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

The prevalence of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae among clinical isolates from a general hospital in Iran

This study was conducted at a 900+ bed general teaching hospital, from May to September 2007, in Iran. The aim of this study was to determine the prevalence of extended-spectrum beta-lactamase (ESBL) producing Escherichia coli and Klebsiella pneumoniae and their antimicrobial pattern. The Kirby-Bauer disk diffusion method and the phenotypic disk confirmatory test were performed for each isolate. The total of 206 isolates including 106 E. coli and 100 K. pneumoniae were collected of which 122 isolates (59.2%) were ESBL positive. The prevalence of ESBL-producing strains was 59.2% (122/206). All the isolates were susceptible to imipenem. Among the ESBL-producing isolates, the sensitivity was from 3.3% to 61.5% for ampicillin to aztreonam. From female isolates (136), 59.5% and from male isolates (70), 58.6% were ESBL-producers. Ratios of isolates from hospitalized patients to out-patients were 94/28 in the ESBL-producing group. The number of ESBL-producing isolates according to the isolation sites showed a significant difference between ESBL-producers and non-producers in blood samples (P < 0.05). This study shows that the prevalence of ESBL strains in Iran is high. It seems necessary for clinicians and medical community personnel to be fully aware of ESBL-producing microorganisms.

Avian incubation inhibits growth and diversification of bacterial assemblages on eggs

Microbial infection is a critical source of mortality for early life stages of oviparous vertebrates, but parental defenses against infection are less well known. Avian incubation has been hypothesized to reduce the risk of trans-shell infection by limiting microbial growth of pathogenic bacteria on eggshells, while enhancing growth of commensal or beneficial bacteria that inhibit or competitively exclude pathogens. We tested this hypothesis by comparing bacterial assemblages on naturally incubated and experimentally unincubated eggs at laying and late incubation using a universal 16S rRNA microarray containing probes for over 8000 bacterial taxa. Before treatment, bacterial assemblages on individual eggs from both treatment groups were dissimilar to one another, as measured by clustering in non-metric dimensional scaling (NMDS) ordination space. After treatment, assemblages of unincubated eggs were similar to one another, but those of incubated eggs were not. Furthermore, assemblages of unincubated eggs were characterized by high abundance of six indicator species while incubated eggs had no indicator species. Bacterial taxon richness remained static on incubated eggs, but increased significantly on unincubated eggs, especially in several families of Gram-negative bacteria. The relative abundance of individual bacterial taxa did not change on incubated eggs, but that of 82 bacterial taxa, including some known to infect the interior of eggs, increased on unincubated eggs. Thus, incubation inhibits all of the relatively few bacteria that grow on eggshells, and does not appear to promote growth of any bacteria.

Bacteria isolated from sewage influent resistant to ciprofloxacin, chloramphenicol and tetracycline

This study assessed the presence of antibiotic-resistant bacteria in sewage influent. Resistance was measured by determining the lowest concentration of antibiotic, in micrograms per milliliter (microg mL(- 1)). To determine the minimum inhibitory concentration (MIC), which is used in diagnostic laboratories, we used the Etest, a plastic strip containing an antibiotic concentration gradient. In total, we sampled five sewage treatment plants of various sizes in Kansas and isolated bacteria resistant to three broad-spectrum antibiotics; ciprofloxacin (1-cyclopropyl-6-fluoro-4-oxo-7-piperazin-1-yl-quinoline-3-carboxylic acid), chloramphenicol 2,2-dichlor-N-[(aR, bR)-b-hydroxy-a-hydroxymethyl-4-nitrophenethyl] acetamide), and tetracycline (2-(amino-hydroxy-ethylidene)-4-dimethylamino-6,10,11,12a-tetrahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione). In total, 25 Gram-negative isolates were found to be resistant to at least one of the antibiotics tested. Some isolates were multi-drug resistant, regardless of the amount of influent the sewage treatment plant received. A Pseudomonas isolate from the smallest sewage treatment plant (approximately 2 million gallons treated per day) showed resistance to all three antibiotics, albeit at low levels (10 microg mL(- 1)). The largest number of bacteria (6 species) were isolated from the largest sewage treatment plant (45 million gallons per day). Regardless, the results of this study are in agreement with similar studies, antibiotic resistance can persist long after the antibiotics have been forgotten.

Characterization of blaKPC-containing Klebsiella pneumoniae isolates detected in different institutions in the Eastern USA

BACKGROUND

The emergence of bla(KPC)-containing Klebsiella pneumoniae (KPC-Kp) isolates is attracting significant attention. Outbreaks in the Eastern USA have created serious treatment and infection control problems. A comparative multi-institutional analysis of these strains has not yet been performed.

METHODS

We analysed 42 KPC-Kp recovered during 2006-07 from five institutions located in the Eastern USA. Antimicrobial susceptibility tests, analytical isoelectric focusing (aIEF), PCR and sequencing of bla genes, PFGE and rep-PCR were performed. Results By in vitro testing, KPC-Kp isolates were highly resistant to all non-carbapenem beta-lactams (MIC(90)s >or= 128 mg/L). Among carbapenems, MIC(50/90)s were 4/64 mg/L for imipenem and meropenem, 4/32 mg/L for doripenem and 8/128 for ertapenem. Combinations of clavulanate or tazobactam with a carbapenem or cefepime did not significantly lower the MIC values. Genetic analysis revealed that the isolates possessed the following bla genes: bla(KPC-2) (59.5%), bla(KPC-3) (40.5%), bla(TEM-1) (90.5%), bla(SHV-11) (95.2%) and bla(SHV-12) (50.0%). aIEF of crude beta-lactamase extracts from these strains supported our findings, showing beta-lactamases at pIs of 5.4, 7.6 and 8.2. The mean number of beta-lactamases was 3.5 (range 3-5). PFGE demonstrated that 32 (76.2%) isolates were clonally related (type A). Type A KPC-Kp isolates (20 bla(KPC-2) and 12 bla(KPC-3)) were detected in each of the five institutions. rep-PCR showed patterns consistent with PFGE.

CONCLUSIONS

We demonstrated the complex beta-lactamase background of KPC-Kp isolates that are emerging in multiple centres in the Eastern USA. The prevalence of a single dominant clone suggests that interstate transmission has occurred.

