Klebsiella pneumoniae pneumonia in patients with rheumatic autoimmune diseases: clinical characteristics, antimicrobial resistance and factors associated with extended-spectrum β-lactamase production

BACKGROUND: Over the past decades, Klebsiella pneumoniae (K. pneumoniae) infections have been increasing and affected immunocompromised patients nosocomially and communally, with extended-spectrum β-lactamase (ESBL) production becoming a major concern. Patients with rheumatic autoimmune diseases, mostly receiving immunosuppressive therapy, are vulnerable to various infections, including K. pneumoniae. However, few have investigated K. pneumoniae infections in this specific population. This study aimed to identify factors associated with ESBL production and mortality of K. pneumoniae pneumonia among patients with rheumatic autoimmune diseases in the Emergency Department. METHODS: We retrospectively investigated patients with rheumatic diseases who were diagnosed with K. pneumoniae pneumonia. The diagnosis of K. pneumoniae pneumonia was based on clinical manifestations, radiological findings and microbiological testing results. Prognostic factors and risk factors for ESBL production were determined with univariate and multivariate logistic regression analysis. Empirical therapy and antimicrobial susceptibility data were also collected. RESULTS: Of 477 K. pneumoniae pneumonia patients, 60 were enrolled into this study. The in-hospital mortality was 28.3%. Septic shock, ICU admission, the need for mechanical ventilation and change of antibiotics due to clinical deterioration, all related to mortality, were included as unfavorable clinical outcomes. Multivariate analysis suggested that ESBL production (OR, 6.793; p = 0.012), initial PCT ≥ 0.5 ng/ml (OR, 5.024; p = 0.033) and respiratory failure at admission (OR, 4.401; p = 0.046) predicted increased mortality. ESBL production was significantly associated with dose of corticosteroids (OR, 1.033; p = 0.008) and CMV viremia (OR, 4.836; p = 0.032) in patients with rheumatic autoimmune diseases. Abnormal leukocyte count (OR, 0.192; p = 0.036) was identified as a protective factor of ESBL-producing K. pneumoniae pneumonia. The most commonly used empirical antibiotic was ceftazidime, while most isolates showed less resistance to carbapenems and amikacin in susceptibility testing. CONCLUSIONS: K. pneumoniae pneumonia could be life-threatening in patients with rheumatic autoimmune diseases. Our findings suggested that ESBL production, initial PCT ≥ 0.5 ng/ml and respiratory failure at admission were independent factors associated with poor prognosis. Dose of corticosteroids and CMV viremia, predicting ESBL production in K. pneumoniae pneumonia, may help make individualized antibiotic decisions in clinical practice.