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Biomedical subjects

T L Pitt

Publications and source records attributed to T L Pitt.

At least 55 records · Page 3Linked to original sources
PubMed1996

Home-use nebulizers: a potential primary source of Burkholderia cepacia and other colistin-resistant, gram-negative bacteria in patients with cystic fibrosis.

Inhalation of aerosols contaminated with gram-negative bacteria generated from home-use nebulizers used by cystic fibrosis (CF) patients may be a primary route for bacterial colonization of the lung. Burkholderia cepacia was isolated from 3 of [corrected] 35 home-use nebulizers, and Stenotrophomonas maltophilia was isolated from 4 of 35 home-use nebulizers. Sputum cultures for two patients whose nebulizers were contaminated with B. cepacia did not yield the organism. However, DNA macrorestriction analysis by pulsed-field gel electrophoresis confirmed that one of two strains of B. cepacia recovered from the nebulizer of a third patient was also present in the sputum of that patient. Although Pseudomonas aeruginosa was isolated from 34 patients, none of the nebulizers were positive for the organism. Sixty-nine percent of nebulizers were contaminated, and up to 16 different environmental colistin-resistant, gram-negative species were identified. The heaviest contamination was found beneath the chamber atomizer. A questionnaire survey showed that the majority of patients (28 of 34) were receiving nebulized colistin and/or gentamicin. Patients who followed recommended instructions for good nebulizer hygienic practice and paid particular attention to drying had minimal or no contamination of their nebulizers.

Adult↗
PubMed1996

Comparison of outbreak and nonoutbreak Acinetobacter baumannii strains by genotypic and phenotypic methods.

Thirty-one Acinetobacter baumannii strains, comprising 14 strains from 14 outbreaks in different northwestern European cities and 17 sporadic strains, were compared by investigating various properties of the strains including biotype, antibiogram, cell envelope protein electrophoretic profile, ribotype pattern, and the band pattern generated by a novel genomic fingerprinting method, named AFLP, which is based on the selective amplification of restriction fragments. Results showed that 12 strains from unrelated outbreaks were linked together in two clusters according to their similarities by these typing methods, whereas sporadic strains were more heterogeneous. Outbreak strains appeared to be markedly more resistant to antibiotics than nonoutbreak strains. The uniformity of typing characters in two sets of outbreak strains suggests that strains in each cluster have a common clonal origin.

Acinetobacter↗
PubMed1995

Klebsiella pneumoniae infections in Greek hospitals. Dissemination of plasmids encoding an SHV-5 type beta-lactamase.

A total of 160 Klebsiella pneumoniae clinical strains consecutively isolated in 14 Greek hospitals in a three-month period was examined. Application of capsular typing using 72 monovalent antisera combined with phage-typing using a set of 15 Klebsiella-specific phages showed the absence of epidemic strains. However, 41% of the isolates examined displayed high level resistance to ceftazidime and aztreonam and, in most of the cases, to more than one aminoglycoside as well as to other antibacterial drugs. Nearly all of these multi-resistant strains were epidemiologically distinct on the basis of their capsular serotype and phage reactivity. After examination of 14 distinct strains, it was found that in nine cases, the resistance characters were readily transferred to Escherichia coli recipients through large self-transmissible plasmids (15-100 MDa). Six of the nine plasmids had equal molecular weight (60 MDa) and displayed similar fragment profiles upon digestion with restriction endonuclease EcoRI. Isoelectric focusing and hydrolytic studies showed that the prominent beta-lactamase produced by the transconjugants harbouring the 60 MDa plasmids and the respective K. pneumoniae parent strains, was an extended-spectrum beta-lactamase of the SHV-5 type. It appears that among K. pneumoniae strains isolated in Greek hospitals a significant resistance rate to both newer beta-lactams and amino-glycosides has been established through the acquisition of promiscuous multi-resistant plasmids which share a high degree of similarity.

Aztreonam↗
PubMed1995

Auxotrophic variants of Pseudomonas aeruginosa are selected from prototrophic wild-type strains in respiratory infections in patients with cystic fibrosis.

