Hypervirulent Klebsiella pneumoniae in Cryptogenic Liver Abscesses, Paris, France

Mobile genetic elements in Klebsiella pneumoniae

Klebsiella pneumoniae is a clinically important pathogenic bacteria that poses a serious threat to human health. In particular, the emergence of hypervirulent and multidrug-resistant K. pneumoniae has posed great challenges in clinical anti-infective therapy. In the K. pneumoniae genome, mobile genetic elements (MGEs), such as plasmids, prophages, transposons, and insertion sequences, enhance bacterial viability and adaptation by mediating the horizontal transfer of virulence genes, antibiotic resistance genes, and other adaptive genes. This paper reviews the types and characteristics of the main MGEs in K. pneumoniae, focusing on their effects on bacterial virulence and antibiotic resistance, with the aim of providing clues for developing infection control measures and new antibacterial drugs.

Diversity of hypervirulent Klebsiella pneumoniae clones causing cryptogenic liver abscesses and metastatic complications in Argentina

Cryptogenic liver abscesses (CLA) caused by hypervirulent Klebsiella pneumoniae (hvKP) strains are emerging in Western countries. The aim of the study was to describe the clinical characteristics of patients from Argentina with hvKP-related CLA as well as the molecular analysis of isolated strains. A retrospective chart review of 15 patients hospitalized in 8 hospitals of Argentina between October 2015 and November 2018 was performed. PCR assays for genes associated with capsular and multilocus sequence typing (MLST) determination and virulence factors were conducted in 8 hvKP isolates from these patients. We found that the mean age of patients was 60 years, 73% of them were men and 40% suffered from diabetes. Bacteremia was detected in 60% of them and 73% had ≥1 metastatic foci of infection. There were no in-hospital deaths, but two patients with endophthalmitis required eye enucleation. Of the 8 studied isolates, 4 belonged to K1 and 4 to K2 serotypes, with the rpmA and iroB genes being present in all of them, and isolates 7 and 5 also harboring the iucA and the rmpA2 genes, respectively. MSLT analysis showed that most of the K1 serotypes belonged to ST23 while a diverse MLST pattern was observed among the K2 strains. In addition, the four hvKP strains associated with metastatic complications and belonging to three distinct sequence types, exhibited the rpmA, iroB and iuc virulence genes. We were able to demonstrate important morbidity associated with this syndrome, a significant diversity in the hvKP clones causing CLA in Argentina, and the potential utility of the rpmA and iroB genes as predictors of virulence.

The pivotal role of IncFIB(Mar) plasmid in the emergence and spread of hypervirulent carbapenem-resistant Klebsiella pneumoniae

The hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) poses a substantial challenge to the global health care. However, the mechanism behind its evolution and transmission remain elusive. Here, four virulence plasmid types were identified from 310 hv-CRKP isolates collected nationwide during 2017-2018, based on their aerobactin (iuc locus) lineage and IncFIB replicons. Notably, pIUC1-IncFIB(K)37 and pIUC1-IncFIB(Mar), representing two epidemic virulence plasmids in Asia and Europe, respectively, accounted for >90% of the hv-CRKP episodes. Analysis of 494 K. pneumoniae isolates (376 from 2010-2013; 118 from 2017-2018) and 2578 public K. pneumoniae genomes indicated the notable role of IncFIB(Mar) plasmids in the hv-CRKP emergence and spread. Conjugation assays showed the helper IncFIB(Mar) plasmid could efficiently transfer into a hypervirulent strain and uniquely retromobilize with pIUC1-IncFIB(K)37 back into CRKP. Thereafter, the IncFIB(Mar) plasmid either lost rapidly or recombined with pIUC1-IncFIB(K)37, generating the hybrid pIUC1-IncFIB(Mar) plasmid. Our findings elucidated formation, evolution, and dissemination trajectories of the two major hv-CRKP strains in different regions.

Antimicrobial resistance in Klebsiella pneumoniae: an overview of common mechanisms and a current Canadian perspective

Klebsiella pneumoniae is a ubiquitous opportunistic pathogen of the family Enterobacteriaceae. K. pneumoniae is a member of the ESKAPEE pathogens (Enterococcus faecium, Staphylococcus aureus, K. pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp., and Escherichia coli), a group of bacteria that cause nosocomial infections and are able to resist killing by commonly relied upon antimicrobial agents. The acquisition of antimicrobial resistance (AMR) genes is increasing among community and clinical isolates of K. pneumoniae, making K. pneumoniae a rising threat to human health. In addition to the increase in AMR, K. pneumoniae is also thought to disseminate AMR genes to other bacterial species. In this review, the known mechanisms of K. pneumoniae AMR will be described and the current state of AMR K. pneumoniae within Canada will be discussed, including the impact of the coronavirus disease-2019 pandemic, current perspectives, and outlook for the future.

Genotypic characterization of hypervirulent Klebsiella pneumoniae (hvKp) in a tertiary care Indian hospital

Hypervirulent Klebsiella pneumoniae (hvKp) is an emerging pathogen and causes endophthalmitis, liver abscess, osteomyelitis, meningitis, and necrotizing soft tissue infections in both immunodeficient and healthy people. The acquisition of the antibiotic resistance genes of hvKp has become an emerging concern throughout the globe. In this study, a total of 74 K. pneumoniae isolates were collected and identified by VITEK2 and blaSHV gene amplification. Out of these, 18.91% (14/74) isolates were identified as hvKp by both phenotypic string test and genotypic iucA PCR amplification. The antibiotic susceptibility revealed that 57.14% (8/14) isolates were multidrug-resistant (MDR) and 35.71% (5/14) isolates were extremely drug-resistant (XDR). All the isolates were resistant to β-lactam, β-lactamase + inhibitor groups of antibiotics, and the least resistance to colistin. Of 14 hvKp isolates, all isolates are positive for iroB (100%), followed by iutA (92.85%), peg344 (85.71%), rmpA (57.14%), and magA (21.42%) genes. Among serotypes, K1 was the most prevalent serotype 21.4% (3/14), followed by K5 14.3% (2/14). The most common carbapenemase gene was blaOXA-48 (78.57%) followed by blaNDM (14.28%) and blaKPC (14.28%) which co-carried multiple resistance genes such as blaSHV (100%), blaCTX-M (92.85%), and blaTEM (78.57%). About 92.85% (13/14) of hvKp isolates were strong biofilm producers, while one isolate (hvKp 10) was the only moderate biofilm producer. The (GTG)5-PCR molecular typing method revealed high diversity among the hvKp isolates in the tertiary care hospital. Our findings suggest that MDR-hvKp is an emerging pathogen and a challenge for clinical practice. In order to avoid hvKp strain outbreaks in hospital settings, robust infection control and effective surveillance should be implemented.

Liver abscess in the caudate lobe caused by Klebsiella pneumoniae: a rare case report and literature review

BACKGROUND

K. pneumoniae liver abscess (KPLA) mostly involves the right lobe. We present a case of K. pneumoniae caudate liver abscess with invasive liver abscess syndrome (ILAS) was rarely identified.

CASE PRESENTATION

A 53-year-old man with elevated glycated hemoglobin with chills, rigors and a fever of five days. The patient presented with tachycardia and fever. Physical examination revealed tenderness over the right abdomen was elicited. In particular, the inflammatory markers were markedly elevated, and computerized tomography (CT) showed pulmonary abscess, pulmonary embolism and caudate liver abscess. The patient's sequential organ failure assessment (SOFA) score was 10 points. Klebsiella pneumoniae was isolated from sputum, urine and blood. With the suspicion of liver abscesses, ILAS and sepsis. The patient was successfully treated with antibiotics. He returned to close to his premorbid function.

CONCLUSION

K. pneumoniae caudate liver abscess was rare. This is the first detailed report of K. pneumoniae caudate liver abscess with invasive liver abscess syndrome. Patients with cryptogenic K. pneumoniae liver abscess are advised to undergo an examination of intestinal barrier function. The study indicates that in patients with K. pneumoniae liver abscess, a caudate liver abscess size of ≤ 9.86 cm² may be characteristic of those suitable for conservative treatment of invasive liver abscess syndrome.

Virulence Factors in Klebsiella pneumoniae: A Literature Review

Klebsiella pneumoniae, a member of the autochthonous human gut microbiota, utilizes a variety of virulence factors for survival and pathogenesis. Consequently, it is responsible for several human infections, including urinary tract infections, respiratory tract infections, liver abscess, meningitis, bloodstream infections, and medical device-associated infections. The main studied virulence factors in K. pneumoniae are capsule-associated, fimbriae, siderophores, Klebsiella ferric iron uptake, and the ability to metabolize allantoin. They are crucial for virulence and were associated with specific infections in the mice infection model. Notably, these factors are also prevalent in strains from the same infections in humans. However, the type and quantity of virulence factors may vary between strains, which defines the degree of pathogenicity. In this review, we summarize the main virulence factors investigated in K. pneumoniae from different human infections. We also cover the specific identification genes and their prevalence in K. pneumoniae, especially in hypervirulent strains.

Community-acquired Klebsiella pneumoniae pneumonia in ICU: a multicenter retrospective study

BACKGROUND

Alongside the recent worldwide expansion of hypervirulent Klebsiella pneumoniae (KP) infections, the available literature regarding cases of community acquired pneumonias (KP-CAP) remains scarce but reports a strikingly high and early mortality. We performed a retrospective multicenter study (7 ICU in France) between 2015 and 2019, comparing prognosis and severity of KP-CAP versus Streptococcus pneumoniae - CAP (SP-CAP).

