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Biomedical subjects

J E Corkill

Publications and source records attributed to J E Corkill.

At least 19 recordsLinked to original sources
PubMed1999

Serratia marcescens pseudobacteraemia in neonates associated with a contaminated blood glucose/lactate analyzer confirmed by molecular typing.

Three episodes of Serratia marcescens pseudobacteraemia occurred on a neonatal intensive care unit. Following the first two cases, one full term and one pre-term infant, the source was identified as a glucose/lactate analyzer. Blood culture and environmental isolates of the organisms involved were indistinguishable when subjected to pulsed-field gel electrophoresis of Spe 1 digests and PCR ribotyping. Failure to recognize pseudobacteraemia in neonates results in inappropriate therapy for the individual and increased antibiotic pressures on the unit. Attention to the possibility of cross infection when using automated analyzers is required to minimize the risks of true or pseudoinfection to patients.

Bacteremia↗
PubMed1998

Flagellin gene variation between clinical and environmental isolates of Burkholderia pseudomallei contrasts with the invariance among clinical isolates.

The flagellin gene sequence from a clinical isolate of Burkholderia pseudomallei was used to design oligonucleotide primers for PCR/RFLP analysis of flagellin gene variation among clinical and environmental isolates of B. pseudomallei. Genes from four clinical and six environmental isolates were amplified and compared by RFLP. The clinical isolates were indistinguishable, but variation was detected among some of the environmental isolates. Sequence analysis of flagellin gene amplified products demonstrated high levels of conservation amongst the flagellin genes of clinical isolates (>99% similarity), compared to the variation observed between the clinical isolates and one of the environmental isolates (<90% similarity). Genomic comparisons with pulsed-field gel electrophoresis (PFGE) revealed differences between the relationships inferred by flagellin genotyping and PFGE, suggesting that a combination of molecular methods may be useful for the subtyping of B. pseudomallei strains.

Bacterial Outer Membrane Proteins↗
PubMed1998

Cross infection between cystic fibrosis patients colonised with Burkholderia cepacia.

Whilst patient to patient spread of the respiratory pathogen Burkholderia cepacia is well recognised between patients with cystic fibrosis, prompting a strict segregation policy, cross colonisation between cystic fibrosis patients already infected with B cepacia has not been described and surveys show a very low incidence of patients with more than one strain. Five adult cystic fibrosis patients with B cepacia are presented who became cross colonised with a second B cepacia (UK epidemic) strain, four of whom then died, three from the cepacia syndrome. These cases show that, amongst segregated patients, cross colonisation with different B cepacia strains is possible, and even in these patients the acquisition of the UK epidemic strain may have a fatal outcome. In future it may be necessary to segregate cystic fibrosis patients colonised with the UK epidemic strain from all other patients with cystic fibrosis.

Adolescent↗
PubMed1997

Characterization of antibiotic resistance plasmids from Bordetella bronchiseptica.

Of 52 antibiotic-resistant Bordetella bronchiseptica isolates from cats, ten carried plasmids. Only two of these plasmids, pLV1400 and pLV1401, were self-transmissible to Escherichia coli K12; both plasmids encoded resistance to ampicillin, tetracycline, sulphonamides, streptomycin and mercuric chloride, and were of incompatibility group P (IncP). Transferable tetracycline resistance has not been reported in B. bronchiseptica previously. The plasmids were identical in size (c.51 kb), restriction endonuclease digestion pattern and gene sequences (trfA and korA) within the IncP replicon. The trfA and korA sequences differed from those of the archetypal IncP plasmids RP4 and R751. Although the two B. bronchiseptica isolates were from epidemiologically and geographically separated cats, pulsed-field gel electrophoresis of their XbaI- or DraI-digested chromosomal DNA indicated that they were genotypically identical. The plasmid-encoded ampicillin resistance was mediated by a penicillinase of molecular weight 49,000, and pI 8.45 which was inhibited by clavulanate (IC50 = 0.1 mg/L) and tazobactam (IC50 = 0.42 mg/L) but not by parachloromercuribenzoate or EDTA. The high-level tetracycline resistance was mediated by a class C efflux mechanism that has not been described previously in this genus. The presence of transferable multi-drug resistance on a promiscuous plasmid may limit options for therapy of respiratory tract infection in companion and farm animals.

Animals↗
PubMed1996

Expression of Aeromonas caviae bla genes in Escherichia coli.

An isolate of Aeromonas caviae 035 carried a 55.5 kb self-transferable plasmid. Transfer of the plasmid to Escherichia coli K12 resulted in the expression of a TEM-like beta-lactamase that was not expressed in parental A. caviae. The bla gene sequence was detectable by DNA hybridization and PCR amplification of the plasmid when extracted from parental A. caviae or from E. coli K12 transconjugants. Sequence analysis of the bla genes revealed in each case an 858 bp open reading frame, differing from the TEM-1 sequence by five nucleotide substitutions. Only one of these resulted in amino acid substitution (at position 162 serine-->arginine). The sequence most closely resembles that of TEM-12.

