Change in Antibiotic Susceptibility Pattern of Clinical Bacterial Isolates from Two Hospitals in Dhaka, Bangladesh over a Period of Three Years

Introduction: It is established that improper use of antibiotics leads to rapid development of bacterial antibiotic resistance. We investigated changes in the antibiotic susceptibility pattern of pathogenic bacteria in a megacity where improper antibiotic use is common.

Methodology: Data on the antibiotic susceptibility pattern of clinical isolates to 28 commonly used antibiotics was obtained from two hospitals at time point A (Jan-Dec 2009, or Nov-Dec 2010) and at about 12-36 months later (time point B), and the data were compared using the one-sided test for equality of proportions. For large samples, tests using Z-score and normal distribution were conducted; for small samples, Fisher’s exact test was performed.

Results: Of the 194 different pairs of isolate clusters compared; 66.5% of the cluster-pairs showed no change in the antibiotic susceptibility pattern. Of the remaining 33.5% of the isolate clusters, the time point B clusters showed a significant decrease in antibiotic susceptibility in 21.1% of the cases, and a significantly higher susceptibility in 12.4% of the cases, compared to the corresponding time point A clusters. The decreased antibiotic susceptibility was observed in 20.0% of the Gram-negative and 24.1% of the Gram-positive bacterial isolate clusters; and the increased antibiotic susceptibility was observed in 10.0% of Gram-negative and 18.5% of Gram-positive bacterial clusters.

Conclusions: Antibiotic resistance and susceptibility of Gram-positive and Gram-negative pathogenic bacteria may significantly change over a period as short as 1-3 years. Continuous vigilance of such changes in a region may allow development of regional strategies for rational antibiotic use.