Hypermucoviscous Phenotype Research Articles

Deciphering Heteroresistance to Colistin in a Klebsiella pneumoniae Isolate from Marseille, France.

Here, we report the description of a colistin-heteroresistant Klebsiella pneumoniae isolate fortuitously isolated from the stool sample of a patient with suspicion of tuberculosis in a public hospital of Marseille, France. In the colistin-resistant subpopulation, a mutation in the mgrB gene leading to a premature stop codon was found, and the hypermucoviscous phenotype was lost. Susceptibility to other antibiotics remained unchanged. To our knowledge, this is the first identification of such a colistin-heteroresistant Klebsiella pneumoniae isolate in France.

Biofilm formation of hypermucoviscous and non-hypermucoviscous Klebsiella pneumoniae recovered from clinically affected African green monkey ( Chlorocebus aethiops sabaeus )

In recent years, an emergent Klebsiella pneumoniae hypermucoviscous (HMV) phenotype has been associated with increased invasiveness and pathogenicity in primates. The HMV phenotype is characterized by different capsular serotypes, associated with several genes including the rmpA (regulator of mucoid phenotype) and magA (mucoviscosity-associated) genes. In African green monkeys (AGM) (Chlorocebus aethiops sabaeus) serotypes K1 and K5 have been implicated in fatal multisystemic abscesses. In order to better understand the epizootiology of this pathogen, the capacity of biofilm production of K.pneumoniae isolates presenting the HMV was compared to non-HMV isolates at three different temperatures (25, 30 and 37°C). The results indicate that HMV and non-HMV isolates display similar capacity to form biofilms at the three different evaluated temperatures. Temperature appears to play a role in the formation of biofilms by K.pneumoniae presenting the HMV phenotype, where larger biofilms were formed at 37°C than at 25°C. Knowledge regarding local environmental sources of K.pneumoniae and the possible role of wildlife in the maintenance of this agent in the area is necessary to develop effective recommendations for the prevention and management of this disease in captive AGM populations.

Invasive liver abscess syndrome caused by Klebsiella pneumoniae with definite K2 serotyping in Japan: a case report.

BackgroundKlebsiella pneumonia is a well-known human pathogen, and recently, a distinct invasive syndrome caused by K. pneumoniae serotypes K1 and K2 has been recognized in Southeast Asia. This syndrome is characterized by primary liver abscess and extrahepatic complications resulting from bacteremic dissemination. We report the first adult case of primary liver abscess caused by the definite K2 serotyped pathogen, with endogenous endophthalmitis in Japan.Case presentationA 64-year-old woman was admitted to a nearby hospital for a high fever and diarrhea. She had visual loss of her right eye, renal dysfunction, and thrombocytopenia within 24 h from admission. She was transferred to our institution. On admission, she had no alteration of mental status and normal vital signs; however, she had almost complete ablepsia of the right eye. Laboratory data showed severe inflammation, liver dysfunction, thrombocytopenia, an increased serum creatinine level, and coagulopathy. Computed tomography showed a low density area in the right lobe of the liver. Invasive liver abscess syndrome probably caused by K. pneumonia was highly suspected and immediately administered broad-spectrum antibiotics for severe sepsis. Concurrently, endogenous endophthalmitis was diagnosed, and we performed vitrectomy on the day of admission. The blood culture showed K. pneumoniae infection. Percutaneous drainage of the liver abscess was also performed. Although she was discharged in a good general condition on day 22, she had complete ablepsia of the right eye. The K2A gene was detected by polymerase chain reaction (PCR), which is consistent with the K2 serotype. PCR was also positive for the virulence-associated gene rmpA. Final diagnosis was invasive liver abscess syndrome caused by K2 serotype K. pneumonia.ConclusionsAlthough the primary liver abscess caused by K. pneumoniae with a hypermucoviscous phenotype is infrequently reported outside Southeast Asia, physicians should recognize this syndrome, and appropriate diagnosis and treatment is essential for saving patients’ lives and preserving organ function, especially for visual acuity.

H-NS Nucleoid Protein Controls Virulence Features of Klebsiella pneumoniae by Regulating the Expression of Type 3 Pili and the Capsule Polysaccharide.