Population variability of the FimH type 1 fimbrial adhesin in Klebsiella pneumoniae

FimH is an adhesive subunit of type 1 fimbriae expressed by different enterobacterial species. The enteric bacterium Klebsiella pneumoniae is an environmental organism that is also a frequent cause of sepsis, urinary tract infection (UTI), and liver abscess. Type 1 fimbriae have been shown to be critical for the ability of K. pneumoniae to cause UTI in a murine model. We show here that the K. pneumoniae fimH gene is found in 90% of strains from various environmental and clinical sources. The fimH alleles exhibit relatively low nucleotide and structural diversity but are prone to frequent horizontal-transfer events between different bacterial clones. Addition of the fimH locus to multiple-locus sequence typing significantly improved the resolution of the clonal structure of pathogenic strains, including the K1 encapsulated liver isolates. In addition, the K. pneumoniae FimH protein is targeted by adaptive point mutations, though not to the same extent as FimH from uropathogenic Escherichia coli or TonB from the same K. pneumoniae strains. Such adaptive mutations include a single amino acid deletion from the signal peptide that might affect the length of the fimbrial rod by affecting FimH translocation into the periplasm. Another FimH mutation (S62A) occurred in the course of endemic circulation of a nosocomial uropathogenic clone of K. pneumoniae. This mutation is identical to one found in a highly virulent uropathogenic strain of E. coli, suggesting that the FimH mutations are pathoadaptive in nature. Considering the abundance of type 1 fimbriae in Enterobacteriaceae, our present finding that fimH genes are subject to adaptive microevolution substantiates the importance of type 1 fimbria-mediated adhesion in K. pneumoniae.

[Coproduction of qnrB and armA from extended-spectrum beta-lactamase-producing Klebsiella pneumoniae]

BACKGROUND

Multidrug-resistant Enterobacteriaceae is a worldwide problem. Although various resistance mechanisms have been recognized with increasing frequency, only a few cases of triple resistance of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae have been reported. This study was designed to evaluate the coexistence of qnr (qnrA, qnrB, and qnrS) and 16S rRNA methylase (armA, rmtA, rmtB, and rmtC) in ESBL-producing K. pneumoniae.

METHODS

We tested 44 isolates of ESBL-producing K. pneumoniae at Chungnam National University Hospital from March to September 2006. Antimicrobial susceptibilities were tested by broth microdilution method, and transconjugation test was performed using E. coli J53 with azide resistance. Search for qnr (qnrA, qnrB, and qnrS) and 16S rRNA methylase (armA, rmtA, rmtB, and rmtC) genes was conducted by PCR amplification, and the genotypes were determined by direct nucleotide sequence analysis of the amplified products. Epidemiologic study was performed by Enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR).

RESULTS

All ESBL-positive strains produced qnrB; however, armA was detected in 68.2%. The coproduction rate of qnrB and armA in ESBL-producing K. pneumoniae was 68.2%. Two types (A and B) were dominant in ERIC-PCR results.

CONCLUSIONS

K. pneumoniae producing qnrB, armA, and ESBL are spreading widely.

Therapeutic potential of bacteriophage in treating Klebsiella pneumoniae B5055-mediated lobar pneumonia in mice

Klebsiella pneumoniae causes infections in humans especially in immunocompromised patients. About 80 % of nosocomial infections caused by K. pneumoniae are due to multidrug-resistant strains. The emergence of antibiotic-resistant bacterial strains necessitates the exploration of alternative antibacterial therapies, which led our group to study the ability of bacterial viruses (known as bacteriophages or simply phages) to treat mice challenged with K. pneumoniae. Phage SS specific for K. pneumoniae B5055 was isolated and characterized, and its potential as a therapeutic agent was evaluated in an experimental model of K. pneumoniae-mediated lobar pneumonia in mice. Mice were challenged by intranasal (i.n.) inoculation with bacteria (108 c.f.u. ml−1). A single intraperitoneal injection of 1010 p.f.u. ml−1 phage administered immediately after i.n. challenge was sufficient to rescue 100 % of animals from K. pneumoniae-mediated respiratory infections. Administration of the phage preparation 3 h prior to i.n. bacterial challenge provided significant protection in infected mice, while even 6 h delay of phage administration after the induction of infection rendered the phage treatment ineffective. The results of this study therefore suggest that the timing of starting the phage therapy after initiation of infection significantly contributes towards the success of the treatment.

Humoral immunity against capsule polysaccharide protects the host from magA+ Klebsiella pneumoniae-induced lethal disease by evading Toll-like receptor 4 signaling

Klebsiella pneumoniae magA (for mucoviscosity-associated gene A) is linked to the pathogenesis of primary pyogenic liver abscess, but the underlying mechanism by which magA increases pathogenicity is not well elucidated. In this study, we investigated the role of the capsular polysaccharides (CPS) in the pathogenesis of magA(+) K. pneumoniae by comparing host immunity to magA(+) K. pneumoniae and a DeltamagA mutant. We found that Toll-like receptor 4 recognition by magA(+) K. pneumoniae was hampered by the mucoviscosity of the magA(+) K. pneumoniae CPS. Interestingly, monoclonal antibodies (MAbs) against magA(+) K. pneumoniae CPS recognized all of the K1 strains tested but not the DeltamagA and non-K1 strains. Moreover, the anti-CPS MAbs protected mice from magA(+) K. pneumoniae-induced liver abscess formation and lethality. This indicates that the K1 epitope is a promising target for vaccine development, and anti-CPS MAbs has great potential to protect host from K1 strain-induced mortality and morbidity in diabetic and other immunocompromised patients in the future.

1,3-Propanediol dehydrogenase from Klebsiella pneumoniae: decameric quaternary structure and possible subunit cooperativity

Klebsiella pneumoniae is a nosocomial pathogen frequently isolated from opportunistic infections, especially in clinical environments. In spite of its potential pathogenicity, this microorganism has several metabolic potentials that could be used in biotechnology applications. K. pneumoniae is able to metabolize glycerol as a sole source of carbon and energy. 1,3-Propanediol dehydrogenase is the core of the metabolic pathway for the use of glycerol. We have determined the crystallographic structure of 1,3-propanediol dehydrogenase, a type III Fe-NAD-dependent alcohol dehydrogenase, at 2.7-A resolution. The structure of the enzyme monomer is closely related to that of other alcohol dehydrogenases. The overall arrangement of the enzyme showed a decameric structure, formed by a pentamer of dimers, which is the catalytic form of the enzyme. Dimers are associated by strong ionic interactions that are responsible for the highly stable in vivo packing of the enzyme. Kinetic properties of the enzyme as determined in the article would suggest that this decameric arrangement is related to the cooperativity between monomers.

Beta2-microglobulin-dependent bacterial clearance and survival during murine Klebsiella pneumoniae bacteremia

Klebsiella pneumoniae is a leading cause of both community-acquired and nosocomial gram-negative bacterial pneumonia. A significant clinical complication of Klebsiella pulmonary infections is peripheral blood dissemination, resulting in a systemic infection concurrent with the localized pulmonary infection. We report here on the critical importance of beta(2)-microglobulin expression during murine K. pneumoniae bacteremia. Beta(2)-microglobulin knockout mice displayed significantly increased mortality upon intravenous inoculation that correlated with increased bacterial burden in the blood, liver, and spleen. As beta(2)-microglobulin knockout mice lack both CD8(+) T cells and invariant NK T cells, mouse models specifically deficient in either cell population were examined to see if this would account for the increased mortality noted in beta(2)-microglobulin knockout mice. Surprisingly, neither CD8 T-cell-deficient (TAP-1 knockout; in vivo anti-CD8 antibody treatment) nor invariant NK (iNK) T-cell-deficient (CD1d knockout, J alpha281 knockout) mice were more susceptible to K. pneumoniae bacteremia. Combined, these studies clearly indicate the importance of a beta(2)-microglobulin-dependent but CD8 T-cell- and iNK T-cell-independent mechanism critical for survival during K. pneumoniae bacteremia.

