Effect of Selected Antibiotics on Biofilm Formed by Salmonella Enterica Serovars Typhi and Paratyphi

Abstract

Salmonella enterica serovars Typhi and Paratyphi are the causative agents of typhoid and paratyphoid, respectively, in human. Salmonella is able to form biofilms whereby members are resistant and persistent in both host and nonhost environments. In the present study the effect of the antibiotics, Azithromycin, Imipenem, Ceftriaxone and Cefixime, on planktonic and biofilm phase clinical isolates of Salmonella enterica serovars Typhi (n = 30) and Paratyphi A (n= 07) was investigated. MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) of planktonic phase bacteria were determined and compared with MRC (Minimum Re-growth Concentration) and MBEC (Minimum Biofilm Eradication Concentration) of biofilm population. The present study indicates that, with the exception of Azithromycin, a considerably higher concentration is needed for all other antibiotics investigated to inhibit growth of test isolates in the biofilm phase. We conclude that the requirement of Azithromycin at sub-MIC concentration to inhibit/kill Salmonella in biofilm is of particular significance in that it can be employed for the eradication of Salmonella spp. biofilms. Bangladesh J Microbiol, Volume 37 Number 2 December 2020, pp 62-65