Klebsiella oxytoca Endocarditis With Complete Heart Block

Klebsiella oxytoca Complex: Update on Taxonomy, Antimicrobial Resistance, and Virulence

Klebsiella oxytoca is actually a complex of nine species-Klebsiella grimontii, Klebsiella huaxiensis, Klebsiella michiganensis, K. oxytoca, Klebsiella pasteurii, Klebsiella spallanzanii, and three unnamed novel species. Phenotypic tests can assign isolates to the complex, but precise species identification requires genome-based analysis. The K. oxytoca complex is a human commensal but also an opportunistic pathogen causing various infections, such as antibiotic-associated hemorrhagic colitis (AAHC), urinary tract infection, and bacteremia, and has caused outbreaks. Production of the cytotoxins tilivalline and tilimycin lead to AAHC, while many virulence factors seen in Klebsiella pneumoniae, such as capsular polysaccharides and fimbriae, have been found in the complex; however, their association with pathogenicity remains unclear. Among the 5,724 K. oxytoca clinical isolates in the SENTRY surveillance system, the rates of nonsusceptibility to carbapenems, ceftriaxone, ciprofloxacin, colistin, and tigecycline were 1.8%, 12.5%, 7.1%, 0.8%, and 0.1%, respectively. Resistance to carbapenems is increasing alarmingly. In addition to the intrinsic bla_OXY, many genes encoding β-lactamases with varying spectra of hydrolysis, including extended-spectrum β-lactamases, such as a few CTX-M variants and several TEM and SHV variants, have been found. bla_KPC-2 is the most common carbapenemase gene found in the complex and is mainly seen on IncN or IncF plasmids. Due to the ability to acquire antimicrobial resistance and the carriage of multiple virulence genes, the K. oxytoca complex has the potential to become a major threat to human health.

First Experimental Evidence for the Presence of Potentially Virulent Klebsiella oxytoca in 14 Species of Commonly Consumed Aquatic Animals, and Phenotyping and Genotyping of K. oxytoca Isolates

Klebsiella oxytoca is a recently emerging pathogen that can cause necrotizing enterocolitis, hemorrhagic colitis, sepsis-associated purpura fulminans, and infective endocarditis in humans. The bacterium is ubiquitous in water and soil environments. Nevertheless, current literature on K. oxytoca in aquatic products is rare. In this study, we surveyed K. oxytoca contamination in 41 species of consumable aquatic animals sold in July, August, and September of 2018 and 2019 in Shanghai, China, 40 of which had no history of carrying this bacterium. K. oxytoca was for the first time isolated from 14 species with high abundance in benthic animals. None of the K. oxytoca isolates (n = 125) harbored toxin genes mviM, tisB, and yqgB. However, a high occurrence of virulence-associated genes was observed, including brkB (73.6%), cdcB (66.4%), pduV (64.8%), and virk (63.2%). Resistance to sulphamethoxazole-trimethoprim (56.0%) was the most predominant among the isolates, followed by chloramphenicol (6.4%), tetracycline (5.6%), and kanamycin (3.2%). Approximately 8.0% of the isolates displayed multidrug resistant phenotypes. Meanwhile, high percentages of the isolates tolerated the heavy metals Cu²⁺ (84.8%), Pb²⁺ (80.8%), Cr³⁺ (66.4%), Zn²⁺ (66.4%), and Hg²⁺ (49.6%). Different virulence and resistance profiles were observed among K. oxytoca isolates in 3 types and 14 species of aquatic animals. The ERIC-PCR-based genome fingerprinting of the 125 K. oxytoca isolates revealed 108 ERIC genotypes with 79 singletons, which demonstrated the genetic diversity of the isolates. The results of this study fill gaps for policy and research in the risk assessment of K. oxytoca in consumable aquatic animals.

Klebsiella oxytoca and Emerging Nosocomial Infections

Klebsiella oxytoca is rising as a significant opportunistic pathogen causing nosocomial infections in neonates as well as adults. This pathogen's prevalence varies from 2 to 24%, but outbreaks of infections due to multidrug-resistant strains can be fatal in immunocompromised individuals with comorbidities. Klebsiella oxytoca is responsible for a wide range of ailments from colitis to infective endocarditis, other than the common urinary and respiratory tract infections. The microbe's pathogenicity has been attributed to cytotoxins' production- Tilivalline and Tilimycin, in some intestinal disorders. Klebsiella oxytoca is reported to be resistant to a wide range of antibiotics. Here, we have tried to showcase a brief overview of the emergence of Klebsiella oxytoca in healthcare facilities and the nature of resistance in this species of Klebsiella.