Aeromonas↗
PubMed1994

Application of pyrolysis mass spectroscopy and SDS-PAGE in the study of the epidemiology of Pseudomonas cepacia in cystic fibrosis.

Representative isolates of Pseudomonas cepacia from 15 cystic fibrosis (CF) patients attending the Respiratory Unit of Alder Hey Childrens' Hospital were investigated by SDS-PAGE of whole-cell polypeptides and by pyrolysis mass spectroscopy (PMS). SDS-PAGE was less discriminatory than PMS. Eleven isolates were indistinguishable by PMS and considered to represent re-isolates of an endemic strain; four isolates were distinct from this group, and from one another. P. cepacia was first isolated on the unit in July 1989 from a patient who had attended a UK selection meeting for a Canadian CF camp. A ward and outpatient segregation policy was introduced, but colonisation of further patients occurred. In August 1991, the Adult CF Association recommended that all social activities involving colonised patients should cease. This, and an increased awareness amongst older CF patients of the risks of person-to-person transmission, was associated with a marked decline in new cases. Social activity and hospital admissions were compared for colonised patients during the year before colonisation with P. cepacia, and matched patients who did not acquire the endemic strain. This showed a significantly higher attendance at CF social events for colonised patients, but no significant association between colonisation and hospital admission. These results are strong indirect evidence that transmission of P. cepacia occurs through social contact outside the hospital environment.

Adolescent↗
PubMed1994

Effect of pH and CO2 on in vitro susceptibility of Pseudomonas cepacia to beta-lactams.

Inhibition of Pseudomonas cepacia (but not Pseudomonas aeruginosa) by beta-lactams was decreased in 5% CO2 in air compared with air alone. The effect of CO2 and pH (range, 6.0 to 8.0) on beta-lactam susceptibility, beta-lactamase expression, and outer membrane proteins was studied in isolates recovered from the sputum of children with cystic fibrosis. Incubation in 5% CO2 decreased the activity of piperacillin, piperacillin/tazobactam, and ceftazidime, although isolates were still clinically sensitive (minimum inhibitory concentrations < 16 mg/L). Cefpirome activity was markedly decreased from a minimum inhibitory concentration of 2.0 to greater than 64 mg/L. On highly buffered 3-(N-morpholino)-propane sulfonic acid media, beta-lactam susceptibility was eliminated at pH greater 7.5. A 2- to 13-fold increase in beta-lactamase activity was demonstrated after growth in 5% CO2 compared with basal aerobic levels for 13 of 15 clinical isolates. beta-Lactamase activity did not vary significantly with pH. Addition of imipenem to media (2.0 mg/L) resulted in hyperproduction of beta-lactamase (180-fold). Isoelectric points varied with cultural conditions, and all beta-lactamases detected were inhibited by clavulanate and tazobactam. Significant hydrolysis of piperacillin and ceftazidime could not be demonstrated. A 36-kD porin was present at all pH tested. Thus, our strains of Pseudomonas cepacia were markedly affected by cultural conditions not normally used in standardized susceptibility tests. However, such conditions may be encountered in the pathologically altered infected lung in cystic fibrosis.

Anti-Bacterial Agents↗
PubMed1993

Plasmid encoded beta-lactamases resistant to inhibition by clavulanic acid produced by calf faecal coliforms.

Two new plasmid encoded beta-lactamase enzymes produced by a strain of Escherichia coli and a strain of Citrobacter freundii isolated from calf faeces have been characterised. Both enzymes were similar to TEM-1 in terms of substrate and inhibition profiles and physical properties but differed from TEM-1 in being far less susceptible to the beta-lactamase inhibitors clavulanic acid or tazobactam. In each case transfer of the plasmid E coli K12 rendered it clinically resistant to the combination of amoxycillin and clavulanic acid. The beta-lactamase from the E coli had an iso-electric point (pI) of 5.4 and was encoded on a plasmid of 95 Kbp which also mediated resistance to tetracycline, sulphonamides, apramycin, streptomycin and gentamicin. The beta-lactamase from the C freundii had a pI of 5.2 and was encoded on a 75 Kbp plasmid which also mediated resistance to trimethoprim, chloramphenicol, apramycin, gentamicin and tobramycin.

Amoxicillin↗
PubMed1993

Selective decontamination with nystatin for control of a Candida outbreak in a neonatal intensive care unit.

