The sequences of seven class D β-lactamases isolated from carbapenem-resistant Acinetobacter baumannii from four continents

ABSTRACTCarbapenem resistance associated with class D β-lactamases is an increasing problem in Acinetobacter baumannii. Most enzymes of this class reported so far belong to two subgroups, 1 and 2; however, a novel class D carbapenemase (OXA-51) has been reported recently which shares 56% and <63% amino-acid identity with subgroups 1 and 2, respectively, and which belongs to a third subgroup. This study describes a further seven novel subgroup 3 β-lactamases in carbapenem-resistant A. baumannii isolates from four continents

Diversity in Acinetobacter baumannii isolates from paediatric cancer patients in Egypt

Acinetobacter baumannii is an important nosocomial pathogen, commonly causing infections in immunocompromised patients. It is increasingly reported as a multidrug-resistant organism, which is alarming because of its capability to resist all available classes of antibiotics including carbapenems. The aim of this study was to examine the genetic and epidemiological diversity of A. baumannii isolates from paediatric cancer patients in Egypt, by sequencing the intrinsic blaOXA -51-like gene, genotyping by pulsed-field gel electrophoresis and multi-locus sequence typing in addition to identifying the carbapenem-resistance mechanism. Results showed a large diversity within the isolates, with eight different blaOXA -51-like genes, seven novel sequence types and only 28% similarity by pulsed-field gel electrophoresis. All three acquired class-D carbapenemases (OXA-23, OXA-40 and OXA-58) were also identified among these strains correlating with resistance to carbapenems. In addition, we report the first identification of ISAba2 upstream of blaOXA -51-like contributing to high-level carbapenem resistance. This indicates the presence of several clones of A. baumannii in the hospitals and illustrates the large genetic and epidemiological diversity found in Egyptian strains

Gram-negative non-fermenting bacteria from food-producing animals are low risk for hospital-acquired infections

The aim of this study was to investigate possible indications of epidemiological relationships between Pseudomonas aeruginosa and Acinetobacter baumannii isolated from food-producing animals and those of clinical origin. Screening for P. aeruginosa and A. baumannii isolates from food-producing animals was carried out on 1381 samples. Susceptibility testing and PCR amplification of resistance genes were determined. Isolate clonal relatedness was established by PFGE. Forty-one P. aeruginosa and 16 A. baumannii were detected. All P. aeruginosa isolates were sensitive to ciprofloxacin, ceftazidime and piperacillin/tazobactam and seven isolates had low-level imipenem resistance. All A. baumannii isolates were sensitive to imipenem, meropenem, ciprofloxacin and piperacillin/tazobactam but were resistant to ceftazidime. The imipenem-resistant P. aeruginosa and ceftazidime-resistant A. baumannii had different PFGE patterns compared to those of human origin. Based on the findings presented here, animal isolates were not multidrug resistant and they do belong to a different pool from those of humans

Rapid acquisition of decreased carbapenem susceptibility in a strain of Klebsiella pneumoniae arising during meropenem therapy

AbstractA strain of Klebsiella pneumoniae (K1) was isolated from a catheterized patient with a urinary tract infection. The patient was subsequently treated with meropenem, after which K. pneumoniae (K2) was once again isolated from the patient's urine. Susceptibility testing showed that strain K1 was fully susceptible to carbapenem antibiotics with the exception of ertapenem, to which it exhibited intermediate resistance, whilst K2 was resistant to ertapenem and meropenem. From pulsed-field gel electrophoresis profiling both strains exhibited identical banding patterns. Both contained CTX-M-15, OXA-1, SHV-1 and TEM-1 β-lactamase genes following PCR analyses. Outer membrane protein analysis demonstrated that K1 and K2 lacked an OMP of c. 40 kDa, with an additional OMP of c. 36 kDa missing from K2. Mutation studies showed that the K2 OMP phenotype could be selected by single-step carbapenem-resistant mutants of K1. Expression of transcriptional activator ramA and efflux pump component gene acrA were up-regulated in both strains by RT-PCR. Neither strain expressed ompK35, but ompK36 was found in both. Sequence analysis revealed gene sequences of ompK35, ompK36 and ramR in both strains; notably, ramR contained a mutation resulting in a premature stop codon. Transconjugation studies demonstrated transfer of a plasmid into E. coli encoding the CTX-M-15, TEM-1 and OXA-1 β-lactamases. We concluded that the carbapenem-resistant phenotype observed from this patient was attributable to a combination of CTX-M-15 β-lactamase, up-regulated efflux and altered outer membrane permeability, and that K2 arose from K1 as a direct result of meropenem therapy