Infective endocarditis by Klebsiella species: a systematic review

This study aimed to systematically analyze all cases of infective endocarditis (IE) by Klebsiella species in the literature. A systematic review of PubMed, Scopus and Cochrane library (through 27^th January 2021) for studies providing epidemiological, clinical, microbiological as well as treatment data and outcomes of IE by Klebsiella species was performed. In this review, a total of 66 studies were included, providing data for 67 patients. A prosthetic valve was present in 16.4%, while the most common causative pathogen was K. pneumoniae followed by K. oxytoca. The aortic valve was the most commonly infected intracardiac site, followed by the mitral valve. The diagnosis was based on transthoracic echocardiography in 46.2%, while the diagnosis was set at autopsy in 9.2% of included patients. Blood cultures were positive in 93.8%. Fever and sepsis were the most frequent clinical presentations, followed by embolic phenomena, paravalvular abscess, and heart failure. Cephalosporins, aminoglycosides, and carbapenems were the most frequently used antimicrobials. Surgical treatment along with antimicrobials was performed in 37.3% of included patients. Clinical cure was noted in 80.3%, while the overall mortality was 19.4%. Infection at the aortic valve was independently associated with mortality by IE. This systematic review gives a comprehensive description of IE by Klebsiella and provides information on epidemiology, clinical manifestations, therapeutic strategies and their outcomes.

Infective Endocarditis Caused by Klebsiella Oxytoca in a Patient with Hemodialysis: A CARE-Compliant Case Report and Review of the Literature

The rarity of endocarditis due to Klebsiella species limits its recognition. We report the case of a 63-year-old man, known to have a tight calcified aortic stenosis presenting with acute heart failure associated with high fever. Klebsiella oxytoca endocarditis was diagnosed based on three sets of positive blood cultures together with fluttering vegetation (11 mm × 14 mm) on the middle segment of the anterior leaflet of the mitral valve. After 6 weeks of intravenous ceftriaxone and gentamicin bi-therapy, the patient had completely recovered. This case illustrates how sporadic this condition is, for which early assessment and proper treatment are crucial to enhance the short outcomes.

Significant PR Prolongation and New Onset Left Bundle Branch Block in Aortic Root Abscess: A Marker of Disease Progression and Poor Prognosis

Infective endocarditis (IE) is a serious medical condition with a high morbidity and mortality rate. Staphylococcus aureus is the most common etiologic organism in IE. While echocardiography plays an important role in diagnosis and management of IE, the electrocardiogram (ECG) is helpful in determination of disease progression as well as in prognostication. We present a case of a 72-year-old man who was diagnosed with IE following methicillin resistant Staphylococcus aureus (MRSA) bacteremia. The course of hospitalization was complicated with multiple septic-embolic strokes and aortic root abscess. Serial ECG revealed PR prolongation and new onset left bundle branch block (LBBB) before the patient became terminal. Our case highlights the utility of serial ECGs monitoring in the patients with IE that may reveal subtle ECG findings, such as PR prolongation and LBBB. These findings which might serve as a clue of the presence of peri-annular extension of IE, help in prognostication and aid in the therapeutic decision-making such as early surgical intervention in these high-risk patients with poor prognosis. In this report, we also present the pathophysiologic mechanisms underlining the ECG changes in patients with aortic valve endocarditis.

A case of Klebsiella oxytoca endocarditis in an intravenous drug user

Non-HACEK Gram-negative bacilli account for only a small percentage of infective endocarditis cases globally. Among those, Klebsiella species account for only about 10% of cases and are most often health-care acquired. We present a rare case of Klebsiella oxytoca endocarditis in a young intravenous drug user.

Characterization and formulation into solid dosage forms of a novel bacteriophage lytic against Klebsiella oxytoca

AIM

To isolate and characterize bacteriophage lytic for the opportunistic pathogen Klebsiella oxytoca and their formulation into a range of solid dosage forms for in-vitro testing.

METHODS AND RESULTS

We report the isolation, genomic and functional characterization of a novel bacteriophage lytic for Klebsiella oxytoca, which does not infect the closely related Klebsiella pneumoniae. This bacteriophage was formulated into suppositories and troches and shown to be released and lyse underlying Klebsiella oxytoca bacteria in an in-vitro model. These bacteriophage formulations were stable for at least 49 days at 4°C.

CONCLUSIONS

The successful in-vitro assay of these formulations here suggests that they could potentially be tested in-vivo to determine whether such a therapeutic approach could modulate the gut microbiome, and control Klebsiella oxytoca overgrowth, during antibiotic therapy regimes.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reports a novel bacteriophage specific for Klebsiella oxytoca which can be formulated into solid dosage forms appropriate for potential delivery in testing as a therapy to modulate gut microbiome during antibiotic therapies.