METHODS

For each KP-CAP, three SP-CAP admitted in ICUs within the same center and within the same 6-month window were selected. When available, KP strains were studied, and bacterial virulence was genetically assessed for virulence factors. The primary outcome was in-hospital mortality. Associations between clinical outcomes and type of infection were tested using univariate and multivariate logistic regressions, adjusted for pairing variables.

RESULTS

Twenty-seven KP-CAP and 81 SP-CAP were included. Respective in-hospital mortality rates were 59% (n = 16) and 17% (n = 14, p < 0.001), despite adequate antibiotic therapy. KP-CAP median time from admission to death was 26.9 h [IQR 5.75-44 h] and were significantly associated with higher rates of multiple organ failures (93% vs. 42%, p < 0.001), disseminated intravascular coagulation (12% vs. 1.3%, p = 0.046), septic shock (median lactate on ICU admission 4.60 vs. 2.90 mmol/L, p = 0.030) and kidney failure (KDIGO-3: 87% vs. 44%, p < 0.001). Interestingly, alcoholism was the only identified predisposing factor of KP-CAP. Severity on ICU admission (2-fold higher for KP-CAP) was the only factor associated with mortality in a multivariate analysis.

CONCLUSION

We described a strong association between KP-CAP infection and higher and earlier mortality when compared to SP-CAP. Moreover, alcoholism was the sole predisposing factor associated with KP-CAP infection. These findings should raise awareness of clinicians involved in the management of severe CAP about this microbiological etiology. Future prospective studies are needed to confirm these results and to design strategies to improve the prognosis of such infections.

The Rapid Emergence of Hypervirulent Klebsiella Species and Burkholderia pseudomallei as Major Health Threats in Southeast Asia: The Urgent Need for Recognition as Neglected Tropical Diseases

The World Health Organization (WHO)'s list of neglected tropical diseases (NTDs) highlights conditions that are responsible for devastating health, social and economic consequences, and yet, they are overlooked and poorly resourced. The NTD list does not include conditions caused by Gram-negative bacilli (GNB). Infections due to GNB cause significant morbidity and mortality and are prevalent worldwide. Southeast Asia is a WHO region of low- and middle-income countries carrying the largest burden of NTDs. Two significant health threats in Southeast Asia are Burkholderia pseudomallei (causing melioidosis) and hypervirulent Klebsiella pneumoniae (HvKp). Both diseases have high mortality and increasing prevalence, yet both suffer from a lack of awareness, significant under-resourcing, incomplete epidemiological data, limited diagnostics, and a lack of evidence-based treatment. Emerging evidence shows that both melioidosis and HvKp are spreading globally, including in high-income countries, highlighting the potential future global threat they pose. In this article, we review both conditions, identifying current trends and challenges in Southeast Asia and areas for future research. We also argue that melioidosis and HvKp merit inclusion as NTDs, and that mandatory global surveillance and reporting systems should be established, and we make an urgent call for research to better understand, detect, and treat these neglected diseases.

Analysis of Plasmids of the Klebsiella pneumoniae Complex Carrying a Cluster of Aerobactin Synthesis Genes as Presented in International Databases

Background. Currently, it is customary to distinguish two pathotypes of Klebsiella pneumoniae — classical and hypervirulent, which have the ability to cause community-acquired infections in healthy people. It has been shown that an increase in virulence is associated with the acquisition of additional genetic material — a plasmid carrying a cluster of aerobactin genes. Aim. To assess the prevalence of the aforementioned virulent plasmids around the globe and in Russia in particular, as well as to identify their key genetic features. Materials and methods. Plasmid sequences were downloaded from PLSDB and BV-BRC databases, annotated with the Abricate and Kleborate programs; cluster analysis was performed using the mge-cluster program, and phylogenetic analysis was performed using the Parsnp program. Results. 296 plasmid sequences isolated from 23 countries from clinical isolates of K.pneumoniae between 2006 and 2021 with a peak in 2019 were analyzed, with more than half of the plasmids coming from China. More than 30 sequence types were identified, among which ST11 and ST23 were predominant. Replicon genes of the IncFIB group were identified in almost all plasmids studied. The pre dominant type of aerobactin in the studied sequences was the first type (iuc1); sequences with iuc3 and iuc5 were also identified. Salmochelin synthesis genes were identified in only 37.1% of sequences; the yersiniabactin cluster was identified in two plasmids from China. 32.1% of plasmids carried resistance genes, of which 7.4% carried extended-spectrum beta-lactase genes and 5% contained carbapenemase genes. Nine clusters of sequences were obtained; almost all plasmids from Russia were assigned to one cluster and were NDM-positive. Together with plasmids from other European countries (Great Britain, Norway, Czech Republic), they formed a separate branch on the phylogenetic tree. Conclusion. Virulent plasmids carrying the aerobactin synthesis gene cluster are distributed globaly, and almost a third of them also carry antibiotic resistance genes.

Infection with Carbapenem-resistant Hypervirulent Klebsiella Pneumoniae: clinical, virulence and molecular epidemiological characteristics

BACKGROUND

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) is gradually becoming the dominant nosocomial pathogens in the healthcare setting.

METHODS

A retrospective study was conducted on patients with CR-KP from July 2021 to May 2022 in a teaching hospital. We identified bacterial isolates, collected the clinical data, and performed antimicrobial susceptibility testing, hypermucoviscosity string test, antimicrobial and virulence-associated genotype, as well as multi-locus sequence typing. CR-hvKP was defined as the presence of some combination of rmpA and/or rmpA2 with iucA, iroB, or peg-344. SPSS was used for data analysis. Univariate logistic regression analyses were used for risk factor and all statistically significant variables were included in the multivariate model. Statistical significance was taken to be P < 0.05.

RESULTS

A total of 69 non-duplicated CR-KP isolates were collected, 27 of which were CR-hvKP. Out of the 69 CR-KP strains under investigation, they were distributed across 14 distinct sequence types (STs), wherein ST11 exhibited the highest prevalence, constituting 65.2% (45/69) of the overall isolates. The principal carbapenemase genes identified encompassed blakpc-2, blaNDM-1, and blaOXA-48, with blakpc-2 prevailing as the predominant type, accounting for 73.9% (51/69). A total of 69 CR-KP strains showed high resistance to common clinical antibiotics, with the exception of ceftazidime/avibactam. The ST11 (P = 0.040), ST65 (P = 0.030) and blakpc-2 ST11 clones (P = 0.010) were found to be highly related to hvKp. Regarding the host, tracheal intubation (P = 0.008), intracranial infection (P = 0.020) and neutrophil count (P = 0.049) were significantly higher in the patients with CR-hvKP. Multivariate analysis showed tracheal intubation to be an independent risk factor for CR-hvKP infection (P = 0.030, OR = 4.131). According to the clinical data we collected, tracheal intubation was performed mainly in the elderly with severe underlying diseases, which implied that CR-hvKP has become prevalent among elderly patients with comorbidities.

CONCLUSIONS

The prevalence of CR-hvKP may be higher than expected in the healthcare setting. CR-hvKP is gradually becoming the dominant nosocomial pathogen, and its prevalence and treatment will be a major challenge. It is essential to enhance clinical awareness and management of CR-hvKP infection.

Rare Hypermucoviscous Klebsiella pneumoniae Liver Abscess in an Active Duty Male Requiring Partial Liver Resection for Definitive Treatment

Antibiotics and drainage have largely replaced hepatic resection for the treatment of liver abscesses in the modern era; however, in cases caused by a rare strain of Klebsiella pneumoniae with a hypermucoviscous phenotype, more aggressive hepatic resection may be required. The patient is a 34-year-old male who presented to Landstuhl Regional Medical Center with a week of epigastric pain. His workup revealed a 6 cm liver abscess with growth to 10 cm in 48 hours. He underwent multiple drainage procedures at Landstuhl and then was transferred to Walter Reed where further surgical drainage was performed. Initial cultures demonstrated K. pneumoniae. He clinically improved and was able to discharge after a 2 week hospitalization. His final remaining surgical drain was removed as an outpatient, but 48 hours after removal, he was admitted to the intensive care unit in septic shock. Imaging revealed a 12 cm liver abscess, and cultures verified hypermucoviscous Klebsiella. After multidisciplinary discussion and counseling, he underwent an open right partial hepatectomy. Postoperatively he gradually recovered from his sepsis and major operation and then returned to his home in Landstuhl. This is a case of a rare hypermucoviscous variant of K. pneumoniae causing a liver abscess resistant to multiple drainage procedures, ultimately requiring open hepatic surgical resection for source control. This remains a last-resort option in the treatment of liver abscesses and should be considered early when caused by this rare strain of Klebsiella.