Klebsiella pneumoniae is an opportunistic pathogen causing nosocomial infections. Main virulence determinants of K. pneumoniae are pili, capsular polysaccharide, lipopolysaccharide, and siderophores. The histone-like nucleoid-structuring protein (H-NS) is a pleiotropic regulator found in several gram-negative pathogens. It has functions both as an architectural component of the nucleoid and as a global regulator of gene expression. We generated a Δhns mutant and evaluated the role of the H-NS nucleoid protein on the virulence features of K. pneumoniae. A Δhns mutant down-regulated the mrkA pilin gene and biofilm formation was affected. In contrast, capsule expression was derepressed in the absence of H-NS conferring a hypermucoviscous phenotype. Moreover, H-NS deficiency affected the K. pneumoniae adherence to epithelial cells such as A549 and HeLa cells. In infection experiments using RAW264.7 and THP-1 differentiated macrophages, the Δhns mutant was less phagocytized than the wild-type strain. This phenotype was likely due to the low adherence to these phagocytic cells. Taken together, our data indicate that H-NS nucleoid protein is a crucial regulator of both T3P and CPS of K. pneumoniae.

Hypermucoviscosity in Clinical Isolates of <i>Klebsiella pneumoniae</i> Correlates with High Multiple Antibiotic Resistance (MAR) Index

Klebsiella pneumoniae is an opportunistic pathogen of medical importance and the capsule and mucoid phenotype in this organism are considered as requisite virulence determinants. A total of 62 clinical samples from ATBUTH were collected and screened for K. pneumoniae. The isolates were identified using standard tests for this organism. The string test was used to detect the mucoid (hypermucoviscous) phenotype and the antimicrobial susceptibility test to 10 antibiotics was carried out with the disk diffusion technique after standardizing inoculum. A K. pneumoniae prevalence of 24% (15/62) was obtained of which 47% (7/15) were mucoid (hypermucoviscous) and 53% (8/15) were non-mucoid. Colonial sizes of the two strains do not reveal any significant differences in growth fitness of the strains. On blood agar, the mucoid and non-mucoid strains had a mean colonial size ± standard deviations of 4.41 ± 0.58 mm and 4.27 ± 0.42 mm respectively. The antibiotic susceptibility rate showed that the mucoid strains compared to the non-mucoid were more resistant to nine out of 10 antibiotics. The mucoid strains were outrightly resistant to augmentin, amoxicillin, septrin, sparfloxacin and perfloxacin. The non-mucoid strains showed no complete resistant to any antibiotic tested but had a higher resistant rate to chloramphenicol only. The Multiple Antibiotic Resistance (MAR) index shows the themucoid strains with a high MAR index range of 0.7 - 1.0 with a median MAR index of 0.8, while the non-mucoid strains had a MAR index of 0.2 - 0.8 with a median MAR index of 0.35. The data suggest that the mucoid phenotype could be associated with extrachromsomal element(s) carrying resistance genes to antibiotics and that these extrachromosomal elements may not harbour resistance determinants to chloramphenicol. Furthermore, the extrachromosomal elements bearing the mucoid phenotype and the resistance elements in the mucoid strains do not significantly impact on the fitness of the cognate strain. Whether these phenotype and resistances that had no fitness cost to the bacterium could significantly affect the virulence of the bacteria in vivo remains to be investigated.

Hypervirulent Klebsiella pneumoniae clones causing bacteraemia in adults in a teaching hospital in Barcelona, Spain (2007–2013)