Twenty-four nutritionally dependent (auxotrophic) Pseudomonas aeruginosa strains were isolated from 20 cystic fibrosis (CF) patients and tested for their amino acid requirements. Two different methods were necessary to identify the nutritional status of all isolates. Methionine was the most common single amino acid required (9 of 24 isolates), followed by leucine and arginine or ornithine. In total, a requirement for 12 different compounds or combination of compounds was demonstrated. Auxotrophic and prototrophic pairs of isolates from the same patient were compared by macrorestriction analysis of DNA in pulsed-field gel electrophoresis. Thirteen of 18 pairs analyzed presented identical restriction fragment length polymorphism profiles following digestion of DNA with XbaI. Three of the remaining pairs showed percentage similarities of 77, 91, and 98%, and the profiles of two pairs could not be compared because of the excessive degradation of their DNA. These results suggest that auxotrophic and prototrophic P. aeruginosa isolates colonizing the same CF patient constitute an isogenic group and raise the possibility that auxotrophs are selected from the prototrophic population during the course of pulmonary infection in CF patients.

Amino Acids↗
PubMed1995

Discriminatory power of three DNA-based typing techniques for Pseudomonas aeruginosa.

We assessed the capacity of three DNA typing techniques to discriminate between 81 geographically, temporally, and epidemiologically unrelated strains of Pseudomonas aeruginosa. The methods, representing powerful tools for hospital molecular epidemiology, included hybridization of restricted chromosomal DNA with toxA and genes coding for rRNA (rDNA) used as probes and macrorestriction analysis of SpeI-digested DNA by pulsed-field gel electrophoresis. The probe typing techniques were able to classify all strains into a limited number of types, and the discriminatory powers were 97.7 and 95.6% for toxA and rDNA typing, respectively. Strains that were indistinguishable on the basis of both toxA and rDNA types defined 12 probe type homology groups. Of these, one contained five strains, three contained three strains each, and eight groups were represented by two strains each. Strains in 10 of the homology groups had the same O serotype. SpeI macrorestriction patterns discriminated between all strains with at least four band differences, which corresponded to a similarity level of 85%. Fifteen pairs of strains were similar at a level of > 75% and differed by only four to seven bands. Of these pairs, 11 belonged to the same probe type homology group, indicating their clonal relatedness. We conclude that macrorestriction analysis of P. aeruginosa with SpeI provides the best means of discrimination between epidemiologically unrelated strains. However, DNA probe typing with either toxA or rDNA reveals information on the strain population structure and evolutionary relationships.

Bacterial Typing Techniques↗
PubMed1995

Auxotrophy of Burkholderia (Pseudomonas) cepacia from cystic fibrosis patients.

The nutritional status of 89 isolates of Burkholderia cepacia from 81 cystic fibrosis (CF) patients was evaluated. Forty of the isolates, from 38 patients, were not able to grow in a minimal medium containing glucose and mineral salts only and were thus auxotrophs. In contrast, all of 29 isolates from non-CF (clinical and environmental) sources were prototrophic. Addition of a pool of amino acids to the minimal medium was sufficient to promote growth of all tested CF auxotrophic isolates. Indeed, phenylalanine, tyrosine, cysteine, methionine, and histidine alone or in combination were required for growth by the majority of the nutritionally deficient B. cepacia isolates. Furthermore, extracts of sputum from CF patients, when added to minimal medium, promoted growth of 29 auxotrophic B. cepacia isolates regardless of their amino acid requirements. Finally, auxotrophic and prototrophic isolates from the same patient exhibited a conserved genotype, as determined by macrorestriction analysis of chromosomal DNA. These results suggest that the auxotrophic mutants are selected from the prototrophic population and maintained by the nutritionally rich environment of the CF airways.

Amino Acids↗
PubMed1995

Latex agglutination for rapid detection of Pseudomonas pseudomallei antigen in urine of patients with melioidosis.

A latex agglutination test for the detection of Pseudomonas pseudomallei antigen in urine was evaluated for the rapid diagnosis of melioidosis. With unconcentrated urine, antigen was detected in only 18% of patients with melioidosis overall. However, when urine was concentrated 100-fold, antigen was detected in 47% overall and in 67% of patients with septicaemia or disseminated infection, in whom a rapid diagnosis is most important. The specificity of the test was 100%. These results compared favourably with an enzyme immunoassay. This latex agglutination test is a simple, rapid and highly specific method of diagnosing melioidosis, and will be particularly useful in areas with limited laboratory facilities.

