Capsular Serotype K1 Research Articles

Prevalence of pathogenic Klebsiella pneumoniae based on PCR capsular typing harbouring carbapenemases encoding genes in Uganda tertiary hospitals

BackgroundKlebsiella pneumoniae is an opportunistic pathogen that has been implicated as one of commonest cause of hospital and community acquired infections. The K. pneumoniae infections have considerably contributed to morbidity and mortality in patients with protracted ailments. The capacity of K. pneumoniae to cause diseases depends on the presence of an array virulence factors. Coexistence and expression of virulence factors and genetic determinants of antibiotic resistance complicates treatment outcomes. Thus, emergence of pathogenic MDR K. pneumoniae poses a great threat to the healthcare system. However, the carriage of antibiotic resistance among pathogenic K. pneumoniae is yet to be investigated in Uganda. We sought to investigate the carbapenem resistance profiles and pathogenic potential based on capsular serotypes of K. pneumoniae clinical isolates.MethodsThis was a cross sectional study involving use of archived Klebsiella pneumoniae isolates collected between January and December, 2019 at four tertiary hospitals in Uganda. All isolates were subject to antimicrobial susceptibility assays to determine phenotypic antibiotic resistance, pentaplex PCR to detect carbapenemases encoding genes and heptaplex PCR to identify capsular serotypes K1, K2, K3, K5, K20, K54 and K57.ResultsThe study found an overall phenotypic carbapenem resistance of 23.3% (53/227) and significantly higher genotypic resistance prevalence of 43.1% (98/227). Over all, the most prevalent gene was blaOXA-48-like (36.4%), followed by blaIMP-type (19.4%), blaVIM-type (17.1%), blaKPC-type (14.0%) and blaNDM-type (13.2%). blaVIM-type and blaOXA-48-like conferred phenotypic resistance in all isolates and 38.3% of isolates that harbored them respectively. Capsular multiplex PCR revealed that 46.7% (106/227) isolates were pathogenic and the predominantly prevalent pathotype was K5 (18.5%) followed by K20 (15.1%), K3 (7.1%), K2 (3.1%) and K1 (2.2%). Of the 106 capsular serotypes, 37 expressed phenotypic resistance; thus, 37 of the 53 carbapenem resistant K. pneumoniae were pathogenic.ConclusionThe high prevalence of virulent and antibiotic resistant K. pneumoniae among clinical isolates obtained from the four tertiary hospital as revealed by this study pose a great threat to healthcare. Our findings underline the epidemiological and public health risks and implications of this pathogen.

First Report of an Extensively Drug-Resistant ST23 Klebsiella pneumoniae of Capsular Serotype K1 Co-Producing CTX-M-15, OXA-48 and ArmA in Spain.

An extensively drug-resistant (XDR) Klebsiella pneumoniae isolate MS3802 from a tracheostomy exudate was whole-genome sequenced using MiSeq and Oxford Nanopore MinION platforms in order to identify the antimicrobial resistance and virulence determinates and their genomic context. Isolate MS3802 belonged to the clone ST23 and presented a capsular serotype K1, associated with hypervirulent K. pneumoniae (hvKp) isolates. The isolate harboured a chromosomally encoded blaCTX-M-15 gene and contained a large IncHI1B hybrid virulence/resistance plasmid carrying another copy of the blaCTX-M-15 and the virulence factors iucABCD-iutA, iroBCDN, rmpA and rmpA2. The carbapenemase gene blaOXA-48 was found in a Tn1999-like transposon and the 16S rRNA methylase armA gen located in the vicinity of other antibiotic-resistant genes on an IncM2 plasmid. This study represents, to the best of our knowledge, the first description of a blaCTX-M-15-, blaOXA-48- and armA-harbouring K. pneumoniae of ST23 and capsular serotype K1 in Spain. Our report emphasizes the importance of implementing new surveillance strategies to monitor the risk of emergence and spread of such XDR and hypervirulent K. pneumoniae isolates.