Novel microchip for in situ TEM imaging of living organisms and bio-reactions in aqueous conditions

A novel and disposable microchip (K-kit) with SiO(2) nano-membranes was developed and used as a specimen kit for in situ imaging of living organisms in an aqueous condition using transmission electron microscopy (TEM) without equipment modification. This K-kit enabled the successful TEM observation of living Escherichia coli cells and the tellurite reduction process in Klebsiella pneumoniae. The K. pneumoniae and Saccharomyces cerevisiae can stay alive in K-kit after continuous TEM imaging for up to 14 s and 42 s, respectively. Besides, different tellurite reduction profiles in cells grown in aerobic and anaerobic environments can be clearly revealed. These results demonstrate that the K-kit developed in this paper can be useful for observing living organisms and monitoring biological processes in situ.

Klebsiella oxytoca: opportunistic infections in laboratory rodents

Opportunistic pathogens have become increasingly relevant as the causative agents of clinical disease and pathological lesions in laboratory animals. This study was conducted to evaluate the role of Klebsiella oxytoca as an opportunistic pathogen in laboratory rodents. Therefore, K. oxytoca-induced lesions were studied from 2004 to early 2006 in naturally infected rodent colonies maintained at The Jackson Laboratory (TJL), Bar Harbor, USA, the Animal Research Centre (Tierforschungszentrum, TFZ) of the University of Ulm, Germany and the Central Animal Facility (ZTM) of the Hannover Medical School, Germany. K. oxytoca infections were observed in substrains of C3H/HeJ mice, which carry the Tlr4(Lps-d) allele; in LEW.1AR1-iddm rats, the latter being prone to diabetes mellitus; in immunodeficient NMRI-Foxn1(nu) mice; and in mole voles, Ellobius lutescens. The main lesions observed were severe suppurative otitis media, urogenital tract infections and pneumonia. Bacteriological examination revealed K. oxytoca as monocultures in all cases. Clonality analysis performed on strains isolated at the ZTM and TFZ (serotyping, pulse field gel electrophoresis [PFGE], enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction, sequencing of 16S rRNA and rpoB genes) revealed that the majority of bacteria belonged to two clones, one in each facility, expressing the capsule type K55 (ZTM) or K72 (TFZ). Two strains, one isolated at the ZTM and one at the TFZ, showed different PFGE and ERIC pattern than all other isolates and both expressed capsule type K35. In conclusion, K. oxytoca is an opportunistic pathogen capable of inducing pathological lesions in different rodent species.

Manno(rhamno)biose-containing capsular polysaccharides of Klebsiella pneumoniae enhance opsono-stimulation of human polymorphonuclear leukocytes

We tested the relationship between the capsular and the O-antigen structures and the ability of bacteria to trigger respiratory burst in human polymorphonuclear leukocytes (PMNL). Capsulated and non-capsulated variants as well as capsule-switched derivatives of Klebsiella serotypes bearing or lacking manno(rhamno)biose repeats in their capsular polysaccharides and expressing either mannose-rich or mannose-poor O antigens were tested for their ability to induce respiratory burst and survive in human PMNL. Luminol-enhanced chemiluminescence (CL) was measured to quantify respiratory burst. Intracellular survival was quantified by determining the viable counts of intracellular bacteria. K serotypes and the capsule-switched derivative lacking manno(rhamno)biose induced significantly lower CL than those expressing manno(rhamno)biose. Manno(rhamno)biose-lacking serotypes survived in the cells significantly better than serotypes expressing these repeats. C1q depletion did not affect CL induced by the manno(rhamno)biose-containing serotype, whereas factor B depletion revealed a significantly reduced CL. Likewise, EGTA in the presence of Mg(2+) significantly decreased CL, but the values were higher than those induced by the bacterium opsonized with factor B-depleted serum. In the presence of EGTA, Mg(2+)-treated factor B-depleted serum revealed a significant reduction in the CL response compared with the responses induced by opsonization with factor B-depleted serum alone. These results indicate, in addition to the alternative pathway, a manno(rhamno)biose pattern recognition of Klebsiella by PMNL probably by the complement lectin pathway.

Analysis of the 16S-23S rRNA gene internal transcribed spacer region in Klebsiella species

The 16S-23S rRNA gene internal transcribed spacer (ITS) regions of Klebsiella spp., including Klebsiella pneumoniae subsp. pneumoniae, Klebsiella pneumoniae subsp. ozaenae, Klebsiella pneumoniae subsp. rhinoscleromatis, Klebsiella oxytoca, Klebsiella planticola, Klebsiella terrigena, and Klebsiella ornithinolytica, were characterized, and the feasibility of using ITS sequences to discriminate Klebsiella species and subspecies was explored. A total of 336 ITS sequences from 21 representative strains and 11 clinical isolates of Klebsiella were sequenced and analyzed. Three distinct ITS types-ITS(none) (without tRNA genes), ITS(glu) [with a tRNA(Glu (UUC)) gene], and ITS(ile+ala) [with tRNA(Ile (GAU)) and tRNA(Ala (UGC)) genes]-were detected in all species except for K. pneumoniae subsp. rhinoscleromatis, which has only ITS(glu) and ITS(ile+ala). The presence of ITS(none) in Enterobacteriaceae had never been reported before. Both the length and the sequence of each ITS type are highly conserved within the species, with identity levels from 0.961 to 1.000 for ITS(none), from 0.967 to 1.000 for ITS(glu), and from 0.968 to 1.000 for ITS(ile+ala). Interspecies sequence identities range from 0.775 to 0.989 for ITS(none), from 0.798 to 0.997 for ITS(glu), and from 0.712 to 0.985 for ITS(ile+ala). Regions with significant interspecies variations but low intraspecies polymorphisms were identified; these may be targeted in the design of probes for the identification of Klebsiella to the species level. Phylogenetic analysis based on ITS regions reveals the relationships among Klebsiella species similarly to that based on 16S rRNA genes.

Expansion and countrywide dissemination of ST11, ST15 and ST147 ciprofloxacin-resistant CTX-M-15-type beta-lactamase-producing Klebsiella pneumoniae epidemic clones in Hungary in 2005--the new 'MRSAs'?

OBJECTIVES

To investigate the molecular epidemiology of ciprofloxacin-resistant CTX-M-15-producing Klebsiella pneumoniae epidemic clones (ECs) isolated from six nosocomial outbreaks and sporadic cases during 2005 in Hungary.

METHODS

Two hundred and eighty-one extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae clinical isolates collected from 41 centres were submitted to the National ESBL Reference Laboratory for further investigations. Of the 281 strains, 75 isolates proved to be SHV producers, whereas 6 isolates were ciprofloxacin-susceptible CTX-M-type ESBL producers. One hundred and ninety-six ciprofloxacin-resistant CTX-M-type beta-lactamase-producing isolates collected from 35 centres were subjected to macrorestriction profile analysis. Furthermore, molecular typing was performed by PCR and sequencing of several antibiotic resistance genes, plasmid profile analysis, transfer of resistance determinants and multilocus sequence typing (MLST).

