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Biomedical subjects

Neil Woodford

Publications and source records attributed to Neil Woodford.

At least 19 recordsLinked to original sources
PubMed2007

In vitro activity of the oxazolidinone RWJ-416457 against linezolid-resistant and -susceptible staphylococci and enterococci.

RWJ-416457, a novel oxazolidinone, had modal MICs of 0.5 to 1 microg/ml for linezolid-susceptible staphylococci and enterococci, versus linezolid MICs for these organisms of 1 or 2 microg/ml. RWJ-416457 MICs for mutants with 23S rRNA mutations were 2 to 32 microg/ml, versus linezolid MICs of 8 to 64 microg/ml; actual values reflected the proportion of gene copies mutated.

Acetamides↗
PubMed2007

Reduced imipenem susceptibility in Klebsiella pneumoniae clinical isolates with plasmid-mediated CMY-2 and DHA-1 beta-lactamases co-mediated by porin loss.

We investigated the resistance mechanisms and clonality among 42 imipenem-non-susceptible Klebsiella pneumoniae isolated at a tertiary care hospital in Korea. Two isolates had bla(VIM-2) alleles, whereas bla(CMY-2)- and bla(DHA-1)-like alleles were detected in 24 and 16 isolates, respectively, with these enzymes confirmed by sequencing for representative isolates. Transfer of bla(CMY-2) and bla(DHA-1) was achieved by conjugation. Addition of 300 mg/L 3-aminophenylboronic acid (APB) reduced the minimum inhibitory concentration for 90% of the organisms (MIC(90)) of imipenem and meropenem eight- and four-fold, respectively, for the bla(CMY-2)- and bla(DHA-1)-positive isolates, confirming the role of these enzymes in resistance. SDS-PAGE of outer membrane proteins for representative isolates showed lack or greatly diminished expression of OmpK35 and OmpK36 porins. Pulsed-field gel electrophoresis of XbaI-restricted genomic DNA revealed two closely related clusters among 23 bla(CMY-2)-positive isolates, whereas those with bla(DHA-1) were more heterogeneous. In conclusion, reduced imipenem susceptibility among K. pneumoniae at this Korean hospital was largely co-mediated by production of plasmid-mediated AmpC beta-lactamases along with lack or greatly diminished expression of OmpK35 and OmpK36 porins.

Anti-Bacterial Agents↗
PubMed2007

Real-time TaqMan PCR for rapid detection and typing of genes encoding CTX-M extended-spectrum beta-lactamases.

The prevalence of CTX-M-producing members of the Enterobacteriaceae is increasing worldwide. A novel, multiplex, real-time TaqMan PCR assay to detect and type bla(CTX-M) genes is described which is an improvement on previously described techniques with respect to reduced assay time, elimination of the need for protracted post-PCR processing and the convenience of a single reaction vessel. Based on beta-lactam antibiogram and MIC data, 478 of 1279 Enterobacteriaceae isolates from clinical blood and urine culture specimens were selected and tested for extended-spectrum beta-lactamase (ESBL) production using phenotypic methods. The new TaqMan assay detected and typed bla(CTX-M) genes in 21 of 28 ESBL-producing isolates.

Ampicillin↗
PubMed2007

Detecting mutations that confer oxazolidinone resistance in gram-positive bacteria.

Resistance to oxazolidinone antibiotics, including linezolid, in Gram-positive bacteria is mediated by single-nucleotide polymorphisms (SNPs) in the 23S ribosomal RNA. A G2576U change (encoded by a G2576T mutation in the rRNA genes) is found in most resistant clinical isolates of enterococci and staphylococci; a variety of changes have been found in resistant mutants selected in vitro. Pyrosequencing can be used to detect SNPs known to confer oxazolidinone resistance, including the G2576T change. Most bacteria have more than one rRNA gene copy and Pyrosequencing can also be used for allele quantification, i.e., to estimate the proportions of mutant vs wild-type alleles. The number of mutated rRNA gene copies correlates roughly with the level of oxazolidinone resistance displayed by resistant isolates. This chapter summarizes the Pyrosequencing assays that have been developed in our laboratory for analyzing oxazolidinone-resistant enterococci and staphylococci.

