State of the art in typing: Klebsiella spp.
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Bacterial Typing Techniques↗
Biomedical subjects
T L Pitt
Publications and source records attributed to T L Pitt.
Immunological cross-reactivity between Enterobacter aerogenes and Klebsiella capsular polysaccharides.
Enterobacter aerogenes capsular polysaccharides (CPS) which cross-react with Klebsiella K3, K21, and K68 CPS were purified. Humans immunized with a vaccine containing Klebsiella K3 and K21 CPS produced antibody which recognized these E. aerogenes CPS. The magnitude of the immune response to the E. aerogenes CPS varied among the serotypes. Passive transfer of an immunoglobulin produced from the plasma of donors immunized with the above vaccine afforded significant protection against challenge with an E. aerogenes strain bearing a capsule which cross-reacts with Klebsiella K3 CPS.
Adult↗
Resistance mechanisms of multiresistant serotype 012 Pseudomonas aeruginosa isolated in Europe.
Serotype 012 Pseudomonas aeruginosa resistant to gentamicin (MIC greater than 4 mg/l) and carbenicillin (MIC greater than 128 mg/l) occur widely in Europe and are homogeneous in their phenotypic and genetic properties. It has been suggested that a single multiresistant strain of this serotype has become widespread. This study examined the resistance mechanisms present in multiresistant serotype 012 P. aeruginosa isolates from Austria, Belgium, France, Greece, Italy, Holland, West Germany and the UK. Disseminated isolates produced a PSE-1 type beta-lactamase, correlating with their resistance to the known substrates of this enzyme (carbenicillin, azlocillin and cefsulodin). These isolates also reacted with gene probes for the aminoglycoside modifying enzymes AAC(6')I and ANT(3'). The probe for AAC(6')I is known to cross-react with the gene for AAC(6')II. The fact that the organisms were resistant to netilmicin, gentamicin, sisomicin and tobramycin, but less so to amikacin, suggested that the latter enzyme was produced rather than AAC(6')I. PSE-1 beta-lactamase and the gene for AAC(6')I/AAC(6')II were absent from the International Antigenic Typing Scheme 012 reference strain, which was sensitive to beta-lactams and aminoglycosides, and also from a multiresistant serotype 012 strain isolated at a London burns unit in 1987. These organisms have been shown previously to be distinct from the disseminated multiresistant strain in their phenotypic properties. Two 012 isolates appeared to have additional resistance determinants to amikacin and isepamicin.
Aminoglycosides↗
Antibody response of fibrocystic patients to homologous 0-typable and 0-defective isolates of Pseudomonas aeruginosa.
Antibody titres to Pseudomonas aeruginosa of sera from 60 adult fibrocystic patients were determined in an enzyme linked immunosorbent assay (ELISA) with whole cells of homologous isolates which had been classified according to 0-antigen state by their reactivity with 0-typing antisera. Patients who were continuously colonised with Ps aeruginosa gave the highest titres: range 1500-64000 (mean 11000) and 500-48000 (mean 9000) with homologous 0-typable and 0-defective isolates, respectively. Lower titres to both varieties of isolates were obtained with recently colonised patients, and non-colonised patients gave titres with reference laboratory strains marginally above those of healthy controls. Serum titres of patients with sequential isolates were strain dependent and did not correlate with the 0-antigen state of the strain. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot analysis of these sera and strains showed antibody binding primarily to high molecular weight 0-repeating units of lipopolysaccharide. It is concluded that the 0-antigen of the strain of Ps aeruginosa used in the ELISA test does not influence the titre obtained with fibrocystic sera, and it is recommended that serum titres should be assessed with a panel of homologous isolates from patients.
Adult↗
Multiresistant serotype O 12 Pseudomonas aeruginosa: evidence for a common strain in Europe.
A survey was made of serotype association and multiple antibiotic resistance in strains of Pseudomonas aeruginosa in Europe. Of 208 epidemiologically distinct strains from 16 laboratories in 10 countries, 48 were resistant to carbenicillin (MIC greater than 128 micrograms/ml) and gentamicin (MIC greater than 4 micrograms/ml), and 12 of these strains were of serotype O 12. Representative O 12 strains from different countries were compared with two multiresistant O 12 strains isolated 5 years apart, from a British burns unit and the antibiotic sensitive serotype reference strain. All O 12 strains were similar by phage and pyocin typing but lysogenic phage profiles indicated that two strains (the later burns isolate and the serotype strain) were distinct from the others. Electrophoretic characterization of outer membrane proteins, lipopolysaccharides and esterase enzymes corroborated the relationship of the strains and restriction fragment length polymorphism of DNA fragments hybridized with a cDNA probe copy of rRNA from P. aeruginosa provided further proof of their relatedness. We propose that the uniformity of characters of multiresistant O 12 P. aeruginosa in Europe is suggestive of a common origin for the strains.
