Monomicrobial necrotizing fasciitis in a white male caused by hypermucoviscous Klebsiella pneumoniae

Molecular Epidemiology of Hypervirulent K. pneumoniae and Problems of Health-Care Associated Infections

The review describes virulence factors of hypervirulent K. pneumoniae (hvKp) including genes determining its virulence and discusses their role in the development of health-care associated infections. The contribution of individual virulence factors and their combination to the development of the hypervirulence and the prospects of using these factors as biomarkers and therapeutic targets are described. Virulence factors of hvKp and "classical" K. pneumoniae strains (cKp) with no hypervirulence genes were compared. The mechanisms of biofilm formation by hvKp and high incidence of its antibiotic resistance are of particular importance for in health care institutions. Therefore, the development of methods for hvKp identification allowing early prevention of severe hvKp infection and novel approaches to abrogate its spreading are new challenges for epidemiology, infection diseases, and critical care medicine. New technologies including bacteriological and molecular studies make it possible to develop innovative strategies to diagnose and treat infection caused by hvKp. These include monitoring of both genetic biomarkers of hvKp and resistance plasmid that carry of virulence genes and antibiotic resistance genes, creation of immunological agents for the prevention and therapy of hvKp (vaccines, monoclonal antibodies) as well as personalized hvKp-specific phage therapies and pharmaceuticals enhancing the effect of antibiotics. A variety of approaches can reliably prepare our medicine for a new challenge: spreading of life-threatening health-care associated infections caused by antibiotic-resistant hvKp strains.

Successful treatment of hypervirulent Klebsiella pneumoniae bacteremia with combination carbapenem and rifampicin

Hypervirulent Klebsiella pneumoniae (hvKP) with a high mucus phenotype, can cause liver abscess and extrahepatic invasive infection. The morbidity of hvKP infections has increased recently. Here we describe a case report of septicemia caused by hvKP due to the term septic arthritis of right knee joint in a 29-year-old male. The patient was persistent fever with a peak temperature at 40.6 °C. However, based on the drug sensitivity, the treatment failed frequently. The patient did not improve clinically on susceptible monotherapy antimicrobial. Combination therapy with meropenem and rifampicin (RFP) lead to clinical improvement and discharge.

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.

Getting hypervirulent Klebsiella pneumoniae on the radar screen

PURPOSE OF REVIEW

Two pathotypes of Klebsiella pneumoniae cause human infections, classical (cKp) and hypervirulent (hvKp) K. pneumoniae. The present understanding of genetic elements, the need for an accurate test to identify hvKp, the clinical implications of infection, the knowledge gap on how and why hvKp colonization transitions to infection, and potential infection prevention and control issues for hvKp are discussed.

RECENT FINDINGS

Infections because of hvKp are increasingly recognized worldwide. Its ability to cause organ and life-threatening disease in healthy individuals from the community merits concern, which has been magnified by increasing descriptions of multiply drug-resistant (MDR) and extensively drug-resistant (XDR) strains. Increased capsule and siderophore production by hvKp relative to cKp are critical virulence traits. Asians are most commonly infected, but whether this is mediated by a genetic susceptibility, or increased exposure and colonization is unknown. Specific studies about the epidemiology and transmission of hvKp are lacking, but precautions are appropriate for MDR/XDR strains and perhaps all infected/colonized individuals.

SUMMARY

hvKp is evolving into an increasingly concerning pathogen, in part because of the development of XDR strains. An accurate test to identify hvKp is needed for optimal clinical care, epidemiological, and research studies. An improved understanding of how infection develops, if a genetic susceptibility exists, and appropriate infection prevention and control measures also are needed.

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.

Colonization, Infection, and the Accessory Genome of Klebsiella pneumoniae

Klebsiella pneumoniae is a Gram-negative pathogen that has a large accessory genome of plasmids and chromosomal gene loci. This accessory genome divides K. pneumoniae strains into opportunistic, hypervirulent, and multidrug-resistant groups and separates K. pneumoniae from two closely related species, Klebsiella variicola and Klebsiella quasipneumoniae. Some strains of K. pneumoniae act as opportunistic pathogens, infecting critically ill and immunocompromised patients. These K. pneumoniae are a common cause of health-care associated infections including pneumonia, urinary tract infections (UTIs), and bloodstream infections. K. variicola and K. quasipneumoniae are often clinically indistinguishable from opportunistic K. pneumoniae. Other strains of K. pneumoniae are hypervirulent, infecting healthy people in community settings and causing severe infections including pyogenic liver abscess, endophthalmitis, and meningitis. A third group of K. pneumoniae encode carbapenemases, making them highly antibiotic-resistant. These strains act as opportunists but are exceedingly difficult to treat. All of these groups of K. pneumoniae and related species can colonize the gastrointestinal tract, and the accessory genome may determine if a colonizing strain remains asymptomatic or progresses to cause disease. This review will explore the associations between colonization and infection with opportunistic, antibiotic-resistant, and hypervirulent K. pneumoniae strains and the role of the accessory genome in distinguishing these groups and related species. As K. pneumoniae infections become progressively more difficult to treat in the face of antibiotic resistance and hypervirulent strains, an increased understanding of the epidemiology and pathogenesis of these bacteria is vital.