Base Sequence↗
PubMed2006

CTX-M: changing the face of ESBLs in Europe.

Since around 2000 - earlier in Poland and Spain and later in France and the UK - dramatic shifts have occurred in the prevalence and types of extended-spectrum beta-lactamases (ESBLs) in Europe. Before this watershed, most producers were nosocomial isolates, often Klebsiella spp. or Enterobacter spp. from specialist care units, and had mutant TEM or SHV ESBLs. Subsequently, CTX-M ESBLs have become dominant, with much greater penetration into Escherichia coli, and with many infections in 'complicated community' patients, usually with underlying disease, recent antibiotic usage, or healthcare contact. The degree of clonality among producers varies with the country, as does the enzyme type produced, with group 9 (CTX-M-9 and -14) enzymes dominant in Spain and group 1 enzymes (particularly CTX-M-3 and -15) dominant elsewhere. Irrespective of the particular enzyme, most producers are multiresistant. These changing patterns present major therapeutic and infection control challenges, with the public health intervention points unclear.

Community-Acquired Infections↗
PubMed2006

Wide geographic spread of diverse acquired AmpC beta-lactamases among Escherichia coli and Klebsiella spp. in the UK and Ireland.

OBJECTIVES: To determine the distribution of acquired AmpC beta-lactamases in 173 isolates of Escherichia coli and Klebsiella spp. submitted to the UK's national reference laboratory for antibiotic resistance. METHODS: MICs were determined and interpreted according to BSAC guidelines. Candidate isolates were those resistant to cefotaxime and/or ceftazidime, irrespective of addition of clavulanic acid. Genes encoding six phylogenetic groups of acquired AmpC enzymes were sought by PCR. Selected isolates were compared by pulsed-field gel electrophoresis (PFGE), and one bla(AmpC) amplicon was sequenced. RESULTS: Genes encoding acquired AmpC enzymes were detected in 67 (49%) candidate E. coli and 21 (55%) Klebsiella spp. Sixty isolates produced CIT-type enzymes, 14 had ACC types, 11 had FOX types and 3 had DHA enzymes. The low-level cephalosporin resistance of the remaining isolates (n = 85; 49%) was inferred to result from reduced permeability or, in E. coli, from hyperexpression of chromosomal ampC. Twenty-four E. coli isolates from one hospital produced a CIT-type enzyme, with 20 of these additionally producing a group 1 CTX-M extended-spectrum beta-lactamase. PFGE indicated that these isolates belonged to UK epidemic strain A, which normally produces CTX-M-15, but no acquired AmpC. Sequencing a representative bla(AmpC) amplicon indicated that in one centre this strain had acquired a novel CMY-2 variant, designated CMY-23. CONCLUSIONS: Diverse acquired AmpC enzymes occur in E. coli and Klebsiella spp. isolates in the UK and Ireland, with CIT types the most common. Producers are geographically scattered, but with some local outbreaks. Acquisition of a CMY-2-like enzyme by E. coli epidemic strain A suggests that these enzymes may be poised to become an important public health issue.

Bacterial Proteins↗
PubMed2006

Molecular epidemiology of multiresistant Escherichia coli isolates from community-onset urinary tract infections in Cornwall, England.

