Hydrolytic and haemolytic activity of Klebsiella pneumoniae and Klebsiella oxytoca

Hydrolytic enzymes and haemolysins are important extracellular substances produced by many bacteria. We investigated 57 K. pneumoniae strains and 40 K. oxytoca strains isolated from clinical materials. We estimated the ability to produce: proteases hydrolyzing milk powder, caseinase, gelatinase, elastase, lecithinase, lipases, DNase and haemolysins on human, sheep and horse erythrocytes on TSA medium with or without 5% Egg Yolk. We detected that K. oxytoca strains produced proteases hydrolyzing milk powder (37.5%), caseinase (15.0%) and gelatinase (17.5%) more frequently than K. pneumoniae strains (respectively 21.0%, 5.3%, 8.9%). None of the analysed Klebsiella spp. strains produced elastase. Only K. pneumoniae strains produced lecithinase (5.3%). Lipases hydrolyzing Tween were produced from 3.5% (for Tween 60 and 80) to 7.0% (for Tween 20). Among K. oxytoca strains only one (2.5%) hydrolyzing Tween 20. DNase was produced by 38.6% of K. pneumoniae strains and by 27.5% K. oxytoca strains. Haemolytic properties on human erythrocytes were detected in 5.3% K. pneumoniae strains on TSA medium and 29,8% on medium with Egg Yolk. In K. oxytoca strains haemolytic properties on human erythrocytes were detected only on medium with Egg Yolk (12.5%). Haemolytic properties on sheep erythrocytes were detected respectively in 21.0% and 22.8% K. pneumoniae strains and in 7.5% K. oxytoca strains on each medium. Haemolytic properties on horse erythrocytes were detected respectively in 33.4% and 52.6% K. pneumoniae strains and in 15.0% and 20.0% K. oxytoca strains.     

Hemolytic activity of Klebsiella pneumoniae and Klebsiella oxytoca

We demonstrated that Klebsiella pneumoniae and Klebsiella oxytoca possess a selective haemolytic activity on rabbit erythrocytes. Thirty one Klebsiella strains (18 strains of K. pneumoniae and 13 strains of K. oxytoca) were isolated from hospitalized patients. The liquid (Trypcase-soy broth--TSB) and solid (Trypcase-soy agar--TSA) medium, containing the red cells were used for the tests. All the screened strains showed a haemolytic effect on rabbit erythrocytes, provided that the supernatants of the cultures were preincubated with beta-mercaptoethanol or calcium chloride. There was no human and sheep erythrocyte lysis.     

Antibiotic susceptibility, serum response and surface properties of Klebsiella species

Altogether 130 clinical isolates of five Klebsiella species (K. pneumoniae, K. planticola, K. oxytoca, K. ornithinolytica and K. terrigena) were characterized, for their susceptibility to five antibiotics, for susceptibility to serum bactericidal activity and for their hydrophobic properties. All strains exhibited ampicillin resistance. Ampicillin/sulbactam, gentamicin and ofloxacin showed effectiveness in 63.1, 67.7 and 71.5% of the Klebsiella isolates. K. planticola manifested the highest level of resistance to these antibiotics. The majority of Klebsiella strains (93.9%) were susceptible to cefuroxime. Sixty-four strains (49.2%) were serum resistant and intermediate serum sensitivity was shown by 57 strains (43.8%). A high percentage of serum resistant strains (65%) was found in K. planticola. Moderately hydrophobic properties determined by adherence of bacteria to xylene were demonstrated in 25 strains (19.2%).     

ESBL-positive and ESBL-negative Klebsiella pneumoniae and Klebsiella oxytoca strains--occurrence in clinical specimens and susceptibility to selected antibiotics

The aim of this study was to evaluated susceptibility to selected antibiotics and occurrence in clinical materials ESBL-positive and ESBL-negative K. pneumoniae and K. oxytoca strains. The susceptibility to selected antibiotics were tested by disk-diffusion method. None of the analysed strains was resistant to imipenem. Among non beta-lactam antibiotics thwe most strains were susceptible to fluoroquinolones. The most frequently K. pneumoniae strains were isolated from urine, K. oxytoca trains were isolated from wounds.     