Detection and characterization of putative hypervirulent Klebsiella pneumoniae isolates in microbiological diagnostics

Hypervirulent Klebsiella pneumoniae strains (hvKp) can cause invasive community-acquired infections in healthy patients of all ages. In this study, the prevalence of putative hvKp in a German tertiary center was investigated and hvKp were characterized by phenotypic and molecular assays. All K. pneumoniae isolates in routine microbiological diagnostics from a single center were screened by string-testing over a period of 6 months. String-test positive (≥ 0.5 mm) isolates were re-evaluated on different media and under various conditions (aerobe, anaerobe). For string-test positive isolates, genes (magA, iutA, rmpA and rmpA2) associated with hypermucoviscosity and hypervirulence were amplified by multiplex PCR. PCR-positive isolates were subjected to whole-genome sequencing and sedimentation and biofilm formation assays. From 1310 screened K. pneumoniae isolates in clinical routine 100 isolates (7.6%) were string test positive. From these, 9% (n = 9) were defined as putative hvKp (string-test+/PCR+). Highest rate of string-test-positive isolates was observed on MacConkey agar under aerobic conditions. Amongst these nine putative hvKp isolates, the international lineage ST23 carrying hvKp-plasmid pKpVP-1 was the most common, but also a rare ST86 with pKpVP-2 was identified. All nine isolates showed hypermucoviscosity and weak biofilm formation. In conclusion, 9% of string-positive, respectively 0.69% of all K. pneumoniae isolates from routine were defined as putative hypervirulent. MacConkey agar was the best medium for hvKp screening.

Prevalence of multidrug-resistant hypervirulent Klebsiella pneumoniae without defined hypervirulent biomarkers in Anhui, China: a new dimension of hypervirulence

Klebsiella pneumoniae is an opportunistic pathogen that mainly causes nosocomial infections and hospital-associated pneumonia in elderly and immunocompromised people. However, multidrug-resistant hypervirulent K. pneumoniae (MDR-hvKp) has emerged recently as a serious threat to global health that can infect both immunocompromised and healthy individuals. It is scientifically established that plasmid-mediated regulator of mucoid phenotype genes (rmpA and rmpA2) and other virulence factors (aerobactin and salmochelin) are mainly responsible for this phenotype. In this study, we collected 23 MDR-hvKp isolates and performed molecular typing, whole genome sequencing, comparative genomic analysis, and phenotypic experiments, including the Galleria mellonella infection model, to reveal its genetic and phenotypic features. Meanwhile, we discovered two MDR-hvKp isolates (22122315 and 22091569) that showed a wide range of hypervirulence and hypermucoviscosity without rmpA and rmpA2 and any virulence factors. In phenotypic experiments, isolate 22122315 showed the highest hypervirulence (infection model) with significant mucoviscosity, and conversely, isolate 22091569 exhibited the highest mucoviscosity (string test) with higher virulence compared to control. These two isolates carried carbapenemase (blaKPC - 2), β-lactamase (blaOXA - 1, blaTEM - 1B), extended-spectrum β-lactamase (ESBL) genes (blaCTX - M - 15, blaSHV - 106), outer membrane protein-coding genes (ompA), fimbriae encoding genes (ecpABCDER), and enterobactin coding genes (entAB, fepC). In addition, single nucleotide polymorphism analysis indicated that both isolates, 22122315 and 22091569, were found to have novel mutations in loci FEBNDAKP_03184 (c. 2084A > C, p. Asn695Thr), and EOFMAFIB_02276 (c. 1930C > A, p. Pro644Thr), respectively. Finally, NCBI blast analysis suggested these mutations are located in the wzc of the capsule polysaccharide (cps) region and are responsible for putative tyrosine kinase. This study would be a strong reference for enhancing the current understanding of identifying the MDR-hvKp isolates that lacked both mucoid regulators and virulence factors.

[Clinical and radiological differences between amoebic and pyogenic liver abscess: A case-control study]

INTRODUCTION

Amoebic liver abscess (ALA) is the fourth cause of mortality by parasitic infection. This study aimed to assess clinical, radiological and therapeutic characteristics of patients admitted for amoebic liver abscess compared to pyogenic abscess in a French digestive tertiary care-centre.

MATERIAL AND METHOD

The charts of patients hospitalized for a liver abscess between 2010 and 2020 were retrospectively assessed then separated in two groups: amoebic liver abscess and pyogenic liver abscess from portal underlying cause. Clinical and radiological data were collected for univariate comparison.

RESULTS

Twenty-one patients were hospitalized during the time of the study for ALA, and 21 patients for pyogenic liver abscess with a portal mechanism. All patients hospitalized for ALA lived in and/or had travelled recently in an endemic area. In comparison with patients hospitalized for pyogenic abscess, patients admitted for ALA were younger (44years old vs. 63years old, P<0.001), had less comorbidities (5% vs. 43% of patients with at least one comorbidity, P<0.01), a longer median duration of symptoms (10days vs. 3days, P=0.015), abdominal pain (86% vs. 52%, P=0.019), and a slighter leucocytosis (9600G/L vs. 15,500G/L, P=0.041) were more frequent. On the abdominal tomodensitometry, density of ALA was higher (34 vs. 25 UH, P<0.01), associated with a focal intra-hepatic biliary dilatation and less often multiloculated.

CONCLUSION

While rare in western countries, amoebic liver abscess care should not be underestimated. The presence of a solitary liver abscess of intermediate density on computed tomography, occurring on a patient returning from an endemic zone should lead the physician to a possible diagnosis of ALA.

Clinical Spectrum and Outcomes of Cryptogenic Klebsiella pneumoniae Liver Abscess in the Americas: A Scoping Review

(1) Background: Cryptogenic Klebsiella pneumoniae liver abscesses are an invasive infection with or without extra hepatic involvement in the absence of hepatobiliary disease or abdominal malignancy. Most of the evidence has emanated from reports from Asia, and previous studies in the Americas have limited clinical characterization. (2) Methods: To understand this syndrome's characteristics on our continent, we conducted a scoping review to identify adult cases of idiopathic, community-acquired monomicrobial K. pneumoniae liver abscess in the Americas. (3) Results: We identified 144 cases spanning 1978-2022. Most cases were reported in males that had traveled or migrated from Southeast or East Asia with diabetes mellitus. Extrahepatic involvement and bacteremia were common, including seeding to the lungs, ocular structures, and central nervous system. Although limited by sample size, the most commonly reported genes were magA or rmpA. Concomitant percutaneous drainage and third generation cephalosporins (alone or in combination with other antibiotics) were frequently used, yet pooled fatality occurred in 9% of the reported cases. (4) Conclusions: The features of cryptogenic K. pneumoniae liver abscess in the Americas mirror those described in Asia, confirming its global dissemination. This condition is increasingly being reported in our continent and carries significant clinical impact due to its systemic invasiveness.

First Italian report of a liver abscess and metastatic endogenous endophthalmitis caused by ST-23 hypervirulent Klebsiella pneumoniae in an immunocompetent individual

BACKGROUND

Klebsiella pneumoniae is a common species in the gut of mammals and is widely distributed in the environment. However, the environmental source of hvKp that precedes gut colonization is unclear, but once that it reaches the gut there is a possible generalized spread y fecal-oral transmission especially in endemic areas. Liver abscess might develop when the bacteria, using its virulence factors, cross the intestinal barrier and invade the liver by the portal circulation. This syndrome, prevalent mostly in Asian countries, is increasingly reported in Western Countries and leaves open questions about the source of infection.

CASE

Here we describe for the first time in Italy, a case of pyogenic liver abscess caused by a hypervirulent Klebsiella pneumoniae (HvKp) complicated by endophthalmitis and other metastatic infections in lung and prostate in an immunocompetent Chinese healthy individual with no recent travel in Asia.

CONCLUSION

This case underlines the need for increased awareness of hypervirulent K. pneumoniae, even in settings where it occurs infrequently and where there are not evident epidemiological links.

A typical multisite invasive infection caused by hvKP: A case report and literature review

RATIONALE

Hypervirulent K. pneumoniae (hvKP) is a new variant of K. pneumoniae that can caused metastatic spreading by blood, including Splenic abscess, endogenous endophthalmitis, purulent meningitis. This report described a case of A typical multisite invasive infection caused by hvKP and carry out a historical review of the literature.

PATIENT CONCERNS

A 55-year-old man was referred to our hospital due to liver abscess. Diabetes was found during this hospitalization. Because of glycemic was uncontrolled, splenic abscess, endogenous endophthalmitis and purulent meningitis occurred during subsequent treatment.

DIAGNOSES

We made s diagnosis of liver abscess and invasive K. pneumoniae liver abscess syndrome through generation sequencing and imaging features.

INTERVENTIONS AND OUTCOMES

The patient recovered and was subsequently discharged after mechanical ventilation, continuous renal replacement therapy, laparoscopic exploration and various antimicrobials.

LESSONS

HvKP are very aggressive and can disseminate to multiple sites, especially in patient who have diabetes, which is a treatment challenge for clinician.

The making of hypervirulent Klebsiella pneumoniae

Klebsiella pneumoniae is a notorious bacterium in clinical practice. Virulence, carbapenem-resistance and their convergence among K. pneumoniae are extensively discussed in this article. Hypervirulent K. pneumoniae (HvKP) has spread from the Asian Pacific Rim to the world, inducing various invasive infections, such as pyogenic liver abscess, endophthalmitis, and meningitis. Furthermore, HvKP has acquired more and more drug resistance. Among multidrug-resistant HvKP, hypervirulent carbapenem-resistant K. pneumoniae (Hv-CRKP), and carbapenem-resistant hypervirulent K. pneumoniae (CR-HvKP) are both devastating for their extreme drug resistance and virulence. The hypervirulence of HvKP is primarily attributed to hypercapsule, macromolecular exopolysaccharides, or excessive siderophores, although it has many other factors, for example, lipopolysaccharides, fimbriae, and porins. In contrast with classical determination of HvKP, that is, animal lethality test, molecular determination could be an optional and practical method after improvement. HvKP, including Hv-CRKP and CR-HvKP, has been progressing. R-M and CRISPR-Cas systems may play pivotal roles in such evolutions. Hv-CRKP and CR-HvKP, in particular the former, should be of severe concern due to their being more and more prevalent.