Development of monospecific polyclonal antibodies against hypervirulent Klebsiella pneumoniae

Abstract. Darniati, Setiyaningsih S, Agungpriyono DR, Handharyani E. 2021. Development of monospecific polyclonal antibodies against hypervirulent Klebsiella pneumoniae. Biodiversitas 22: 99-105. The aim of the research was to produce monospecific antibodies against Klebsiella pneumoniae serotype K1 and K2. Klebsiella pneumonia isolates were recovered from pneumonic lungs of Aceh cattle. The bacteria were identified by rpoB (RNA polymerase β subunit) PCR amplification specific for K. pneumoniae. The presence of capsule cluster gene magA and k2A was used to characterize capsular serotype K1 and K2, respectively. Antisera were produced using serial immunization of New Zealand White rabbits with K. pneumoniae serotypes K1 and K2. The presence of antibodies was determined by using immunodiffusion test and purification was performed by immunoaffinity purification method. K. pneumoniae antibodies began to appear on the 14th day after the first injection and progressively intensified after the 1st and 2nd booster. The cross-reactivity between the antigen was eliminated by absorbing the antisera with the opposite antigen and several serotypes of non-K1/K2. After purification, serum protein concentrations were substantially decreased from 58.48 µg/µL and 53.99 µg/µL to 2.38 µg / µL and 3.72 µg / µL for K1 and K2, respectively). The SDS-PAGE analysis showed two bands with molecular weight at 54 kDa and 25 kDa representing the heavy and light chains of immunoglobulin G, respectively. Purified polyclonal antiseras against K. pneumoniae serotypes K1 and K2 showed high affinity and specificity for homologous antigens in immunodiffusion and direct agglutination tests, and immunohistochemical staining.

Clinical Features and Risk Factors Associated With 30-Day Mortality in Patients With Pneumonia Caused by Hypervirulent Klebsiella pneumoniae (hvKP).

BackgroundReports on metastatic or invasive infections by hypervirulent Klebsiella pneumoniae (hvKP) have increased recently. However, the effects of its virulence on clinical course and outcomes in pneumonia patients have rarely been addressed. We assessed and compared the clinical features of hvKp and classic K. pneumoniae (cKP) strains isolated from patients with pneumonia caused by K. pneumoniae. We also investigated the effects of virulence factors and the K. pneumoniae capsular serotypes K1 and K2 on mortality.MethodsIn this retrospective study, we enrolled 91 patients diagnosed as having pneumonia caused by K. pneumoniae and obtained their demographic and clinical data from medical records. We evaluated genes for K1 and K2, antimicrobial susceptibility, and the virulence genes rmpA, iutA, entB, ybtS, kfu, mrkD, and allS. Strains that possessed rmpA and iutA were defined as hvKP (N=39), while the remaining were classified as cKP (N=52). Odds ratio (OR) for the risk factors associated with 30-day mortality was calculated using the binary logistic regression model.ResultsThe 30-day mortality in all patients was 23.1%; it was 17.9% (7/39) in the hvKP group and 26.9% (14/52) in the cKP group (P=0.315). Bacteremia (OR=38.1; 95% confidence interval [CI], 2.5–570.2), altered mental status (OR=8.8; 95% CI, 1.7–45.0), and respiratory rate >30 breaths/min (OR=4.8; 95% CI, 1.2–20.0) were independent risk factors for 30-day mortality in all patients.ConclusionsOur results suggest that hypervirulence determinants do not have a significant effect on 30-day mortality in patients with pneumonia caused by K. pneumoniae.

Community-acquired infection caused by the uncommon hypervirulent Klebsiella pneumoniae ST66-K2 lineage.

Klebsiella pneumoniae (Kp) reference strain Kp52.145 is widely used in experimental Klebsiella pathophysiology. Since 1935, only one other strain of the same sublineage (sequence type ST66, capsular serotype K2) was isolated (AJ210, Australia). Here, we describe a community-acquired invasive infection caused by a ST66-K2 Kp strain in France. Four hypermucoviscous Kp isolates responsible for acute otitis media, meningitis, bacteraemia and bacteriuria, respectively, were obtained from a patient with a history of chronic alcoholism and diabetes mellitus, and infected with HIV. The isolates were characterized by phenotypic and genomic methods. The four genetically identical ST66-K2 isolates presented a full antimicrobial susceptibility profile, including to ampicillin, corresponding to a single strain (SB5881), which was more closely related to AJ210 (135 SNPs) than to Kp52.145 (388 SNPs). Colibactin and yersiniabactin gene clusters were present on the integrative and conjugative element ICEKp10 in the chromosome. The two plasmids from Kp52.145 were detected in SB5881. In addition to carrying genes for virulence factors RmpA, aerobactin and salmochelin, plasmid II has acquired in SB5881, the conjugation machinery gene cluster from plasmid I. We report the first case of community-acquired infection caused by a hypervirulent ST66-K2 Kp strain in Europe. This demonstrates the long-term persistence of the high-virulence and laboratory model ST66-K2 sublineage. The combination of a conjugative apparatus and major virulence genes on a single plasmid may contribute to the co-occurrence of hypervirulence and multidrug resistance in single Kp strains.