Klebsiella pneumoniae produces no histamine: Raoultella planticola and Raoultella ornithinolytica strains are histamine producers

Histamine fish poisoning is caused by histamine-producing bacteria (HPB). Klebsiella pneumoniae and Klebsiella oxytoca are the best-known HPB in fish. However, 22 strains of HPB from fish first identified as K. pneumoniae or K. oxytoca by commercialized systems were later correctly identified as Raoultella planticola (formerly Klebsiella planticola) by additional tests. Similarly, five strains of Raoultella ornithinolytica (formerly Klebsiella ornithinolytica) were isolated from fish as new HPB. R. planticola and R. ornithinolytica strains were equal in their histamine-producing capabilities and were determined to possess the hdc genes, encoding histidine decarboxylase. On the other hand, a collection of 61 strains of K. pneumoniae and 18 strains of K. oxytoca produced no histamine.     

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%).     

Incidence of Klebsiella species in surface waters and their expression of virulence factors.

To investigate the occurrence of different Klebsiella spp. in aquatic environments, a total of 208 samples of natural surface waters was examined. From half (53%) of these samples, 123 Klebsiella strains were isolated, the most common species being Klebsiella pneumoniae. A comparison of these isolates to a group of 207 clinical K. pneumoniae isolates demonstrated that water isolates of K. pneumoniae, unlike those of K. oxytoca and K. planticola, are as capable as clinical isolates of expressing putative virulence factors such as serum resistance and capsular polysaccharides, pili, and siderophores.     

The use of purine compounds as sole sources of carbon and nitrogen by Klebsiella species

Sixty-one strains of Enterobacteriaceae were tested for purine assimilation, including twenty-five Klebsiella pneumoniae, seventeen K. oxytoca and nineteen others. Only K. pneumoniae and K. oxytoca were able to use guanosine triphosphate, xanthine, hypoxanthine, or uric acid as sole sources of carbon and nitrogen. When guanosine triphosphate was used as sole source of nitrogen and carbon, the lag phase was prolonged. The addition of glucose did not affect the maximum number of viable cells for K. pneumoniae ATCC 29665, but produced an increase for strain K. oxytoca ATCC 13030. In the case of uric acid, ATCC 29665 had a more distinct lag phase of growth than ATCC 13030. Apart from this, they appeared to be very similar. On solid chemically defined GTP medium, some strains of Klebsiella were able to produce a water-soluble brown pigment.     

Fermentation and evaluation of Klebsiella pneumoniae and K. oxytoca on the production of 2,3-butanediol

Klebsiella is one of the genera that has shown unbeatable production performance of 2,3-butanediol (2,3-BD), when compared to other microorganisms. In this study, two Klebsiella strains, K. pneumoniae (DSM 2026) and K. oxytoca (ATCC 43863), were selected and evaluated for 2,3-BD production by batch and fed-batch fermentations using glucose as a carbon source. Those strains' morphologies, particularly their capsular structures, were analyzed by scanning electron microscopy (SEM). The maximum titers of 2,3-BD by K. pneumoniae and K. oxytoca during 10 h batch fermentation were 17.6 and 10.9 g L(-1), respectively; in fed-batch cultivation, the strains showed the maximum titers of 50.9 and 34.1 g L(-1), respectively. Although K. pneumoniae showed higher productivity, SEM showed that it secreted large amounts of capsular polysaccharide, increasing pathogenicity and hindering the separation of cells from the fermentation broth during downstream processing.     

Taxonomic position of Klebsiella atlantae and Klebsiella edwardsii.

The taxonomic position of two species of the genus Klebsiella (K. atlantae and K. edwardsii) is being introduced. 211 strains of different origin were studied: 80 strains of K. pneumoniae, 46 strains of K. oxytoca, 50 strains of K. atlantae and 35 strains of K. edwardsii. Sixty biochemical characteristics were determined 40 of these pertaining to carbohydrate metabolism. It was discussed whether both are to be considered species or biotypes of another Klebsiella species, however, by determining citrate as carbon source, by MR test and by tests on malonate, gluconate, methyl-xyloside, 1 (--) sorbose, inulin, amylose, methyl-d-mannoside, glycogen, melezitose, VP test, amygdalin, d-tartrate and gas from glucose, we arrived at the conclusion that both could be considered species of the genus. These conclusions were confirmed by the determination of biotypes of both (according to C. Richard). Later, we expect to study their participation in human infective processes and their sensitivity by antibiotic therapy.     

