Bacteriology and clinical outcomes of pleural infections in Singapore: an 8-year retrospective observational study.

BACKGROUND

Pleural infections pose significant clinical challenges due to diagnostic delays, poor culture yield, and rising regional incidence. Local microbial data is vital to inform empirical therapy, particularly given geographical variation and low pleural fluid culture positivity. We aim to describe the microbiological profile of pleural infections in Singapore and identify factors associated with culture positivity and mortality.

METHODS

A retrospective study was conducted on patients diagnosed with pleural infections at Tan Tock Seng Hospital between July 2016 and March 2024. Clinical, biochemical, and microbiological data of community and hospital-acquired pleural infections were analysed and compared. Logistic regression identified predictors for pleural fluid culture positivity and mortality.

RESULTS

A total of 561 patients had pleural infections. Culture positivity was 29.2%, with Streptococcus anginosus, Klebsiella pneumoniae, and anaerobes being most common organisms isolated. There was a predominance of gram-positive organisms for community-acquired infections, while gram-negative organisms being more prevalent in hospital-acquired infections. Patients with hospital-acquired infections had higher mortality (in-hospital: 26.1% vs. 7.2%, P<0.001). Culture positivity was associated with higher comorbidity index, neutrophil-to-lymphocyte ratio, hospital-acquired infection, and elevated lactate dehydrogenase (LDH). Age, comorbidity burden and hospital-acquired infection were independent predictors of mortality, while there was no pathogen-specific effect on outcomes.

CONCLUSIONS

The bacteriology of local pleural infections differs from that previously published of the region. Reasons for these may include an older population, the impact of vaccinations, and high burden of comorbidities such as diabetes and relatively high incidence of lung cancer in the region. The low culture positivity indicates the limitations of conventional culture methods and underscores the need for efforts to improve microbiological detection.