous antibiotic surveillance, infection control practices and an effective antibiotic policy are required to address the problem of MBL – associated infections. Keywords: Acinetobacter species, MBL detection.

Elevated Level of Imipenem-Resistant Gram-Negative Bacteria Isolated from Patients Attending Health Centers in North Gondar, Ethiopia.

BackgroundThe frequent identification of resistant bacteria in hospitals constantly presents antimicrobial therapy with a challenge. Imipenem, once considered an extremely powerful antibiotic against multidrug-resistant bacterial infections, is losing its effectiveness. Its use in empirical therapy with inadequate or nonexistent antimicrobial stewardship programs has further triggered bacterial resistance in low-income countries. Therefore, this study aimed at identifying imipenem-resistant Gram-negative bacteria from patients who were referred to health centers in North Gondar, Ethiopia.MethodsA total of 153 sputum samples were used to isolate Gram-negative bacteria. The isolates, which were resistant to imipenem, were identified by standard biochemical tests and 16S rRNA sequencing. The Kirby-Bauer disk diffusion method was used to determine the sensitivity or resistance of the isolate to diverse antimicrobial agents.ResultsThe study identified 79 imipenem-resistant bacterial isolates from eight genera with clinically relevant microorganisms, including Acinetobacter baumannii (20.77%), Klebsiella pneumoniae (19.48%), Pseudomonas aeruginosa (16.88%), and Serratia marcescens (14.28%). Overall, imipenem-resistant bacterial isolates were detected in 31 samples (20.26%). Additionally, a remarkably high level of resistance to most antibiotics was observed among isolates of Klebsiella pneumoniae and Acinetobacter baumannii. Gentamycin is the most active antibiotic against many of the isolates, while β-lactams appear to be less effective.ConclusionThe study indicated that many Gram-negative bacteria were resistant to imipenem with parallel resistances to other antimicrobials. Hence, the prescription of imipenem within the region should be according to the antibiotic resistance profiles of the multi-drug resistant bacteria.

<p>Zinc Chelator N,N,N′,N′-Tetrakis(2-Pyridylmethyl)Ethylenediamine Reduces the Resistance of <em>Mycobacterium abscessus</em> to Imipenem</p>

PurposeImipenem is one of the very few effective options for treating Mycobacterium abscessus (M. abscessus) infections; the development of imipenem resistance is a major health concern.Materials and MethodsThe susceptibility of 194 clinical M. abscessus isolates to imipenem was determined. The ability of imipenem to synergize with N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), a zinc chelator and a metallo-β-lactamases (MBLs) inhibitor, to inhibit M. abscessus growth was also assessed.ResultsM. abscessus exhibited an elevated resistance to imipenem (MIC50 = 16 mg/L, MIC90 = 64 mg/L). A combination of TPEN and imipenem synergized to inhibit the growth of 100% of imipenem-resistant and 79.2% of imipenem-resistance intermediate isolates; no synergy was observed treating imipenem-sensitive isolates. A remarkable decrease in the MIC50 (from 16 to 4 mg/L) and MIC90 (from 64 to 8 mg/L) of imipenem was observed when it was combined with TPEN; the portion of imipenem-resistant isolates also decreased (from 48.4% to 0%). Consistent with these results demonstrating synergy, a time-kill assay showed the addition of TPEN significantly improved the bactericidal activity of imipenem toward M. abscessus. Similarly, EDTA (a potent MBLs inhibitor) promoted the anti-M. abscessus activity of imipenem in a disk assay, corroborating the effect of TPEN and supporting the role of MBLs in imipenem resistance exhibited by some isolates.ConclusionThese findings demonstrate that TPEN can reduce the resistance of M. abscessus to imipenem and suggest that the inhibition of MBLs activity is the underlying mechanism.