Development of risk factor-based scoring system for detection of hypervirulent Klebsiella pneumoniae bloodstream infections

BackgroundHypervirulent Klebsiella pneumoniae (HVKp) infections have distinct clinical manifestations from classical K. pneumoniae infections. The hallmark of HVKp infections are liver abscess formation and metastatic infections. Due to the severe sequelae of these complications, method to identify patients at-risk of HVKp infections should be developed.ResultsA retrospective cohort study of 222 patients with K. pneumoniae bloodstream infections (BSIs) was performed. Patient demographics, clinical manifestations, and bacterial characteristics were investigated. Ten cases of liver abscesses were identified. Characteristics such as community-onset BSIs, hypermucoviscosity phenotype, and capsular serotype K1 were identified as risk factors for HVKp infections. A scoring system was developed based on the risk factors. The area under the receiver operating characteristic curve for the scoring system was 0.90. A score of ≥ 2 points provided sensitivity and specificity of 0.70 and 0.94, respectively.ConclusionsSimple scoring system was developed for the diagnosis of HVKp infections. The system allows early identification of patients with K. pneumoniae BSIs in whom hypervirulent infections should be evaluated. Prospective evaluation is expected.

A Simple Scoring Algorithm That Predicts Abscesses in Adults with Community-Onset Klebsiella pneumoniae Bacteremia: Hypermucoviscosity Matters.

IntroductionKlebsiella pneumoniae is a pathogen commonly found in community-onset bacteremia. It causes an invasive syndrome that is frequently presented by metastatic infections and abscesses elsewhere and that is necessary for surgical or drainage intervention. To achieve a scoring algorithm to identify patients with community-onset K. pneumoniae bacteremia (CoKPB) who are at risk for abscess occurrences, a retrospective cohort study consisting of adults with CoKPB was conducted.MethodsA 6-year cohort study consisting of adults having community-onset monomicrobial K. pneumoniae bacteremia was conducted. In addition to clinical variables collected from medical records, the hypermucoviscosity (HMV)-related gene (rmpA and magA) and an HMV phenotype were integrated into the proposed scoring algorithm.ResultsOf the 258 eligible adults, only 79 (30.6%) had abscesses related to bacteremia. Besides the presence of magA (ie, capsular serotype K1) and the HMV-phenotype, five clinical predictors were significantly associated with abscesses in a multivariate analysis: male gender, comorbidities with diabetes mellitus or neurological disorders, recent chemotherapy, and high c-reactive protein levels. Together, these predictors were used to calculate the CoKPB abscess score. Based on the scoring algorithm, a cut-off value of +2 yielded the high sensitivity (93.7%) and the acceptable specificity (50.8%); the area under the ROC curve was 0.83.ConclusionA simple scoring algorithm that has substantial sensitivity and satisfactory specificity was proposed and the importance of the HMV phenotype or capsular K1 serotype was emphasized. The proposed predictive model needs external validation, but this scoring algorithm might be convenient and useful for clinicians.

Characteristics of Hypervirulent Klebsiella pneumoniae: Does Low Expression of rmpA Contribute to the Absence of Hypervirulence?