Identification of vaccine candidate antigens of an ESBL producing Klebsiella pneumoniae clinical strain by immunoproteome analysis

Klebsiella pneumoniae is an opportunistic pathogen which causes pneumoniae, urinary tract infections and septicemia in immunocompromised patients. Hospital outbreaks of multidrug-resistant K. pneumoniae, especially those in neonatal wards, are often caused by strains producing the extended-spectrum-beta-lactamases (ESBLs). An immunoproteome based approach was developed to identify candidate antigens of K. pneumoniae for vaccine development. Sera from patients with acute K. pneumoniae infections (n = 55) and a control group of sera from healthy individuals (n = 15) were analyzed for reactivity by Western blot against ESBL K. pneumoniae outer membrane proteins separated by 2-DE. Twenty highly immunogenic protein spots were identified by immunoproteomic analysis. The immunogenic proteins that are most frequently recognized by positive K. pneumoniae sera were OmpA, OmpK36, FepA, OmpK17, OmpW, Colicin I receptor protein and three novel proteins. Two of the vaccine candidate genes, OmpA (Struve et al. Microbiology 2003, 149, 167-176) and FepA (Lai, Y. C. et al.. Infect Immun 2001, 69, 7140-7145), have recently been shown to be essential in colonization and infection in an in vivo mouse model. Hence, these two immunogenic proteins could serve as potential vaccine candidates.     

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.     

Pathogenic potential of environmental Klebsiella pneumoniae isolates

Klebsiella pneumoniae is an important opportunistic pathogen and a frequent cause of nosocomial infections. K. pneumoniae infections can occur at nearly any body site; however, urinary tract infections and infections of the respiratory tract predominate. Infections are frequently preceded by gastrointestinal colonization, and the gastrointestinal tract is believed to be the most important reservoir for transmission of the bacteria. In contrast to many other bacterial pathogens, K. pneumoniae is ubiquitous in nature. Several studies have described Klebsiella isolates of environmental origin to be nearly identical to clinical isolates with respect to several phenotypic properties. However, the pathogenic potential of environmental K. pneumoniae isolates is essentially unknown. We have evaluated the virulence of K. pneumoniae strains of environmental and clinical origin directly in animal models, i.e. in urinary tract infection and intestinal colonization models. Furthermore, the ability to adhere to and invade human epithelial cell lines was examined. Although strain-to-strain differences were observed in the individual infection models, overall, strains of environmental origin were found to be as virulent as strains of clinical origin. The ubiquity of K. pneumoniae in nature and the general ability of K. pneumoniae strains to infect susceptible hosts might explain the high frequency of opportunistic infections caused by this species.     

Detection, prevalence, purification and characterization of lecithinase of Klebsiella pneumoniae

Lecithinase activity in Klebsiella is a rare trait as out of 208 strains of Klebsiella belonging to 3 species, viz. K. pneumoniae (168), K. planticola (29) and K. oxytoca (11), only 4 strains of K. pneumoniae produced lecithinase positive colonies on egg-yolk-agar. Although cell lysates of 16 K. pneumoniae yielded positive results for lecithinase assay on egg-yolk-agar, 19 strains were detected positive for lecithinase with ELISA using anti-lecithinase serum. Release of up to 52.12% cell-bound lecithinase could be achieved with polymyxin-B treatment at 100 micrograms/ml concentration. Purified lecithinase was determined to be a high molecular weight (70 kDa), crystalizable, anionic (pI, 3.5) protein. It possessed cytolytic, haemolytic and dermonecrotic activities but did not induce fluid accumulation in rabbit ileal loop or infant mouse guts. It was inactivated by boiling, trypsin and chymotrypsin treatment and alkaline pH. Serologically, it was related to lecithinase of Aeromonas caviae and phospholipase-C of Salmonella.     