OBJECTIVES: To study the clonality of gentamicin-resistant, extended-spectrum beta-lactamase (ESBL)-negative and ESBL-producing Escherichia coli isolated from community-onset urinary tract infections (UTIs) in Cornwall. METHODS: Isolates were identified by API, susceptibilities were determined by local disc testing, and MICs were determined at the reference laboratory, both interpreted using BSAC guidelines. bla(CTX-M) genes were sought by PCR, and isolates were compared by PFGE. RESULTS: In the years 2004 and 2005, 69 E. coli were submitted by Truro (Cornwall) laboratory for reference laboratory testing: these included 14 gentamicin-resistant, ESBL-negative isolates; 45 with group 1 CTX-M enzymes; seven with group 9 CTX-M enzymes; and three with non-CTX-M ESBLs. By PFGE, nine gentamicin-resistant, ESBL-negative E. coli were distinct (<85% similarity) from all the ESBL producers, but three were related to producers of group 1 CTX-M enzymes, and two isolates were related to a non-CTX-M ESBL producer. An outbreak strain was identified, represented by 11 gentamicin-resistant and one gentamicin-susceptible isolates, all with group 1 CTX-M enzymes, and two gentamicin-resistant, ESBL-negative isolates. This was distinct by PFGE from nationally distributed CTX-M-producing strains. Five of nine patients infected with this strain had been on the same ward in a local hospital; four presented with community-onset UTIs; one inpatient developed a hospital-acquired bacteraemia. Of the other four patients presenting with community-onset UTIs, three were admitted to different hospitals and the fourth had only attended an outpatient clinic. CONCLUSIONS: Community-onset, ESBL-producing and non-producing E. coli were diverse. Two ESBL-negative isolates were closely related to a local CTX-M-producing outbreak strain, suggesting gain or loss of a bla(CTX-M)-carrying plasmid. An outbreak strain was linked with prior hospital admission and appeared not to represent genuine community acquisition.

Community-Acquired Infections↗
PubMed2006

Mutators among CTX-M beta-lactamase-producing Escherichia coli and risk for the emergence of fosfomycin resistance.

OBJECTIVES: Fosfomycin is a possible oral treatment for lower urinary tract infections caused by Escherichia coli with CTX-M extended-spectrum beta-lactamases but is vulnerable to mutational resistance. Hypermutability among natural E. coli populations might facilitate the emergence of resistance to fosfomycin. We therefore examined the prevalence of mutators amongst urinary isolates of E. coli producing CTX-M beta-lactamases. METHODS: Urinary E. coli isolates with CTX-M beta-lactamases (n = 220) were screened for resistance to both rifampicin and fosfomycin, as well as a mutator phenotype, by rifampicin and fosfomycin disc assays. Mutation frequencies for 10 isolates, identified as mutators by the initial disc screen, were determined in triplicate on agar with rifampicin or fosfomycin at 4x MIC and with fosfomycin or nitrofurantoin at 256 mg/L. RESULTS: The disc screen identified 10 likely mutators and quantitative tests indicated that 9 of these had mutation frequencies of 8.0 x 10(-6)-1.5 x 10(-4) for fosfomycin and 0.1-2.3 x 10(-6) for rifampicin. These mutators were diverse in terms of PFGE type and 4 of the 10 were confirmed as strong mutators with rifampicin and fosfomycin. Only the strongest mutator isolate and hypermutable MutS(-) control strain consistently gave single-step mutants resistant to 256 mg/L fosfomycin. No nitrofurantoin-resistant mutants were selected from any isolate, although they could be selected from the hypermutable MutS(-) control strain. CONCLUSIONS: Mutator phenotypes were found among E. coli expressing CTX-M beta-lactamases and were independent of strain type. These had an increased propensity to fosfomycin resistance.

Anti-Bacterial Agents↗
PubMed2006

The beta-lactamase threat in Enterobacteriaceae, Pseudomonas and Acinetobacter.

Over the past 60 years, the use of successive generations of beta-lactam antibiotics has selected successive generations of beta-lactamase enzymes, each more potent than the last. Currently, rising problems include CTX-M extended-spectrum beta-lactamases (ESBLs), plasmid-mediated AmpC beta-lactamases and KPC carbapenemases in Enterobacteriaceae, while OXA- and metallo- carbapenemases are of growing importance in Acinetobacter spp. and (less so) in other non-fermenters. Escherichia coli isolates with CTX-M ESBLs are spreading multiresistance in the community and in hospitals, while carbapenemase-producing Acinetobacter spp., mostly from intensive care, are among the most multiresistant nosocomial bacteria known and are often susceptible only to polymyxins and, potentially, tigecycline. This review discusses the epidemiology and microbiology of these resistance problems, along with possible solutions.

Acinetobacter↗
PubMed2006

In vivo development of ertapenem resistance in a patient with pneumonia caused by Klebsiella pneumoniae with an extended-spectrum beta-lactamase.