BlaNDM-1, blaKPC, blaOXA-181- as the major mediators of carbapenem resistance in carbapenemase producing Escherichia coli and Klebsiella species isolated from a tertiary care hospital in Bangladesh

Background and objectives: Carbapenem resistance is an emerging problem worldwide. Detection of carbapenem resistance genes is important to institute appropriate therapy and to initiate preventive measures. This study was conducted to determine the presence of carbapenemase enzyme producing Escherichia coli and Klebsiella species in a tertiary care hospital of Bangladesh, as well as to observe the patterns of antibiotic resistance and carbapenem resistance genes among them.
 Methodology: Total 166 Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca were isolated from urine, wound swab, pus, sputum and blood samples of patients of Dhaka Medical College Hospital. Antibiotic susceptibility test was performed by disk-diffusion technique. Carbapenemase producers were detected phenotypically by Double-disk synergy (DDS) test, Modified Hodge test (MHT) and Combined disk (CD) assay. Minimum inhibitory concentration (MIC) of imipenem was done by agar dilution method among carbapenemase producing strains. Genotypically carbapenemase genes (blaNDM-1, blaVIM, blaIMP, blaKPC, blaOXA-48/blaOXA-181) among the imipenem resistant Escherichia coli and Klebsiella species were detected by polymerase chain reaction (PCR). Sequencing was done to differentiate blaOXA-181 gene from blaOXA-48 gene. Class 1 integron were also detected by PCR using specific primer among carbapenemase producers.
 Results: Thirty seven (22.29%) imipenem resistant isolates were detected during disk-diffusion technique, among them 16 (43.24%) carbapenemase producers were detected by MHT, 20 (54.05%) by DDS test, 22 (59.46%) by CD assay and 23 (62.16%) by PCR. Out of 23 carbapenemase producing strains, MIC of imipenem ranged from 4 μg/ml up to ≥128 μg/ml. NDM-1 (43.24%) was the dominant genotype in imipenem resistant strains followed by KPC (21.62%) and OXA-181 (18.92%). Class 1 integron were present in 16 (69.57%) of the genotypically identified carbapenemase producers.
 Conclusion: The results of this study showed high proportion of carbapenemase enzyme producing Escherichia coli and Klebsiella species in Bangladesh. Genes encoding carbapenemase enzymes including blaNDM-1, blaKPC, blaVIM, blaIMP and blaOXA-181 were responsible for imipenem resistance. blaNDM-1 producers are increasing and blaKPC and blaOXA-181 producers are emerging in Bangladesh. Regular surveillance of antibiotic resistance should be done in every tertiary care hospital to prevent spread of these strains.
 Bangladesh J Med Microbiol 2020; 14 (2): 25-29

Detection of bla NDM-1 Encoding Imepenemase among the Imipenem-Resistant Gram-Negative Bacilli Isolated from Various Clinical Samples at a Tertiary Care Hospital of Eastern Nepal: A Descriptive Cross-Sectional Study.

Background Carbapenem resistance among Gram-negative isolates caused by the production of the metallo-β-lactamase (MBL) enzyme is being increasingly reported worldwide. One of the newly emerged metallo-β-lactamases is New Delhi metallo-β-lactamase. Data regarding its occurrence in hospital setting and percentage prevalence among different Gram-negative bacterial isolates are lacking in our part. This study has been undertaken for determining the presence of the bla NDM-1 gene among the clinical isolates of imipenem-resistant Gram-negative bacteria in a tertiary care center in Dharan, Nepal. Methods A total of 75 imipenem-resistant Gram-negative isolates were studied. These were screened for metallo-β-lactamase (MBL) production by phenotypic assays such as double-disc synergy test (DDST) and combined disc diffusion test (CDDT). PCR was performed for the molecular detection of gene NDM-1. Ten-disc method was performed to detect the presence of ESBL, AmpC, carbapenamase, and K1 β-lactamase production. Results Using the molecular method, bla NDM-1 was detected in 36% of the isolates. Phenotypically, double-disc synergy test (DDST) and combined disc diffusion test (CDST) detected MBL production in 38.7% and 37.3% of the isolates, respectively. Ten-disc method detected ESBL in 26.6% of the isolates, but none of the isolates was found to be AmpC, carbapenamase, and K1 β-lactamase producers. Conclusion A high percentage of the NDM-1 producer was noted among imipenem-resistant GNB. Apart from performing only antimicrobial sensitivity test, phenotypic and molecular screening should be employed to find out the actual number of metallo-β-lactamase producers and the existence of the resistance gene.