Anti-Bacterial Agents↗
O-antigen specificities of the serotype strains of Serratia marcescens.
O antigens of the 24 O-serotype strains of Serratia marcescens were investigated in dot enzyme immunoassay with whole-cell antigens and by immunoblotting with lipopolysaccharide (LPS) antigens. Three pairs of strains, O2/O3, O6/O7, and O12/O14, had indistinguishable LPS antigens, despite having distinct specificities in agglutination tests with whole-cell antigens. Strong cross-reactions were also found in LPS antigens from strains O9/O15, O17/O19, O10/O22, and O16/O20. No high-molecular-weight LPS corresponding to O-side-chain material was detected in strain O11 or O13. A panel of absorbed antisera was prepared to facilitate the detection of a reduced set of LPS antigens in a dot enzyme immunoassay. We conclude that there are discrepancies between the existing serotypes as defined by agglutination tests and the antigenic composition of LPS antigens extracted from the serotype strains and that surface antigens other than LPS make a major contribution to the definition of serotype in the species.
Agglutination Tests↗
Improved O-serotyping method for Serratia marcescens.
In a previous study, we found that some O serotypes of Serratia marcescens, as defined by agglutination tests, were not based on lipopolysaccharide (LPS) O antigens. We developed a dot enzyme immunoassay with a high degree of LPS specificity and tested 104 distinct clinical strains. Only 7 of the 24 existing O antigens were found in more than one strain: O12/O14 (30.8% of strains examined), O21 (12.5%), O8 (8.7%), O6/O7 (5.8%), O4 (3.8%), O18 (2.9%), and O9 (2.9%). Two new antigens, S1254 (13.5%) and S3255 (3.8%), were also found. Agglutination tests with O antisera identified the LPS antigen in only 36 strains. Prodigiosin production was restricted to serotypes O8, O6, and S3255 and strains with a rough or semirough LPS phenotype. Dot immunoassay appears to offer greater accuracy than agglutination tests for serotype identification in S. marcescens.
Agglutination Tests↗
Epidemiological typing of Enterobacter aerogenes.
The applicability of Enterobacter cloacae and Klebsiella typing reagents for classifying clinical strains of Enterobacter aerogenes was evaluated. Of 75 strains, none were agglutinated by E. cloacae O antisera or were sensitive to E. cloacae bacteriophages. In contrast, 70 strains reacted with Klebsiella capsular antisera. Two-thirds of the strains were lysed by Klebsiella typing phages. A set of five E. aerogenes bacteriocin producers classified 92% of strains into 15 sensitivity types. In conclusion, E. aerogenes may be typed with Klebsiella reagents, and the simple bacteriocin test provides further discrimination between strains. The limited number of capsular antigens in the species and their apparent similarity to Klebsiella capsular antigens warrant further investigation.
Agglutination Tests↗
Lipopolysaccharide and virulence of Pseudomonas aeruginosa.
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Animals↗
Epidemiological typing of Pseudomonas aeruginosa.
Current knowledge of the typing of Pseudomonas aeruginosa and new methods for characterizing strains are reviewed. A combination of serotyping as a primary screen with pyocin typing for finer discrimination between isolates gives valid epidemiological data, is within the scope of most clinical laboratories and is to be recommended. Phage typing and H typing do provide good discrimination but are not reproducible in practice because a reaction-difference rule has to be applied to phage patterns, and diphasic variation reduces the accuracy of the identification of flagellar antigens. A problem remains with cystic fibrosis isolates, which show considerable heterogeneity in surface properties. For these strains pyocin production typing by the revised method of Govan is indicated. Newer techniques such as isoenzyme profile and DNA probes of the chromosome require independent evaluation and due to their technical difficulty may not be adopted in a routine context for some years to come.
Antigens, Bacterial↗
Serratia marcescens infection associated with early abortion in cows and buffaloes.
