1318. Clinical and Molecular Characteristics of Hypermucoviscous Klebsiella pneumoniae Causing Pneumonia in Korea

Abstract Background Invasive Klebsiella pneumoniae (K. pneumoniae) was emerged in Asia, well-known for community-onset liver abscess. Healthcare-associated pneumonia caused by hypervirulent K. pneumoniae has been reported in recent studies. The purpose of this study was to evaluate the clinical and molecular characteristics of hypervirulent K. pneumoniae compared with classic K. pneumoniae in respiratory infection. Methods The study was performed on 163 K. pneumoniae isolates of respiratory infections collected from Keimyung University of Dongsan Medical Center from November 2013 to November 2015; group A, as classic K. pneumoniae and group B, as hypervirulent K. pneumoniae. Hypermucoviscous phenotype was confirmed with string test. Capsular serotypes, rmpA, magA, allS, mrkD, entB, kfu, and iutA were identified using specific primers by polymerase chain reaction. The biofilm mass was determined using the microtiter plate assay measured by optical density (OD, 570nm). Results A total 163 patients were analyzed, 100 (61.3%) of group A and 68 (38.7%) of group B. Community-acquired pneumonia was observed in 49.2% of group B and 18.0% of group A (p=0.001). Underlying diseases except chronic lung disease were more associated with group A. Mean age (72.6±11.7 vs. 68.8±12.5 years, p=0.051) and antimicrobial resistant rates were higher in group A. Mechanical ventilators (21.0% vs. 36.5%, p=0.030) was more associated with group B. Concordances of initial antibiotics (57.5% vs. 92.1%, p=0.001) were more observed in group B. Biofilm formation and infection related 30-day mortality showed no differences between the two groups. Conclusion Contrary to our expectations, hypervirulent K. pneumoniae was more associated with community-acquired pneumonia in this study. Compared to classic K. pneumoniae, hypervirulent K. pneumoniae showed more association with severe pneumonia and less association with underlying diseases. In respiratory infection, biofilm formation was not different according to hypermucoviscousity. Disclosures All Authors: No reported disclosures

. Workflow Conclusion. Limitations include a low prevalence of renal failure in the study population, and lack of a standardized respiratory infection evaluation. Our results suggest that empiric coverage for P. aeruginosa may not be needed at our center in this cohort of older patients with clinical characteristics sometimes thought to be risk factors for P. aeruginosa.

Clinical and Molecular Characteristics of Hypermucoviscous Klebsiella pneumoniae Causing Pneumonia in Korea
Ji Yeon Lee, n/a 1 ; Hyun Ah Kim, n/a 1 ; Miri Hyun, n/a 1 ; 1 Keimyung University School of Medicine, Daegu, Taegu-jikhalsi, Republic of Korea

Session: P-73. Respiratory Infections -Bacterial
Background. Invasive Klebsiella pneumoniae (K. pneumoniae) was emerged in Asia, well-known for community-onset liver abscess. Healthcare-associated pneumonia caused by hypervirulent K. pneumoniae has been reported in recent studies. The purpose of this study was to evaluate the clinical and molecular characteristics of hypervirulent K. pneumoniae compared with classic K. pneumoniae in respiratory infection.
Methods. The study was performed on 163 K. pneumoniae isolates of respiratory infections collected from Keimyung University of Dongsan Medical Center from November 2013 to November 2015; group A, as classic K. pneumoniae and group B, as hypervirulent K. pneumoniae. Hypermucoviscous phenotype was confirmed with string test. Capsular serotypes, rmpA, magA, allS, mrkD, entB, kfu, and iutA were identified using specific primers by polymerase chain reaction. The biofilm mass was determined using the microtiter plate assay measured by optical density (OD, 570nm).

Results.
A total 163 patients were analyzed, 100 (61.3%) of group A and 68 (38.7%) of group B. Community-acquired pneumonia was observed in 49.2% of group B and 18.0% of group A (p=0.001). Underlying diseases except chronic lung disease were more associated with group A. Mean age (72.6±11.7 vs. 68.8±12.5 years, p=0.051) and antimicrobial resistant rates were higher in group A. Mechanical ventilators (21.0% vs. 36.5%, p=0.030) was more associated with group B. Concordances of initial antibiotics (57.5% vs. 92.1%, p=0.001) were more observed in group B. Biofilm formation and infection related 30-day mortality showed no differences between the two groups.
Conclusion. Contrary to our expectations, hypervirulent K. pneumoniae was more associated with community-acquired pneumonia in this study. Compared to classic K. pneumoniae, hypervirulent K. pneumoniae showed more association with severe pneumonia and less association with underlying diseases. In respiratory infection, biofilm formation was not different according to hypermucoviscousity.
Disclosures. Background. Hospital-acquired and ventilator-associated pneumonia (HAP/VAP) cause significant morbidity and mortality. Guidelines recommend broad-spectrum empiric antibiotic therapy, including treatment for Pseudomonas aeruginosa (PSAR) and methicillin-resistant Staphylococcus aureus (MRSA), followed by de-escalation (DE). This study sought to assess the impact of DE on treatment failure.
Methods. This single-center retrospective cohort study screened all adult patients with a discharge diagnosis code for pneumonia from 2016-2019. Patients were enrolled if they met pre-defined criteria for HAP/VAP ≥48 hours after admission. Date of pneumonia diagnosis was defined as day 0. Spectrum scores were calculated, and DE was defined as a score reduction on day 3 versus day 1. Patients with DE were compared to patients with no de-escalation (NDE). Data were compared using chi-square, Mann-Whitney U, or T-tests. The primary outcome was composite treatment failure, defined as all-cause mortality or re-admission for pneumonia within 30 days of diagnosis, analyzed using a Cox proportional hazards analysis to control for confounding variables.

Session: P-73. Respiratory Infections -Bacterial
Background. Lefamulin is a first-in-class, oral and IV pleuromutilin antibiotic approved in the US, EU, and Canada for the treatment of community-acquired bacterial pneumonia (CABP) in adults. Lefamulin inhibits bacterial protein synthesis via a unique mechanism of action and its potency against S. aureus has been well established. We evaluated the in vitro activity of lefamulin against S. aureus from patients with cystic fibrosis (CF).
Methods. Unique isolates (n=224) were collected from the lower respiratory tract (LRT) of children (≤17 years old) with CF and LRT infection. Organisms were from qualified respiratory specimens and determined to be the probable cause of infection by the participant center. The isolates were collected in 2018-2020 from 22 medical centers in 11 countries and tested by broth microdilution methods at JMI Laboratories. Most isolates were from the US (43.3%), Spain (24.1%), France (20.5%), and Costa Rica (7.1%).