Antibiotic susceptibility and molecular mechanisms of cephalosporins resistance in Klebsiella isolates from patients with hospital-acquired infections]

Antibiotic susceptibility of nosocomial Klebsiella isolates from inpatients of 30 medical centres in 15 various regions of Russia was studied. In total 212 strains were tested. The Klebsiella genus was represented by the following species: Klebsiella pmeumoniae ss. pneumoniae (182 isolates, 85.8%), Klebsiella pneumonia ss. ozaenae (1 isolate, 0.5%), Klebsiella oxytoca (29 isolates, 13.7%). The susceptibility was determined by the broth microdilution method. Carbapenems (imipenem and meropenem) remained to be the most active antibacterial agents. However, 1 imipenem resistant strain and 2 meropenem resistant strains were isolated. As for the 3rd generation cephalosporins, the lowest MICs were observed with the use of the inhibitor-protected agents, such as ceftazidime/clavulanic acid (MIC50 0.25 mcg/ml, MIC90 64 mcg/ml). 48.8%, 16.9%, 29.7% and only 10.5% of the isolates was susceptible to cefepime, cefotaxime, ceftazidime and cefoperazone respectively. Detecting of the beta-lactamase genes (TEM, SHV and CTX) was performed by PCR in 42 strains of Klebsiella pneumoniae ss. pneumoniae. Alone or in various combination the TEM type beta-lactamases were detected in 16 (38.1%) isolates. SHV and CTX were detected in 29 (69%) and 27 (64.3%) isolates respectively. Combinations of 2 and 3 different determinants of resistance to beta-lactams were revealed in 23.8% and 26.2% of the isolates respectively. No isolates producing class B MBL among the carbapenem resistant nosocomial Klebsiella strains were detected.     

Profiles of the utilization of 20 amino acids as the only source of nitrogen and carbon in bacteria of the genera Klebsiella, Enterobacter, Serratia, Escherichia

The profiles of the utilization of 20 protein amino acids in 118 Klebsiella pneumoniae sub- sp. pneumoniae, K. oxytoca, K. planticola, K. mobilis, Enterobacter cloacae, Serratia marscescens, S. liquefaciens, Escherichia coli strains isolated from clinical material were studied. The utilization of amino acids was determined on minimal saline agar containing amino acid as the only source of nitrogen and carbon; the results were evaluated after 72-hour incubation at 37 degrees C. 17 profiles of amino-acid utilization were thus determined, most of them genus-specific in enterobacteria: Klebsiella (profiles No. 1--6, 9, 10), Enterobacter (No. 11--13), Serratia (No. 14--16), Escherichia (No. 17). The full coincidence of amino-acid utilization profiles in bacteria of K. mobilis (No. 1, 6) and K. pneumoniae subsp. pneumoniae with out of such profiles in bacteria of the genera Enterobacter, Serratia, Escherichia was established, which confirmed that K. mobilis (formerly Enterobacter aerogenes) belonged to the genus Klebsiella.     