Four sequential extended-spectrum beta -lactamase-producing isolates of Klebsiella pneumoniae were obtained from a patient after treatment with ertapenem and cultured. The first and fourth isolates were susceptible to ertapenem, whereas the second and third were resistant. All 4 isolates belonged to the same strain and produced a group 1 CTX-M enzyme; additionally, the resistant isolates had lost a porin.

Aged, 80 and over↗
PubMed2006

Fluoroquinolone resistance and plasmid addiction systems: self-imposed selection pressure?

Multi-antibiotic-resistant Gram-negative pathogens are becoming more prevalent and an association exists between chromosomally conferred fluoroquinolone resistance and the presence of plasmid-borne resistances, such as extended spectrum beta-lactamases. This link is not wholly explained by strain spread or the presence of fluoroquinolone-modifying enzymes. Plasmid-encoded toxin-antitoxin addiction systems enforce plasmid maintenance in bacteria and, like fluoroquinolones, some toxins target DNA gyrase. Bacteria can develop resistance to these toxins, which would free the cell of the plasmid addiction and allow it to ditch the "excess baggage". We hypothesize that these plasmid-encoded gyrase toxins might contribute to, or predispose towards, clinically significant fluoroquinolone resistance, and that the plasmid-encoded quinolone resistance determinant, Qnr, may facilitate this. Establishing the extent and mechanisms of cross-resistance to toxins and fluoroquinolones will aid the management of resistance and may contribute to the development of novel antimicrobials.

Anti-Bacterial Agents↗
PubMed2006

Multiplex PCR for genes encoding prevalent OXA carbapenemases in Acinetobacter spp.

Carbapenem resistance in Acinetobacter baumannii is a growing public health concern and is most often mediated by OXA carbapenemases. We describe a novel multiplex polymerase chain reaction (PCR) assay able to detect and distinguish alleles encoding three subgroups of acquired OXA carbapenemases (OXA-23-like, OXA-24-like and OXA-58-like) that are scattered in Acinetobacter spp., and a fourth subgroup, OXA-51-like, which appears to be intrinsic to Acinetobacter baumannii. Isolates belonging to two prevalent UK A. baumannii 'OXA' clones (OXA-23 clones 1 and 2) had alleles encoding both an intrinsic OXA-51-like and an acquired OXA-23 enzyme, whereas isolates of the 'SE clone' had only an intrinsic bla(OXA-51-like) allele. Genes encoding OXA-58 were detected (with bla(OXA-51-like)) in a cluster of related isolates from a single hospital. This simple assay will assist in monitoring the mechanisms responsible for carbapenem resistance in Acinetobacter spp.

Acinetobacter↗
PubMed2006

The role of ISAba1 in expression of OXA carbapenemase genes in Acinetobacter baumannii.

ISAba1 was found in all widespread clones of Acinetobacter baumannii in the United Kingdom. All isolates studied had a blaOXA-51-like carbapenemase gene; some also had blaOXA-23-like and/or blaOXA-58-like. Among isolates with blaOXA-51-like as sole carbapenemase gene, only those with ISAba1 adjacent to blaOXA-51-like were carbapenem resistant. Minor differences in blaOXA-51-like sequence were observed in resistant and susceptible isolates. Isolates with blaOXA-23-like in addition were consistently resistant to carbapenems; in all of these ISAba1 lay upstream of blaOXA-23-like, but was not associated with blaOXA-51-like. These results suggest that ISAba1 is providing the promoter for blaOXA-51-like and, probably, for blaOXA-23-like.

Acinetobacter baumannii↗
PubMed2006

Occurrence of OXA-58-like carbapenemases in Acinetobacter spp. collected over 10 years in three continents.

OXA-58 is a recently described carbapenemase from Acinetobacter spp. in Europe. We examined earlier worldwide Acinetobacter collections and found bla(OXA-58) in 30 carbapenem-nonsusceptible isolates, including several isolates collected in Argentina and Kuwait in 1995 and 1996 and in a British outbreak strain from 2000. Most isolates (28 of 30) also had bla(OXA-51). We conclude that bla(OXA-58) is geographically widespread and has occurred in Acinetobacter spp. for over 10 years.

Acinetobacter↗