High Mortality and Relapse Rates of Melioidosis (Burkholderia pseudomallei infections) in Singapore

Background:

Burkholderia pseudomallei is regarded as a bioterrorism threat and a common cause of community acquired infections in the tropics. Singapore is a small urban city without paddy fields and farming land spaces, but we continue to see cases of melioidosis. We report our 10-year clinical experience of patients with melioidosis managed in Singapore General Hospital and looked at the trends in the epidemiology, clinical features and mortality.

Methods:

Patients with a positive culture for B. pseudomallei during the period 1 Jan 2001 to 31 Dec 2010 were retrospectively identified and their case records were reviewed.

Results:

Among 170 patients, 82.4% were male and were mostly blue-collar workers. Diabetes mellitus was reported in 51.8% and cigarette smoking in 53.4%. The duration of symptoms was less than 2 weeks in 57.0%, sub-acute in 23.0% and more than 1 month in 20.0%. Bacteremia was present in 70.0% and lung disease in 71.8%. All initial isolates were susceptible to ceftazidime and only 1 isolate was intermediate susceptible to imipenem.

Among 156 patients started on induction therapy, 62.8% received only ceftazidime and 85.9% received more than 10 days of induction therapy. Among 126 patients who received maintenance therapy, 67.5% received the combination of co-trimoxazole and doxycycline and 61.1% received at least 20 weeks of therapy. Mortality rate was 25.9% with 16.5% attributable to melioidosis. Most (65.9%) deaths occurred early during the initial hospitalisation, with a median time to death of 6 days. Among the 142 survivors, there were 23.2% recurrences with the majority (69.7%) occurring in patients with incomplete treatment and a median time to recurrence of 53 days.

Conclusion:

In urbanised Singapore, our high mortality and recurrence rates are of concern. This highlights that melioidosis is still a serious infection locally and a need for aggressive therapeutics. We stress that prompt disease recognition with early appropriate treatment and compliance to therapy is critical. In-vitro antagonism between co-trimoxazole and doxycycline may have contributed to the high recurrence rates. A review of our traditional practice of using combination co-trimoxazole and doxycycline in the maintenance therapy and the recent shift in practice toward using co-trimoxazole only is underway.