Antimicrobial Resistance of Hypervirulent Klebsiella pneumoniae: Epidemiology, Hypervirulence-Associated Determinants, and Resistance Mechanisms

Klebsiella pneumoniae is one of the most clinically relevant species in immunocompromised individuals responsible for community-acquired and nosocomial infections, including pneumonias, urinary tract infections, bacteremias, and liver abscesses. Since the mid-1980s, hypervirulent K. pneumoniae, generally associated with the hypermucoviscosity phenotype, has emerged as a clinically significant pathogen responsible for serious disseminated infections, such as pyogenic liver abscesses, osteomyelitis, and endophthalmitis, in a generally younger and healthier population. Hypervirulent K. pneumoniae infections were primarily found in East Asia and now are increasingly being reported worldwide. Although most hypervirulent K. pneumoniae isolates are antibiotic-susceptible, some isolates with combined virulence and resistance, such as the carbapenem-resistant hypervirulent K. pneumoniae isolates, are increasingly being detected. The combination of multidrug resistance and enhanced virulence has the potential to cause the next clinical crisis. To better understand the basic biology of hypervirulent K. pneumoniae, this review will provide a summarization and discussion focused on epidemiology, hypervirulence-associated factors, and antibiotic resistance mechanisms of such hypervirulent strains. Epidemiological analysis of recent clinical isolates in China warns the global dissemination of hypervirulent K. pneumoniae strains with extensive antibiotic resistance in the near future. Therefore, an immediate response to recognize the global dissemination of this hypervirulent strain with resistance determinants is an urgent priority.

Differential host susceptibility and bacterial virulence factors driving Klebsiella liver abscess in an ethnically diverse population

Hypervirulent Klebsiella pneumoniae is an emerging cause of community-acquired pyogenic liver abscess. First described in Asia, it is now increasingly recognized in Western countries, commonly afflicting those with Asian descent. This raises the question of genetic predisposition versus geospecific strain acquisition. We leveraged on the Antibiotics for Klebsiella Liver Abscess Syndrome Study (A-KLASS) clinical trial ongoing in ethnically diverse Singapore, to prospectively examine the profiles of 70 patients together with their isolates' genotypic and phenotypic characteristics. The majority of isolates belonged to capsule type K1, a genetically homogenous group corresponding to sequence-type 23. The remaining K2, K5, K16, K28, K57 and K63 isolates as well as two novel cps isolates were genetically heterogeneous. K1 isolates carried higher frequencies of virulence-associated genes including rmpA (regulator of mucoid phenotype A), kfu (Klebsiella ferric uptake transporter), iuc (aerobactin), iro (salmochelin) and irp (yersiniabactin) than non-K1 isolates. The Chinese in our patient cohort, mostly non-diabetic, had higher prevalence of K1 infection than the predominantly diabetic non-Chinese (Malays, Indian and Caucasian). This differential susceptibility to different capsule types among the various ethnic groups suggests patterns of transmission (e.g. environmental source, familial transmission) and/or genetic predisposition unique to each race despite being in the same geographical location.

Necrotizing fasciitis caused by hypermucoviscous Klebsiella pneumoniae in a Filipino female in North America

Necrotizing fasciitis caused by Klebsiella pneumoniae has been described in Southeast Asia, but has only recently begun to emerge in North America. The hypermucoviscous strain of K. pneumoniae is a particularly virulent strain known to cause devastatingly invasive infections, including necrotizing fasciitis. Here we present the first known case of necrotizing fasciitis caused by hypermucoviscous K. pneumoniae in North America.

