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Biomedical subjects

T L Pitt

Publications and source records attributed to T L Pitt.

At least 109 records · Page 6Linked to original sources
PubMed1986

Inhibition of Pseudomonas aeruginosa from cystic fibrosis by selective media.

Pseudomonas Isolation Agar (selective agent, Irgasan, 25 mg/1) and Pseudomonas Selective Agar (selective agents, cetrimide 200mg/1 and nalidixic acid 15 mg/1) inhibited some strains of P aeruginosa from cystic fibrosis sputum but did not inhibit isolates from other sources. Of 200 cystic fibrosis isolates, 22 were inhibited by 16 mg/1 Irgasan, 45 by 8 mg/1 nalidixic acid, and 15 by 128 mg/1 cetrimide. We recommend that cystic fibrosis sputum should be cultured on selective and non-selective media to maximise the isolation of P aeruginosa.

Carbanilides↗
PubMed1985

Evaluation of three serological tests for detection of antibody to Pseudomonas aeruginosa in human sera.

Four hundred and ninety-five sera from 325 patients from whom Pseudomonas aeruginosa had been isolated and 86 control sera were tested for antibody by indirect haemagglutination tests (HAT) and complement fixation tests (CFT) using a polyvalent pseudomonas serotype-specific vaccine antigen, PEV-02. Sera were also tested by countercurrent immunoelectrophoresis (CIE) for precipitins to a species-specific protein antigen. Control sera gave titres of 160 or less by HAT and 20 or less by CFT. 2-Mercaptoethanol resistant antibody titres (immunoglobulin G) were below 40 for all control sera and none of the latter contained precipitins to common antigen. Of 325 patients, 156 (48%) gave titres of 320 or greater by HAT and of these, 114 (73%) showed elevated immunoglobulin G titres. Less patients with positive blood cultures than expected were positive by HAT and more patients with bone infections gave raised immunoglobulin G titres than expected. Cystic fibrosis patients were invariably seropositive by all tests. There was a correlation between positive CIE and CFT tests, especially in patients who were positive by HAT. Approximately half of 83 patients tested gave a serotype-specific antibody response. The tests were of little value in confirming clinically evident acute infections, but in cases of doubtful infection they did provide confirmatory evidence of an antibody response in approximately one-third of patients culture-positive for Pseudomonas aeruginosa.

Antibodies, Bacterial↗
PubMed1985

PSE-4 beta lactamase: a serotype-specific enzyme in Pseudomonas aeruginosa.

PSE-4 enzyme is the most common plasmidic beta lactamase in Pseudomonas aeruginosa but its production is invariably non-transferable by conjugation. Of 20 PSE-4+ isolates from 10 separate sources, 16 were serotype O:16 and two belonged to the related O:2(b) serotype. One of the two remaining organisms was not O-typable and the other was agglutinated by several unrelated antisera. Examination of additional O:16 strains confirmed the unusual frequency of PSE-4 enzyme in this serotype. None of the PSE-4+ strains was able to transfer carbenicillin resistance in mating experiments and none contained extrachromosomal DNA. Two explanations of the relationship between enzyme production and O antigenicity are proposed. PSE-4 production may be transmissible, perhaps by transduction, between strains of O:16 or related serotypes, or PSE-4+ P. aeruginosa may represent a disseminated subtype. A third hypothesis, that the PSE-4 coding element carried serotype determinants, was discounted. PSE-4+ and PSE-4- P. aeruginosa strains of O:16 and related serotypes were found to represent a definite cluster by their phage-susceptibility pattern and pyocin type (type 1). The only characters linked to PSE-4 production were resistance to spectinomycin, streptomycin and sulphonamide and the genes responsible for these characters seemed to occur on the PSE-4 coding element.

Anti-Bacterial Agents↗
PubMed1984

Role of lipopolysaccharide in virulence of Pseudomonas aeruginosa.

