Endogenous Endophthalmitis Caused by ST66-K2 Hypervirulent Klebsiella pneumoniae, United States

Prevalence and features of hypervirulent Klebsiella pneumoniae in respiratory specimens at a US hospital system

Hypervirulent Klebsiella pneumoniae (hvKp) strains are considered to be relatively rare in the United States, but cases are increasingly reported. We prospectively and serially collected K. pneumoniae clinical isolates identified in respiratory specimens at a health system in Western Pennsylvania between 2020 and 2022. A total of 273 K. pneumoniae isolates from 216 unique patients were analyzed for markers of hypervirulence by both string test for a hypermucoid phenotype and multiplex PCR to detect isolates carrying cardinal virulence genes rmpA, rmpA2, iutA, and iro. Of the 273 isolates, 13 (4.8%) tested positive by string test including 11 nonduplicate K. pneumoniae isolates, and two of these (0.7%) were positive by PCR for virulence genes rmpA, rmpA2, iutA, and iro. The latter two putative hvKp strains, belonging to sequence types ST23-K1 and ST86-SLV-K2, possessed pLVPK-like plasmids, and were collected from community-associated infections in individuals without known travel histories. Both putative hvKp strains and two additional string test-positive strains were resistant to killing by human serum. The hvKp strains caused significant pneumonia in mice infected by oropharyngeal aspiration, with significantly higher weight loss and increased bacterial burden in the lungs of mice infected with the KL1 (ST23) strain compared to the KL2 (ST86-SLV) strain. We also observed decreased survival of mice infected with the KL1 strain compared to the KL2 strain. These findings add to the growing body of evidence suggesting that hvKp strains, once considered endemic to Asia, may now be circulating in North America.IMPORTANCECertain lineages of Klebsiella pneumoniae are increasingly recognized to cause severe community-associated infection, but information on their prevalence in the United States is limited. In a prospective, sequential cohort of 273 K. pneumoniae respiratory isolates, we identified two of them as genetically defined hypervirulent K. pneumoniae. The isolates were from local residents who developed community-onset pneumonia, suggesting that hypervirulent K. pneumoniae may already be present in the community.

Clinical features, treatment and prognosis of patients with endogenous infectious endophthalmitis

PURPOSE

To investigate whether the clinical characteristics, treatment and prognosis of endogenous infectious endophthalmitis (EIE) have changed over the past 5 years.

METHODS

Retrospectively analyze all articles about EIE published in the PubMed, Web of Science, and Embase databases from 2017 to 2021.

RESULTS

A total of 128 patients and 147 eyes (46 left and 60 right) were included in the study. The mean age at diagnosis was 51 ± 19 years. The most common risk factors were diabetes and intravenous drug use. From 2017 to 2021, Klebsiella was the most common pathogenic microorganism (22%), and vitreous culture had the highest positivity rate. The most common complaint was blurred vision. The mean visual acuity (logMAR) at onset was 2.84, and the clinical symptoms were vitreal inflammation and opacity (63%), ocular pain (37%), and conjunctival congestion (36%). The ocular inflammation could be reduced by intraocular antibiotics or vitrectomy. However, the visual prognosis, with a mean logMAR of 2.73; only 50% of the eyes reached a visual acuity level of finger count and above. Changes in diagnostics over the past 5 years have mainly manifested as more diverse microorganism culture methods. In addition to conventional culture methods, PCR, sputum culture and aqueous humour culture are also commonly used for the diagnosis of pathogenic bacteria, improving the positive culture rate and visual prognosis.

CONCLUSION

The prognosis of EIE is poor. It is recommended to pay attention to the pathogenic bacteria culture results and accompanying systemic diseases and to diagnose and treat patients as soon as possible.