Klebsiella pneumoniae necrotizing fasciitis of the leg in an elderly French woman

Klebsiella pneumoniae necrotizing fasciitis is a rare infection in regions outside of Asia. Here, we present a case of necrotizing fasciitis of the leg caused by K. pneumoniae in a 92-year-old French woman hospitalized in a geriatric rehabilitation unit. The patient initially presented with dermohypodermitis of the leg that developed from a dirty wound following a fall. A few hours later, this painful injury extended to the entire lower limb, with purplish discoloration of the skin, bullae, and necrosis. Septic shock rapidly appeared and the patient died 9 hours after the onset of symptoms. The patient was Caucasian, with no history of travel to Asia or any underlying disease. Computed tomography revealed no infectious metastatic loci. Blood cultures showed growth of capsular serotype K2 K. pneumoniae strains with virulence factors RmpA, yersiniabactin and aerobactin. This rare and fatal case of necrotizing fasciitis caused by a virulent strain of K. pneumoniae occurred in a hospitalized elderly woman without risk factors. Clinicians and geriatricians in particular should be aware of this important albeit unusual differential diagnosis.

Increasing occurrence of antimicrobial-resistant hypervirulent (hypermucoviscous) Klebsiella pneumoniae isolates in China

BACKGROUND

New hypervirulent variants of Klebsiella pneumoniae (hvKP) are emerging globally, most of which exhibit antimicrobial susceptibility.

METHODS

A retrospective study was conducted in 88 patients with cultures positive for K. pneumoniae hospitalized in the Beijing You'an Hospital from April 2010 to June 2012. The clinical and molecular data of the hvKP isolates (defined as string test positive) were compared with those of the classic K. pneumoniae (cKP) isolates.

RESULTS

Overall, 33.0% (29/88) of K. pneumoniae isolates were hvKP. Univariate analysis revealed the following risk factors for hvKP: virulence gene rmpA (odds ratio [OR], 16.92 [95% confidence interval {CI}, 4.842-59.145]), capsule antigens K1 (OR, 3.355 [95% CI, 1.153-9.768]) and K2 (OR, 9.280 [95% CI, 0.987-87.250]), alcoholic hepatitis (OR, 7.435 [95% CI, 1.397-39.572]), liver abscess (OR, 9.068 [95% CI, 1.747-47.061]), metastatic infection (OR, 2.752 [95% CI, 1.100-6.886]), community-acquired infection (OR, 10.432 [95% CI, 3.623-30.033]), sputum isolation (OR, 0.312 [95% CI, .095-1.021]), and HIV infection (<0.001 [not applicable]). Multivariate analysis implicated rmpA (OR, 17.398 [95% CI, 4.224-71.668]) and community-acquired infection (OR, 6.844 [95% CI, 1.905-24.585]) as independent risk factors. The proportion of hvKP isolates increased from April to December 2010, January to September 2011, and October 2011 to June 2012 (to 25.5%, 26.7%, and 54.5%, respectively). Resistance to 14 of 19 tested antimicrobials was found to be significantly greater in cKP compared to hvKP. Importantly, resistance to all the tested antimicrobials, except carbapenems and amikacin, was observed in a proportion of hvKP strains, 17% (5/29) of which expressed extended-spectrum β-lactamase. Furthermore, antimicrobial resistance in hvKP strains increased over time.

CONCLUSIONS

HvKP strains are being isolated from patients in China with increasing frequency and constitute an increasing proportion of K. pneumoniae strains, indicating an increasing propensity for the acquisition of antimicrobial resistance.

A five-year review of necrotising fasciitis in a tertiary referral unit

Introduction

Necrotising fasciitis is a life-threatening illness that is often difficult to diagnose. Immediate debridement and intravenous antibiotic therapy are required to limit the spread of infection. This five-year audit aimed to review the number and outcomes of all cases of necrotising fasciitis admitted to a tertiary referral unit and to assess the validity of the Laboratory Risk Indicator for Necrotising Fasciitis (LRINEC) scoring system.

Methods

A retrospective analysis of patient notes over the five-year period from October 2006 to October 2011 was undertaken. The LRINEC score was calculated for each patient to evaluate its usefulness.

Results

Overall, 15 patients were diagnosed with necrotising fasciitis. Three patients died. The median age of patients was 51.0 years (range: 34–76 years). There were no obvious predisposing factors in 8 cases but patients had a median of 2.0 co-morbidities. The most common infective agent, present in five patients, was Group A Streptococcus. Other monomicrobial agents included Group G Streptococcus and Klebsiella pneumoniae. Polymicrobial infections were less common than monomicrobial infections and two patients had a polymicrobial infection including methicillin-resistant Staphylococcus aureus. Although the LRINEC scoring system identified 12 of the 15 patients as having a high or intermediate likelihood of necrotising fasciitis, 3 were classified as low likelihood.

Conclusions

This limited case series strongly suggests that the LRINEC system is too insensitive for diagnosis.