Virulent hypermucoviscous Klebsiella pneumoniae strains associated with the magA and rmpA genes have mainly emerged in Asia. We analysed the frequency and the clinical and molecular epidemiology of K. pneumoniae bacteraemia isolates obtained over a 7-year period (2007–2013). Fifty-three of 878 K. pneumoniae invasive isolates (5.4%) showed a hypermucoviscous phenotype (by the string test). Of these, 16 (30.2%) were magA+/rmpA+, 12 (22.6%) were magA−/rmpA+, and the remaining 25 (47.2%) were magA−/rmpA−. After multilocus sequence typing and wzi sequencing, all magA+/rmpA+ isolates were serotype K1 and sequence type (ST)23. Of the 12 magA−/rmpA+ isolates, nine were K2 (ST380, ST86, ST65, ST25 and ST493), and three magA−/rmpA+ isolates had the new wzi allele 122, an unknown serotype, and the new ST1013. The remaining isolates, which were magA−/rmpA−, showed different serotypes and STs. Patients with magA+/rmpA+ or magA−/rmpA+K. pneumoniae bacteraemia more frequently had pyogenic liver abscesses (PLAs) and pneumonia than patients with magA−/rmpA−K. pneumoniae bacteraemia (respectively: 21.4% vs. 8%, p 0.26; and 17.9% vs. 0%, p 0.05). In fact, magA−/rmpA− isolates were similar to the those termed ‘classic’ K. pneumoniae isolates causing bacteraemia, the urinary and biliary tracts being the main foci of infection. In conclusion, hypervirulent clones (CC23K1, CC86K2, CC65K2, and CC380K2) were infrequent among K. pneumoniae isolates causing bacteraemia in our geographical area. A hypermucoviscous phenotype as determined with the string test is not enough to recognize these clones; additional molecular studies are needed. Patients with magA+ and/or rmpA+K. pneumoniae bacteraemia more frequently had PLAs and pneumonia than patients without hypermucoviscosity genes.

Potential virulence of Klebsiella sp. isolates from enteral diets.

We aimed to evaluate the potential virulence of Klebsiella isolates from enteral diets in hospitals, to support nosocomial infection control measures, especially among critical-care patients. Phenotypic determination of virulence factors, such as capsular expression on the external membrane, production of aerobactin siderophore, synthesis of capsular polysaccharide, hemolytic and phospholipase activity, and resistance to antibiotics, which are used therapeutically, were investigated in strains of Klebsiella pneumoniae and K. oxytoca. Modular industrialized enteral diets (30 samples) as used in two public hospitals were analyzed, and Klebsiella isolates were obtained from six (20%) of them. The hypermucoviscous phenotype was observed in one of the K. pneumoniae isolates (6.7%). Capsular serotypes K1 to K6 were present, namely K5 and K4. Under the conditions of this study, no aerobactin production, hemolytic activity or lecithinase activity was observed in the isolates. All isolates were resistant to amoxicillin and ampicillin and sensitive to cefetamet, imipenem, chloramphenicol, gentamicin and sulfamethoxazole-trimethoprim. Most K. pneumoniae isolates (6/7, 85.7%) from hospital B presented with a higher frequency of resistance to the antibiotics tested in this study, and multiple resistance to at least four antibiotics (3/8; 37.5%) compared with isolates from Hospital A. The variations observed in the antibiotic resistance profiles allowed us to classify the Klebsiella isolates as eight antibiotypes. No production of broad-spectrum β-lactamases was observed among the isolates. Our data favor the hypothesis that Klebsiella isolates from enteral diets are potential pathogens for nosocomial infections.

Clinical and microbiological characteristics of Klebsiella pneumoniae liver abscess in East China.

BackgroundKlebsiella pneumoniae has been the dominant pathogen for liver abscesses in several Asian countries. Although the prevalence of K. pneumoniae liver abscess (KLA) in mainland China is increasing recently, the clinical and microbiological characteristics of KLA in China have not been elucidated.MethodsClinical and microbiology characteristics of 45 consecutive patients with KLA from a tertiary teaching hospital in China between June 2008 and June 2012 were retrospectively evaluated.ResultsVast majority of the strains were susceptible to main antimicrobial agents. Most of K. pneumoniae strains from pyogenic liver abscess patients belonged to K1/K2 serotype (68.9% for K1 serotype and 20% for K2 serotype). All K. pneumoniae strains were rmpA positive, and 68.9% of these strains were magA positive. Overall, 57.8% (26/45) of K. pneumoniae strains belonged to ST23. Twenty-five of 26 ST23 K. pneumoniae isolates (96.2%) from KLA patients were magA-positive and K1 serotype. Only 28.9% (13/45) of KLA isolates exhibited hypermucoviscous phenotype, which is clinically used as the characteristic of hypervirulent K. pneumoniae (hvKP). Liver abscess sizes in patients infected with hvKP were tend to be larger than those in patients infected with cKP. There was no significant association between the microbiological and clinical characteristics including serotypes, magA and rmpA genotypes, and STs with the metastatic infection and prognosis of KLA.ConclusionsNeither the serotypes, magA and rmpA genotypes, nor the STs of K. pneumoniae were associated with the metastatic infection and prognosis of KLA. However, further studies with larger sample are needed in the future.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-015-0899-7) contains supplementary material, which is available to authorized users.