RESULTS

PFGE revealed the existence of three genetic clusters defined as ECs, where 129 isolates belonged to the previously described Hungarian EC (HEC), 46 isolates to epidemic clone II (EC II) and 21 isolates to epidemic clone III (EC III), respectively. All isolates harboured plasmids ranging from 2.0 to 230 kb. PstI digestion of plasmid DNA from transconjugants/transformants revealed diverse restriction patterns from distinct ECs. Sequence analysis of beta-lactamase genes from 19 selected isolates detected bla(CTX-M-15) and bla(OXA-1) in strains from all three ECs and bla(TEM-1) in EC III isolates located on large plasmids. ISEcpI associated with CTX-M-15 was detected only on a 50 kb non-conjugative plasmid from EC III. MLST identified three allelic profiles: ST 15 (HEC), ST 11 (EC III) and the novel ST 147 (EC II), which correspond to the PFGE clusters, respectively.

CONCLUSIONS

In 2005, 97% of all CTX-M-producing K. pneumoniae isolates detected across Hungary were highly ciprofloxacin-resistant CTX-M-15 producers and represented just three stable genetic clones.

Molecular and biochemical characterization of SHV-56, a novel inhibitor-resistant beta-lactamase from Klebsiella pneumoniae

A clinical strain of Klebsiella pneumoniae was found to possess the chromosomal gene bla(SHV-56), encoding a new inhibitor-resistant beta-lactamase with a pI of 7.6. SHV-56 is derived from SHV-11 by the single substitution K234R. This mutation therefore evidences a new critical site for inhibitor resistance among SHV enzymes.

Hypermucoviscosity as a virulence factor in experimental Klebsiella pneumoniae endophthalmitis

PURPOSE

Klebsiella pneumoniae is a common cause of endogenous bacterial endophthalmitis, a disease that frequently results in a poor visual outcome. Hypermucoviscosity has been identified as a virulence factor among clinical bacteremia isolates of K. pneumoniae. In this study, an experimental murine model of K. pneumoniae endophthalmitis was established, and the role of hypermucoviscosity in its pathogenesis was analyzed.

METHODS

C57BL/6J mice were intravitreously injected with 100 CFU of hypermucoviscous (HMV+) or nonhypermucoviscous (HMV-) K. pneumoniae. Intraocular bacterial growth, retinal function, gross pathology, and inflammatory responses were monitored every 3 hours until the eyes lost significant (>90%) retinal function, or the infection appeared to clear.

RESULTS

The HMV+ strain grew logarithmically in eyes until approximately 15 hours postinfection (PI), reaching a stationary phase of growth at approximately 8.0 log(10) CFU/eye. The HMV- strain grew logarithmically to approximately 7.6 log(10) by 18 hours, but bacterial count declined to approximately 6.4 log(10) CFU/eye by 21 hours PI. Eyes infected with the HMV+ strain retained approximately 35% a-wave and <10% b-wave function by 18 hours PI. These eyes also had a cumulative clinical score of 14+ by 18 hours and underwent phthisis between 21 and 24 hours. Eyes infected with the HMV- strain had a cumulative clinical score of <6 and retained >60% a-wave and >50% b-wave function throughout 21 hours. Five of 7 eyes had <100 CFU HMV- K. pneumoniae at 27 hours PI.

CONCLUSIONS

The findings demonstrate the site-threatening consequences of K. pneumoniae endophthalmitis and the importance of the hypermucoviscosity phenotype in the pathogenesis of experimental K. pneumoniae endophthalmitis.

The first major extended-spectrum beta-lactamase outbreak in Scandinavia was caused by clonal spread of a multiresistant Klebsiella pneumoniae producing CTX-M-15

Between May and December 2005, 64 multidrug-resistant isolates of Klebsiella pneumoniae were detected from patients admitted to Uppsala University Hospital. This represented a dramatic increase in ESBL-producing K. pneumoniae compared to previous years. To investigate the epidemiology and to characterize the resistance mechanisms of the isolates, a study was initiated. Antibiotic susceptibility was determined by means of the Etest and the disc diffusion method. Extended-spectrum beta-lactamase (ESBL) production was identified by clavulanic acid synergy test and confirmed with PCR amplification followed by DNA sequencing. DNA profiles of the isolates were examined with pulsed-field gel electrophoresis (PFGE). All isolates were resistant or exhibited reduced susceptibility to cefadroxil, cefuroxime, cefotaxime, ceftazidime, aztreonam, piperacillin/tazobactam, ciprofloxacin, tobramycin, and trimethoprim-sulfamethoxazole. They produced ESBL of the CTX-M-15 type, and the involvement of a single K. pneumoniae clone was shown. This is the first major clonal outbreak of multiresistant ESBL-producing K. pneumoniae in Scandinavia. The outbreak demonstrates the epidemic potential of enterobacteria containing ESBLs of the CTX-M type, even in a country with a relatively low selective pressure and a low prevalence of multiresistant bacteria.

Multisystemic abscesses in African green monkeys (Chlorocebus aethiops) with invasive Klebsiella pneumoniae--identification of the hypermucoviscosity phenotype

Invasive Klebsiella pneumoniae is an emerging disease of humans characterized by abscesses in the liver or other sites involving bacteria with the unique hypermucoviscosity phenotype. Over several months, 7 African green monkeys in our research colony developed abscess formation in multiple locations and succumbed to disease. K. pneumoniae was identified by bacterial culture in 6 monkeys and immunohistochemistry in 1 additional monkey. All monkeys had been housed in, or had contact with monkeys housed in, 1 animal room in our facility. All affected monkeys had 1 or more abscesses, most notably in the abdomen, but also affecting the lungs, cerebellum, and skin. Abdominal abscesses and associated adhesions entrapped loops of bowel, forming palpable masses. Abdominal masses were located at the root of the mesentery, the ileocecocolic junction, or the pelvic inlet. In 1 case, culture, serotyping, and polymerase chain reaction (PCR) analysis of the bacterial isolate identified K. pneumoniae expressing the hypermucoviscosity phenotype and capsular serotype K2 and determined that the K. pneumonia was genetically rmpA(+)/magA(-).