Multidrug-resistant hypervirulent Klebsiella pneumoniae (MDR-hvKP) has been increasingly reported and is now recognized as a significant threat to public health; however, characterization of MDR-hvKP has not been systematically investigated. In the present study, 124 of 428 (28.92%) K. pneumoniae clinical isolates collected from January 2010 to December 2016 were identified with aerobactin and defined as hvKP; these included 94 non-MDR-KP, 20 extended-spectrum β-lactamase-producing K. pneumoniae (ESBL-KP), and 10 carbapenem-resistant K. pneumoniae (CR-KP) isolates. The remaining 304 isolates without presence of virulence factor aerobactin were defined as classic K. pneumoniae (cKP). The antimicrobial resistance rate of cKP was significantly higher than that of the hvKP isolates in the non-MDR-KP group, but showed no significant differences in the ESBL-KP and CR-KP groups. The detection frequencies of capsular serotype K1 (magA), hypermucoviscosity, sequence type 23 (ST23), and the virulence gene rmpA were significantly higher in the hvKP than cKP isolates in all three groups (P < 0.05). Most of the hypervirulent ESBL-KP and CR-KP isolates were K non-typeable (16/30) and harbored at least one gene for virulence (26/30). The hypervirulent ESBL-KP isolates primarily carried blaCTX–M (12/20, 60%) genes, and the hypervirulent CR-KP isolates mainly carried blaNDM–1 (8/10, 80%) genes. Moreover, three hypervirulent ESBL-KP and two hypervirulent CR-KP isolates showed resistance to tigecycline but were sensitive to colistin. The transcriptional levels of rmpA in cKP were much lower than that in hvKP isolates in all three groups. Furthermore, overexpression of rmpA in the rmpA-low-expression cKP isolates could enhance bacterial virulence in the mouse infection experiment. In conclusion, our data suggest that the capsular serotype K1 (magA), rmpA, hypermucoviscosity, and ST23 were strongly associated with hvKP in non-MDR-KP, ESBL-KP, and CR-KP groups, and low rmpA expression levels contributed to the absence of hypervirulent phenotype.

Acquisition of Plasmid with Carbapenem-Resistance Gene blaKPC2 in Hypervirulent Klebsiella pneumoniae, Singapore.

The convergence of carbapenem-resistance and hypervirulence genes in Klebsiella pneumoniae has led to the emergence of highly drug-resistant superbugs capable of causing invasive disease. We analyzed 556 carbapenem-resistant K. pneumoniae isolates from patients in Singapore hospitals during 2010–2015 and discovered 18 isolates from 7 patients also harbored hypervirulence features. All isolates contained a closely related plasmid (pKPC2) harboring blaKPC-2, a K. pneumoniae carbapenemase gene, and had a hypervirulent background of capsular serotypes K1, K2, and K20. In total, 5 of 7 first patient isolates were hypermucoviscous, and 6 were virulent in mice. The pKPC2 was highly transmissible and remarkably stable, maintained in bacteria within a patient with few changes for months in the absence of antimicrobial drug selection pressure. Intrapatient isolates were also able to acquire additional antimicrobial drug resistance genes when inside human bodies. Our results highlight the potential spread of carbapenem-resistant hypervirulent K. pneumoniae in Singapore.

Hypervirulent Klebsiella pneumoniae serotype K1 clinical isolates form robust biofilms at the air-liquid interface.

The prevalence of a new hypervirulent and hypermucoviscous K. pneumoniae phenotype (Hmv) is increasing worldwide, mainly linked to serotypes K1 and K2. Since capsular thickness can directly affect the capability to form biofilms, we aimed to evaluate the association between the Hmv phenotype with adhesion and biofilm formation in a collection of clinical K. pneumoniae isolates.We selected 38 Hmv clinical isolates [15 serotype K1; 9 serotype K2; 3 non-K1/K2 (rmpA+); 11 non-K1/K2 (rmpA-)] and 7 non-Hmv clinical isolates. The Hmv phenotype was assessed through the mucoviscosity test. Serum resistance was determined by bacterial viability tests in pooled human serum. Adhesion was evaluated with the Biofilm Ring Test®, and biofilm formation was identified by crystal violet staining (Solid-Liquid, SLI-biofilm) or visual examination (Air-Liquid, ALI-biofilm).This study linked for the first time the formation of robust ALI-biofilm plugs by K. pneumoniae to the capsular serotype K1, a group of hypervirulent strains which are generally highly susceptible to the antimicrobial agents. Among all the studied isolates, the capsular serotype K1 presented lower initial adhesion despite having the adhesins mrkD and fimH but higher ALI-biofilm formation than isolates with other capsular serotypes (K2 or non-K1/K2). This structure might confer increased resistance to a group of hypervirulent K. pneumoniae serotype K1.