Expansion and evolution of a virulent, extensively drug-resistant (polymyxin B-resistant), QnrS1-, CTX-M-2-, and KPC-2-producing Klebsiella pneumoniae ST11 international high-risk clone.

In this study, we report the early expansion, evolution, and characterization of a multiresistant Klebsiella pneumoniae clone that was isolated with increasing frequency from inpatients in a tertiary-care university hospital in Brazil. Seven carbapenem- and quinolone-resistant and polymyxin B-susceptible or -resistant K. pneumoniae isolates isolated between December 2012 and February 2013 were investigated. Beta-lactamase- and plasmid-mediated quinolone resistance (PMQR)-encoding genes and the genetic environment were investigated using PCR, sequencing, and restriction fragment length polymorphism (RFLP). Clonal relatedness was established using XbaI-pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and phylogenetic group characterization. Plasmid analyses included PCR-based replicon typing (PBRT) and hybridization of the S1-PFGE product, plasmid MLST, and conjugation experiments. Virulence potential was assessed by PCR by searching for 10 virulence factor-encoding genes (ureA, fimH, kfuBC, uge, wabG, magA, mrkD, allS, rmpA, and cf29a) and by phenotypic tests to analyze the hypermucoviscous phenotype. The genetic context of a multidrug-resistant and extensively drug-resistant K. pneumoniae ST11-KpI clone harboring IncFIIk-Tn4401a-blaKPC-2, qnrS1, and blaCTX-M-2 was found. Moreover, three isolates displayed high resistance to polymyxin B (MICs = 32, 32, and 128 mg/liter) as well as mucous and hypermucoviscous phenotypes. These bacteria also harbored ureA, fimH, uge, wabG, and mrkD, which code for virulence factors associated with binding, biofilm formation, and the ability to colonize and escape from phagocytosis. Our study describes the association of important coresistance and virulence factors in the K. pneumoniae ST11 international high-risk clone, which makes this pathogen successful at infections and points to the quick expansion and evolution of this multiresistant and virulent clone, leading to a pandrug-resistant phenotype and persistent bacteria in a Brazilian hospital.

Potential Virulence of Klebsiella Isolated from Enteral DietsVirulence of Klebsiella and Enteral Diets

Objective: To evaluate the potential virulence of Klebsiella isolates from enteral diets in hospitals, in order to support nosocomial infection control measures, especially among critical patients. Methods: Capsular phenotypic expression of the external membrane, production of aerobactin siderophore, quantity of capsular polysaccharide, hemolytic and phospholipase activity and resistance to antibiotics that are used therapeutically were investigated in 15 strains of K. pneumoniae and six of K. oxytoca. These isolates were obtained from enteral diets in two public hospitals in the state of Minas Gerais, Brazil. Results: The hypermucoviscous phenotype was observed in one of the K. pneumoniae isolates (6.7%). Capsular serotypes of types K1 to K6 were seen to be present, of which four were K5 isolates of K. pneumoniae and one was K4. Under the conditions of this study, no aerobactin production, hemolytic activity or lecithinase activity was observed. All the isolates presented resistance to the antibiotics amoxicillin and ampicillin, but they were sensitive to the antibiotics cefetamet, imipenem, cloranfenicol, gentamicin and sulfamethoxazole/trimethoprim. The K. pneumoniae isolates that originated from hospital B presented higher frequency of resistance to the antibiotics evaluated and multiple resistances to at least four antibiotics. The variations in the profile of resistance to antibiotics among the Klebsiella isolates made it possible to classify them into eight antibiotypes. No production of broad-spectrum β -lactamases was observed among the isolates. Conclusion: The data obtained through this study favor the hypothesis that Klebsiella isolates from enteral diets are potential pathogens for nosocomial infections.

