Evaluation of Disk Potentiation Test (DPT) and Double Disk Synergy Test (DDST) for The Detection of Metallo-β-Lactamases (MBLs) in Clinical Isolates of Bangladesh

Objective: Increasing the emergence of Metallo-β-lactamase (MBL) producing gram-negative bacteria and their dexterous horizontal transmission demands rapid and accurate detection. This study was conducted to determine a suitable method to promptly detect MBL-producing gram-negative bacteria. Methods: A total of 103 gram-negative bacteria were identified from various clinical samples at a tertiary care hospital in Dhaka city. MBL producers were detected by two phenotypic methods, the Disk Potentiation Test (DPT) and the Double Disk Synergy Test (DDST) based on β-lactam chelator combinations where EDTA/SMA has been used as an inhibitor and Imipenem, Ceftazidime as substrates. Results: 103 isolates which were identified as Escherichia coli spp, Klebsiella spp, Pseudomonas spp, Acinetobacter spp, Proteus spp, Providencia spp were found to be multidrug-resistant in antibiogram test. Isolates showed complete resistance (100%) to Imipenem, Meropenem, and Amoxiclav. The highest carbapenem-resistant etiological agents were Acinetobacter spp 40 (38.8%) followed by Pseudomonas spp 27 (26.2%), Klebsiella spp 26 (25.2%), Escherichia coli 8 (7.8%), Proteus spp 1 (1%) and Providencia spp 1 (1%). DPT method detected significantly (p = 0.000009) a higher number of MBL-producers (Imipenem with 0.5 M EDTA n = 61, 59.2% & Ceftazidime with 0.5 M EDTA n = 56, 54.4%) compared to the DDST method (Imipenem -0.5 M EDTA n = 43, 41.7%, Imipenem – SMA n = 38, 36.9% & Ceftazidime -0.5 M EDTA n = 15, 14.6%). Conclusion: Pieces of evidence suggest that DPT is a more sensitive method than DDST and could be recommended for identifying MBL-producing bacteria in Bangladeshi hospitals for the proper management of patients, to reduce time constraints and treatment costs.

Occurrence of Extended Spectrum Beta Lactamase Encoding Genes among Urinary Pathogenic <i>Escherichia coli</i>and <i>Klebsiella pneumoniae</i>Isolates Obtained from a Tertiary Hospital in Gombe Nigeria

This study was conducted to assess the occurrence and nature of extended-spectrum beta lactamase (ESBL) producing Escherichia coli and Klebsiella pneumoniae isolates from patients who presented with urinary tract infection at Federal Teaching Hospital Gombe. Isolates collected were recovered on MacConkey agar at 35°C and were identified as members of Enterobacteriaceae, and further screened for antimicrobial susceptibility and resistance by disc diffusion method. Isolates resistant to oxyimino-cephalosporins were confirmed as ESBL producers using Double Disks Synergy Test (DDST). The study shows 66% resistance to ceftriaxone (30 μg) in K. pneumoniae, which was the highest value recorded and a 51% resistance to cefpodoxime (10 μg) in E. coli. The sensitivity of E. coli and K. pneumoniae isolates to cefpodoxime (10 μg) were 49% and 33.9% respectively. ESBLs were detected among 40% (40/100) of E. coli and 54.13% (59/109) of K. pneumoniae isolates. Molecular characterization of ESBL encoding genes among E. coli isolates using multiplex-PCR showed 10% prevalence of SHV gene and 5% prevalence for CTX-M gene while TEM gene was not detected. In K. pneumoniae isolates, 5% prevalence was recorded for each of the three genes screened. The study revealed a co-occurrence of SHV and CTX-M in 75% of the E. coli and 70% of the K. pneumoniae isolates;the occurrence of all the three genes was seen in 10% and 5% of K. pneumoniae and E. coli respectively. Multiplex-PCR method provided an efficient and rapid detection of ESBL related genes, hence could be used in epidemiological studies among ESBL isolates. Monitoring dissemination and transmissions of ESBL producers are highly recommended for optimum patient care and preventing the spread of multidrug resistant (MDR) pathogens.