Biochemical and serological investigations on clinical isolates of klebsiella

Capsular polysaccharide and lipopolysaccharide O type analysis of Klebsiella pneumoniae isolates by genotype in China

Klebsiella pneumoniae is a common pathogen associated with nosocomial infections and is characterised serologically by capsular polysaccharide (K) and lipopolysaccharide O antigens. We surveyed a total of 348 non-duplicate K. pneumoniae clinical isolates collected over a 1-year period in a tertiary care hospital, and determined their O and K serotypes by sequencing of the wbb Y and wzi gene loci, respectively. Isolates were also screened for antimicrobial resistance and hypervirulent phenotypes; 94 (27.0%) were identified as carbapenem-resistant (CRKP) and 110 (31.6%) as hypervirulent (hvKP). isolates fell into 58 K, and six O types, with 92.0% and 94.2% typeability, respectively. The predominant K types were K14K64 (16.38%), K1 (14.66%), K2 (8.05%) and K57 (5.46%), while O1 (46%), O2a (27.9%) and O3 (11.8%) were the most common. CRKP and hvKP strains had different serotype distributions with O2a:K14K64 (41.0%) being the most frequent among CRKP, and O1:K1 (26.4%) and O1:K2 (17.3%) among hvKP strains. Serotyping by gene sequencing proved to be a useful tool to inform the clinical epidemiology of K. pneumoniae infections and provides valuable data relevant to vaccine design.

Complex interactions of Klebsiella pneumoniae with the host immune system in a Galleria mellonella infection model

Worldwide, Klebsiella pneumoniae is an increasingly problematic opportunistic pathogen, with the emergence of carbapenem-resistant isolates of special importance. The mechanisms of virulence are poorly understood, and the current study utilized the invertebrate model Galleria mellonella to investigate facets of the virulence process. A range of UK clinical isolates and reference strains was assessed in Galleria by measuring survival as an end point. The clinical strains showed a range of virulence, with the majority of strains (68 %) causing greater than 50 % mortality at a challenge dose of 1×105 c.f.u. Three additional intermediate read-outs were developed to allow the mechanisms of virulence of Klebsiella to be dissected further. The release of lactate dehydrogenase as a marker of cell damage was the best predictor of virulence. Melanization as a marker of the insect innate immune system and ability to proliferate within Galleria as a marker of immune evasion also broadly correlated with survival but with some notable exceptions. No direct correlation was observed between virulence and either K1 or other defined capsular types, the carriage of defined virulence factors or particular functional phenotypes. Overall, the study showed that Galleria can provide significant insights into the mechanisms of virulence, and that this can be applied to the study of opportunistic human pathogens.

Molecular genetic methods in diagnosis and direct characterization of acute bacterial central nervous system infections

Acute bacterial infection of the central nervous system requires rapid and adequate management. Etiological diagnosis is hence crucial. Moreover, the epidemic threat of certain bacteria necessitates a reliable characterization of the involved bacterial strains to follow the spread of epidemic strains. Conventional identification and characterization of etiological agents are basically based on culture and identification of bacterial markers most frequently by serological assays. Molecular identification and characterization of bacteria have been employed. They provide more reliable analysis of bacterial isolates. Molecular methods for non-culture diagnosis of bacterial infections have recently been developed. In many cases, the molecular assays have decreased the identification time of positive cultures and rescued detection of pathogens in culture-negative clinical samples.

Molecular serotyping of Klebsiella species isolates by restriction of the amplified capsular antigen gene cluster

