Anaerobic Bacteremia Spectrum, Risk Factors and Susceptibility Pattern from a Clinical Laboratory in Pakistan

Abstract

Introduction and Objectives: Patients with malignancy, immunosuppression and recent surgery are particularly at risk of developing bacteremia with anaerobic organisms. Accurate and early identification of anaerobic bacteremia is crucial as these infections are associated with high mortality. In this study we have assessed the spectrum of bacteremic anaerobic isolates and compared their associated risk factors and susceptibility pattern with non-bacteremic anaerobic strains. These associations were also determined in Bacteroides vs. non-Bacteroides bacteremia.
Material and Methods: This study was conducted in Aga Khan University Clinical Laboratory. All the anaerobes isolated from blood and other sources during two study periods (2010-2011) and (2014-2017) were included. Anaerobes were identified and MICs of metronidazole were determined. Association of risk factors such as intra-abdominal infections, malignancy, liver disease,
diabetes mellitus and infective endocarditis with bacteremic and non bacteremic anaerobes was evaluated. Similar associations were also determined for Bacteroides and non Bacteroides bacteremia.

Results: A total of 72 isolates were isolated from blood and 155 from other sources during the two study periods. Over all 29% (21/72) bacteremic and 16.1% (25/155) of non-bacteremic isolates were resistant to metronidazole (p value = 0.239). Odd of developing anaerobic bacteremia was significantly higher in patients with intra-abdominal infections and liver disease. The odds of developing bacteremia were 3.6 times higher in elderly patients. Patients with anaerobic bacteremia had almost 7 times higher
mortality rate than non-bacteremia cases. Metronidazole resistance was found to be significantly associated with Bacteroides bacteremia.
Conclusion: This study shows that anaerobes are an important cause of bacteremia especially in cases with intra-abdominal infections, with liver disease and old age. It is associated with higher rates of mortality if not treated appropriately. Proper empirical therapy should be given to patients with these risk factors.

Key Words: Anaerobic bacteremia, risk factors, Bacteroides bacteremia, Non-Bacteroides bacteremia