Enhancement of bacterial competitive fitness by apramycin resistance plasmids from non-pathogenic Escherichia coli

The study of antibiotic resistance has in the past focused on organisms that are pathogenic to humans or animals. However, the development of resistance in commensal organisms is of concern because of possible transfer of resistance genes to zoonotic pathogens. Conjugative plasmids are genetic elements capable of such transfer and are traditionally thought to engender a fitness burden on host bacteria. In this study, conjugative apramycin resistance plasmids isolated from newborn calves were characterized. Calves were raised on a farm that had not used apramycin or related aminoglycoside antibiotics for at least 20 months prior to sampling. Of three apramycin resistance plasmids, one was capable of transfer at very high rates and two were found to confer fitness advantages on new Escherichia coli hosts. This is the first identification of natural plasmids isolated from commensal organisms that are able to confer a fitness advantage on a new host. This work indicates that reservoirs of antibiotic resistance genes in commensal organisms might not decrease if antibiotic usage is halted

First report of Ciprofloxacin resistance among Klebsiella Pneumoniae harbouring the qnra1 gene and producing shv-5 extended-spectrum beta-lactamase in Scotland

This article is the first report of Ciprofloxacin resistance among Kebsiella Pneumoniae harbouring the qnra1 gene and producing shv-5 extended-spectrum beta-lactamase in Scotlan

Molecular epidemiology and antimicrobial resistance pattern of extended-spectrum-&#946;-lactamase-producing Enterobacteriaceae in Glasgow, Scotland

&lt;b&gt;Objectives&lt;/b&gt; To establish the molecular epidemiology and antimicrobial resistance pattern of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae harbouring blaCTX-M in Glasgow, Scotland.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Methods&lt;/b&gt; During a 12 week period, Enterobacteriaceae isolates obtained from urine samples were collected and susceptibility testing performed. Isolates were screened for the presence of blaCTX-M by multiplex PCR and selected Escherichia coli genes were subsequently sequenced. PFGE analysis was performed on selected E. coli isolates in order to identify clonal relationships.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Results&lt;/b&gt; There were 155 phenotypically confirmed non-duplicate Enterobacteriaceae isolates obtained from urine samples. blaCTX-M was identified in 131/155 (84.5%) of the ESBL-producing isolates, with CTX-M group 1 enzymes accounting for 103/131 (78.6%) of these. The remaining 24 isolates carried other blaCTX-M types, including CTX-M group 2, CTX-M group 9 and an unidentifiable combination designated CTX-M group G2/Gx. A sample of 46/97 (47.4%) CTX-M-positive E. coli isolates was chosen for PFGE and demographic information regarding the source of the isolates was collated. Eight E. coli clusters were identified by PFGE; however, they did not achieve the 85% cut-off to demonstrate clonality. Nitrofurantoin resistance was significantly greater in the E. coli isolates expressing a non-CTX-M group 1 ESBL when compared with the E. coli isolates expressing a CTX-M group 1 ESBL.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Conclusions&lt;/b&gt; As seen in other British studies, blaCTX-M has become the predominant ESBL type in Glasgow, Scotland. The PFGE results show that four different CTX-M groups appear to be circulating in the community and within all four hospitals in the locality. There is little correlation between strain genotype and CTX-M group, thus it is unlikely that cross-infection alone is the driver. It is possible that plasmid migration of CTX-M genes within the E. coli population is occurring