DETECTION OF METALLO BETA - LACTAMASES AMONG ENTEROBACTERIACEAE ISOLATES AT A TERTIARY CARE HOSPITAL, SOUTH INDIA

Background : The spread of carbapenem resistant bacteria has caused grave concern due to the limited choice in antibiotics for treating infections caused by them. The emergence of metallo beta-lactamse (MBL) producing gram negative bacilli poses a therapeutic challenge and is of serious concern for infection control in hospital environment. Materials & Methods: A total of 475 non repeat clinical isolates of family Enterobacteriaceae were included in the study. Resistance to imipenem was determined in isolates by disc diffusion & minimum inhibitory concentration (MIC) method. Imipenem resistant isolates were tested for MBL production by combined disc diffusion test and modified Hodge test. Results: Out of the 475 Enterobacteriaceae strains, 20 showed resistance to imipenem. MBL activity was detected in all 20 (4.2%) isolates by combined disc diffusion test, in 18 isolates by modified Hodge test. The MBL producing isolates included clinical strains of Klebsiella spp (45%), E. coli (40%), Citrobacter spp (15%). Majority of the MBL isolates were from Intensive care unit (65%), from patients with comorbid conditions and with invasive devices. MBL producing isolates showed high level of resistance to aminoglycosides and fluoroquinolones but all were susceptible to colistin. Conclusion : The need of the hour is to detect MBL producing isolates for better patient outcomes, to execute prompt infection control measures and decrease the escalation of resistance.

Activity of ceftolozane-tazobactam and comparators against gram-negative bacilli: Results from the study for monitoring antimicrobial resistance trends (SMART – Brazil; 2016–2017)

Multi-drug resistant Gram-negative bacilli (GNB) have been reported as cause of serious hospital-acquired infections worldwide. The aim of this study was to investigate the in vitro activity of ceftolozane-tazobactam compared to other agents against GNB isolated from patients admitted to Brazilian medical centers between the years 2016 and 2017. Presence of β-lactamase encoding genes was also evaluated. MethodsAntimicrobial susceptibility testing of GNB isolated from intra-abdominal (IAI), respiratory (RTI), and urinary tract infections (UTI) was performed according to ISO 227-1 guidelines and interpreted following CLSI and BrCAST/EUCAST guidelines. Qualifying Enterobacteriaceae isolates were screened for the presence of β-lactamase genes by PCR followed by DNA sequencing. Results1748 GNB collected from UTI (45.2%), IAI (25.7%) and RTI (29.1%) were evaluated. Ceftolozane-tazobactam remained highly active (94.7%) against E. coli isolates. Among K. pneumoniae, susceptibility rates were 85.9% and 85.4% for amikacin and colistin, whereas ceftolozane-tazobactam (44.1% susceptible) and carbapenems (55.2-62.2% susceptible) showed poor activity due to blaKPC-2. Against E. cloacae amikacin, imipenem, and meropenem retained good activity (>90%). Ceftolozane-tazobactam was the most potent β-lactam agent tested against P. aeruginosa (90.9% susceptible), including ceftazidime and imipenem resistant isolates. β-lactamase encoding genes testing was carried out in 433 isolates. blaCTX-M variants were predominant in E. coli, P. mirabilis and E. cloacae. Among the K. pneumoniae molecularly tested, most carried blaKPC (68.5%), with all harboring blaKPC-2, except two isolates carrying blaKPC-3 or blaKPC-30. ESBL encoding genes, mainly CTX-M family, were frequently detected in K. pneumoniae, plasmid-mediated AmpC were rare. A variety of PDC encoding genes were detected in P. aeruginosa isolates with five isolates harboring MBL and one KPC encoding genes. ConclusionCeftolozane-tazobactam was very active against E. coli, P. mirabilis and P. aeruginosa isolates and could constitute an excellent therapeutic option including for those isolates resistant to extended-spectrum cephalosporins and carbapenems but not producers of carbapenemases.