Virulence factors and clinical patterns of multiple-clone hypermucoviscous KPC-2 producing K. pneumoniae

Carbapenemase-producing Klebsiella pneumoniae (CRKP) are increasingly reported worldwide being necessary the local epidemiological monitoring. Our aim was to characterize the hypermucoviscous CRKP isolates collected in our hospital during a 6 months period. Carriage of the carbapenemase genes (blaKPC, blaNDM, blaVIM and blaOXA-48), extended spectrum β-lactamases (blaSHV-2, blaCTX-M) and the virulence genes (magA, k2A, rmpA, wabG, uge, allS, entB, ycfM, kpn, wcaG, fimH, mrkD, iutA, iroN, hly and cnf-1) were determined by multiplex-PCR. Genetic relationship among the isolates was performed by PFGE and MLST. A total of 35 isolates were recovered, being the urinary and respiratory tract the most common infection sites (34.2%). The blaKPC-2 gene was present in all the isolates, coexisting with blaCTX-M-2 (45.7%), blaSHV-2 (28.6%), and blaCTX-M-2/blaSHV-2 (14.3%). The capsular serotype K2 corresponded with 68.6% of the isolates. Virulence factors frequency were variable [adhesins (97.1%), siderophores (94.3%) and phagocytosis resistance (wabG 48.5%, uge 80% and ycfM 57.1%)]. A total of 10 STs were identified although 40% of them clustered on ST25-CC65, and 17% to ST17. The incidence of KPC-2-producing K. pneumoniae reported by the hospital was 0.290 per 1000 admissions. In summary we described an epidemic scenario of multidrug resistant hypermucoviscous KPC-2 producing ST25 K. pneumoniae in our institution.

Virulence and resistance determinants of Klebsiella pneumoniae isolated from a Portuguese tertiary university hospital centre over a 31-year period

IntroductionThe rapid and complex evolution of bacterial resistance mechanisms in Klebsiella pneumoniae producing extended-spectrum β-lactamases and carbapenemases in Klebsiella pneumoniae is one of the most significant threats to public health. However, questions and controversies regarding the interactions between resistance and virulence in multidrug-resistant K. pneumoniae isolates remain unclear. MethodsA retrospective cohort study was performed with 100 K. pneumoniae isolates recovered from a tertiary care university hospital centre in Lisbon over a 31-year period. Resistance and virulence determinants were screened using molecular methods (PCR, M13-PCR and MLST). ResultsThe predominant virulence profile (fimH, mrkDv1, khe) was shared by all isolates, indicative of an important role of type 1 and 3 fimbrial adhesins and haemolysin, regardless of the type of β-lactamase produced. However, accumulation of virulence factors was identified in KPC-3-producers, with a higher frequency (p<0.05) of capsular serotype K2 and iucC aerobactin when compared with non-KPC-3 β-lactamases or carbapenemases. Additionally, 9 different virulence profiles were found, indicating that the KPC-3 carbapenemase producers seem to adapt successfully to the host environment and maintain virulence via several pathways. ConclusionThis study describes an overlapping of multidrug-resistance and virulence determinants in ST-14K2 KPC-3 K. pneumoniae clinical isolates that may impose an additional challenge in the treatment of infections caused by this pathogen.

Whole genome assembly and functional portrait of hypervirulent extensively drug-resistant NDM-1 and KPC-2 co-producing Klebsiella pneumoniae of capsular serotype K2 and ST86.

To characterize an emergent carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) strain, NUHL30457, which co-produces NDM-1 and KPC-2 carbapenemases. We performed WGS analysis on a clinical carbapenemase-producing hypervirulent K. pneumoniae (CP-hvKP) strain NUHL30457. Sequence data were analysed using comparative genomics and phylogenetics. WGS was used to perform MLST, capsular genotyping and identification of virulence and antimicrobial resistance genes. The virulence of NUHL30457 was analysed by serum killing assay, neutrophil phagocytosis and mouse lethality assay. The NUHL30457 strain was carbapenem resistant and belonged to ST86 and serotype K2. A significant increase in resistance to serum killing and antiphagocytosis was found in the NUHL30457 strain compared with the reference strain. The murine lethality assay showed an LD50 of 2.5 × 102 cfu for the NUHL30457 strain, indicating hypervirulence. WGS revealed that NUHL30457 has a single 5.3 Mb chromosome (57.53% G + C content) and four plasmids in the range 49.2-215.7 kb. The incompatibility group (Inc)N plasmid p30457-4 carried the blaNDM-1 and qnrS1 genes. The IncFII(K) plasmid p30457-3 also carried an array of resistance elements, including blaCTX-M-65, blaTEM-1 and blaKPC-2. The IncHI1/IncFIB plasmid p30457-1, which carried virulence genes, was identical to a pLVPK plasmid reported previously. To the best of our knowledge, this is the first report to isolate an ST86 hvKP strain that co-produces NDM-1 and KPC-2 carbapenemase. Further investigation is required to reinforce our understanding of the epidemiology and virulence mechanisms of this clinically significant CP-hvKP.

