Clinical and Genomic Characterization of Carbapenem-Resistant Klebsiella pneumoniae with Concurrent Production of NDM and OXA-48-like Carbapenemases in Southern California, 2016-2022

The global emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has become a critical public healthcare concern due to treatment challenges and high mortality. In recent years, there has been an increase in cases of CRKP co-producing New Delhi metallo-β-lactamases (NDM) and oxacillinase 48 (OXA-48)-like carbapenemases in the US. The aim of this study was to correlate the clinical and genomic characteristics of CRKP co-producing NDM and OXA-48-like carbapenemases isolated from patients in Southern California since 2016. Whole-genome sequencing was performed on clinical isolates obtained from various sources, including blood, abdominal fluid, wounds, and urine. Genetic diversity was observed in these CRKP, including ST-14, ST-16, ST-167, ST-437, ST-2096, and ST-2497 lineages. Phylogenetic analysis revealed two closely related clusters (ST-14 and ST-2497), with single nucleotide polymorphism (SNP) differences ranging from 0 to 36, suggesting a possible local spread of these CRKP. Significant antimicrobial resistance (AMR) genes were identified in these CRKP, including bla_NDM-1, bla_NDM-5, bla_OXA-232, bla_OXA-181, bla_CTX-M-15, armA, tet(A), and tet(D). Moreover, pColKP3-type and Inc-type plasmids known to harbor AMR genes were also detected in these isolates. Most of the patients infected with this rare type of CRKP died, although their severe comorbidities also played important roles in their demise. Our study highlighted the extremely limited treatment options and poor clinical outcomes associated with these dual-carbapenemase-producing CRKP. Real-time genomic surveillance of these unusual and deadly CRKP can provide critical information for infection prevention and treatment guidance.

Catheter-Related Bloodstream Infection Caused by Mycolicibacterium iranicum, California, USA

We describe a case of catheter-related bacteremia caused by Mycolicibacterium iranicum in the United States. The case highlights the value of using next-generation sequencing to identify infrequent and emerging pathogens and the challenges associated with choosing appropriate treatments because of limited knowledge of drug resistance mechanisms in those emerging pathogens.

1457. Epidemiology of Human Herpesvirus-6 Meningoencephalitis in Los Angeles County, 2016-2020

Background

Human herpesvirus 6 (HHV-6) is ubiquitous and a known central nervous system (CNS) pathogen. However, HHV-6 in cerebrospinal fluid (CSF) without clinical findings of meningoencephalitis (ME) may not represent true infection, but rather, asymptomatic viral reactivation, chromosomal integration, or latent activation. With the introduction in 2015 of a rapid polymerase chain reaction (PCR) multiplex panel that simultaneously tests for 14 CNS pathogens, reports of HHV-6 PCR positive ME have increased. We sought to understand the epidemiology of HHV-6 ME by evaluating reported cases in Los Angeles County (LAC) between 2016-2020.

Methods

ME is a reportable condition in LAC. We reviewed clinical, laboratory, and radiologic data for all HHV-6 PCR positive cases reported in LAC between 2016-2020. We developed case classification categories, “unlikely,” “possible,” and “likely”, based on symptoms, CSF profile, and alternative diagnoses (see Table 1).

Results

A total of 67 HHV-6 ME cases were reported (see Table 2). Reports increased over time, with one in 2016, 12 in 2017, 17 in 2018, 20 in 2019, and 17 in 2020. Median age was 9 months (range 0d-78y), and 47 (70%) were < three years old. Forty-four (66%) were male. Six (9%) were immunocompromised, including one hematopoietic stem cell transplant recipient. Nineteen (28%) had abnormal CSF, and eight (12%) received therapy for HHV-6.

Five cases (7%) were classified as “likely” HHV-6 ME, 12 (18%) “possible,” and 50 (75%) “unlikely”. The “likely” cases ranged in age from 7 months to 12 years old, and none were immunocompromised. One received antiviral therapy and was discharged to a rehabilitation facility, the other four were discharged home with full recovery.

Conclusion

The significance of HHV-6 in CSF remains challenging to determine both clinically and epidemiologically. In the setting of increased testing, increasing detection of HHV-6 in CSF may not reflect increasing rates of HHV-6 ME. The majority of reported HHV-6 ME cases were “unlikely” based on our classification. Classifying cases with alternative diagnoses as ‘unlikely” may miss cases with multiple true infections, particularly in the immunocompromised. It is important to consider clinical presentation, CSF profile and other diagnoses to understand the true burden of HHV-6 ME.

Disclosures

All Authors: No reported disclosures.

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.

Disguised as Ovarian Tumor: A Rare Case of Uterine Abscess due to Hypervirulent Klebsiella pneumoniae Infection

Hypervirulent Klebsiella pneumoniae (hvKp) causes invasive infections in the community setting. We report a rare case of uterine abscess due to hvKp, which appeared as a large-sized ovarian tumor-like pelvic mass. A timely laboratory warning of possible hvKp prompted correct diagnosis and helped guide perioperative decision making, contributing to successful treatment.