Microevolution of CG23-I Hypervirulent Klebsiella pneumoniae during Recurrent Infections in a Single Patient

CG23-I lineage constitutes the majority of hypervirulent Klebsiella pneumoniae. A diabetic patient suffered six episodes of infections caused by CG23-I K. pneumoniae. A total of nine isolates were collected in 2020. We performed whole-genome sequencing to elucidate the within-patient evolution of CG23-I K. pneumoniae. The maximum pairwise difference among the nine longitudinally collected isolates was five single nucleotide polymorphisms. One of the mutations was at the Asp87 position of GyrA. Four indels were identified, including an initiator tRNAfMet duplication, a tRNAArg deletion, a 7-bp insertion, and a 22-bp deletion. All 9 isolates had the genomic features of CG23-I K. pneumoniae, a chromosome-borne ICEKp10, and a large virulence plasmid. The carriage of a complete set of genes for the biosynthesis of colibactin by ICEKp10 gave the nine isolates an ability to cause DNA damage to RAW264.7 cells. Compared with the initial isolate, the last isolate with an additional copy of initiator tRNAfMet grew faster in a nutrient-limiting condition and exhibited enhanced virulence in BALB/c mice. Collectively, we characterized the within-patient microevolution of CG23-I K. pneumoniae through an in-depth comparison of genome sequences. Using the in vitro experiments and mouse models, we also demonstrated that these genomic alterations endowed the isolates with advantages to pass through in vivo selection. IMPORTANCE CG23-I is a significant lineage of hypervirulent Klebsiella pneumoniae. This study characterizes the within-patient microevolution of CG23-I K. pneumoniae. Selective pressures from continuous use of antibiotics favored point mutations contributing to bacterial resistance to antibiotics. The duplication of an initiator tRNAfMet gene helped CG23-I K. pneumoniae proliferate to reach a maximal population size during infections. For longer persistence inside a human host, the large virulence plasmid evolved with more flexible control of replication through duplication of the iteron-1 region. With the genomic alterations, the last isolate had a growth advantage over the initial isolate and exhibited enhanced virulence in BALB/c mice. This study gives us a deeper understanding of the genome evolution during the within-patient pathoadaptation of CG23-I K. pneumoniae.

Clinical and genomic characterization of hypervirulent Klebsiella pneumoniae (hvKp) infections via passive surveillance in Southern California, 2020–2022

Hypervirulent Klebsiella pneumoniae (hvKp) is more invasive and virulent than classical K. pneumoniae, and requires specialized treatment. To raise clinical awareness, this study determined the prevalence, clinical characteristics, and genomic epidemiology of hvKp infections in Southern California (SoCal) by conducting a passive surveillance in a single large academic medical center. We report here that hvKp infections were more common than expected, accounting for 2.6% of invasive K. pneumoniae infections, and presented with a wide disease spectrum, occasionally mimicking tumors, even co-infecting a COVID-19 patient. Most infections were community acquired with no recent international travel, suggesting hvKp strains are circulating in the community. Genomic analysis revealed genetic diversity, with the K1-ST23 lineage predominating but not clonal, and multiple sequence types of K2 including a SoCal unique K2-ST66 sublineage that had been unrecognized. Our findings highlight the urgency of heightened awareness of hvKp infection in the US, the need for rapid diagnosis of hvKp, and the necessity of implementing robust surveillance programs for hvKp at the institutional or local level.

Emergence of K1 ST23 and K2 ST65 hypervirulent klebsiella pneumoniae as true pathogens with specific virulence genes in cryptogenic pyogenic liver abscesses Shiraz Iran

Hypervirulent Klebsiella pneumoniae (hvKp) pathotype is emerging worldwide in pyogenic liver abscesses (PLAs). However, the role of virulence factors in pathogenicity remains unclear. On the other hand, the epidemiology of PLAs in Iran is unknown. From July 2020 to April 2022, bacterial species were isolated and identified from the drainage samples of 54 patients with PLAs. K. pneumoniae as the most common pathogen of pyogenic liver abscesses was identified in 20 (37%) of the 54 patients. We analyzed the clinical and microbiological characteristics of K. pneumoniae-related pyogenic liver abscesses. Antibiotic susceptibility testes and string test were performed. 16S rRNA, antibiotic resistance, and virulence genes were determined by polymerase chain reaction amplification. Clonal relatedness of isolates was identified by multilocus sequence typing. Virulence levels were assessed in the Galleria mellonella larval infection model. Four hvKp isolates (K1/K2) were found to be responsible for cryptogenic PLAs, and 16 classical K. pneumoniae isolates (non-K1/K2) were associated with non-cryptogenic PLAs. Three capsular serotype K1 strains belonged to sequence type 23 (ST23) and one K2 strain to ST65. Meanwhile, the non-K1/K2 strains belonged to other STs. ST231 was the most common strain among the classical K. pneumoniae strains. Compared with the non-K1/K2 strains, capsular serotypes K1/K2 strains were less resistant to antibiotics, had positive string test results, and had more virulence genes. In Galleria mellonella, a concentration of 10⁶ colony-forming units of the K1 hvKp strain resulted in 100% death at 24 hours, confirming the higher virulence of the hvKp strain compared with cKp. K. pneumoniae isolates represented that the acquisition of any plasmid or chromosomal virulence genes contributes to pathogenicity and high prevalence in PLAs. Meanwhile, hvKp isolates with a specific genetic background were detected in cryptogenic PLAs.

Hypervirulent Klebsiella Pneumoniae, an Emerging Cause of Endogenous Endophthalmitis in A French Center: A Comparative Cohort Study

INTRODUCTION

Klebsiella pneumoniae (KP) is the most common cause of endogenous endophthalmitis (EE) in Asia, but data in Europe are scarce. We describe eight cases of KP EE compared to a cohort of EE in a French center.

METHODS

EE cases were retrospectively studied between January 2014 and January 2021. KP EE cases were analyzed to assess clinical, microbiological features, and outcome.

RESULTS

Among the 33 EE cases identified, the first causative agent (24%, n = 8) was KP, mainly (7/8) with hypervirulent phenotype (hvKP). All but one of these cases occurred from December 2019 to January 2021. Contrary to non-KP patients, KP patients had multiple extraocular infective foci (p = .006), all presented with liver abscesses (p < .001), 50% had cerebral involvement (p = .13). Visual outcome was poor in both groups.

CONCLUSION

KP is an emerging cause of EE in a French center, consistently associated with liver abscesses, frequent cerebral involvement, and predominance of hvKP strains.

Large retrospective study analysing predictive factors of primary treatment failure, recurrence and death in pyogenic liver abscesses

PURPOSE

Pyogenic liver abscess (PLA) is a severe disease, which unfavourable evolution remains frequent. Our objective was to assess predictive factors of unfavourable outcome in patients with PLA.

METHODS

We conducted a retrospective study in a French tertiary care centre. All patients admitted for PLA between 2010 and 2018 were included. Unfavourable course was defined as the occurrence of a primary treatment failure (PTF), recurrence of PLA after an initial cure, or death within 3 months after diagnosis. Hazard ratios (95% CI) were calculated with multivariable Cox proportional hazard models.

RESULTS

302 patients were included among which 91 (30.1%) patients had an unfavourable outcome because of PTF, recurrence or death in 55 (18.2%), 28 (9.2%) and 32 (10.6%) patients, respectively. Hepatic metastases (HR 2.08; 95% CI 1.04-4.15), a nosocomial infection (2.25; 1.14-4.42), portal thrombosis (2.12; 1.14-3.93), and the isolation of Enterococcus spp. (2.18; 1.22- 3.90) were independently associated with PTF. Ischemic cholangitis (6.30; 2.70-14.70) and the isolation of Streptococcus spp. (3.72; 1.36-10.16) were associated with the risk of recurrence. Charlson comorbidity index (HR 1.30 per one point; 95% CI 1.15-1.46; p < 0.001), portal thrombosis (3.53; 1.65-7.56) and the presence of multi-drug-resistant organisms (3.81; 1.73-8.40) were associated with mortality within 3 months following PLA diagnosis. PLA drainage was the only factor associated with a lower mortality (0.14; 0.06-0.34).

CONCLUSION

Identification of specific risk factors may help to improve the management of PLA and to elaborate targeted recommendations according to patient's and disease's characteristics.