Characterization of Klebsiella pneumoniae type 1 fimbriae by detection of phase variation during colonization and infection and impact on virulence

Klebsiella pneumoniae is recognized as an important gram-negative opportunistic pathogen. The ability of bacteria to adhere to host structures is considered essential for the development of infections; however, few studies have examined the influence of adhesion factors on K. pneumoniae virulence. In this study, we cloned and characterized the type 1 fimbria gene cluster of a clinical K. pneumoniae isolate. Although this cluster was not identical to the Escherichia coli type 1 fimbria gene cluster, an overall high degree of structural resemblance was demonstrated. Unique to the K. pneumoniae fim gene cluster is the fimK gene, whose product contains an EAL domain, suggesting that it has a role in regulation of fimbrial expression. Like expression of type 1 fimbriae in E. coli, expression of type 1 fimbriae in K. pneumoniae was found to be phase variable, and an invertible DNA element (fim switch) was characterized. An isogenic type 1 fimbria mutant was constructed and used to evaluate the influence of type 1 fimbriae in different infection models. Type 1 fimbriae did not influence the ability of K. pneumoniae to colonize the intestine or infect the lungs, but they were determined to be a significant virulence factor in K. pneumoniae urinary tract infection. By use of a PCR-based assay, the orientation of the fim switch during colonization and infection was investigated and was found to be all "off" in the intestine and lungs but all "on" in the urinary tract. Our results suggest that during colonization and infection, there is pronounced selective pressure in different host environments for selection of either the type 1 fimbriated or nonfimbriated phenotype of K. pneumoniae.

Capsular polysaccharide synthesis regions in Klebsiella pneumoniae serotype K57 and a new capsular serotype

Community-acquired pyogenic liver abscess caused by Klebsiella pneumoniae is an emerging infectious disease. We explored the capsular polysaccharide synthesis (cps) regions of three non-K1, non-K2 K. pneumoniae strains, A1142, A7754, and A1517, from Taiwanese patients experiencing pyogenic liver abscess. Two of the strains, A1142 and A7754, belonged to capsular serotype K57, while the third belonged to a new capsular serotype, different from the previously reported 77 serotypes. Deletion and complementation experiments suggested that a unique K57 gene, a homologue of wzy, was essential for K57 capsular synthesis and confirmed that this gene cluster was a genetic coding region for K57. Compared to K1 and K2 strains, the three strains were all serum sensitive, suggesting that host factors might also be involved in the three patients. PCR using primers from specific genes for K57 was more sensitive and specific than traditional serotyping. The remaining strain, A1517, did not react to the antisera from any of the 77 serotypes, and none of the 77 reference strains reacted to the serum against this strain. Moreover, PCR analyses using various primer pairs from the serotype-specific open reading frames did not reveal cross-reactivity to any of the 77 reference strains, suggesting that this strain likely represents a new capsular type. We conclude that sequences from these two cps regions are very useful in detecting K57 and the new cps genotype.

Seasonal variation in Klebsiella pneumoniae bloodstream infection on 4 continents

BACKGROUND

Klebsiella pneumoniae causes serious, life-threatening infections in humans in endemic and epidemic settings. The objective of this study was to determine whether the incidence of K. pneumoniae bloodstream infection (BSI) was higher during warm months.

METHODS

We analyzed surveillance data from 2001-2006 at 4 hospitals located on 4 continents. Incidence rates (IRs) and IR ratios (IRRs) were determined using multivariable Poisson regression.

RESULTS

In total, 1189 cases of K. pneumonia BSIs occurred during 6,671,337 patient-days. The IR of K. pneumoniae BSI during the 4 warmest months of the year was 2.23/10,000 patient-days, whereas the IR of K. pneumoniae BSI for the other 8 months was 1.55/10,000 patient-days (IRR, 1.46 [95% confidence interval, 1.04-2.06]; P= .03). In contrast, no seasonal variation was identified in rates of BSI due to Enterobacter or Serratia species. Using Poisson regression, we showed that temperature (P< .0001) and dew point (a marker for relative humidity; P< .0001) were both linearly predictive of increasing rates of K. pneumoniae BSI.

CONCLUSIONS

Environmental pressures may lead to an increase in the IR of K. pneumoniae BSI during the warmest months of the year.

Upper and lower urinary tract infection caused by Klebsiella pneumoniae serotype K2 and CTX-M-15 beta-lactamase-producing serotype K1: a case report and characterization of serum killing resistance

CTX-M-15 beta-lactamase-producing Klebsiella pneumoniae serotype K1 was isolated from a patient with fatal upper urinary tract infection (UTI) complicated by sepsis caused by K. pneumoniae serotype K2. Transfer of a CTX-M-15 beta-lactamase plasmid from the K1 to the K2 strain was observed. However, plasmid acquisition by the K2 strain did not occur in vivo, suggesting that the K1 strain might not have contributed directly to the upper UTI. In addition, effects of K serotypes and plasmid acquisition on K. pneumoniae serum resistance were examined.

Monitoring and identification of bacteria associated with safety concerns in the manufacture of São Jorge, a Portuguese traditional cheese from raw cow's milk

The aim of this study was to assess the hygienic quality of raw milk used in the manufacture of São Jorge, a Protected Denomination of Origin Portuguese semihard cheese, as well as to ascertain the sanitary conditions prevailing during its processing. Viable counts of Enterobacteriaceae and Micrococcaceae were accordingly obtained, pertaining to 21 independent batches (including samples of raw milk, curd, and cheeses after 1, 3, and 4 months of ripening), from 7 dairy farms. Standard plate counts (log CFU per milliliter or per gram) ranged from 6.1 to 8.6 in raw milk, whereas they ranged from 7.0 to 8.0 in 4-month-old cheeses. Viable counts of Enterobacteriaceae ranged between 5.9 and 7.0 in raw milk and between 0.0 and 1.3 in 4-month-old cheeses. Species identified within this family encompassed Klebsiella oxytoca, Klebsiella cloacae, Klebsiella pneumoniae, Enterobacter sakazakii, and Escherichia coli; Klebsiella ornithinolytica, Klebsiella terrigena, and Serratia odorifera were detected only in raw milk. No Salmonella whatsoever could be detected in any of the samples. Viable counts of Micrococcaceae ranged between 4.7 and 5.9 and between 1.3 and 3.3 in raw milk and 4-month-old cheeses, respectively. Species identified within this family encompassed Staphylococcus sciuri, Staphylococcus epidermidis, Staphylococcus saprophyticus (which was found mainly in ripened cheeses), and Staphylococcus aureus (which was not detected in 4-month-old cheeses). Accompanying physicochemical analyses included determination of moisture, salt, and pH. Statistical analyses revealed a negative correlation between salt content and viable numbers of Enterobacteriaceae in cheese, whereas in the case of Micrococcaceae, a more negative correlation was found between viable numbers and moisture content than between viable numbers and pH. The results of our study indicate, in general, poor milk handling conditions in all farms, given that the indicators total mesophile and Enterobacteriaceae counts were high, between 100- and 1,000-fold those enforced by international standards pertaining to the matrices in question. However, by the time of regular consumption (i.e., after 4 months of ripening), São Jorge cheeses exhibit low levels of contamination by Enterobacteriaceae and S. aureus, as well as absence of Salmonella.

Outbreak of OXY-2-Producing Klebsiella oxytoca in a renal transplant unit

We describe a Klebsiella oxytoca infection outbreak in a renal transplant unit that involved seven patients. All strains belonged to a single pulsed-field gel electrophoresis pattern and were resistant to amoxicillin-clavulanate, cefuroxime, piperacillin-tazobactam, and aztreonam but susceptible to ceftriaxone, ceftazidime, cefepime, and imipenem. Chromosomal beta-lactamase hyperproduction was caused by a point mutation in the bla(OXY-2) gene promoter region.