Virulence Factors, Capsular Serotypes and Antimicrobial Resistance of Hypervirulent Klebsiella pneumoniae and Classical Klebsiella pneumoniae in Southeast Iran.

The present study was conducted to investigate the distribution of virulence factors, capsular serotypes and antibiotic resistance properties of classical Klebsiella pneumoniae (cKP) and hypermucoviscous/hypervirulent Klebsiella pneumoniae (hvKP) isolated from different clinical specimens in Kerman, south-east of Iran. A total of 146 K. pneumoniae isolates were obtained from different clinical specimens. HvKP isolates were identified using the string test. Genes of capsular serotypes K1, K2, K5, K20, K54 and K57 and virulence-associated genes, rmpA, kfu, fimH, mrkD, allS, iutA, magA, entB and ybtS were evaluated by PCR. Antimicrobial susceptibility was also determined using the disc diffusion method. Out of 146 K. pneumoniae isolates, 22 (15.1 %) were hvKP. More than half of the hvKP isolates, 13 (59.1%), belonged to non-K1, K2, K5, K20, K54, K57 serotypes. Out of 22 hvKP isolates, 3 and 3 had K1 and K2 serotypes respectively. Among all isolates, entB 140 (95.9%) and mrkD 138 (94.5%) were the most common virulence genes. RmpA, iutA and kfu were associated with hvKP isolates (P-value <0.05). However, no significant difference was found in fimH, allS, mrkD, entB and ybtS genes between hvKP and cKP strains. HvKP exhibited significantly lower resistance rates to all antimicrobial agents than cKP, except to trimethoprim-sulphamethoxazole and ampicillin (P-value <0.05). The frequency of hvKP was low, but overall, the prevalence of virulence-related genes was higher in hvKP than cKP. HvKP was not related to specific serotypes. Furthermore, hvKP isolates were more susceptible to antimicrobial agents compared to cKP isolates.

Virulence and resistance determinants of Klebsiella pneumoniae isolated from a Portuguese tertiary university hospital centre over a 31-year period

IntroductionThe rapid and complex evolution of bacterial resistance mechanisms in Klebsiella pneumoniae producing extended-spectrum β-lactamases and carbapenemases in Klebsiella pneumoniae is one of the most significant threats to public health. However, questions and controversies regarding the interactions between resistance and virulence in multidrug-resistant K. pneumoniae isolates remain unclear. MethodsA retrospective cohort study was performed with 100 K. pneumoniae isolates recovered from a tertiary care university hospital centre in Lisbon over a 31-year period. Resistance and virulence determinants were screened using molecular methods (PCR, M13-PCR and MLST). ResultsThe predominant virulence profile (fimH, mrkDv1, khe) was shared by all isolates, indicative of an important role of type 1 and 3 fimbrial adhesins and haemolysin, regardless of the type of β-lactamase produced. However, accumulation of virulence factors was identified in KPC-3-producers, with a higher frequency (p<0.05) of capsular serotype K2 and iucC aerobactin when compared with non-KPC-3 β-lactamases or carbapenemases. Additionally, 9 different virulence profiles were found, indicating that the KPC-3 carbapenemase producers seem to adapt successfully to the host environment and maintain virulence via several pathways. ConclusionThis study describes an overlapping of multidrug-resistance and virulence determinants in ST-14K2 KPC-3 K. pneumoniae clinical isolates that may impose an additional challenge in the treatment of infections caused by this pathogen.

Clinical and microbiological characteristics and occurrence of Klebsiella pneumoniae infection in Japan.