Emergence of Hypervirulent ST11-K64 Klebsiella pneumoniae Poses a Serious Clinical Threat in Older Patients

The carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) poses a severe therapeutic challenge to global public health, and research on CR-hvKP in older patients remain limited. In this study, we aimed to investigate the clinical and molecular characteristics and risk factors of CR-hvKP infections in older patients. We retrospectively investigated older patients with carbapenem-resistant Klebsiella pneumoniae (CRKP) infections in the intensive care unit (ICU) between January 2020 and December 2020. The clinical data, and microbiological data including antimicrobial susceptibility testing, phenotype experiment and detection of carbapenemases, string test, virulence genes, capsular serotype-specific (cps) genes, and multilocus sequence typing, of the CR-hvKP group defined by the presence of any one of the virulence genes, including rmpA, rmpA2, iucA, iroN, and peg-344 were compared with those of CR-non-hvKP strains. Of the 80 CRKP strains, 51 (63.8%) met the definition of CR-hvKP. The main mechanism of resistance to carbapenems was the presence of the bla_KPC−2 gene. Sequence type (ST)11 (81.3%, 65/80) and ST15 (16.3%, 13/80) were the most common STs in CRKP strains. The minimum inhibitory concentration (MIC)₅₀ values of the CR-hvKP group against the six tested antibiotics (ceftazidime, ceftazidime-avibactam, imipenem-avibactam, tigecycline, levofloxacin, and Cefoperazone-Sulbactam) exhibited elevated levels than the CR-non-hvKP group. Ceftazidime and imipenem by combining avibactam (4 μg/mL) significantly decreased the MIC₉₀ values more than 16-fold than ceftazidime and imipenem alone against Klebsiella pneumoniae carbapenemase (KPC)-2-producing K. pneumoniae. Cardiovascular disease [odds ratio (OR) = 11.956] and ST11-K64 (OR = 8.385) appeared to be independent variables associated with CR-hvKP infection by multivariate analysis. In conclusion, higher MICs of the last line antibiotic agents (ceftazidime-avibactam, tigecycline) might be a critical consideration in the clinical management of older patients where the concentration of these toxic antibiotics matters because of underlying comorbidities. Caution regarding KPC-2-producing ST11-K64 CR-hvKP as being new significant “superbugs” is required as they are widespread, and infection control measures should be strengthened to curb further dissemination in nosocomial settings in China.

Spontaneous and postsurgical/traumatic Klebsiella pneumoniae meningitis: two distinct clinico-microbiological entities

OBJECTIVES

To analyze and compare the characteristics and outcomes of spontaneous meningitis (SM) versus postsurgical/traumatic meningitis (PSTM) due to Klebsiella pneumoniae.

METHODS

A retrospective multicentric cohort study of all K. pneumoniae meningitis cases managed between January 2007 and May 2018 was carried out in seven university hospitals in the Paris area. The microbiological characteristics of 16 available K. pneumoniae isolates were further analyzed, and the genomes of seven of those isolated from SM were sequenced.

RESULTS

Among 35 cases, 10 were SM and 25 were PSTM. SM cases more severe than PSTM cases, with higher septic shock (p = 0.004) and in-hospital mortality rates (p = 0.004). In contrast, relapse occurred in five patients from the PSTM group versus no patients from the SM group. All K. pneumoniae strains recovered from SM but none of those recovered from PSTM displayed hypervirulent phenotypic (positive string test) and genotypic (genes corresponding to capsular serotypes K1 or K2; virulence genes rmpA and iutA) characteristics (p < 0.0001). PSTM tended to be more frequently polymicrobial (p = 0.08) and caused by an extended-spectrum β-lactamase producing strain (p = 0.08) than SM.

CONCLUSIONS

SM and PSTM are two entities differing both from a clinical and a microbiological standpoint. SM appears to be a more serious infection, induced by hypervirulent K. pneumoniae strains.

Molecular epidemiology of hypervirulent Klebsiella pneumoniae: a systematic review and meta-analysis

Classical (CKp) and hypervirulent (hvKp) Klebsiella pneumoniae are two different circulating pathotypes. The aim of this study was to assess the prevalence, epidemiology and molecular relatedness of hvKps using a systemic review and meta-analysis. The data extracted from Medline, Embase, and Web of Science and finally 14 studies met the eligible criteria. To combine prevalence proportions of all studies, we performed the metaprop command embedded in the Meta package software. Totally, of 1814 K. pneumoniae isolates, 21.7% (394/1814) were hvKp. The molecular typing showed that all hvKp isolates were grouped into 50 different sequence types (STs) of them ST23, ST11, ST65 and ST86 were common. K1, K2 and K64 were dominant capsule serotypes that strongly related to ST23, ST65 and ST11, respectively. It seems that clonal group 23 (CG23) is associated with liver abscess and CG11 related to various clinical sources.

Detection of extensively drug-resistant and hypervirulent Klebsiella pneumoniae ST15, ST147, ST377 and ST442 in Iran

In this study, we focused on the emergence of extensively drug-resistant (XDR), pandrug-resistant (PDR), and hypervirulent Klebsiella pneumoniae (hvKP) in Iran. During 2018 to 2020 a total of 52 K. pneumoniae isolates were collected from different clinical specimens. The hvKP isolates were identified by PCR amplification of virulence and capsular serotype-specific genes. Hypermucoviscous K. pneumoniae (hmKP) were identified by string test. Carbapenem-resistant hvKP (CR-hvKP), multidrug-resistant hvKP (MDR-hvKP), extensively drug-resistant hvKP (XDR-hvKP), and pandrug-resistant hvKP (PDR-hvKP) were determined by disc diffusion method, Carba-NP test and PCR method. XDR-hvKP isolates were typed by multilocus sequence typing (MLST). Among all K. pneumoniae isolates 14 (26.9%) were identified as hvKP and 78.6% (11/14) of them were hmKP however, none of the classic K. pneumoniae (cKP) isolates were hmKP. The predominant capsular serotype of hvKP was K2 (42.85%) followed by K1 (35.71%). The prevalence of MDR-hvKP, XDR-hvKP and PDR-hvKP isolates were 6 (42.9%), 5 (35.7%) and 1 (7.1%), respectively. ESBL production was found in 85.7% of hvKP isolates and most of them carried bla TEM gene (78.6%) and 6 isolates (42.9%) were CR-hvKP. Among hvKP isolates, 1 (7.1%), 2 (14.3%), 3 (21.4%), 8 (28.6%), and 11 (78.6%) carried bla NDM-6, bla OXA-48, bla CTX-M, bla SHV, and bla TEM genes, respectively. According to MLST analysis, 2, 1, 1, and 1 XDR-hvKP isolates belonged to ST15, ST377, ST442, and ST147, respectively. The occurrence of such isolates is deeply concerning due to the combination of hypervirulence and extensively drug-resistance or pandrug-resistance.

The face of hypervirulent Klebsiella pneumoniae isolated from clinical samples of two Iranian teaching hospitals

Hypervirulent Klebsiella pneumoniae (hvKp) has emerged as a pathogen of global concern. In this study, both phenotypic and genotypic tests were used to detect hvKp. Antimicrobial resistance profiles and clonal relatedness of clinical isolates were also determined. We found that 34.2% (163/477) of the isolates were tellurite resistant, and among them 102 hvKp isolates detected with iucA or iutA or peg-344 as molecular markers. The blaSHV (80.4%), followed by blaCTX-M-15 (76.5%) and blaTEM (67.6%), blaOXA-48 (53.9%), and blaNDM-1 (32.3%) were detected, while blaKPC-1 was not present in any hvKp isolates. It was found that the majority of hvKp isolates belonged to capsular serotype K20 and ompK36 group C, which is related to clonal group (CG) 23 (e.g. ST23). A high percentage of multidrug-resistant hvKp (76.6%) and high resistance to imipenem (67%) indicated a serious problem that should be addressed in the clinical setting.

A case of neck abscess caused by rare hypervirulent Klebsiella pneumoniae, capsular type K20 and sequence type 420

Background

This case report describes a neck abscess caused by a strain of Hypervirulent Klebsiella pneumoniae in a middle aged man with diabetes without a history of travel to East and South East Asia. This case report is of notable significance as Hypervirulent Klebsiella pneumoniae neck abscesses are rarely seen in the UK and are very infrequently documented in individuals who have not first travelled to the high prevalence areas of East and South East Asia.

Case presentation

This case report describes a 53 year old diabetic man who contracted a Hypervirulent Klebsiella pneumoniae neck abscess which led to the development of sepsis. Klebsiella pneumoniae was cultured from blood cultures and fluid aspirated from the abscess grew the pathogen with same antimicrobial susceptibility. Hypervirulence was demonstrated after the samples were analysed, at the Antimicrobial Resistance and Healthcare Associated Infections Reference Unit Public Health England Colindale, and found to contain the K20 (rmp)A and rmpA2 virulence genes.

Discussion

Hypervirulent Klebsiella pneumoniae is a Gram-negative, encapsulated, non-motile bacillus notable for its ability to metastatically spread and cause potentially life threatening infections in otherwise healthy adults, but especially in those with diabetes. Genes responsible for the production of hyperviscous mucoid polysaccharide capsules and siderophores, such as those isolated in this case, enable the bacteria to more efficiently evade the hosts immune system and disseminate and invade surrounding and distant tissues. Data from Public Health England shows Hypervirulent Klebsiella pneumoniae are rare in the UK. A review of current literature also showed Hypervirulent Klebsiella pneumoniae almost exclusively occur in those who have traveled to East and South East Asia.

Conclusions

This case reported a rare Hypervirulent Klebsiella pneumoniae neck abscess outside of, and without travel to, East and South East Asia. This raises concerns about future, potentially life threatening, Hypervirulent Klebsiella pneumoniae infections becoming more widespread without the need for endemic travel. This concern is further exacerbated by the growing global challenge of antimicrobial resistance.