Serratia marcescens was isolated in pure culture from cases of septic abortion in 4 cows on one farm and 10 buffaloes on two other farms. A reddish vaginal discharge was observed after abortion in all animals and in the internal organs of the aborted fetuses. All but two of the isolates produced prodigiosin, and two of the isolates from buffaloes were atypical in that they fermented raffinose. O-serological, bacteriophage and bacteriocin typing revealed four different strains. All cows were infected by the same strain, and this strain was also isolated from the semen of a breeding bull on the same farm. In another farm a strain of serotype O 14 was isolated from 6 of 10 buffaloes, and two other distinct strains were isolated from the remainder. The strain from the cattle was sensitive to gentamicin and so were two of the buffalo isolates. The infected cows were treated with intra-uterine gentamicin and the organism disappeared from cervical mucus after 3 days. Each animal after abortion showed a raised titre of agglutinating antibody to their respective isolate. A survey of 1172 healthy buffaloes and cattle gave an incidence of 1.8% with raised titres towards S. marcescens.
Abortion, Septic↗
Comparison of polyclonal rabbit antisera with monoclonal antibodies for serological typing of Pseudomonas aeruginosa.
A panel of 219 distinct strains of Pseudomonas aeruginosa were serotyped with a set of monoclonal antibodies prepared against the serotype strains of the Homma scheme (J. Y. Homma, Jpn. J. Exp. Med. 46:329-336, 1976). A total of 87.6% were typable, and there was very good agreement with the corresponding polyclonal serotype. A high proportion of strains that were polyagglutinating or nontypable with polyclonal antisera were agglutinated by antibody towards Homma group M.
Agglutination Tests↗
Subdivision of O serotypes of Pseudomonas aeruginosa with monoclonal antibodies.
Sixteen murine monoclonal antibodies (MAbs) against serotypes O2, O5, and O16 (serogroup II) and subtypes O2b and O5d of Pseudomonas aeruginosa were evaluated by agglutination and enzyme-linked immunosorbent assay. Six MAbs that exhibited different specificities were compared with absorbed rabbit O-type antisera for the serotyping of 55 clinical isolates of serogroup II. There was good agreement between the antibodies for strains of serotypes O2 and O2b, but MAbs revealed reproducible differences between strains that were indistinguishable with rabbit antisera. The greater serotype specificity of MAbs was illustrated by the fact that only 5 of 20 strains which were agglutinated by rabbit antiserum O16 reacted with the MAb to that serotype. One antibody, M89, that reacted with 27 of 55 serogroup II strains, apparently bound to core lipopolysaccharide epitopes. Three MAbs to the frequent serotype O6 identified six subtypes, one of which accounted for over half of the clinical strains, while two subtypes were represented by single strains only. Overall, MAbs provided a greater discrimination between strains of P. aeruginosa of the same serotype than did absorbed polyclonal antisera.
Agglutination Tests↗
Serotypes and biochemical profiles of British hospital strains of Enterobacter cloacae in relation to site of infection and antibiotic susceptibility.
Comparisons were made between the O-serotype, API 20E profile, site of isolation and antimicrobial resistance of clinical isolates of Enterobacter cloacae. Correlations were found between autoagglutinable strains and urinary-tract infection, and API 20E profile 3305573 and strains isolated from blood. The proportion of strains sensitive to amikacin, gentamicin, cefotaxime, cefuroxime and trimethoprim were 100%, 93%, 91%, 83% and 89%, respectively. No individual resistances or patterns of resistance were associated with O-serotype or biochemical profile. Strains isolated from urinary-tract infections were the most resistant, 40% being resistant to five or more antimicrobials compared to 18%, 12% and 4% for strains from blood, wounds and sputum, respectively. There were no readily identifiable phenotypes within E. cloacae that possessed unique characteristics that could contribute to infections in hospitals.
Anti-Bacterial Agents↗
New bacteriophage typing scheme for subdivision of the frequent capsular serotypes of Klebsiella spp.
A bacteriophage typing scheme for hospital isolates of Klebsiella spp. was developed. The scheme was designed specifically as a secondary typing method to discriminate between strains of serotypes K2, K3, and K21 but proved to be an efficient general typing method for strains of most serotypes. The set of 15 phages gave 87.3% typeability on 236 strains of more than 70 different serotypes. Typeability within the K2, K3, and K21 strains was 93, 89, and 91%, respectively. There was a mean of 3.2 reactions strain-1 for all phage-typeable strains. Of the serologically nontypeable strains, 76.7% were susceptible to one or more phages. The most common pattern accounted for only 7% of the strains. The lytic patterns were reproducible if strains were typed on the same day, but differences were observed if strains were stored for 1 week or more before retyping. A total of 96.5% of the strains were typeable by a combination of capsular serology and phage typing.