PurposeKlebsiella pneumoniae is a pathogen that causes pneumonia and urinary tract infection. Hypervirulent K. pneumoniae strains often show hypermucoviscosity, are of the K1 or K2 serotype, and harbor the rmpA and magA genes. However, the differences in the prevalence of K. pneumoniae with these hypervirulent characteristics between the infection and colonization status are not well understood. Therefore, in this study, we compared the clinical and microbiological characteristics of K. pneumoniae isolated from urine or sputum samples of cases of infection and colonization.Patients and methodsThis retrospective study was conducted at a tertiary care teaching hospital in Tokyo, Japan. Patients whose sputum or urine tested positive for the presence of K. pneumoniae isolates were randomly included in the study. Clinical and microbiological data were collected from medical records.ResultsOf the 130 cases investigated, 68 and 62 cases showed the presence of K. pneumoniae in the sputum and urine, respectively. There were 49 infection cases, including 21 in the sputum group and 28 in the urine group. The infections were not accompanied by liver abscess. Of the 130 K. pneumoniae isolates, 25 (19.2%) showed capsular serotype K1 or K2, whereas 33 (25.4%) showed hypermucoviscosity. The prevalence of virulence genes magA, allS, rmpA, mrkD, uge, kfu-BC, and wabG was 10% (all in K1), 13.1%, 16.9%, 85.4%, 79.2%, 36.9%, and 91.5%, respectively. In both the sputum and urine groups, there was no difference in the characteristics of patients with infection and those with colonization. Analysis of microbiological characteristics revealed that only rmpA was significantly more frequent in the infection cases than in the colonization/asymptomatic cases in both the sputum and urine groups.ConclusionThe rmpA-positive K. pneumoniae isolates were dominant in the infection cases compared with those in the colonization/asymptomatic cases, suggesting that rmpA may play a crucial role in the development of urinary tract infection and pneumonia.

Occurrence and characterization of hyperviscous K1 and K2 serotype in Klebsiella pneumoniae.

BACKGROUND:Klebsiella pneumoniae causes both nosocomial and community-associated infections. Hypervirulent K. pneumoniae (hvKP), new variant of K. pneumoniae, can cause invasive infections in young healthy individuals as well as in the immunocompromised population. Hypervirulent strains frequently belong to capsular serotypes K1 or K2. Emergence of antimicrobial resistance in hvKP is a cause for concern.AIM AND OBJECTIVE:The present study was done to detect the K1 and K2 serotypes among clinical isolates of K. pneumoniae, spectrum of infections caused by them and presence of common beta-lactamases encoding genes in them.MATERIALS AND METHODS:A total of 370 isolates of K. pneumoniae, isolated from various clinical samples over a period of 1 year was included in this study. Antibiotic susceptibility testing to various classes of antimicrobials was done as per Clinical and Laboratory Standard Institute guidelines. The presence of K2A (specific to serotype K2), magA (specific to serotype K1), and rmpA genes was detected by multiplex polymerase chain reaction (PCR). Extended-spectrum beta-lactamases (TEM, SHV, and CTX-M), plasmid-mediated AmpCs (MOX, CIT, DHA, ACC, EBC, and FOX), and carbapenemase genes (IMP, VIM, NDM, KPC, and OXA-48) were also determined by PCR.RESULTS:Among the 370 isolates, 8 harbored K2A gene and one harbored magA. rmpA gene was detected in three isolates along with K1 or K2 serotypes. Seven K2A-positive isolates were resistant to one or more classes of antimicrobials. The studied ESBL genes were present in four isolates. Two isolates harbored carbapenemase genes (NDM-1, OXA-48) along with ESBLs.CONCLUSION:K2 serotype is more prevalent among hvKP isolates. They can harbor ESBLs and Carbapenemase genes. K1 serotype is rather uncommon in K. pneumoniae. Acquisition of multidrug-resistant genes by these strains adds to their virulence and limits the treatment options.

Antimicrobial susceptibility and microbiological and epidemiological characteristics of hypermucoviscous Klebsiella pneumoniae strains in a tertiary hospital in Hangzhou, China.

