Emerging New Delhi metallo-ß-lactamase-1-type-producing Gram-negative bacteria isolated from Cairo University Pediatric Hospital, Cairo, Egypt.

New Delhi metallo-ß-lactamase (NDM) compromises the efficacy of almost all ß-lactam antibiotics, including carbapenems. This study aimed to screen for the blaNDM-1-type gene and NDM-1-type carbapenemase production among Gram-negative bacteria in Cairo University Pediatric Hospital (Cairo, Egypt). Among 382 Gram-negative clinical isolates collected over the period October 2013 to May 2014, 100 clinical isolates showing reduced carbapenem (imipenem and meropenem) susceptibility were included in this study. Initial phenotypic screening for NDM enzyme production was performed by Etest for metallo-ß-lactamases (EMBL). Genotypic detection of the blaNDM-1-type gene was done by TaqMan real-time PCR. Metallo-ß-lactamase production was detected in 23% of the isolates by EMBL, whereas 24% of the isolates were found to be positive for the blaNDM-1-type gene by real-time PCR. The EMBL sensitivity was 79.2%, specificity was 94.7%, positive predictive value was 82.6%, negative predictive value was 93.5% and overall accuracy was 91.0%. Seventeen (70.8%) of blaNDM-1-type-positive cases were hospital-acquired in origin, whilst 7 cases (29.2%) were community-acquired. Eleven isolates (45.8%) harbouring blaNDM-1-type were found in critical care units. In conclusion, the high prevalence of blaNDM-1-type carbapenemase gene among Gram-negative bacteria, with its great potential for spread in intensive care units, warrants the attention of a nationwide surveillance programme to contain its spread.

The Role of OmpK35, OmpK36 Porins, and Production of ß-Lactamases on Imipenem Susceptibility in Klebsiella pneumoniae Clinical Isolates, Cairo, Egypt.

BACKGROUND: OmpK35 and OmpK36 are the major outer membrane porins of Klebsiella pneumoniae. We aimed to study the effect of combined porin loss and production of extended-spectrum ß-lactamases (ESBLs) on imipenem susceptibility among K. pneumoniae clinical isolates. MATERIALS AND METHODS: This study included 91 suspected ESBL-producing K. pneumoniae clinical isolates, isolated from different patient specimens at the Cairo University hospital from January to June 2010. All isolates were subjected to genotypic analysis of the outer membrane protein gene expression using reverse transcription-PCR (RT-PCR) and analysis of OmpK35/36 of 38 isolates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). RESULTS: By RT-PCR, loss of Omp35 was detected in 78 (85.7%) isolates, loss of Omp36 was detected in 64 (70.32%), and loss of both porins was detected in 62 (68.1%). Out of 91 isolates, 45 (49.5%) were resistant to cefoxitin, and 17 (18.7%) were confirmed as derepressed AmpC producers. Omp35 was lost in all FOX-resistant isolates, whereas Omp36 was lost in 42 (93.3%) (p-value 0.002). The mean of ceftazidime inhibition zone diameter was significantly decreased among ESBL-producing isolates with loss of Omp35/36 (p-value 0.041 and 0.006), respectively. The mean of imipenem minimal inhibitory concentration (MIC) was markedly increased to 8.55 µg/ml among AmpC-producing isolates with Omp35/36 loss, while the mean of imipenem MIC among the 66 confirmed ESBL producers was 0.32 µg/ml. CONCLUSION: Imipenem MIC was markedly increased among K. pneumoniae isolates showing AmpC production with loss of both porins OmpK35/36. Meanwhile, the association of porin OmpK35/36 loss with ESBL production was not a direct cause of resistance to imipenem.