In vitro Biofilm Formation Ability of Clinical Isolates of Salmonella enterica Serovars Typhi and Paratyphi

Abstract

In the present study the ability of clinical isolates of Salmonella enterica serovars Typhi (n = 30) and Paratyphi A (n = 11) to form biofilm on abiotic surface was investigated. All isolates were found capable of biofilm formation in a microtitre plate assay. Upon optimization of biofilm formation by the test isolates, Adherence test medium (ATM) was found to be the best medium for biofilm formation by both S. enterica serovars Typhi and Paratyphi. Growth was optimized by incubation at 37°C in an orbital shaker set at 150 rpm for 48-72 hours. Biofilms were best detected when washed with PBS (1X), stained with crystal violet (1%) and subsequently washed with acetone (33%). Optical density (OD) readings were better correlated with growth at 570 nm when compared to 600 nm. Of the 28 Salmonella Typhi isolates, 17 (61%) were very strong biofilm producers, 8 (29%) were strong biofilm producers and 3 (11%) were moderate biofilm producers. On the other hand, out of 13 S. Paratyphi, 9 (69%) were very strong biofilm producers, 3 (23%) were strong biofilm formers and 1 (8%) was a moderate biofilm producer. None of them were weak biofilm producers. The present study raises concern from a public health point of view because the ability of the clinical isolates to form biofilm would indicate their ability of being transmitted from abiotic surface to uninfected host giving rise to disease.

Bangladesh J Microbiol, Volume 31, Number 1-2,June-Dec 2014, pp 35-39