Hypervirulent Klebsiella pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKP), especially multidrug-resistant hvKP (MDR-hvKP) infections, are distributed globally, and lead to several outbreaks with high pathogenicity and mortality in immunocompetent individuals. This is usually characterized by a rapidly metastatic spread resulting in multiple pyogenic tissue abscesses. To date, even though the explanation of hypervirulent factors of hvKP has been identified, it still remains to be fully understood. The most common key virulence agents of hvKP included (1) siderophore systems for iron acquisition, (2) increased capsule production, (3) the colibactin toxin, (4) hypermucoviscosity, and so on. Several hypervirulence factors have been renewed, and the evolution of MDR-hvKP has been deeply explored recently. We aim to describe a chain of key virulence agents attributed to the lethality of hvKP and MDR-hvKP. In this review, recent advances in renewed factors in hypervirulence were summarized, and potential therapeutic targets are explored. Novel co-existence of hypervirulence agents and multidrug-resistant elements, even the superplasmid, was screened. Superplasmid simultaneously harbours hypervirulence and multidrug-resistant genes and can mobile autonomously by its complete conjugative elements. Research into related immunity has also gained traction, which may cause multiple invasive infections with higher mortality rates than classical ones, such as neutrophil- and complement-mediated activity. The evolution of virulence and multidrug resistance is accelerating. More reliable methods for identifying hvKP or MDR-hvKP must be investigated. Furthermore, it is critical to investigate innovative treatment targets in the future.

Gram-Negative Endogenous Endophthalmitis: A Systematic Review

Background: Gram-negative bacteria are causative agents of endogenous endophthalmitis (EBE). We aim to systematically review the current literature to assess the aetiologies, risk factors, and early ocular lesions in cases of Gram-negative EBE. Methods: All peer-reviewed articles between January 2002 and August 2022 regarding Gram-negative EBE were included. We conducted a literature search on PubMed and Cochrane Controlled Trials. Results: A total of 115 studies and 591 patients were included, prevalently Asian (98; 81.7%) and male (302; 62.9%). The most common comorbidity was diabetes (231; 55%). The main aetiologies were Klebsiella pneumoniae (510; 66.1%), Pseudomonas aeruginosa (111; 14.4%), and Escherichia coli (60; 7.8%). Liver abscesses (266; 54.5%) were the predominant source of infection. The most frequent ocular lesions were vitreal opacity (134; 49.6%) and hypopyon (95; 35.2%). Ceftriaxone (76; 30.9%), fluoroquinolones (14; 14.4%), and ceftazidime (213; 78.0%) were the most widely used as systemic, topical, and intravitreal anti-Gram-negative agents, respectively. The most reported surgical approaches were vitrectomy (130; 24.1%) and evisceration/exenteration (60; 11.1%). Frequently, visual acuity at discharge was no light perception (301; 55.2%). Conclusions: Gram-negative EBEs are associated with poor outcomes. Our systematic review is mainly based on case reports and case series with significant heterogeneity. The main strength is the large sample spanning over 20 years. Our findings underscore the importance of considering ocular involvement in Gram-negative infections.

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.

Successful treatment of acute respiratory distress syndrome caused by hypervirulent Klebsiella pneumoniae with extracorporeal membrane oxygenation and continuous renal replacement therapy: A case report and literature review

Hypervirulent Klebsiella pneumoniae (hvKP) causes invasive infections and leads to high morbidity and mortality rates. Here, we report the case of a Chinese man with diabetes mellitus who developed acute respiratory distress syndrome and septic shock due to hvKP belonging to the K1 strain. The patient was treated with venovenous extracorporeal membrane oxygenation and continuous renal replacement therapy, in combination with antibiotics and recovered well. Clinicians should be aware of fatal infections caused by hvKP and investigate the best treatment options for patients at various stages of infection.

Genetic and Functional Characterization of a Conjugative KpVP-2-Type Virulence Plasmid From a Clinical Klebsiella pneumoniae Strain

The main mechanism of virulence in Klebsiella pneumoniae is the acquisition of K. pneumoniae virulence plasmids (KpVPs), which include two dominant types, namely, KpVP-1 (carrying iuc1, iro1, rmpA, and rmpA2) and KpVP-2 (carrying iuc2, iro2, and rmpA). Both are non-conjugative and associated with different hypervirulent clones. In contrast to KpVP-1 reported in K1, K2, and other serotypes of K. pneumoniae, KpVP-2 was only reported in K2 strains and rarely characterized. In this study, we identified a conjugative KpVP-2-type virulence plasmid from a clinical hypervirulent K. pneumoniae strain. This plasmid was generated by the integration of conjugative transfer genes into the KpVP-2-type plasmid Kp52.145 II and could be readily conjugated to Escherichia coli strain EC600 and K. pneumoniae strains of various types which are clinically existing, mediating hypervirulence. Furthermore, this kind of conjugative KpVP-2-type virulence plasmid has been disseminated in clinical settings in Hong Kong and other regions of the world. The generation of conjugative virulence plasmid may promote its transmission and explain the evolution of this type of virulence plasmid.

