Detection of metallo β-lactamase production and antibiotic resistance with E-test method in pseudomonas, acinetobacter and klebsiella strains, in Turkey

Spread of Enterobacter cloacae carrying blaNDM-1, blaCTX-M-15, blaSHV-12 and plasmid-mediated quinolone resistance genes in a surgical intensive care unit in Croatia

The objective of this study was to describe a hospital cluster of NDM-1-producing Enterobacter cloacae infections observed in the surgical intensive care unit (ICU) of a tertiary-care hospital at Pula, Croatia. NDM-1-producing E. cloacae strains isolated from clinical samples were screened by PCR for the presence of carbapenemases. Genetic relatedness of NDM-1-producing E. cloacae strains was determined by multilocus sequence typing (MLST). During the period October 2013 to April 2014, four patients, with overlapping hospital stay in the surgical ICU, developed severe infections caused by E. cloacae demonstrated to produce carbapenemases. According to MLST, all strains belonged to ST133 and were positive by PCR for the blaNDM-1 carbapenemase gene, for blaCTX-M-15 and blaSHV-12 extended-spectrum β-lactamase (ESBL) genes, and for blaTEM-1 and blaOXA-1 narrow-spectrum β-lactamase genes. They were negative for other carbapenemases genes including blaOXA-48, blaVIM and blaKPC as well as for AmpC and the armA and rmtB aminoglycoside resistance genes. All strains were positive for the HI2 replicon, suggesting that an IncHI2 plasmid is likely the plasmid carrying the blaNDM-1 gene. Infection control measures were implemented after the first case although they were not effective in avoiding spread of this organism to other patients in the surgical ICU. In conclusion, the evolving epidemiology of NDM-producing micro-organisms and the interspecies diffusion of this resistance mechanism to emerging pathogens such as E. cloacae necessitate the setting up of strong and urgent joint measures to control the spread of NDM carbapenemase especially in the ICU setting.

Pomegranate pericarp extract enhances the antibacterial activity of ciprofloxacin against extended-spectrum β-lactamase (ESBL) and metallo-β-lactamase (MBL) producing Gram-negative bacilli

A methanolic extract of Punica granatum (pomegranate) fruit pericarp (PGME) was tested in combination with ciprofloxacin against extended-spectrum β-lactamase (ESBL) producing Escherichia coli, Klebsiella pneumoniae, and metallo-β-lactamase (MBL) producing Pseudomonas aeruginosa, which were screened for their resistance profile against fluoroquinolone antibiotics. The minimum inhibitory concentrations (MIC) of ciprofloxacin and PGME, alone, were determined, and synergy of ciprofloxacin-PGME combinations evaluated by checkerboard assay and fractional inhibitory concentration (FIC). Nineteen out of forty-nine strains exhibited synergy with ciprofloxacin (FIC of 0.125-0.5 for ciprofloxacin) further verified by agar-well assay. This could be due to the bacterial efflux pump inhibitor (EPI) activity of the polyphenolic constituents of PGME. However, the isolates exhibiting a high level of ciprofloxacin resistance did not respond to ciprofloxacin-PGME combinations, which could be due to target site modification not influenced further by EPI activity of PGME. Again, some strains were sensitive or weakly resistant to ciprofloxacin, which exhibited 'indifference' to the combination, probably due to a lack of over-expressed efflux mechanism. Thus, a synergy of a ciprofloxacin-PGME combination was demonstrated for the first time against ESBL- and MBL-producing Gram-negative bacilli, and the efficacy of an existing drug improved with the help of an inexpensive alternative therapy.

Molecular characterisation of the metallo-beta-lactamase genes in imipenem-resistant Gram-negative bacteria from a university hospital in southern Taiwan

In this study, 260 non-replicate imipenem-resistant Gram-negative bacteria isolated between January 2002 and December 2006 were subjected to a screening test for detection of metallo-beta-lactamase (MBL) using the Etest containing imipenem and ethylene diamine tetra-acetic acid (EDTA). Among the 260 strains, 123 (47.3%) appeared to produce MBL. Of these 123 strains, 113 (91.9%) were found by polymerase chain reaction (PCR) to carry MBL genes of types blaVIM-2, blaVIM-3, blaVIM-11 (blaVIM-11a), blaIMP-8 and novel blaIMP-24. One strain of Serratia marcescens harboured two MBL genes (blaVIM-11 and blaIMP-8) simultaneously. Of the 123 strains, 116 strains (94.3%) carrying the intI1 gene and 21 strains carrying integron-associated blaVIM-3, blaVIM-11 and blaIMP-8 genes were identified among Acinetobacter baumannii, Pseudomonas aeruginosa, Acinetobacter haemolyticus and S. marcescens. Using pulsed-field gel electrophoresis (PFGE) and Southern hybridisation with the blaVIM gene probe for I-CeuI-digested genomic DNA, P. aeruginosa 9527 strain harboured two class 1 integron-associated MBL genes in the chromosome, including blaVIM-3-orf2-aacA4 and novel bla(VIM-3)-orf2-aacA4-aadB-aacA4. This is the first description of the blaVIM-11 gene spreading among P. aeruginosa and A. baumannii strains in southern Taiwan. This finding suggests that clinical spread of this blaVIM-11 gene is a matter of great concern for carbapenem resistance in southern Taiwan.

Detection of metallo-β-lactamase–producing Pseudomonas aeruginosa strains isolated from burn patients in Ahwaz, Iran

The antimicrobial activities of 6 common antimicrobial agents including carbapenems were tested against 100 clinical Pseudomonas aeruginosa isolates using a disk diffusion method. All imipenem (IPM)-resistant isolates were screened for metallo-beta-lactamase (MBL) production by Etest assay and were subsequently subjected to polymerase chain reaction (PCR) analysis with the bla(IMP) and bla(VIM) genes. Of 41 IPM-nonsusceptible isolates detected, 8 (19.51%) appeared to produce MBL, as determined by Etest. Using PCR assay, these isolates were positive for bla(VIM) genes, whereas none were positive for bla(IMP) genes.