Involvement of Enterobacter cloacae in the mortality of the fish, Mugil cephalus

AIMS

To identify the causative agent of the mortality in the fish, Mugil cephalus, in Muttukadu lagoon.

METHODS AND RESULTS

An enteric bacterium from the kidneys of moribund fish M. cephalus, was isolated and identified as Enterobacter cloacae (MK). Mugil cephalus was experimentally infected by this isolate and was re-isolated from the kidneys of the moribund fish. Enterobacter cloacae isolates from the lagoon water (MW1, MW2 and reference strain ATCC 13047) and the reference strain were not able to induce similar pathogenesis. The putative factor imparting pathogenicity to the MK isolate was identified as a cationic molecule, which migrated towards the cathode on agarose gel electrophoresis.

CONCLUSIONS

The Ent. cloacae (MK) isolate harbouring a cationic factor was the causative agent for the mortality of M. cephalus, found in Muttukadu lagoon.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reveals that human enteric bacteria MK which is considered as nonpathogenic to fish, may become pathogenic to fish when it harbours this cationic factor. This cationic factor is found to be pathogenic to the fish M. cephalus leading to mortality. It was also found to be pathogenic to mice. Therefore, the shuttling of Ent. cloacae, harbouring cationic factor, between human and fish may be of human health importance.

The characterization of functions involved in the establishment and maturation of Klebsiella pneumoniae in vitro biofilm reveals dual roles for surface exopolysaccharides

The ability to form biofilm is seen as an increasingly important colonization strategy among both pathogenic and environmental Klebsiella pneumoniae strains. The aim of the present study was to identify abiotic surface colonization factors of K. pneumoniae using different models at different phases of biofilm development. A 2200 K. pneumoniae mutant library previously obtained by signature-tagged mutagenesis was screened in static and dynamic culture models to detect clones impaired at early and/or mature stages of biofilm formation. A total of 28 mutants were affected during late phases of biofilm formation, whereas 16 mutants displayed early adhesion defect. These mutants corresponded to genes involved in potential cellular and DNA metabolism pathways and to membrane transport functions. Eight mutants were deficient in capsule or LPS production. Gene disruption and microscopic analyses showed that LPS is involved in initial adhesion on both glass and polyvinyl-chloride and the capsule required for the appropriate initial coverage of substratum and the construction of mature biofilm architecture. These results give new insight into the bacterial factors sequentially associated with the ability to colonize an abiotic surface and reveal the dual roles played by surface exopolysaccharides during K. pneumoniae biofilm formation.

Transgenic tissue-type plasminogen activator expression improves host defense during Klebsiella pneumonia

BACKGROUND

Severe pneumonia is associated with a local inhibition of fibrinolysis in the lung as reflected by strongly reduced pulmonary plasminogen activator activity.

OBJECTIVES

To study the effect of elevation of local plasminogen activator activity during pneumonia caused by the common respiratory pathogen Klebsiella pneumoniae.

METHODS

Female C57Bl/6 mice were inoculated intranasally with a replication-defective adenoviral vector expressing human tissue-type plasminogen activator or a control vector 24 h before intranasal infection with K. pneumoniae.

RESULTS

Mice infected with Klebsiella via the airways developed overt pneumonia, which was accompanied by a downregulation of pulmonary tissue-type plasminogen activator levels at protein and mRNA levels. Pulmonary overexpression of human tissue-type plasminogen activator resulted in increased fibrinolytic activity in the lungs during pneumonia, as indicated by higher D-dimer levels and reduced fibrin deposition. Interestingly, overexpression of tissue-type plasminogen activator markedly improved host defense against pneumonia: mice treated with the tissue-type plasminogen activator vector displayed less bacterial growth and dissemination, attenuated distant organ injury and a reduced mortality.

CONCLUSIONS

These data demonstrate that local elevation of plasminogen activator activity in the lungs improves host defense against severe gram-negative pneumonia and sepsis.

Klebsiella pneumoniae multiresistance plasmid pMET1: similarity with the Yersinia pestis plasmid pCRY and integrative conjugative elements

Background

Dissemination of antimicrobial resistance genes has become an important public health and biodefense threat. Plasmids are important contributors to the rapid acquisition of antibiotic resistance by pathogenic bacteria.

Principal Findings

The nucleotide sequence of the Klebsiella pneumoniae multiresistance plasmid pMET1 comprises 41,723 bp and includes Tn1331.2, a transposon that carries the bla_TEM-1 gene and a perfect duplication of a 3-kbp region including the aac(6′)-Ib, aadA1, and bla_OXA-9 genes. The replication region of pMET1 has been identified. Replication is independent of DNA polymerase I, and the replication region is highly related to that of the cryptic Yersinia pestis 91001 plasmid pCRY. The potential partition region has the general organization known as the parFG locus. The self-transmissible pMET1 plasmid includes a type IV secretion system consisting of proteins that make up the mating pair formation complex (Mpf) and the DNA transfer (Dtr) system. The Mpf is highly related to those in the plasmid pCRY, the mobilizable high-pathogenicity island from E. coli ECOR31 (HPI_ECOR31), which has been proposed to be an integrative conjugative element (ICE) progenitor of high-pathogenicity islands in other Enterobacteriaceae including Yersinia species, and ICE_Kp1, an ICE found in a K. pneumoniae strain causing primary liver abscess. The Dtr MobB and MobC proteins are highly related to those of pCRY, but the endonuclease is related to that of plasmid pK245 and has no significant homology with the protein of similar function in pCRY. The region upstream of mobB includes the putative oriT and shares 90% identity with the same region in the HPI_ECOR31.

Conclusions

The comparative analyses of pMET1 with pCRY, HPI_ECOR31, and ICE_Kp1 show a very active rate of genetic exchanges between Enterobacteriaceae including Yersinia species, which represents a high public health and biodefense threat due to transfer of multiple resistance genes to pathogenic Yersinia strains.

Contribution of fucose-containing capsules in Klebsiella pneumoniae to bacterial virulence in mice

Bacterium Klebsiella pneumoniae (KP) contains a prominent capsule. Clinical infections usually are associated with pneumonia or urinary tract infection (UTI). Emerging evidence implicates KP in severe liver abscess especially in diabetic patients. The goal of this study was to investigate the capsular polysaccharides from KP of liver abscess (hepatic-KP) and of UTI-KP. The composition of capsular polysaccharides was analyzed by capillary high-performance liquid chromatography (HPLC, Dionex system). The terminal sugars were assayed by binding ability to lectins. The results showed that the capsule of a hepatic KP (KpL1) from a diabetic patient contained fucose, while the capsule from UTI-KP (KpU1) did not. The absence of fucose was verified by the absence of detectable polymerase chain reaction (PCR) fragment for fucose synthesis genes, gmd and wcaG in KpU1. Mice infected with the KpL1 showed high fatality, whereas those infected with the KpU1 showed high survival rate. The KpL1 capsule was reactive to lectins AAA and AAL, which detect fucose, while the KpU1 capsule was reactive to lectin GNA, which detects mannose. Phagocytosis experiment in mouse peritoneal cavity indicated that the peritoneal macrophages could interact with KpU1, while rare association of KpL1 with macrophages was observed. This study revealed that different polysaccharides were displayed on the bacterial capsules of virulent KpL1 as compared with the less virulent KpU1. Interaction of KpU1 with mice peritoneal macrophages was more prominent than that of KpL1. The possession of fucose might contribute to KpL1 virulence by avoiding phagocytosis since fucose on bacteria had been implicated in immune evasion.