Genomic surveillance for multidrug-resistant or hypervirulent Klebsiella pneumoniae among United States bloodstream isolates

BACKGROUND

Klebsiella pneumoniae strains have been divided into two major categories: classical K. pneumoniae, which are frequently multidrug-resistant and cause hospital-acquired infections in patients with impaired defenses, and hypervirulent K. pneumoniae, which cause severe community-acquired and disseminated infections in normal hosts. Both types of infections may lead to bacteremia and are associated with significant morbidity and mortality. The relative burden of these two types of K. pneumoniae among bloodstream isolates within the United States is not well understood.

METHODS

We evaluated consecutive K. pneumoniae isolates cultured from the blood of hospitalized patients at Northwestern Memorial Hospital (NMH) in Chicago, Illinois between April 2015 and April 2017. Bloodstream isolates underwent whole genome sequencing, and sequence types (STs), capsule loci (KLs), virulence genes, and antimicrobial resistance genes were identified in the genomes using the bioinformatic tools Kleborate and Kaptive. Patient demographic, comorbidity, and infection information, as well as the phenotypic antimicrobial resistance of the isolates were extracted from the electronic health record. Candidate hypervirulent isolates were tested in a murine model of pneumonia, and their plasmids were characterized using long-read sequencing. We also extracted STs, KLs, and virulence and antimicrobial resistance genes from the genomes of bloodstream isolates submitted from 33 United States institutions between 2007 and 2021 to the National Center for Biotechnology Information (NCBI) database.

RESULTS

Consecutive K. pneumoniae bloodstream isolates (n = 104, one per patient) from NMH consisted of 75 distinct STs and 51 unique capsule loci. The majority of these isolates (n = 58, 55.8%) were susceptible to all tested antibiotics except ampicillin, but 17 (16.3%) were multidrug-resistant. A total of 32 (30.8%) of these isolates were STs of known high-risk clones, including ST258 and ST45. In particular, 18 (17.3%) were resistant to ceftriaxone (of which 17 harbored extended-spectrum beta-lactamase genes) and 9 (8.7%) were resistant to meropenem (all of which harbored a carbapenemase genes). Four (3.8%) of the 104 isolates were hypervirulent K. pneumoniae, as evidenced by hypermucoviscous phenotypes, high levels of virulence in a murine model of pneumonia, and the presence of large plasmids similar to characterized hypervirulence plasmids. These isolates were cultured from patients who had not recently traveled to Asia. Two of these hypervirulent isolates belonged to the well characterized ST23 lineage and one to the re-emerging ST66 lineage. Of particular concern, two of these isolates contained plasmids with tra conjugation loci suggesting the potential for transmission. We also analyzed 963 publicly available genomes of K. pneumoniae bloodstream isolates from locations within the United States. Of these, 465 (48.3%) and 760 (78.9%) contained extended-spectrum beta-lactamase genes or carbapenemase genes, respectively, suggesting a bias towards submission of antibiotic-resistant isolates. The known multidrug-resistant high-risk clones ST258 and ST307 were the predominant sequence types. A total of 32 (3.3%) of these isolates contained aerobactin biosynthesis genes and 26 (2.7%) contained at least two genetic features of hvKP strains, suggesting elevated levels of virulence. We identified 6 (0.6%) isolates that were STs associated with hvKP: ST23 (n = 4), ST380 (n = 1), and ST65 (n = 1).

CONCLUSIONS

Examination of consecutive isolates from a single center demonstrated that multidrug-resistant high-risk clones are indeed common, but a small number of hypervirulent K. pneumoniae isolates were also observed in patients with no recent travel history to Asia, suggesting that these isolates are undergoing community spread in the United States. A larger collection of publicly available bloodstream isolate genomes also suggested that hypervirulent K. pneumoniae strains are present but rare in the USA; however, this collection appears to be heavily biased towards highly antibiotic-resistant isolates (and correspondingly away from hypervirulent isolates).