Abstract
Background
Substandard or falsified antibiotics can account for therapeutic failure even when laboratory susceptibility testing reports the causative organism as susceptible. Ceftriaxone is the most prescribed antibiotic in the Buea Health District, yet no published data have evaluated the in vitro potency of the many commercial ceftriaxone brands sold in the district. This study assessed the antibacterial activity and inter-product variability of ceftriaxone brands sold in the Buea Health District.
Methods
In this analytical cross-sectional laboratory study, ceftriaxone was purchased from medicine outlets across the Buea Health District. Antibacterial activity was screened by the agar well diffusion method, and MIC was determined against Escherichia coli ATCC 25922 and two known ceftriaxone-susceptible clinical isolates. Test of association between brand cost and MIC acceptability was examined using logistic regression.
Results
Thirty-two ceftriaxone products from 14 brands (coded A-N) were retained. All 32 products showed measurable antibacterial activity against the test organisms. Nine out of the 32 products (28.1%) showed unacceptable MIC against E. coli ATCC 25922. Brand A and brand L recorded the lowest and highest MIC respectively against all three test organisms. Of the 9 products with an unacceptable MIC against E. coli ATCC 25922, four belonged to Brand L. Ceftriaxone costing <1,000 XAF was significantly and independently associated (aOR = 21.96, CI: 1.48–326.48; p = 0.025) with unacceptable MIC against E. coli ATCC 25922 as compared to those costing ≥1,000 XAF.
Conclusion
All 32 ceftriaxone products sold across the Buea Health District had antibacterial activity against Escherichia coli ATCC 25922 and the two clinical isolates tested. However, approximately one in four ceftriaxone antibiotics tested showed an unacceptable MIC against the reference strain and this reduced potency was significantly associated with low-cost products. These findings support routine antibiotic potency surveillance to prevent therapeutic failure and reinforce confidence in susceptibility-guided prescribing.