Population‐Based Surveillance for Hypermucoviscosity Klebsiella pneumoniae Causing Community‐Acquired Bacteremia in Calgary, Alberta

The characteristics of hypermucoviscosity isolates among Klebsiella pneumoniae causing community-acquired bacteremia were investigated. The hypermucoviscous phenotype was present in 8.2% of K pneumoniae isolates, and was associated with rmpA and the K2 serotype; liver abscesses were the most common clinical presentation. The present analysis represents the first population-based surveillance study of hypermucoviscosity among K pneumoniae causing bacteremia.

Septic Arthritis Subsequent to Urosepsis Caused by Hypermucoviscous <i>Klebsiella pneumoniae</i>

We herein report the first case of septic arthritis caused by rmpA-positive hypermucoviscous community-acquired K. pneumoniae that followed urosepsis in a 65-year-old Japanese woman. The patient responded well to drainage of the abscesses and treatment with cefazolin. Although this virulent phenotype of K. pneumoniae has been primarily reported in Hong Kong, we confirmed that 18/50 isolates obtained in our hospital over the past five years displayed the hypermucoviscous phenotype. Therefore, clinicians should consider the possibility of an increasing prevalence of rmpA-positive hypermucoviscous K. pneumoniae infection in Japan and be particularly vigilant for invasive clinical manifestations, even in patients with urinary tract infections.

Survey of Klebsiella pneumoniae bacteraemia in two South Australian hospitals and detection of hypermucoviscous phenotype and magA/rmpA genotypes in K . pneumoniae isolates

Clinical patterns of Klebsiella pneumoniae bacteraemia vary geographically. An invasive syndrome involving abscess formation has emerged in recent years. Putative virulence factors associated with this syndrome include colony hypermucoviscosity, and magA and rmpA genes. We studied epidemiologic and microbiologic characteristics of K. pneumoniae bacteraemia at two South Australian hospitals and identified cases of K. pneumoniae invasive syndrome. We determined the frequency of the hypermucoviscosity, magA and rmpA genes among bacteraemic and selected non-bacteraemic isolates. Thirty-one patients with K. pneumoniae bacteraemia treated between June 2010 and July 2011 were included. Existing records were examined for relevant clinical and microbiological data. Urinary and wound isolates were also examined. Hypermucoviscosity was identified by a positive string test, whilst polymerase chain reaction detected magA and rmpA positive isolates. Of 31 blood culture isolates, 22 were associated with community-acquired infection. Biliary infection was the commonest source, occurring in ten patients. Three patients had K. pneumoniae invasive syndrome, all of Asian extraction (p = 0.0044). Four blood isolates demonstrated one or more of hypermucoviscosity, magA or rmpA; three were from patients with liver abscesses. Liver abscess isolates were all K1 serotype and had similar PFGE profiles. This study augments understanding of local epidemiology and microbiology of K. pneumoniae bacteraemia. It confirms local emergence of K. pneumoniae invasive syndrome and implicates the role of magA and rmpA genes in its pathogenesis.

Appearance of Klebsiella Pneumoniae Liver Abscess Syndrome in Argentina: Case Report and Review of Molecular Mechanisms of Pathogenesis

Klebsiella pneumoniae liver abscess syndrome (KLAS) is an emerging invasive infection caused by highly virulent community-acquired strains of K. pneumoniae displaying hypermucoviscosity. The salient features of this syndrome include the presence of bacteremia, primary monomicrobial liver abscess, and metastatic complications. A previously healthy Argentinean man presented with fever and found to have liver abscess caused by K. pneumoniae with metastatic seeding of gastric wall. Cultures from blood and liver abscess grew hypermucoviscous K1 K. pneumoniae with sequence type (ST) 23 by multilocus sequence typing (MLST), positive for rmpA (regulator of mucoid phenotype A), wzyKpK1 (capsular polymerase) and aerobactin genes. The hypermucoviscous phenotype of this K. pneumoniae isolate was readily identified by the "string test" (colonies formed a long string when touched with a loop). The patient responded favourably to percutaneous drainage of the abscess and antibiotics. This is the first documented report of KLAS described in Argentina, and may signal the emergence of this syndrome in South America.