致肝脓肿高毒力肺炎克雷伯菌的表型及分子特征

目的 探究导致肝脓肿高毒力肺炎克雷伯菌的分子特征。方法 用VITEK-2细菌鉴定仪鉴定2014年1月至2016年1月丽水市中心医院肝脓肿患者脓肿穿刺液中分离的细菌。应用拉丝试验鉴定菌株的高粘性,用多位点序列分型（MLST）和血清型分型（K分型）对菌株进行分子分型,并用S1核酸酶脉冲场凝胶电泳（S1-PFGE）对菌株质粒谱进行分析。结果 57例肝脓肿患者接受肝脏脓肿穿刺引流并做脓液培养。44例患者的脓液培养到不同的致病菌,培养阳性率为77.2%。在培养到的44株病原菌中,其中2株为大肠埃希菌,产酸克雷伯菌、金黄色葡萄球菌各1株,而肺炎克雷伯菌为40株,占肝脓肿致病菌的90.9%。40株肺炎克雷伯菌中,拉丝阳性率为67.5%（27/40）,K1为主要血清分型,占62.5%（25/40）,其次为K2型,占17.5%（7/40)。ST23为主要ST分型,占47.5%（19/40）,其次为ST86和ST65,各占7.5%（3/40）。同时发现一些未报道过的致肝脓肿肺炎克雷伯菌新ST分型,如ST218、ST1941、ST76、ST2159、ST660和ST485。40株致肝脓肿肺炎克雷伯菌中总共检测到12种质粒谱,包括带有一个质粒、多个质粒或不带质粒的谱型。其中带有一个近220 kb的质粒谱为主要谱型,共涉及19株菌,占47.5%,12株菌带有一个质粒,大小为140~250 kb。4株菌带有2个或3个质粒,5株菌不含有质粒。结论 拉丝试验和血清学分型不能鉴定所有的高毒力肺炎克雷伯菌;高毒力肺炎克雷伯菌很多为ST23型,但其进化整体上较为分散;高毒力肺炎克雷伯菌菌株可以不携带质粒。     

Confirmation of Escherichia coli and its distinction from Klebsiella species by gas and indole formation at 44 and 44.5 degrees C

AIMS: In the enumeration of coliform bacteria, confirmation of Escherichia coli has been based upon gas and indole production at the elevated incubation temperature. The test for gas production has recently been questioned. The aim of this study was to investigate the impact of gas production test on the reliability of confirmation of E. coli. METHODS AND RESULTS: The impact of several media on growth, gas and/or indole formation was tested at 44 and 44.5 degrees C using 547 environmental isolates. These were mainly E. coli, Klebsiella pneumoniae, K. oxytoca and Enterobacter cloacae strains. Another set of 250 faecal and environmental klebsiellae were tested for their maximum temperature for growth (Tmax) and for gas formation. Escherichia coli and even K. pneumoniae grew well in all the media, but gas production was more dependent on the medium used. Growth of the mainly gas negative Ent. cloacae and K. oxytoca strains was still more sensitive to the medium and incubation conditions. Tryptophan salt broth was the most productive medium for the indole test, followed by lauryl tryptose mannitole and tryptone mannitol ricinoleate broth (TRM). Tmax of K. oxytoca was clearly lower than Tmax of K. pneumoniae but a rather high fraction of its isolates produced indole at 44.5 degrees C. CONCLUSIONS: False-positive E. coli confirmation is possible if gas production is not tested for and the confirmation is based on indole test only. SIGNIFICANCE AND IMPACT OF THE STUDY: Erroneous positive results on routine analysis for E. coli can occur.     

Role of microbiological surveillance in the choice of antibacterial therapy for intestinal Klebsiella infection in infants

Data on the frequency of intestinal infections caused by Klebsiella spp. in infants at the age of 1 month to 1 year and antibiotic resistance of K. pneumoniae and K. oxytoca isolates from newborns and infants aged 1 month to 1 year are presented. The frequency of the Klebsiella isolates from the newborns and infants at the age of 1 month to 1 year with acute intestinal infections amounted to 17.7 +/- 1.4 and 42.5 +/- 1.4 per cent, respectively. The majority of the clinical strains had a multiple resistance to 7-9 drugs. The overwhelming majority of the strains were sensitive to gentamicin, monomycin, kanamycin, neomycin and polymyxin B.     

Protective activity of a cell-free Klebsiella vaccine in relation to different Klebsiella pneumoniae serovars

The capacity of dried Klebsiella cell-free vaccine, obtained from strain No. 204 by the disintegration of microbial cells with hydroxylamine, for protecting mice from Klebsiella septic infection caused by the homologous serovar and 9 heterologous serovars of K. pneumoniae was studied. The newly developed preparation was found capable of stimulating immunity not only to the homologous K. pneumoniae serovar, but also to other K. pneumoniae heterologous serovars: K1, K9, K11, K16, K20, K61. The protective capacity of the preparation with respect to these serovars was not inferior to that of the vaccines prepared by the same method from the corresponding homologous strains. The capacity of the vaccine to protect mice from Klebsiella sepsis was manifested irrespective of the virulence of the strains used for challenge.