Intrauterine infection with Klebsiella pneumoniae: report of a case and literature review

We report a case of intrauterine Klebsiella pneumoniae infection that resulted in premature rupture of membranes and fetal demise at 20 weeks' gestation in a pregnancy achieved by in vitro fertilization. Postmortem findings included massive panlobar pneumonia, the presence of abundant gram-negative, rod-shaped bacteria within the pulmonary air spaces and the lumen of the gastrointestinal tract, and fetal lung and blood cultures positive for Klebsiella pneumoniae. The placenta showed severe acute chorioamnionitis associated with a brisk fetal inflammatory response (umbilical cord and chorionic plate vasculitis). Marked pancreatic fibrosis was noted, indicative of a preceding necrotizing pancreatitis. In spite of this fulminant histopathologic evidence of intrauterine infection, the infection was clinically silent. This represents, to our knowledge, the 1st reported case of fatal intrauterine Klebsiella pneumoniae infection fully supported by conclusive fetal and placental histopathological evidence.

Antibiotic-associated diarrhea: candidate organisms other than Clostridium difficile

BACKGROUND/AIMS

The direct toxic effects of antibiotics on the intestine can alter digestive functions and cause pathogenic bacterial overgrowth leading to antibiotic-associated diarrhea (AAD). Clostridium difficile (C. difficile) is widely known to be responsible for 10 approximately 20% of AAD cases. However, Klebsiella oxytoca, Clostridium perfringens, Staphylococcus aureus, and Candida species might also contribute to AAD.

METHODS

We prospectively analyzed the organisms in stool and colon tissue cultures with a C. difficile toxin A assay in patients with AAD between May and December 2005. In addition, we performed the C. difficile toxin A assays using an enzyme-linked fluorescent assay technique. Patients were enrolled who had diarrhea with more than three stools per day for at least 2 days after the initiation of antibiotic treatment for up to 6 approximately 8 weeks after antibiotic discontinuation.

RESULTS

Among 38 patients (mean age 59 +/- 18 years, M:F =18:20), the organism isolation rates were 28.9% (11/38) for stool culture, 18.4% (7/38) for colon tissue cultures and 13.2% (5/38) for the C. difficile toxin A assay. The overall rate of identification of organisms was 50.0% (19/38). Of the five patients that had a positive result by the C. difficile toxin A assay, two had no organism isolated by the stool or colon tissue culture. The organisms isolated from the stool cultures were C difficile (4), Klebsiella pneumoniae (K. pneumoniae) (3), Candida species (3), and Staphylococcus aureus (1). C. difficile (4) and K. pneumoniae (3) were isolated from the colon tissue culture.

CONCLUSIONS

For C. difficile negative AAD patients, K. pneumoniae, Candida species and Staphylococcus aureus were found to be potential causative organisms.

Virulence characteristics of Klebsiella and clinical manifestations of K. pneumoniae bloodstream infections

Differences in clinical manifestations are due to virulence factors expressed by the organism.

We studied 455 consecutive episodes of Klebsiella pneumoniae bacteremia occurring in 7 countries. Community-acquired pneumonia and an invasive syndrome of liver abscess, meningitis, or endophthalmitis occurred only in Taiwan and South Africa. Infections by K1 and K2 capsular serotype, the mucoid phenotype, and aerobactin production were important determinants of virulence. The mucoid phenotype was seen in 94% of isolates in patients with community-acquired pneumonia and in 100% of isolates that caused the invasive syndrome in Taiwan and South Africa, compared with only 2% of isolates elsewhere. Mortality of mice injected with mucoid strains (69%) was strikingly higher than that occurring in mice injected with nonmucoid strains (3%, p<0.001). Differences in clinical features of bacteremic infection with K. pneumoniae are due to the virulence factors expressed by the organism.

Klebsiella pneumoniae meningitis in a 38-year-old Chinese traveller with impaired glucose tolerance: a new emerging syndrome?

Early diagnosis and appropriate empirical treatment of bacterial meningitis reduce morbidity and mortality. Prevalence rates of different causative pathogens associated with bacterial meningitis can depend on age, the underlying medical condition, way of infection and geographical distribution. Klebsiella pneumoniae represents an infrequent cause of community-acquired meningitis in South-East Asia and North-East Asia, where it accounts for 20% of all bacterial meningitis, frequently associated with septic metastatic complications. We describe a case of K. pneumoniae meningitis, diplopia and chemosis in a recently immigrated patient with impaired glucose tolerance. The reason for the high prevalence of metastatic septic infections caused by K. pneumoniae in Taiwan and South-East Asia remains unclear: high prevalence in this area of serotype K1 and K2 and the expression of a novel locus called magA conferring to bacterium an elevated phagocytosis resistance and an active proliferation ability have been suggested. A high degree of suspicion for this etiology must be taken into account in immigrants from China and Taiwan. Due to a very high lethality, guidelines on empiric treatment should be considered in the management of bacterial meningitis, with the patients geographical origin and the clinical syndrome (meningitis and endophtalmitis) as potential risk factors for K. pneumoniae infection.

Complicated catheter-associated urinary tract infections due to Escherichia coli and Proteus mirabilis

Catheter-associated urinary tract infections (CAUTIs) represent the most common type of nosocomial infection and are a major health concern due to the complications and frequent recurrence. These infections are often caused by Escherichia coli and Proteus mirabilis. Gram-negative bacterial species that cause CAUTIs express a number of virulence factors associated with adhesion, motility, biofilm formation, immunoavoidance, and nutrient acquisition as well as factors that cause damage to the host. These infections can be reduced by limiting catheter usage and ensuring that health care professionals correctly use closed-system Foley catheters. A number of novel approaches such as condom and suprapubic catheters, intermittent catheterization, new surfaces, catheters with antimicrobial agents, and probiotics have thus far met with limited success. While the diagnosis of symptomatic versus asymptomatic CAUTIs may be a contentious issue, it is generally agreed that once a catheterized patient is believed to have a symptomatic urinary tract infection, the catheter is removed if possible due to the high rate of relapse. Research focusing on the pathogenesis of CAUTIs will lead to a better understanding of the disease process and will subsequently lead to the development of new diagnosis, prevention, and treatment options.