Utility of Acute Physiology and Chronic Health Evaluation (APACHE II) in Predicting Mortality in Patients with Pyogenic Liver Abscess: A Retrospective Study

Pyogenic liver abscess (PLA) is a major life-threatening disease with varied clinical features. This study aimed to determine predictors of mortality in patients with PLA using criteria determined upon admission. We retrospectively examined the data of 324 hospitalized adults in whom liver abscesses were confirmed using abdominal ultrasound and/or computed tomography. The relationship between various risk factors was assessed using multivariate analysis. A total of 109 (33.6%) patients were admitted to the intensive care unit (ICU). The overall mortality rate was 7.4% and was higher among ICU patients than non-ICU patients (21.1% vs. 0.5%, p < 0.001). PLA patients with an Acute Physiology and Chronic Health Evaluation (APACHE) II score ≥18 had a 19.31-fold increased risk, and those with concomitant infections had a 34.33-fold increased risk of 30-day mortality according to multivariate analysis. The estimated area under the receiver operating characteristic curve for predicting 30-day mortality revealed that APACHE II score ≥18 (sensitivity of 75% and specificity of 84%, p < 0.0001) had better discriminative power than Sequential Organ Failure Assessment (SOFA) ≥6 (sensitivity of 81% and specificity of 66%, p < 0.0001). APACHE II has shown better discrimination ability than SOFA in predicting mortality in PLA patients. To improve outcomes in patients with PLA, future management strategies should focus on high-risk patients.

Importation of Entamoeba histolytica and predominance of Klebsiella pneumoniae in liver abscesses: a 7-year retrospective cohort study from the United Arab Emirates

BACKGROUND

There is a dearth of information on liver abscesses in the United Arab Emirates. Herein, we describe the clinical features of liver abscesses and determine their incidence rates and clinical outcomes.

METHODS

We retrospectively reviewed the clinical charts of adult patients with a primary diagnosis of liver abscess at a major hospital over a 7-year period.

RESULTS

Amongst 45 patients, 82.2% (37/45) had a pyogenic liver abscess (PLA) and 17.8% (8/45) had amoebic liver abscesses (ALA). Overall, patients were young (median age 42 years, IQR 35-52), mostly males (77.8%, 35/45) from the Indian subcontinent (55.6%, 25/45), presented with fever (88.9%, 40/45) and abdominal pain (88.9%, 40/45), and had a solitary abscess on imaging (71.1% (32/45). Crude annual incidence rates were 35.9/100,000 hospital admissions (95% CI 26.2-48.0) and 5.9/100,000 inhabitants (95% CI 4.3-7.9). All ALA patients were from the Indian subcontinent (100%, 8/8). Klebsiella pneumoniae was the most frequent pathogen in PLA (43.2% [16/37], 95% CI 27.1-60.5%). The hospital stay was shorter in ALA (7.5 days, IQR 7-8.5) than in PLA (14 days, IQR 9-17). No deaths were recorded within 30 days of hospitalisation.

CONCLUSIONS

ALA was exclusively seen in migrants from the Indian subcontinent, suggesting importation. Further research to characterise K. pneumoniae isolates and assess potential risk factors is needed.

Genetic diversity and evolution of the virulence plasmids encoding aerobactin and salmochelin in Klebsiella pneumoniae

Virulence plasmids of hypervirulent Klebsiella pneumoniae (hvKp) have the potential to transfer to drug-resistant strains or integrate with other plasmids, facilitating the genome evolution of threatening pathogens. We conducted an in-depth analysis of the publicly available 156 complete genome sequences of hvKp together with a multi-region clinical cohort of 171 hvKp strains from China to provide evidence for the virulence plasmid evolution. Virulence plasmids were frequently detected in the ST23 and ST11 K. pneumoniae strains. Multidrug-resistant hvKp (MDR-hvKp) occupied a large proportion of hvKp, and the coexistence of virulence and resistance plasmids may be the major cause. Virulence plasmids commonly possessed multiple replicons, of which IncFIB_K was the most prevalent (84.6%). We identified 49 IncFIB_K alleles among 583 IncFIB_K plasmids, and they could be divided into Clades I, II, and III. We further observed that conjugative and non-conjugative virulence plasmids could be distinguished by IncFIB_K genetic diversity, and IncFIB_K subtyping could also indirectly indicate a chimeric preference of conjugative virulence plasmids. On this basis, we developed an open-access web tool called KpVR for IncFIB_K subtyping. In conclusion, the genetic diversity of IncFIB_K virulence plasmids could be used for tracking the evolution of virulence plasmids, and further preventing the emergence of MDR-hvKp strains.

Virulence Factors in Hypervirulent Klebsiella pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKP) has spread globally since first described in the Asian Pacific Rim. It is an invasive variant that differs from the classical K. pneumoniae (cKP), with hypermucoviscosity and hypervirulence, causing community-acquired infections, including pyogenic liver abscess, pneumonia, meningitis, and endophthalmitis. It utilizes a battery of virulence factors for survival and pathogenesis, such as capsule, siderophores, lipopolysaccharide, fimbriae, outer membrane proteins, and type 6 secretion system, of which the former two are dominant. This review summarizes these hvKP-associated virulence factors in order to understand its molecular pathogenesis and shed light on new strategies to improve the prevention, diagnosis, and treatment of hvKP-causing infection.

Outer membrane vesicles derived from hypervirulent Klebsiella pneumoniae stimulate the inflammatory response

Hypervirulent Klebsiella pneumoniae (hvKP), an increasing important pathotype, was initially recognized as a cause of severe liver abscesses and subsequently as a cause of other complications posing a clinical threat. Outer membrane vesicles (OMVs) secreted from abundant gram-negative bacteria are considered an important vehicle for delivery of effector molecules to target cells. However, the products and role in bacterial pathogenesis of OMVs secreted from hvKP, have not yet been determined. In order to examine the production of OMVs from hvKP and to determine their effects on the stimulation of the host innate immune response, we used ultracentrifugation to obtain homogeneous OMVs from hvKP ATCC 1706 cultured in vitro. Proteomic analysis was performed and hvKP OMVs were found to contain diverse proteins. Furthermore, hvKP OMVs exhibited discrepant cytotoxic effects on different cell types, in vitro. The vesicles induced the expression of proinflammatory cytokines including interleukin (IL)-6 and IL-8 in host cells. In addition, transtracheal injection of hvKP OMVs in wild-type mice led to an inflammatory response manifested by elevated levels of pro-inflammatory mediators including IL-6, IL-8 and TNF-α in bronchoalveolar lavage fluid (BAL), in accord with in vitro experiments. However, hvKP OMVs were insufficient to kill mice. In summary, OMVs originating from hvKP may serve to provoke the inflammatory response.

Typical imaging finding of hepatic infections: a pictorial essay

Hepatic infections are frequent in clinical practice. Although epidemiological, clinical and laboratory data may suggest hepatic infection in certain cases, imaging is nearly always necessary to confirm the diagnosis, assess disease extension and its complications, evaluate the response to treatment, and sometimes to make differential diagnoses such as malignancies. Ultrasound (US) is usually the first-line investigation, while computed tomography (CT) and magnetic resonance imaging (MRI) provide better characterization and a more precise assessment of local extension, especially biliary and vascular. The purpose of this article is to describe the typical features and main complications of common hepatic infections. Familiarity with the radiological features of this entity can help suggest the correct diagnosis and the need for further studies as well as determine appropriate and timely treatment.

Pyogenic Liver Abscess and Endogenous Endophthalmitis Due to K64-ST1764 Hypervirulent Klebsiella pneumoniae: A Case Report

RATIONALE

Klebsiella pneumoniae (K. pneumoniae, KP) are divided into two types: classic K. pneumoniae (cKP) and hypervirulent K. pneumoniae (hvKP). hvKP causes liver abscess and metastatic infection. Here, we report one case with pyogenic liver abscess (PLA) and endogenous endophthalmitis (EE) due to a relatively rarely reported serotype of K. pneumoniae in China.

PATIENT CONCERNS

An 80-year old man presented with nausea, vomiting, and epigastric discomfort for 2 weeks.

DIAGNOSES

PLA was identified by CT scan and abdominal ultrasound. Urgent ophthalmologic consultation was performed. B-scan ocular ultrasound was done and he was diagnosed as EE.

INTERVENTIONS

Antibiotic treatment, intravitreal injection of eyes and eye drops were given. Percutaneous needle aspiration, evisceration, and drainage of the right eye were performed.

OUTCOMES

Cultures of the blood, the aspirated pus from the liver abscess, and the contents of the eyeball all yielded K. pneumoniae with a positive string test. The capsular serotype was K64. According to the existence of multiple virulence genes and the severe invasive clinical manifestation, this strain is regarded as a hvKp strain. Multilocus sequence typing (MLST) revealed the sequence type (ST) of this strain was K64-ST1764. Antimicrobial resistance genes, bla _NDM-1 and bla _KPC-2, were not detected in the genome. The patient lost his eyesight but his symptoms subsided. During 15 months follow-up, the result was satisfactory.

LESSONS

Here, we report one case with PLA due to a relatively rarely reported serotype of K. pneumoniae in China. This K64 K. pneumoniae strain is confirmed as hvKp by multiple methods. It is noteworthy that the sequence type is K64-ST1764 instead of the commonest ST11. Moreover, this strain is not considered a K. pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) or a carbapenem-resistant K. pneumoniae (CRKP) as it is usually. Further follow-up and research are required to investigate this strain.