Selective decontamination of the digestive tract (SDD) with oral nystatin was evaluated as a measure to control an outbreak of Candida infection in a neonatal intensive care unit (NICU). Seventy-six out of 106 neonates who carried Candida spp. received the main study manoeuvre (the application of oral nystatin in the throat and stomach) during the 12-month open trial. One third of the neonates weighed < 1500 g whilst about half were being ventilated. The mean stay was 33.2 d (SD +/- 46.9). Two cases with candidaemia within a fortnight were associated with a yeast carriage rate in the NICU of about 50%; more than 80% of the isolates were Candida parapsilosis. During the implementation period there were four new neonates with fungaemia caused by C. parapsilosis. Once the carriage rate dropped below 5% (P < 0.001), no new cases of systemic infection with the outbreak strain were recognized in the following 8 months. It took 3.5 months to control the outbreak. The observation that all other clinical diagnostic samples were free from Candida suggests that translocation from throat or gut into the systemic circulation occurred. SDD with oral nystatin was effective in reducing the yeast carriage index (mean index 1.93, before SDD; 0.45, after SDD; P < 0.001). A significant reduction of carriage, both in rates and indices, is thought to have contributed to the control of this candida outbreak.

Candidiasis↗
PubMed1992

Effects of CO2 and pH on inhibition of TEM-1 and other beta-lactamases by penicillanic acid sulfones.

Incubation in 5% CO2 reduced the inhibition zones of piperacillin-tazobactam (75/10 micrograms) disks for Escherichia coli strains with TEM-1, TEM-2, and SHV-1 beta-lactamases. Similarly, MICs of piperacillin-tazobactam and other penicillin-sulfone combinations for TEM producers were up to 500-fold higher at pH 6.5 than at pH 8.0. This effect was greatest for organisms with high levels of enzyme activity. CO2 and mild acidity did not affect the susceptibility of beta-lactamase-negative strains to penicillin-sulfone combinations, and the effects of these conditions were variable for organisms with beta-lactamases other than TEM-1, TEM-2, and SHV-1. These last observations discounted acid-mediated inactivation of piperacillin or tazobactam. MICs of amoxicillin or piperacillin alone or with clavulanate for TEM and SHV producers were affected only less than or equal to 16-fold by 5% CO2 or acidity, indicating that the greater effects seen with the penicillin-sulfone combinations depended on the behavior of the sulfones and not on that of the penicillins. This pH effect was studied in detail for TEM-1 enzyme. Inhibition of this enzyme by sulfones but not clavulanate varied grossly with pH, with 50% inhibitory concentrations of tazobactam and sulbactam up to 300-fold higher at pH 6.5 than at 8.0. By contrast, the hydrolytic activity of TEM-1 enzyme for substrates and its level of production varied threefold or less between pH 6.5 and pH 8.0. Increased inhibition at pH 8.0 reflected sequestration of the enzyme into a secondary noncovalent complex rather than increased irreversible inactivation.

Carbon Dioxide↗
PubMed1991

Characterization of a beta-lactamase produced by Pseudomonas paucimobilis.

A novel beta-lactamase enzyme produced by a strain of Pseudomonas paucimobilis is described. The enzyme differs from other recorded beta-lactamases from Gram-negative aerobic bacteria. It was constitutive, and had the characteristics of a penicillinase. One single band of beta-lactamase activity at pI 4.6 was seen on iso-electric focusing. The enzyme had a molecular mass of 30 kDa. The beta-lactamase was strongly inhibited by tazobactam, sulbactam and clavulanic acid but not by the thiol residue inhibitors p-chloromercuribenzoate and p-chloromercuriphenylsulphonic acid, or by metallo-enzyme inhibitors. Plasmid DNA was not demonstrable, suggesting that the enzyme was chromosomally encoded.

Cephalosporins↗
PubMed1987

Evaluation of the skin disinfecting activity and cumulative effect of chlorhexidine and triclosan handwash preparations on hands artificially contaminated with Serratia marcescens.

The initial and cumulative efficacy of two antiseptic handwash preparations in eliminating Serratia marcescens from hands was evaluated on volunteers. Two antiseptics with persistent skin antibacterial activity, 4% chlorhexidine gluconate in detergent and 1.5% triclosan in natural soap, were studied in a new protocol designed according to Food and Drug Administration guidelines. After a single handwash, both preparations exhibited a degerming action statistically superior to the mechanical elimination of the marker organism that was achieved by the nonmedicated controls. Following a further nine hand recontamination sequence with 10(9) colony-forming units (cfu)/mL S marcescens (mean predisinfection baseline, log10 6.6), the efficacy of chlorhexidine and triclosan was significantly augmented: the mean log10 reduction factors were 4.15 and 3.78, respectively. In the absence of internationally accepted testing standards for antiseptic handwash products, the significance of protocol variables is discussed. The advantages to preventative microbiology of antiseptics with persistent skin antibacterial activity are highlighted.

Chlorhexidine↗