Clonal dissemination of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates in a Korean hospital

In this study, we investigated the molecular characteristics of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates that were recovered from an outbreak in a Korean hospital. A new multilocus sequence typing (MLST) scheme for K. pneumoniae based on five housekeeping genes was developed and was evaluated for 43 ESBL-producing isolates from an outbreak as well as 38 surveillance isolates from Korea and also a reference strain. Overall, a total of 37 sequence types (STs) and six clonal complexes (CCs) were identified among the 82 K. pneumoniae isolates. The result of MLST analysis was concordant with that of pulsedfield gel electrophoresis. Most of the outbreak isolates belonged to a certain clone (ST2), and they produced SHV-1 and CTX-M14 enzymes, which was a different feature from that of the K. pneumoniae isolates from other Korean hospitals (ST20 and SHV-12). We also found a different distribution of CCs between ESBL-producing and -nonproducing K. pneumoniae isolates. The MLST method we developed in this study could provide unambiguous and well-resolved data for the epidemiologic study of K. pneumoniae. The outbreak isolates showed different molecular characteristics from the other K. pneumoniae isolates from other Korean hospitals.

Gram-negative pathogen Klebsiella oxytoca is associated with spontaneous chronic otitis media in Toll-like receptor 4-deficient C3H/HeJ mice

CONCLUSION

This report confirms the presence of gram-negative Klebsiella bacteria in the middle ear of the C3H/HeJ mouse by culture, polymerase chain reaction (PCR), and electron microscopy. Identification of the bacterial pathogen supports the C3H/HeJ mouse as an excellent model for spontaneous chronic otitis media and its effects on the middle and inner ear.

OBJECTIVES

The C3H/HeJ mouse has a single amino acid substitution in its Toll-like receptor 4, making it insensitive to endotoxin and suppressing initiation of the innate immune system. This study explored the bacteriology of the resultant middle ear infection by culture, PCR, histology, and electron microscopy.

MATERIALS AND METHODS

Twelve-month-old C3H/ HeJ mice were screened positive for spontaneous otitis media. Tympanocentesis and blood cultures of mice were carried out under sedation. Middle ear aspirate material and blood samples were then sent for culture and PCR. Mice were then sacrificed for bright-field and electron microscopy analysis.

RESULTS

All tympanocentesis and blood specimens grew gram-negative Klebsiella oxytoca, which was confirmed by PCR. Histopathology confirmed an intense inflammatory reaction and gram-negative bacteria in the middle and inner ears. Electron microscopy of the middle ears revealed abundant rod-shaped Klebsiella bacteria, both free and being engulfed by neutrophils.

Characterization and identification of virulent Klebsiella oxytoca isolated from abalone (Haliotis diversicolor supertexta) postlarvae with mass mortality in Fujian, China

An epidemic of mass mortality of abalone (Haliotis diversicolor supertexta) postlarvae aged 40 days or less has existed across south coast of China since the second half of 2002. Among 20 bacterial strains isolated from diseased abalone postlarvae on 2216E marine agar plates during an outbreak of postlarval disease in August 2005, a predominant strain (designated strain 20) was demonstrated to be virulent to postlarvae with an LD(50) value of 1.0x10(5) colony forming units (CFUml(-1)) on day 4, while the other 19 strains were either avirulent (16 strains) or weakly virulent (3 strains). The same bacterium could be re-isolated from postlarvae after bacterial challenge using 2216E marine agar plates. Preliminary toxicity tests of ECPs of strain 20 revealed that at 2.77mgproteinml(-1), crude ECPs completely liquefied postlarvae within 24h, leaving only shells. API 20E analysis identified strain 20 as Klebsiella oxytoca. 16S and ITS rDNA sequencing and phylogenetic analyses further confirmed this identification. Antibiotic susceptibility tests showed that strain 20 exhibited 94% of susceptibility to 16 various antibiotics tested and only showed resistance to streptomycin. Results of this work demonstrated that K. oxytoca is also linked to this epidemic in Fujian, China. This is considered to be the first report regarding K. oxytoca involved in the mass mortality of postlarval abalone in south China and the world.

Application of PCR ribotyping and tDNA-PCR for Klebsiella pneumoniae identification

PCR analysis of 16S-23S internal transcribed spacer (PCR ribotyping) and tRNA intergenic spacer (tDNA-PCR) were evaluated for their effectiveness in identification of clinical strains of Klebsiella pneumoniae and differentiation with related species. For this purpose both methods were applied to forty-three clinical isolates biochemically identified as K. pneumoniae subsp. pneumoniae isolated from patients clinical specimens attended at five hospitals in three Brazilian cities. References strains of K. pneumoniae subsp. pneumoniae, K. pneumoniae subsp. ozaenae, K. oxytoca, K. planticola and Enterobacter aerogenes were also analyzed. Both PCR methods showed specific patterns for each species. A conserved PCR ribotype pattern was observed for all clinical K. pneumoniae isolates, while differing from other related analyzed species. tDNA-PCR revealed five distinct patterns among the K. pneumoniae clinical isolates studied, demonstrating a predominant group with 90.6% of isolates presenting the same pattern of K. pneumoniae type strain. Both PCR-based methods were not able to differentiate K. pneumoniae subspecies. On the basis of the results obtained, both methods were efficient to differentiate the Klebsiella species analyzed, as well as E. aerogenes. Meanwhile tDNA-PCR revealed different tRNA arrangements in K. pneumoniae, suggesting intra-species heterogeneity of their genome organization, the polymorphism of the intergenic spacers between 16S and 23S rRNA genes appears to be highly conserved whithin K. pneumoniae clinical isolates, showing that PCR ribotyping can be an useful tool for identification of K. pneumoniae isolates.

Klebsiella pneumoniae flocculation dynamics

The bacterial pathogen Klebsiella pneumoniae is a cause of community- and hospital-acquired lung, urinary tract and blood stream infections. It is a common contaminant of indwelling catheters and it is theorized in that context that systemic infection follows shedding of aggregates off of surface-adherent biofilm colonies. In an effort to better understand bacterial proliferation in the host bloodstream, we develop a PDE model for the flocculation dynamics of Klebsiella pneumoniae in suspension. Existence and uniqueness results are provided, as well as a brief description of the numerical approximation scheme. We generate artificial data and illustrate the requirements to accurately identify proliferation, aggregation, and fragmentation of flocs in the experimental domain of interest.

Gene cloning and characterization of KdeA, a multidrug efflux pump from Klebsiella pneumoniae

We cloned a gene related to multidrug resistance from a drug-resistant Klebsiella pneumoniae strain MGH78578. We designated the gene kdeA, which encodes a protein possessing 12 hydrophobic regions. The deduced amino acid sequence of KdeA is similar to that of MdfA, a well-characterized multidrug efflux pump from Escherichia coli. Introduction of the kdeA gene into cells of the drug-hypersusceptible E. coli strain KAM32 resulted in elevated minimum inhibitory concentrations of chloramphenicol, norfloxacin, acriflavine, and ethidium bromide. We observed elevated energy-dependent ethidium efflux activity with cells carrying kdeA compared with control cells. We also observed expression of kdeA in cells of K. pneumoniae under normal growth conditions.