Hypermucoviscous Klebsiella pneumoniae (HMKP) has been increasingly observed among clinical isolates. This study sought to examine the microbiological and epidemiological characteristics of HMKP strains in a tertiary hospital in Hangzhou, China. HMKP isolates were collected and were identified via matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). A string test was performed for the hypermucoviscous phenotype. Susceptibility to various antimicrobial agents was determined. Multilocus sequence typing (MLST), capsular serotypes and virulence-associated genes of HMKP isolates were assessed. A total of 42 HMKP strains with a positive string test were collected, of which 32 (76.2%) were carbapenem-susceptible HMKP (CS-HMKP) and 10 (23.8%) were carbapenem-resistant HMKP (CR-HMKP). CS-HMKP strains were more susceptible to antimicrobial agents than CR-HMKP strains. Capsular serotypes K1 (38.1%; 16/42) and K2 (11.9%; 5/42) were the main capsular serotypes of all HMKP isolates. K57 was first reported in CR-HMKP strains. ST163 was the main sequence type (37.5%; 12/32) among CS-HMKP strains, whilst ST11 was unique to CR-HMKP strains. The regulator of the mucoid phenotype A gene (rmpA) and other virulence factors (allS, kfu, iutA, entB, iroN, fimH and wabG) were present in >80% of HMKP strains. Patients with CR-HMKP strains had a higher mortality rate than those with CS-HMKP strains. Capsular serotypes K1 and K2 were the main capsular serotypes of the isolated HMKP strains. The emergence of CR-HMKP should be a concern as it was associated with an increased mortality rate, especially for ST11 CR-HMKP strains, demonstrating the global epidemic of carbapenem resistance.

Whole-Genome-Sequencing characterization of bloodstream infection-causing hypervirulent Klebsiella pneumoniae of capsular serotype K2 and ST374

ABSTRACT Hypervirulent K. pneumoniae variants (hvKP) have been increasingly reported worldwide, causing metastasis of severe infections such as liver abscesses and bacteremia. The capsular serotype K2 hvKP strains show diverse multi-locus sequence types (MLSTs), but with limited genetics and virulence information. In this study, we report a hypermucoviscous K. pneumoniae strain, RJF293, isolated from a human bloodstream sample in a Chinese hospital. It caused a metastatic infection and fatal septic shock in a critical patient. The microbiological features and genetic background were investigated with multiple approaches. The Strain RJF293 was determined to be multilocis sequence type (ST) 374 and serotype K2, displayed a median lethal dose (LD50) of 1.5 × 102 CFU in BALB/c mice and was as virulent as the ST23 K1 serotype hvKP strain NTUH-K2044 in a mouse lethality assay. Whole genome sequencing revealed that the RJF293 genome codes for 32 putative virulence factors and exhibits a unique presence/absence pattern in comparison to the other 105 completely sequenced K. pneumoniae genomes. Whole genome SNP-based phylogenetic analysis revealed that strain RJF293 formed a single clade, distant from those containing either ST66 or ST86 hvKP. Compared to the other sequenced hvKP chromosomes, RJF293 contains several strain-variable regions, including one prophage, one ICEKp1 family integrative and conjugative element and six large genomic islands. The sequencing of the first complete genome of an ST374 K2 hvKP clinical strain should reinforce our understanding of the epidemiology and virulence mechanisms of this bloodstream infection-causing hvKP with clinical significance.

Klebsiella pneumoniae in Singapore: Hypervirulent Infections and the Carbapenemase Threat.

Klebsiella pneumoniae remains a major pathogen responsible for localized infections such as cystitis and pneumonia, and disseminated infections that may result in severe sepsis and death. Invasive disease such as liver abscesses and endogenous endophthalmitis are associated with capsular serotypes K1 and K2. These infections require a prolonged course of antimicrobial treatment which has evolved over the years from inpatient treatment to outpatient parenteral antibiotic therapy. The emergence of plasmid-mediated resistance began with extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases. This was followed by carbapenemase genes and now plasmid transmissible colistin resistance (mcr), thus limiting viable treatment options. Plasmid-mediated carbapenemase production in Singapore was first reported in 1996. Carbapenemase production has since become the predominant mechanism of carbapenem resistance and incidence rates continue to increase over time. Although carbapenemases can occur in all Enterobacteriaceae, K. pneumoniae are the most common carrier of carbapenemase genes. Alternative treatment options are urgently required before the simplest infections, let alone invasive infections are left potentially untreatable. Clinical management requires guidance from robust laboratory testing methods to optimize patient outcomes. We explore past and present trends in treatment of K. pneumoniae infections, and discuss future treatment options and gaps in knowledge for further study.