Clinical and phenotypic differences between classic and hypervirulent Klebsiella pneumonia: an emerging and under-recognized pathogenic variant

The purpose of this study was to increase awareness, gain insight into acquisition, and assess the virulence of the hypervirulent (hypermucoviscous) clinical variant (hvKP) that is entrenched in the Pacific Rim but emerging in Western countries. A case of community-acquired liver abscess with metastatic spread to the spleen is described. Comparative in vitro and in vivo virulence studies on this isolate (hvKP1) and four randomly chosen blood isolates of "classic" K. pneumonia strains (cKP1-4) were performed. Cases of hvKP infection are occurring in Western countries and are under-recognized. A hypermucoviscous phenotype is a surrogate laboratory marker for this variant. The propensity of hvKP strains for metastatic spread in non-compromised hosts is both a defining and unusual trait. The mode of acquisition in the described case was unclear but potential means are discussed. hvKP1 was more resistant to complement and neutrophil-mediated bactericidal activity and was more virulent in a rat subcutaneous abscess model than cKP1-4. Recognition of the hypermucoviscous phenotype, defined by a positive "string-test", will alert the microbiologist or clinician that the infecting strain may be a hvKP, which is hypervirulent compared to cKP. This will improve our understanding of the epidemiology and clinical spectrum of infection, which may be more extensive than appreciated.

InvasiveKlebsiella pneumoniaeInfections, California, USA

Invasive<i>Klebsiella pneumoniae</i>Infections, California, USA

Hypermucoviscous Phenotype Expressed by an Isolate of Uropathogenic Escherichia coli: an Overlooked and Underappreciated Virulence Factor

Uropathogenic Escherichia coli (UPEC) strains are classified as extraintestinal pathogenic E. coli with a special predilection for the urinary tract. Among the virulence factors enabling urinary tract invasion are fimbriae, afimbrial adhesions, siderophores, and several secreted toxins. Biofilm formation and capsular K antigens also aid colonization of the urinary tract. This report describes perhaps the first documentation of a hypermucoviscous phenotype of a UPEC strain isolated from the urine of a 54-year-old patient with chronic emphysematous pyelonephritis leading to nephrectomy of his right kidney. Culture of the patient's urine grew highly viscous colonies which rendered a “stringing” phenomenon when an inoculating needle was passed through the colonies analogous to that produced by liver-invasive strains of Klebsiella pneumoniae. Stained preparations of colony teasings emulsified in India ink and examined microscopically (×1,000) revealed two distinct halos enveloping the bacillary form. The inner halo was indicative of a capsule, while the second viscous halo enveloped the entire complex. While mucoid E. coli strains have been isolated from various clinical specimens, none have been reported to have been tested for the stringing phenomenon indicative of the hypermucoviscous phenotype, which may be a common occurrence but overlooked as a distinctive virulence characteristic of UPEC strains.

Quand l’évolution de notre société fragilise la construction parentale : impacts sur la santé de l’enfant

In recent years, Klebsiella pneumoniae has emerged as a leading cause of nosocomial infection owing to the rising prevalence of multidrug-resistant strains, particularly carbapenem-resistant isolates. In this study, the complete genome sequence of carbapenem-resistant K. pneumoniae SWU01 was determined.Antimicrobial susceptibilities and hypermucoviscous phenotype were determined by the disk diffusion method and positive string test, respectively. Multilocus sequence typing (MLST) was performed using the K. pneumoniae MLST database, and capsular serotype was analysed using the BIGSdb-Kp database with the nucleotide sequence of the variable region (CD1-VR2-CD2) of wzc. The complete genome sequence was obtained via the PacBio RS II platform, and antimicrobial resistance genes were identified using ResFinder 2.1.SWU01 was resistant to all antibiotics tested except polymyxin B and minocycline. This strain showed a hypermucoviscous phenotype with serotype K47 belonging to the ST11 clone. The complete genome consists of a 5 536 506-bp circular chromosome and a 162 552-bp plasmid, with a G+C content of 57.4%. A total of 5537 protein-coding sequences, 85 tRNAs, 25 rRNAs, 12 non-coding RNA genes and 157 pseudogenes were identified in the genome. Thirteen acquired antibiotic resistance genes were detected (eight in the chromosome and five in the plasmid).Here we present the first whole-genome sequence of a carbapenem-resistant hypermucoviscous K. pneumoniae isolate SWU01 with capsular serotype K47 belonging to ST11 from a patient in China, which may serve as a reference sequence for further understanding of the pathogenesis and multidrug resistance mechanisms of this species.