Antigens, Bacterial↗
PubMed1993

Epidemiology of Pseudomonas aeruginosa infection in cystic fibrosis and the use of strain genotyping.

We describe a study of the epidemiology of Pseudomonas aeruginosa (PA) infection in a group of adults with cystic fibrosis who attended a week-long summer camp in the U.K. Sputum samples were collected from 17 patients at the beginning and at the end of the holiday period. Examination of previous sputum samples had identified 11 patients who were chronically colonised with PA. They shared accommodation during the holiday. The sputum samples from these 11 patients were analysed so as to identify the strains of PA by their genotypic characters. All patients were colonised by unique strains before the beginning of the holiday, with the exception of two pairs of patients whose isolates were indistinguishable. After the holiday, eight of the 11 patients harboured strains of the same genotype as was found in their pre-holiday specimens. In three patients, a strain present post-holiday was different from that found in the pre-holiday specimen. In addition, in the case of one patient, two different genotypes were found in the pre-holiday specimen, only one of which was present after the holiday. Evidence of cross-infection of PA during the holiday was not found. Even so, evidence of person-to-person transmission of PA both within the hospital environment and through social contact is presented and discussed.

Adolescent↗
PubMed1993

Comparison of serotype, biotype and bacteriocin type with rDNA RFLP patterns for the type identification of Serratia marcescens.

Variations in rDNA gene loci in DNA digests of 209 clinical isolates of Serratia marcescens were determined with an Escherichia coli rRNA probe. Forty-one restriction fragment length polymorphism patterns (ribotypes) were identified, based on the size of 4-14 (mean 7.5) hybridization bands. The patterns differed by more than a single band in 98% of pair-wise comparisons. On a subset of 76 isolates, ribotyping proved to be marginally more discriminating than biotyping (discrimination index 0.92 v. 0.89) followed by serotyping (0.87) and bacteriocin typing (0.74). About one-third of isolates belonged to unique ribotypes and only two ribotypes exceeded 5% in frequency (23.0 and 6.4% respectively). A combination of serotype or biotype with ribotyping defined a similar number of strains, although none of the methods alone was sufficiently discriminatory to identify strains. We conclude that due to the accessibility of biotyping and the lack of commercially available antisera for S. marcescens, the biotype and ribotype together provide reliable markers of strain identity.

Bacterial Typing Techniques↗
PubMed1993

Rapid extraction of high purity chromosomal DNA from Serratia marcescens.

Rapid non-specific degradation of Serratia marcescens DNA extracted with guanidium thiocyanate, occurred within 10 min of incubation with restriction endonuclease enzymes. The described modified method based on chemical and enzymatic deproteinization produced preparations of Ser. marcescens DNA of high yield and quality which did not autodegrade when incubated with restriction endonucleases.

Chromosomes, Bacterial↗
PubMed1993

Epidemic of Pseudomonas cepacia in an adult cystic fibrosis unit: evidence of person-to-person transmission.

An epidemic of Pseudomonas cepacia occurred in an adult cystic fibrosis center in the United Kingdom, despite a policy of segregation of infected and noninfected patients within the hospital. Investigation of the outbreak by ribotyping and pulsed-field gel electrophoresis to characterize P. cepacia strain genomes together with inquiry into social contacts between patients revealed evidence of person-to-person transmission outside the hospital environment. Segregation policies aimed at reducing the spread of this infection in the cystic fibrosis community need to encompass patient contacts outside the hospital environment.

Adolescent↗
PubMed1993

Correlation of typing methods for Acinetobacter isolates from hospital outbreaks.

Four methods, namely, biotyping, cell envelope protein electrophoresis, ribotyping, and comparison of antibiograms, were used for strain identification of Acinetobacter isolates from five outbreaks in hospitals. There was good agreement among the methods for the identification of an index strain, but biotyping and the comparison of antibiograms were the least discriminatory.

Acinetobacter↗