The objective of the present work was to develop a molecular method that would enable determination of the capsular serotypes of Klebsiella isolates without the use of antiserum. PCR amplification of the capsular antigen gene cluster (cps) was followed by digestion with the restriction enzyme HincII (cps PCR-restriction fragment length polymorphism [RFLP] analysis). The profiles (C patterns) obtained for 224 strains representing the 77 known K serotypes showed 3 to 13 fragments ranging in size from 0.2 to 4.4 kb. A total of 97 distinct C patterns were obtained; 100% of 61 pairs of samples tested twice showed reproducible C patterns. The C patterns were K-type specific; i.e., the C pattern(s) of any K serotype was distinct from the C patterns of all other K serotypes, with the only exceptions being serotypes K22 and K37, which are known to cross-react. For 12 of 17 K types for which at least two strains were included, C-pattern variations were found among strains with the same K serotype. Therefore, cps PCR-RFLP analysis has a higher discriminatory power than classical K serotyping. C-pattern identity was observed among strains with a given K type that were collected many years apart and from distinct sources, indicating C-pattern stability. Only 4.5% of the strains were nontypeable, because of unsuccessful PCR amplification (whereas 8 to 23% are nontypeable by classical K serotyping). Three of four noncapsulated strains analyzed showed recognizable C patterns. The K serotypes of 18 (82%) of 22 recent Klebsiella pneumoniae clinical isolates could be deduced from their C patterns. In conclusion, cps PCR-RFLP analysis allows determination of the K serotype, while it is easier to perform and more discriminatory than classical serotyping.

Twenty-three years of Klebsiella phage typing: a review of phage typing of 12 clusters of nosocomial infections, and a comparison of phage typing with K serotyping

OBJECTIVE

To review phage typing of 12 clusters of nosocomial Klebsiella infections which occurred between 1974 and 1997, and to compare phage typing and K serotyping. Materials and methods A total of 489 clinical and laboratory Klebsiella isolates were phage typed using 110 different phage preparations and K typed by counter current immunoelectrophoresis against 77 K antisera.

RESULTS

A total of 152 phage types (PT) and 82 K types were found. Thirty-six phage types and 14 K types were represented only by the reference type strains. Of the remaining 68 K types, 60 could be subdivided into from two to 10 phage types. Ten out of 12 clusters of nosocomial Klebsiella infections could be verified as outbreaks by phage typing, whereas two clusters were found to be accumulations of sporadic cases. K typing performed retrospectively confirmed these results. In addition, for a subset of 104 epidemiologically unrelated isolates, O typing and pulsed field gel electrophoresis typing data were available. Based on these results the discriminative power of phage typing was found to be comparable with that of K typing, but phage types were less stable and reproducible.

CONDITIONS

In an outbreak situation, phage typing was found to be very useful, although it seems less suitable for long-term surveillance purposes.

Klebsiella spp. as nosocomial pathogens: epidemiology, taxonomy, typing methods, and pathogenicity factors

Bacteria belonging to the genus Klebsiella frequently cause human nosocomial infections. In particular, the medically most important Klebsiella species, Klebsiella pneumoniae, accounts for a significant proportion of hospital-acquired urinary tract infections, pneumonia, septicemias, and soft tissue infections. The principal pathogenic reservoirs for transmission of Klebsiella are the gastrointestinal tract and the hands of hospital personnel. Because of their ability to spread rapidly in the hospital environment, these bacteria tend to cause nosocomial outbreaks. Hospital outbreaks of multidrug-resistant Klebsiella spp., especially those in neonatal wards, are often caused by new types of strains, the so-called extended-spectrum-beta-lactamase (ESBL) producers. The incidence of ESBL-producing strains among clinical Klebsiella isolates has been steadily increasing over the past years. The resulting limitations on the therapeutic options demand new measures for the management of Klebsiella hospital infections. While the different typing methods are useful epidemiological tools for infection control, recent findings about Klebsiella virulence factors have provided new insights into the pathogenic strategies of these bacteria. Klebsiella pathogenicity factors such as capsules or lipopolysaccharides are presently considered to be promising candidates for vaccination efforts that may serve as immunological infection control measures.

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.