A Klebsiella pneumoniae ST307 outbreak clone from Germany demonstrates features of extensive drug resistance, hypermucoviscosity, and enhanced iron acquisition

BACKGROUND

Antibiotic-resistant Klebsiella pneumoniae are a major cause of hospital- and community-acquired infections, including sepsis, liver abscess, and pneumonia, driven mainly by the emergence of successful high-risk clonal lineages. The K. pneumoniae sequence type (ST) 307 lineage has appeared in several different parts of the world after first being described in Europe in 2008. From June to October 2019, we recorded an outbreak of an extensively drug-resistant ST307 lineage in four medical facilities in north-eastern Germany.

METHODS

Here, we investigated these isolates and those from subsequent cases in the same facilities. We performed whole-genome sequencing to study phylogenetics, microevolution, and plasmid transmission, as well as phenotypic experiments including growth curves, hypermucoviscosity, siderophore secretion, biofilm formation, desiccation resilience, serum survival, and heavy metal resistance for an in-depth characterization of this outbreak clone.

RESULTS

Phylogenetics suggest a homogenous phylogram with several sub-clades containing either isolates from only one patient or isolates originating from different patients, suggesting inter-patient transmission. We identified three large resistance plasmids, carrying either NDM-1, CTX-M-15, or OXA-48, which K. pneumoniae ST307 likely donated to other K. pneumoniae isolates of different STs and even other bacterial species (e.g., Enterobacter cloacae) within the clinical settings. Several chromosomally and plasmid-encoded, hypervirulence-associated virulence factors (e.g., yersiniabactin, metabolite transporter, aerobactin, and heavy metal resistance genes) were identified in addition. While growth, biofilm formation, desiccation resilience, serum survival, and heavy metal resistance were comparable to several control strains, results from siderophore secretion and hypermucoviscosity experiments revealed superiority of the ST307 clone, similar to an archetypical, hypervirulent K. pneumoniae strain (hvKP1).

CONCLUSIONS

The combination of extensive drug resistance and virulence, partly conferred through a "mosaic" plasmid carrying both antibiotic resistance and hypervirulence-associated features, demonstrates serious public health implications.

Nosocomial infection by Klebsiella pneumoniae among neonates: a molecular epidemiological study

BACKGROUND

Nosocomial infection by Klebsiella pneumoniae (Kp) and drug resistance of Kp among neonates is a major concern. Hypervirulent K. pneumoniae (hvKp) infections are gradually increasing worldwide. Carbapenem-resistant hvKp infection has brought challenges to clinical treatment.

AIM

To evaluate the changes in drug resistance trends of Kp strains in neonatal intensive care unit (NICU) nosocomial infections, to analyse drug resistance genes and virulence genes of carbapenem-resistant K. pneumoniae (CRKP) and to identify whether these CRKP strains are hvKp.

METHODS

A total of 80 neonates with Kp nosocomial infections from 2013 to 2018 were retrospectively studied. Drug susceptibility testing was performed on 80 Kp strains, among which the 12 CRKP strains were further studied.

FINDINGS

Kp accounted for 26.9% of nosocomial infections in the NICU. CRKP strains accounted for 15.0%. Among the 80 nosocomial infection Kp strains, CRKP strains accounted for 33.3% and 53.3% in 2017 and 2018 respectively. One of the 12 CRKP strains was positive in the drawing test. The 12 CRKP strains were divided into four complete genome sequence types: cgST1 (N = 2), cgST2 (N = 1), cgST3 (N = 1), and cgST4 (N = 8). Among genes that mediated carbapenem resistance, strains of cgST4 carried NDM-5, strains of cgST2 and cgST3 carried NDM-1, and strains of cgST1 carried IMP-4. None of the 12 CRKP strains carried rmpA/rmpA2 (highly related with hvKp).

CONCLUSION

Nosocomial infections of CRKP among neonates are becoming common, but no hvKp was found among the CRKP strains in this study.

Whole genome sequencing to decipher the virulence phenotype of hypervirulent Klebsiella pneumoniae responsible for liver abscess, Marseille, France

We described three clinical cases of pyogenic liver abscess caused by hypervirulent Klebsiella pneumoniae (hvKp) successfully treated by prolonged antibiotherapy, in which one case was complicated by endophthalmitis. Whole genome sequencing helped to confirm the diagnosis of these hvKp strains, which belong to clonal complexes CC86 and CC23 and carried hvKp-associated genes (magA and/or rmpA). This syndrome is increasingly reported in France and Europe and raises questions about the source of infection.

Endogenous Klebsiella endophthalmitis as the presentation of both Klebsiella liver abscess and underlying anti-IFN-3 autoimmunity

This case study is one of the first ever reported examples of infection in a patient with anti-IFN-3 autoimmunity and demonstrates how overwhelming infection can sometimes present with visual symptoms. We report the case of a previously fit middle-aged patient presenting with painless loss of vision and loss of appetite. Examination showed choroidal abscess and a pan-uveitis, leading to admission for vitreous biopsy. Klebsiella pneumoniae was isolated both in the vitreous and in blood cultures. Subsequent investigation discovered a liver abscess which was treated with percutaneous drainage. Despite the administration of intravitreal antibiotics from the time of presentation, intravenous antibiotics and vitrectomy on the same day, the patient proceeded to need enucleation 19 days later, and now has only light perception in the remaining eye. The strong association between K. pneumoniae endophthalmitis and underlying liver abscess leads to a significant mortality rate. Early diagnosis is essential, with prompt aggressive treatment with antibiotics, but sadly the visual prognosis remains poor. In cases of suspected choroidal abscess, initiation of sepsis screen and immediate empirical treatment is vital to improve this prognosis. This patient had no significant past medical history, no known immunocompromise, was not diabetic and had no recent significant foreign travel. However, further immunological analysis demonstrated the presence of anti-IFN-3 antibodies, a hitherto under-reported potential cause of increased susceptibility to infection, and so cases of sepsis in previously healthy individuals should be considered for further immunology assessment.

Fluoroquinolones as an alternative treatment for Klebsiella pneumoniae liver abscess and impact on hospital length of stay

Klebsiella pneumoniae liver abscess (KPLA) is an endemic disease in East Asia. Patients with KPLA usually require prolonged intravenous (i.v.) β-lactam therapy and hospitalisation. Fluoroquinolones have high oral bioavailability and the potential to shorten the duration of i.v. therapy. The aim of this study was to investigate the feasibility of fluoroquinolones as an alternative treatment for KPLA in Taiwan. Consecutive patients with KPLA in a medical centre in Taiwan between July 2012 and August 2019 were retrospectively enrolled. Clinical characteristics and outcomes were compared between cases treated with β-lactams and fluoroquinolones. A multivariate logistic regression model and propensity-score adjusted analysis were performed to identify independent risk factors for prolonged hospitalisation. A total of 234 patients with KPLA were identified during the study period. Most patients received β-lactams (n = 199; 85.0%), whilst only 35 (15.0%) received fluoroquinolones as the major therapy. Fluoroquinolones had similar clinical efficacy to β-lactams even in critically ill patients. Patients treated with fluoroquinolones had a shorter i.v. antibiotics duration (18.9 ± 7.6 days vs. 28.5 ± 14.7 days; P < 0.001) and hospital length of stay (LOS) (20.9 ± 8.3 days vs. 29.5 ± 16.2 days; P < 0.001) than patients treated with β-lactams. Major therapy with fluoroquinolones was an independent protective factor for hospital LOS > 14 days in all patients and for hospital LOS > 21 days in critically ill patients. In conclusion, fluoroquinolones were an effective alternative treatment for KPLA that resulted in a shorter duration of i.v. therapy and hospital LOS.

The emergence of carbapenemase blaNDM genotype among carbapenem-resistant Enterobacteriaceae isolates from Egyptian cancer patients

Carbapenem resistance among Enterobacteriaceae is a major concern that is increasingly reported worldwide. The objective of this study is to determine the incidence of carbapenem resistance as well as to investigate for carbapenemase-encoding genes among Enterobacteriaceae clinical isolates from cancer patients at different cancer institutes in Egypt. This determination was a cross-sectional study with a total of 135 clinical isolates collected over a period of 1 year. All isolates were sub-cultured on ChromID agar and subjected to phenotypic and molecular detection of carbapenemases. Most of the Enterobacteriaceae isolates were MDR with high resistance rates against tested antimicrobials. Overall, the results of PCR assays revealed that 89.62% (121/135) of isolates harbored one or more of the carbapenemase-encoding genes, while phenotypic assays revealed the production of carbapenemases in 68.88% (93/135) of isolates. BlastN analysis against the non-redundant genome sequences available in the GenBank database revealed that the blaNDM-1 gene was the most prevalent genotype of carbapenemases in 93/135 (68.88%), followed by blaOXA-48 44/135 (32.59%), blaOXA-23 42/135 (31.11%), and blaKPC-2 2/135 (1.48%). Klebsiella pneumoniae isolates harbored the highest number of carbapenemase-encoding genes 34/121 (28.09%). The high prevalence of carbapenemases and/or their encoding genes among MDR Enterobacteriaceae bacteria in Egypt is alarming, thus, the management of serious infections caused by Enterobacteriaceae, particularly in cancer patients will be challenging to clinicians. Carbapenemase blaNDM genotype is emerging in cancer healthcare settings in Egypt, which could be the cause of the current increase in carbapenemase-producing Enterobacteriaceae.