Bacteriophage Typing↗
A comparison of strains of Serratia marcescens isolated from neonates with strains isolated from sporadic and epidemic infections in adults.
As a result of the increased number of outbreaks of Serratia marcescens in special care baby units in the UK, a study was undertaken to compare strains isolated from outbreaks of neonatal infection with strains isolated from outbreaks of infections in adults and with isolates from sporadic infections. None of the biochemical, serological, bacteriological markers examined could distinguish the three groups of strains. When considered as groups there was no difference in the ability of the strains to survive desiccation on hands. Strains from neonatal and sporadic infections were more sensitive to antibiotics than adult epidemic strains. The feature common to all of the neonatal strains tested was the ability to agglutinate one or more species of erythrocytes in the presence of mannose. Only one strain in each of the other two groups possessed mannose resistant haemagglutinins.
Adult↗
Polyagglutinating and non-typable strains of Pseudomonas aeruginosa in cystic fibrosis.
Serologically polyagglutinating (PA) and non-typable (NT) strains of Pseudomonas aeruginosa are frequently isolated from cystic fibrosis (CF) patients, but are uncommon in other patients. From serologically typical parent strains, we isolated two variants (one PA, the other NT) which differed from the parent in bacteriophage susceptibility or in sensitivity to the bactericidal action of normal human serum. The PA and NT variants (strains 7/1 and 18S respectively) reacted with antiserum to the parent strains 7 and 18R but did not absorb homologous specific O antibody from antiserum to the parent strains. In contrast the parent strains absorbed anti-PA and anti-NT antibodies from antisera to the variant strains. The yield of lipopolysaccharide (LPS) from acetone-dried cells of the parent strain 7 was similar to that of the PA derivative; but the NT strain 18S yielded only half the LPS of its parent strain. LPS of the variant 7/1 gave a banding profile by SDS-PAGE similar to that of the parent LPS 7, but lacked high-molecular-weight components. LPS of the variant 18S appeared to be grossly different in profile from LPS 18R. Of 533 isolates of P. aeruginosa that were tested with O antisera and with antisera to the two variants, 15% were O-typable and 22% were O-non-typable; 26% reacted with anti-PA serum alone, 10% with anti-NT serum alone, and 27% were agglutinated by both sera. There was a statistically significant correlation between serum sensitivity of CF isolates and their reaction with the PA or NT antisera.
Agglutination Tests↗
Dissociation of surface properties and "intrinsic" resistance to beta lactams in Pseudomonas aeruginosa.
Carbenicillin resistance in strains of Pseudomonas aeruginosa isolated in Britain is mediated more frequently by "intrinsic factors" than by beta-lactamase production. Intrinsically carbenicillin-resistant isolates almost invariably were more resistant to azlocillin, cefoperazone, cefotaxime, ceftazidime, chloramphenicol, tetracycline and nalidixic acid than were carbenicillin-susceptible strains. This cross-resistance to different classes of antimicrobials suggested an impermeability-based mechanism of resistance, perhaps involving the outer membrane. The structure and composition of the outer membrane of the pseudomonas cell also influences the O-serotype specificity and the susceptibility to many bacteriophages. We therefore examined these properties for possible relationships to antibiotic resistance. Carbenicillin-resistant (122) and -sensitive (127) P. aeruginosa strains from 24 hospitals were compared. Serotype O:1, O:3, O:6, O:10 and O:11 strains predominated in both groups. Non-typable and polyagglutinating strains were infrequent in both groups. With one possible exception, none of 18 bacteriophages showed a significant preference for carbenicillin-resistant or -sensitive strains. Variation between strains was observed in the electrophoretic profile of LPS and this could be related in part to serotype, but not to antibiotic resistance. Our results contrast with those of earlier small-scale studies which have claimed relationships between surface properties and antibiogram in P. aeruginosa, and suggest that interpretation of the minor changes in LPS sometimes observed in association with the development of antibiotic resistance in vitro requires caution.
Anti-Bacterial Agents↗