Comparison of the antibody responses to the 77 Klebsiella capsular types in ankylosing spondylitis and various rheumatic diseases

The production of antibodies to Klebsiella capsular polysaccharides was measured in sera from either HLA-B27-positive (HLA-B27+) or HLA-B27-negative (HLA-B27-) patients with classical ankylosing spondylitis (n = 54). These sera were compared with sera from patients with various rheumatic diseases (n = 82) and HLA-B27+ or HLA-B27- healthy individuals (n = 85). All sera were analyzed by means of an enzyme-linked immunosorbent assay specific to each of the 77 Klebsiella serotypes. The sera from HLA-B27+ patients with ankylosing spondylitis showed a significantly higher antibody frequency to the capsular types K26, K36, and K50 than the sera from HLA-B27- ankylosing spondylitis patients, patients with psoriatic arthritis, systemic lupus erythematosus, rheumatoid arthritis, or reactive arthritis after Yersinia enterocolitica infection, or healthy controls (P < 0.02). The antibodies were of the immunoglobulin G type. No significant antibody response to the other 74 Klebsiella serotypes, noncapsulated mutants of K26, K36, and K50, or preparations of Citrobacter, Serratia, Hafnia, or Morganella spp. or Streptococcus pneumoniae could be detected. The results might suggest a specific association between these capsular types and HLA-B27+ ankylosing spondylitis and might imply their predominance in this disease.

Serum antibodies to Klebsiella capsular polysaccharides in ankylosing spondylitis

OBJECTIVE

To measure antibodies to Klebsiella capsular polysaccharides in the sera of HLA-B27 positive patients with ankylosing spondylitis (AS), compared with HLA-B27 positive and HLA-B27 negative healthy control subjects.

METHODS

Antibodies were detected by means of an enzyme-linked immunosorbent assay specific for each of the 77 known Klebsiella serotypes.

RESULTS

Significantly elevated frequencies and titers of antibodies to capsular polysaccharides K26, K36, and K50 were detected in sera from AS patients, compared with controls.

CONCLUSION

These results suggest the predominance of Klebsiella serotypes K26, K36, and K50 in patients with AS.

Use of small fragment restriction endonuclease analysis (SF-REA) for epidemiological fingerprinting of Klebsiella oxytoca

A group of infections caused by Klebsiella oxytoca was observed among preterm neonates in a neonatal intensive care unit (NICU) of a pediatric hospital in Osnabrück, Germany. The presence of unique antimicrobial susceptibility patterns among the bacterial isolates prompted an investigation to determine whether a limited spread of one single strain existed. All 4 K. oxytoca isolates from the NICU and, in addition, 50 epidemiologically non-related strains were fingerprinted by small fragment restriction endonuclease analysis (SF-REA). From an analysis of silver-strained EcoR I-generated restriction fragment patterns of whole-cell DNA in polyacrylamide gels, it was evident that the 4 NICU isolates were closely related, whereas all epidemiologically unrelated strains exhibited different patterns. From the results of this study, DNA fingerprinting by SF-REA is proposed as a useful tool for investigating the epidemiological relatedness of K. oxytoca strains of clinical and environmental origin.

Pulsed-field gel electrophoresis for differentiation of hospital isolates of Klebsiella pneumoniae

Restriction enzyme analysis by pulsed-field gel electrophoresis (PFGE) was developed for differentiation of hospital isolates of Klebsiella pneumoniae. Restriction patterns generated by SpeI digestion of genomic DNAs of 36 isolates from patients in two major teaching hospitals established 34 PFGE types. All strains were typable by this technique and the SpeI restriction patterns were reproducible, stable and easy to interpret. As PFGE profiles generated were heterogenous, the incidence of cross-infection appeared to be low in each of the hospitals. The higher discriminatory power of PFGE when compared to conventional restriction endonuclease analysis (REA) suggests that this technique will be very useful for epidemiological investigations of nosocomial K. pneumoniae outbreaks.

Isolation of Klebsiella terrigena from human feces: biochemical reactions, capsule types, and antibiotic sensitivity

Colonization of the human intestinal tract by a newly proposed species, K. terrigena, was investigated. 5377 different stool specimens from healthy persons (food handlers) yielded 50 isolates (0.9%). Biochemically, low frequencies in the degradation of urea, dulcitol, and utilization of citrate at 37 degrees C were found when compared to K. pneumoniae. At 30 degrees C, urea hydrolysis was observed twice as often as at 37 degrees C. Apart from ampicillin, K. terrigena was susceptible to 12 other antimicrobial drugs tested. Multiple drug resistance was rare, few isolates being resistant against 2-4 antibiotic agents. Capsule typing revealed 30 different serotypes, K 70 and K 14 were the most frequent. Six strains expressed capsule types K 2 and K 5, which have been reported to be associated with virulence in K. pneumoniae. A possible pathogenic role of K. terrigena is discussed.