The role of lipopolysaccharide (LPS) in the virulence of Pseudomonas aeruginosa was studied. The virulence of several P. aeruginosa strains for burned mice was found to be directly related to the dispersion of LPS into either the phenol or the water phase after extraction. Virulence decreased as the proportion of LPS recovered from the phenol phase increased. No similar correlation was observed when several other strain characteristics were investigated. This phenomenon was studied in greater detail by using the "smooth"-specific phage E79 to select mutants altered in LPS structure. One such mutant, PA220-R2, was extensively characterized. LPS isolated from PA220-R2 was found to be completely deficient in high-molecular-weight polysaccharide material. This alteration rendered the strain serum sensitive and dramatically changed the reaction with O-specific typing sera and sensitivity to typing phages. However, motility, toxin A and elastase production, and 22 metabolic functions remained unchanged. PA220-R2 was found to be comparatively nonvirulent, with a 50% lethal dose more than 1,000-fold higher than that of its parent for burned mice. This was due to the inability of PA220-R2 to establish an infection in burned skin.

Animals↗
PubMed1983

Infection with netilmicin resistant Serratia marcescens in a special care baby unit.

An outbreak of colonisation and infection with a netilmicin resistant strain of Serratia marcescens occurred in a special care baby unit. S marcescens was isolated from a total of 13 babies; significant infection occurred in five, of whom two died. Epidemiological investigation failed to detect a common source but gastrointestinal colonisation of babies formed a prolonged and possibly important reservoir for infection. Containment proved difficult until the unit was closed to new admissions, and even then spread to a temporary unit ensued. O Serotyping and bacteriophage typing disclosed a single epidemic strain. This produced an aminoglycoside acetylating enzyme (AAC(6')) conferring resistance to netilmicin and tobramycin and moderate resistance to amikacin. Use of gentamicin resulted in the isolation of serratia with increased resistance to all aminoglycosides, and, similarly, increased resistance to third generation cephalosporins emerged with their use.

Acetyltransferases↗
PubMed1983

Pseudomonas aeruginosa colonisation in an intensive therapy unit: role of cross infection and host factors.

Despite the sparsity of Pseudomonas aeruginosa in the environment colonisation and infection with this organism was found at several sites by selective culture in 20 out of 46 patients in an intensive therapy unit. Three patients developed Ps aeruginosa pneumonia. Serial serogrouping and phage typing identified multiple strains in the unit and in the same patient. Rectal carriage occurred in 16 patients but rectal strains did not subsequently appear in tracheal aspirates; strains varied in their affinity for the upper respiratory tract. Colonisation was not directly related to length of stay and was detected in 16 of those colonised within 24 hours of admission. In intubated patients, who were colonised more frequently than those not intubated, upper respiratory tract colonisation correlated strongly with low initial arterial pH values. Personnel were probably responsible for cross infection among patients when the unit was busy. Strain differences and the susceptibility of patients also influenced colonisation and infection. Elimination of major reservoirs of Ps aeruginosa and compliance with procedures to control cross infection remain essential if patients in hospital are to escape colonisation by the organism.

Cross Infection↗
PubMed1983

Bactericidal activity of serum from cystic fibrosis patients for Pseudomonas aeruginosa.

The bactericidal action of serum from 61 adult patients with cystic fibrosis (CF) against autologous and heterologous strains of Pseudomonas aeruginosa has been studied. CF serum had a similar bactericidal action to normal human serum (NHS) against a reference panel of strains. Six CF sera had a selective inability to kill autologous strains of pseudomonas, which were sensitive to NHS and to sera from other CF patients. The six sera had normal levels of complement and immunoglobulin and were bactericidal to other strains. A titratable blocking factor was present in these sera and it interfered with the bactericidal action of NHS on the appropriate strain. This factor was present in the IgG-containing fractions of serum obtained by ion-exchange chromatography, but was not removed from the serum by absorption with the pseudomonas strain. Some CF sera may fail to kill sensitive strains of pseudomonas because of the development of a blocking IgG antibody against naturally occurring bactericidal IgM antibody.

Adolescent↗
PubMed1983

O serotyping scheme for Enterobacter cloacae.