Hypervirulent Klebsiella pneumoniae - clinical and molecular perspectives

Hypervirulent Klebsiella pneumoniae (hvKp) has emerged as a concerning global pathogen. hvKp is more virulent than classical K. pneumoniae (cKp) and capable of causing community-acquired infections, often in healthy individuals. hvKp is carried in the gastrointestinal tract, which contributes to its spread in the community and healthcare settings. First recognized in Asia, hvKp arose as a leading cause of pyogenic liver abscesses. In the decades since, hvKp has spread globally and causes a variety of infections. In addition to liver abscesses, hvKp is distinct from cKp in its ability to metastasize to distant sites, including most commonly the eye, lung and central nervous system (CNS). hvKp has also been implicated in primary extrahepatic infections including bacteremia, pneumonia and soft tissue infections. The genetic determinants of hypervirulence are often found on large virulence plasmids as well as chromosomal mobile genetic elements which can be used as biomarkers to distinguish hvKp from cKp clinical isolates. These distinct virulence determinants of hvKp include up to four siderophore systems for iron acquisition, increased capsule production, K1 and K2 capsule types, and the colibactin toxin. Additionally, hvKp strains demonstrate hypermucoviscosity, a phenotypic description of hvKp in laboratory conditions that has become a distinguishing feature of many hypervirulent isolates. Alarmingly, multidrug-resistant hypervirulent strains have emerged, creating a new challenge in combating this already dangerous pathogen.

Targeting the Sugary Armor of Klebsiella Species

The emergence of multidrug-resistant strains of Gram-negative Klebsiella species is an urgent global threat. The World Health Organization has listed Klebsiella pneumoniae as one of the global priority pathogens in critical need of next-generation antibiotics. Compared to other Gram-negative pathogens, K. pneumoniae accumulates a greater diversity of antimicrobial-resistant genes at a higher frequency. The evolution of a hypervirulent phenotype of K. pneumoniae is yet another concern. It has a broad ecological distribution affecting humans, agricultural animals, plants, and aquatic animals. Extracellular polysaccharides of Klebsiella, such as lipopolysaccharides, capsular polysaccharides, and exopolysaccharides, play crucial roles in conferring resistance against the host immune response, as well as in colonization, surface adhesion, and for protection against antibiotics and bacteriophages. These extracellular polysaccharides are major virulent determinants and are highly divergent with respect to their antigenic properties. Wzx/Wzy-, ABC-, and synthase-dependent proteinaceous nano-machineries are involved in the biosynthesis, transport, and cell surface expression of these sugar molecules. Although the proteins involved in the biosynthesis and surface expression of these sugar molecules represent potential drug targets, variation in the amino acid sequences of some of these proteins, in combination with diversity in their sugar composition, poses a major challenge to the design of a universal drug for Klebsiella infections. This review discusses the challenges in universal Klebsiella vaccine and drug development from the perspective of antigen sugar compositions and the proteins involved in extracellular antigen transport.

Isolation and characterization of a sequence type 25 carbapenem-resistant hypervirulent Klebsiella pneumoniae from the mid-south region of China

Background

The molecular characterization of carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) isolates is not well studied. Our goal was to investigate the molecular epidemiology of CR-hvKP strains that were isolated from a Chinese hospital.

Results

All clinical carbapenem-resistant K. pneumoniae (CR-KP) isolates were collected and identified from patient samples between 2014 and 2017 from a Chinese hospital. The samples were subjected to screening for CR-hvKP by string test and the detection of the aerobactin gene. CR-hvKP isolates were further confirmed through neutrophil phagocytosis and a mice lethality assay. The CR-hvKP isolates were investigated for their capsular genotyping, virulence gene profiles, and the expression of carbapenemase genes by PCR and DNA sequencing. Multilocus sequence type (MLST) and pulsed-field gel electrophoresis (PFGE) were performed to exclude the homology of these isolates. Twenty strains were identified as CR-hvKP. These strains were resistant to imipenem and several other antibiotics, however, most were susceptible to amikacin. Notably, two isolates were not susceptible to tigecycline. Capsular polysaccharide synthesis genotyping revealed that 17 of the 20 CR-hvKP strains belonged to the K2 serotype, while the others belonged to serotypes other than K1, K2, K5, K20, and K57. The strains were found to be positive for 10 types of virulence genes and a variety of these genes coexisted in the same strain. Two carbapenemase genes were identified: bla_KPC-2 (13/20) and bla_NDM-1 (1/20). PFGE typing revealed eight clusters comprising isolates that belonged to MLST types ST25, ST11 and ST375, respectively. PFGE cluster A was identified as the main cluster, which included 11 isolates that belong to ST25 and mainly from ICU department.

Conclusions

Our findings suggest that hospital-acquired infections may contribute in part to the CR-hvKP strains identified in this study. It also suggests that ST25 CR-hvKP strain has a clonal distribution in our hospital. Therefore, effective surveillance and strict infection control strategies should be implemented to prevent outbreak by CR-hvKP strains in hospitals setting.

Hypervirulent Klebsiella pneumoniae

Hypervirulent K. pneumoniae (hvKp) is an evolving pathotype that is more virulent than classical K. pneumoniae (cKp). hvKp usually infects individuals from the community, who are often healthy. Infections are more common in the Asian Pacific Rim but are occurring globally. hvKp infection frequently presents at multiple sites or subsequently metastatically spreads, often requiring source control. hvKp has an increased ability to cause central nervous system infection and endophthalmitis, which require rapid recognition and site-specific treatment. The genetic factors that confer hvKp's hypervirulent phenotype are present on a large virulence plasmid and perhaps integrative conjugal elements. Increased capsule production and aerobactin production are established hvKp-specific virulence factors. Similar to cKp, hvKp strains are becoming increasingly resistant to antimicrobials via acquisition of mobile elements carrying resistance determinants, and new hvKp strains emerge when extensively drug-resistant cKp strains acquire hvKp-specific virulence determinants, resulting in nosocomial infection. Presently, clinical laboratories are unable to differentiate cKp from hvKp, but recently, several biomarkers and quantitative siderophore production have been shown to accurately predict hvKp strains, which could lead to the development of a diagnostic test for use by clinical laboratories for optimal patient care and for use in epidemiologic surveillance and research studies.

Antibiotic-resistant hypervirulent Klebsiella pneumoniae causing community- acquired liver abscess: an emerging disease

We report a case of a patient with fatal community-acquired pyogenic liver abscess (CA-PLA) caused by multi drug-resistant, hypervirulent, Klebsiella pneumoniae (mdrhvKP). HvKP causing PLA has been described in East and South East Asia and it is recognized as an emerging infection worldwide. The syndrome is characterized by cryptogenic liver abscess formation without a previous history of hepatobiliary or colonic disease and metastatic spread of infection via the bloodstream to distant sites, including lungs, central nervous system and other organ systems. Diabetes mellitus is a recognized risk factor. Most previously reported cases have involved antibiotic susceptible strains of hvKP although reports of bloodstream infections caused by resistant strains, including carbapenemase producers, are increasing. Our report highlights the need for awareness of this devastating infection in patients presenting with sepsis and liver abscess without underlying hepatobiliary or colonic disease.

Hypervirulent Klebsiella pneumoniae K1 liver abscess and endogenous endophthalmitis in a Caucasian man

Invasive Liver Abscess Syndrome is the most frequent of a number of infectious syndromes caused by hypervirulent Klebsiella pneumoniae clones. While incidences peak in Southeast Asia, travels to Asia and Asian ethnicity are independent risk factors for infection in the western countries, although non-Asians are infected as well. Although challenging, a prompt diagnosis is of utmost importance to ensure adequate treatment and improve overall survival and visual outcome in cases with ocular involvement.

Clinical bacteriology in low-resource settings: today's solutions

Low-resource settings are disproportionately burdened by infectious diseases and antimicrobial resistance. Good quality clinical bacteriology through a well functioning reference laboratory network is necessary for effective resistance control, but low-resource settings face infrastructural, technical, and behavioural challenges in the implementation of clinical bacteriology. In this Personal View, we explore what constitutes successful implementation of clinical bacteriology in low-resource settings and describe a framework for implementation that is suitable for general referral hospitals in low-income and middle-income countries with a moderate infrastructure. Most microbiological techniques and equipment are not developed for the specific needs of such settings. Pending the arrival of a new generation diagnostics for these settings, we suggest focus on improving, adapting, and implementing conventional, culture-based techniques. Priorities in low-resource settings include harmonised, quality assured, and tropicalised equipment, consumables, and techniques, and rationalised bacterial identification and testing for antimicrobial resistance. Diagnostics should be integrated into clinical care and patient management; clinically relevant specimens must be appropriately selected and prioritised. Open-access training materials and information management tools should be developed. Also important is the need for onsite validation and field adoption of diagnostics in low-resource settings, with considerable shortening of the time between development and implementation of diagnostics. We argue that the implementation of clinical bacteriology in low-resource settings improves patient management, provides valuable surveillance for local antibiotic treatment guidelines and national policies, and supports containment of antimicrobial resistance and the prevention and control of hospital-acquired infections.