Hypervirulent (hypermucoviscous) Klebsiella pneumoniae: a new and dangerous breed

A new hypervirulent (hypermucoviscous) variant of Klebsiella pneumoniae has emerged. First described in the Asian Pacific Rim, it now increasingly recognized in Western countries. Defining clinical features are the ability to cause serious, life-threatening community-acquired infection in younger healthy hosts, including liver abscess, pneumonia, meningitis and endophthalmitis and the ability to metastatically spread, an unusual feature for enteric Gram-negative bacilli in the non-immunocompromised. Despite infecting a healthier population, significant morbidity and mortality occurs. Although epidemiologic features are still being defined, colonization, particularly intestinal colonization, appears to be a critical step leading to infection. However the route of entry remains unclear. The majority of cases described to date are in Asians, raising the issue of a genetic predisposition vs. geospecific strain acquisition. The traits that enhance its virulence when compared with “classical” K. pneumoniae are the ability to more efficiently acquire iron and perhaps an increase in capsule production, which confers the hypermucoviscous phenotype. An objective diagnostic test suitable for routine use in the clinical microbiology laboratory is needed. If/when these strains become increasingly resistant to antimicrobials, we will be faced with a frightening clinical scenario.

Klebsiella pneumoniae cervical necrotizing fasciitis originating as an abscess

Cervical necrotizing fasciitis is a rapidly progressive and devastating infection that is usually caused by a polymicrobial infection including group A Streptococcus and anaerobes. We present a case of a newly diagnosed diabetic man who underwent transoral drainage of a Klebsiella pneumoniae paraglottic abscess, which, despite culture-directed antibiotics, progressed to cervical necrotizing fasciitis with descending mediastinitis. The patient required 12 surgical debridements and sternotomy, but survived and was discharged on hospital day 40. To our knowledge, this is the first case of cervical necrotizing fasciitis caused by a K pneumoniae infection in the United States. The significance of this unusual presentation is discussed.

Recent trend of necrotizing fasciitis in Taiwan: focus on monomicrobial Klebsiella pneumoniae necrotizing fasciitis

BACKGROUND

Necrotizing fasciitis (NF) is a rapidly progressive, life-threatening soft-tissue infection that is traditionally caused by group A Streptococcus (GAS) or mixed aerobic/anaerobic bacteria. Monomicrobial Klebsiella pneumoniae NF (KP-NF) has been reported since 1996 but has not yet been systematically studied.

METHODS

We retrospectively studied consecutive NF cases treated at a university hospital in Taiwan during 1997-2010 and investigated the clinical characteristics and outcomes associated with monomicrobial KP-NF, using monomicrobial GAS-NF as a reference. We also analyzed the virulence gene profiles of the isolated K. pneumoniae strains.

RESULTS

Of 134 NF cases, 88 were monomicrobial, of which the most common pathogens were GAS (n = 16) and K. pneumoniae (n = 15). Monomicrobial KP-NF entailed a moderate risk of limb loss (20% vs 25%; P = 1.000) and high mortality (47% vs 19%; P = .135), and it was more likely to involve bacteremia (80% vs 31%; P = .011), concomitant distant abscesses (27% vs 0%; P = .043), and underlying immunocompromising conditions (100% vs 63%; P = .018), compared with GAS-NF. The isolated K. pneumoniae strains (n = 10) were of capsular polysaccharides genotype K1 (n = 4), K54/K20/K5 (n = 4), K2 (n = 1), and K16 (n = 1). All strains carried rmpA, iucABCDiutA, and iroA. Genotype K1 strains had a significantly higher risk of concomitant distant abscesses, compared with non-K1 strains (75% vs 0%; P = .033).

CONCLUSIONS

K. pneumoniae has become a common pathogen of monomicrobial NF in Taiwan. Physicians treating patients with monomicrobial KP-NF should be aware of the risk of concomitant distant abscesses, particularly in cases caused by genotype K1.

Necrotizing fasciitis following psoas muscle abscess caused by hypermucoviscous Klebsiella pneumoniae

A 59-year-old Japanese diabetic woman was admitted to a small private hospital with general malaise, fever, and a 1-month history of low back pain. A computed tomography scan of the abdomen revealed left abdominal necrotizing fasciitis with suspected left psoas muscle abscess. She was transferred to Gunma University Hospital, received antibiotic therapy, and underwent debridement of the infected subcutaneous tissue, fascia, and necrotic left psoas muscle. She was transferred to the intensive care unit to receive mechanical ventilation and inotropic support. Blood culture showed growth of Klebsiella pneumoniae, from which hypermucoviscosity was detected by the string test. She was extubated on day 5 of hospitalization and transferred to a general ward on day 14. Free skin grafting was performed on day 76, and she was discharged on day 134 without any complications.