In vivo activity of human-simulated regimens of imipenem alone and in combination with relebactam against Pseudomonas aeruginosa in the murine thigh infection model.

Imipenem/relebactam is a carbapenem/β-lactamase inhibitor combination with in vitro activity against Pseudomonas aeruginosa and Enterobacterales, including KPC producers. To provide translational data to support the clinical utility of the imipenem/relebactam 500/250 mg q6h regimen using a human-simulated regimen (HSR) of imipenem/relebactam, compared with imipenem alone, against a phenotypically and genotypically diverse population of P. aeruginosa. Twenty-nine P. aeruginosa isolates, including KPC (n = 6), PDC (n = 9), PAO (n = 4), GES (n = 5) and VIM (n = 1) producers, were used for the in vivo efficacy studies. Neutropenic mice were thigh-inoculated and randomized to receive HSRs of either imipenem 500 mg q6h, imipenem 1 g q8h, imipenem/relebactam 500/250 mg q6h or saline. Twenty-seven of the 29 isolates examined were imipenem resistant, with 24/29 isolates showing imipenem MICs of ≥32 mg/L. The addition of relebactam decreased the MICs up to 64-fold; imipenem/relebactam MICs ranged from 0.25 to >32 mg/L. Efficacies of the imipenem monotherapies and the imipenem/relebactam therapy were comparable for the two imipenem-susceptible organisms. Among the imipenem-resistant isolates, an increased mean growth was observed in the imipenem 500 mg q6h HSR and 1 g q8h HSR treatment groups of 1.31 ± 1.01 and 0.18 ± 1.67 log10 cfu/thigh, respectively. In contrast, a ≥2 log reduction in bacterial density was observed in 27/29 (93%) of the imipenem-resistant isolates subjected to imipenem/relebactam 500/250 mg q6h HSR. The imipenem/relebactam 500/250 mg q6h HSR demonstrated superior in vivo activity compared with the conventionally employed imipenem regimens against MDR P. aeruginosa over a wide range of imipenem/relebactam MICs.

Genetic diversity and in vitro activity of ceftazidime/avibactam and aztreonam/avibactam against imipenem-resistant Enterobacteriaceae isolates in Southwest China: A single-centre study

ObjectivesThe aim of this study was to investigate the molecular mechanisms of imipenem resistance in Enterobacteriaceae and to assess the antimicrobial activities of ceftazidime/avibactam (CAZ/AVI) and aztreonam/avibactam (ATM/AVI) against imipenem-resistant clinical isolates in a tertiary hospital in China. MethodsA total of 91 imipenem-resistant Enterobacteriaceae were collected and genes encoding carbapenemases, ESBLs, AmpC β-lactamases and porins were detected using PCR. MICs and susceptibility were determined using in-house-prepared broth microdilution panels and were interpreted according to CLSI breakpoints. ResultsImipenem-resistant isolates comprising 54 Klebsiella pneumoniae, 18 Escherichia coli, 8 Enterobacter cloacae, 6 Serratia marcescens, 3 Klebsiella oxytoca and 2 Klebsiella aerogenes were collected independently. Five different carbapenemase genes were identified, namely blaKPC-2 (n = 60), blaNDM-5 (n = 14), blaNDM-1 (n = 11), blaKPC-3 (n = 4) and blaIMP-4 (n = 1). Among the 91 carbapenem-resistant Enterobacteriaceae (CRE), 85 isolates harboured at least one ESBL and/or AmpC gene, including 5 strains without carbapenemase-encoding genes. Moreover, 31 K. pneumoniae carried ompK35 and/or ompK36 mutations. MLST results showed that the K. pneumoniae belonged to 12 different STs, with ST11 being predominant (29/54; 53.7%). Overall, 17.6%, 25.3%, 41.8%, 65.9% and 100% of the CRE strains were susceptible to amikacin, trimethoprim/sulfamethoxazole, tetracycline, CAZ/AVI and ATM/AVI, respectively. ConclusionThis study revealed that CRE isolates differ significantly in their species, STs, porins and carbapenemase genes in a single Chinese hospital. ATM/AVI exhibited potent activity against CRE isolates, even for the most notorious double-carbapenemase-producers with porin defects, whereas CAZ/AVI was active against all the non-metallo-β-lactamase-producing isolates.