A serotyping scheme for Enterobacter cloacae based on heat-stable somatic antigens is described. A total of 28 antisera were prepared in rabbits, and titers of agglutinins were high (greater than 640). Some cross-reactions were observed, and 11 sera required absorption before routine use. Of 300 clinical isolates from 66 hospitals, 77.6% were typable, 11.4% were not agglutinated by any of the sera, and 11.0% were autoagglutinable in saline. The eight most frequent serotypes were O3 (21.3%), O8 (13.3%), O1 (7.6%), O13 (5.0%), O9 (4.7%), O10 (3.0%), O16 (3.0%), and O25 (3.0%).

Agglutination Tests↗
PubMed1982

Types of Pseudomonas aeruginosa isolated from horses.

Pseudomonas aeruginosa isolates from equine clinical material were categorised according to their serotype and phage type. Epidemiological evidence showed that serotypes 02a, 03, 04, 06, 09 and 010 were the cause of genital and non-genital infections; somatic type 03 accounted for 50 per cent of isolates. The laboratory tests used were of no value in predicting whether or not a particular isolate was likely to be a venereal pathogen, but all the serotypes encountered had the potential to be pathogenic, given a favourable environment in which to multiply.

Animals↗
PubMed1981

Preparation of agglutinating antisera specific for the flagellar antigens of Pseudomonas aeruginosa.

H-specific agglutinating sera to Pseudomonas aeruginosa were prepared by immunisation with partially purified flagella. The results of agglutination and immobilisation tests with rabbit sera prepared against the flagella of six H-type strains showed that the sera had high titres and were H specific. Cross-absorption tests revealed that one strain (H-3) possessed a distinct antigen not present in any of the others. Two groups of strains (H-1, H-2 and H-5; H-4 and H-6) each possessed a distinct major antigen. Members of these two groups could be distinguished by their minor antigens.

Agglutination↗
PubMed1981

A comparison of flagellar typing and phage typing as means of subdividing the O groups of Pseudomonas aeruginosa.

Strains of Pseudomonas aeruginosa from hospitals were typed by O and H serology and bacteriophage typing. The H sera were prepared against purified flagella of six type strains. The most common O serogroups were O6, O11, O16 and O10, and together these groups represented more than half of the total number of strains. O subgrouping proved useful for the further division of groups O2 and O6. Percentage H typability was high, and many H patterns were found. Comparison of H typing and phage typing as a means of making subdivisions within O groups showed that, although the general discriminatory power of the two methods was similar, H typing performed better than phage-typing in the more common O serogroups.

Bacteriophage Typing↗
PubMed1980

The epidemiological type identification of Serratia marcescens from outbreaks of infection in hospitals.

A study of serological, bacteriocine and phage typing of Serratia marcescens was made. Specific O-antisera of adequate titre were relatively simple to prepare but H-antisera exhibited many heterologous agglutination reactions amongst the type strains. Most of these cross-reactions were not reproduced when immobilization tests with H-sera were performed. Direct haemagglutination tests were used to establish the presence of fimbriae amongst the H-type strains and the results of agglutination tests with non-fimbriate variants of strains indicated that fimbrial antibody in high titre was present in some sera. Replicate typing of 100 pairs of cultures by the phage-typing method indicated that small variations in pattern were common and that larger variations occurred occasionally. Therefore differences in pattern of less than two strong reactions should not be taken as evidence that strains can be distinguished. Cultures of S. marcescens, 273 in total, from six outbreaks of infection in British and European hospitals were typed by O-serology, H agglutination and immobilization tests, phage typing and bacteriocine susceptibility by a cross-streaking method. The typability of strains by each method was high but the results suggested that no single method was sufficiently discriminating to be used alone for typing. Comparison of the H-type and typing patterns of members of the same O serogroup from incidents of infection showed that reliable results were obtained by H-typing or by phage and bacteriocine typing after the application of the appropriate 'difference' rule. The greatest discrimination between strains of the same O-group was obtained by the use of H-typing or phage typing.

Aged↗