Epidemiological fingerprinting of Klebsiella pneumoniae by small-fragment-restriction-endonuclease-analysis (SF-REA)

Epidemiological fingerprinting of Klebsiella pneumoniae was performed by restriction endonuclease analysis (REA) of whole cell DNA. 11 isolates from 4 patients in an intensive care unit and 80 unrelated strains were examined in this study. DNA was cleaved with restriction endonuclease EcoR I, electrophoresed on 10% polyacrylamide gels, and restriction fragment patterns were visualized by silver staining. The analysis of small fragments within the cleavage patterns (SF-REA) yielded sufficient information for reliable strain identification. The gel patterns of unrelated strains exhibited marked differences by direct visual comparison. In contrast, the isolates from the ICU could only be subdivided into 2 types, supporting our suspicion of nosocomial infections in some of these patients. SF-REA was evaluated with regard to interstrain discriminatory ability, reproducibility, and practicability. Our results indicate that SF-REA may be used as a rapid, precise and reliable technique in typing K. pneumoniae strains.

Identification of species and capsular types of Klebsiella clinical isolates, with special reference to Klebsiella planticola

In the 77 reference strains for Klebsiella K types, there are 17 strains (22.1%) of Klebsiella planticola, 6 strains (7.8%) of Klebsiella oxytoca, 1 strain (1.3%) of Klebsiella terrigena, and 53 strains (68.8%) of Klebsiella pneumoniae. The species K. planticola, which was originally isolated from botanical and aquatic environments and hence thus named, was also identified at high incidence (81 strains, 18.5%) among the 439 recent clinical isolates of Klebsiella species. Among these K. planticola strains of hospital origin, 52 (64%) were isolated from sputum, 17 (21%) from urine, and the remaining 12 (15%) from other sources. The capsular types of these isolates were determined by the gel precipitation reaction. Seventy of 81 K. planticola isolates (86.4%) were typable by antisera to Klebsiella reference strains for K types and the K types of the clinical isolates distributed to 35 kinds of K types. The proportion of typable strains among clinical isolates of K. planticola was very similar to those in K. pneumoniae (87.5%) and K. oxytoca (86.0%).

Comparison of biochemical and serological typing results and antimicrobial susceptibility patterns in the epidemiological investigation of Klebsiella spp

An analysis of the serological and biochemical typing results of 925 clinical isolates of klebsiella revealed that biotyping and serotyping of klebsiella could replace each other for epidemiological purposes. The combination of both typing methods provided even more epidemiological information in analysing clusters of particular serotypes and biotypes in time. Clustering serotypes, mainly of neonatal origin, were nearly uniformly more resistant to the antibiotics in common use than other serotypes. Biotyping as well as serotyping of klebsiella isolates recovered from environmental surveys in the neonatal ward showed that epidemic and non-epidemic klebsiella isolates could occasionally be cultured from the environment and from the staff.

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.

Comparative investigations of Klebsiella species of clinical origin: plasmid patterns, biochemical reactions, antibiotic resistances and serotypes

A total of 124 K. pneumoniae and 52 K. oxytoca isolates obtained from clinical specimens was investigated for plasmid patterns, biochemical reactions, antibiotic resistances and serotypes regarding to the distribution and relationships of these characters. A great diversity of plasmid patterns, bio/serotypes and resistance patterns was revealed. About 90% of strains contained plasmid DNA and up to seven plasmid bands per isolate could be shown. For K. pneumoniae, serotype 7 and for K. oxytoca, type 55 were most common. In general, little difference between both species was found and characters were similarly distributed. With respect to the site of isolation, serotype 7 was predominating in K. pneumoniae strains from the respiratory tract. Highly multiple-resistant organism were found in the largest number in specimens from the urogenital tract, in the lowest in specimens from wounds. Extensive statistical analyses did not detect any relationship among the characters investigated.