STUDY OF THE USES AND RESULTS OF PLATELET RICH PLASMA IN CHRONIC NON HEALING WOUNDS

Carbapenems have been used as the last resort antimicrobials in the treatment of serious infections caused by gram negative bacteria. The rate of carbapenem resistance in non-glucose fermenting gram negative bacilli has been gradually increasing worldwide over last 10 years. These organisms can also cause life threating infections which are difficult to treat. Aim: This study was conducted to identify phenotypically for the presence of Carbapenemase production in glucose non-fermenting bacilli. Materials and methods: Among 200 Imipenem resistant isolates, 62 imipenem resistant samples showed glucose non-fermenting bacilli. All the isolates were tested for anti-microbial susceptibility (HI-Media Mumbai) by Kirby-Bauer disk diffusion method on Muller-Hinton agar. Carbapenemase production was detected by Modified-Hodge test, Combined Disc test, and AmpC Disc test phenotypically. Results. Out of 62 imipenem resistant isolates of glucose non-fermenting bacilli, 49 isolates were Pseudomonas spp. and 13 isolates were Acinetobacter spp.. Out of 62 , 13 were MHT positive, 36 were CDT positive and 14 were AmpC positive, 16 were Multiple enzyme producers, 17 were Non-Enzyme producers. Conclusion: Carbapenem resistance rate was more in Acinetobacter spp. than Pseudomas spp.. Our study has implicated the severity of carbapenem resistant non-fermenters, which are effecting the infection control activities among hospital setup.

Study of Carbapenemase Producing Non-Glucose Fermenters in Tertiary Care Hospital

Carbapenems have been used as the last resort antimicrobials in the treatment of serious infections caused by gram negative bacteria. The rate of carbapenem resistance in non-glucose fermenting gram negative bacilli has been gradually increasing worldwide over last 10 years. These organisms can also cause life threating infections which are difficult to treat. Aim: This study was conducted to identify phenotypically for the presence of Carbapenemase production in glucose non-fermenting bacilli. Materials and methods: Among 200 Imipenem resistant isolates, 62 imipenem resistant samples showed glucose non-fermenting bacilli. All the isolates were tested for anti-microbial susceptibility (HI-Media Mumbai) by Kirby-Bauer disk diffusion method on Muller-Hinton agar. Carbapenemase production was detected by Modified-Hodge test, Combined Disc test, and AmpC Disc test phenotypically. Results. Out of 62 imipenem resistant isolates of glucose non-fermenting bacilli, 49 isolates were Pseudomonas spp. and 13 isolates were Acinetobacter spp.. Out of 62 , 13 were MHT positive, 36 were CDT positive and 14 were AmpC positive, 16 were Multiple enzyme producers, 17 were Non-Enzyme producers. Conclusion: Carbapenem resistance rate was more in Acinetobacter spp. than Pseudomas spp.. Our study has implicated the severity of carbapenem resistant non-fermenters, which are effecting the infection control activities among hospital setup.