BEHAVIOUR OF MARINE MICROFLORA TOWARDS ANTIBIOTICS I. SENSITIVITY TOWARDS CHLORTETRA CYCLINE (CTC)

Abstract

The sensitivity of 61 cultures of bacteria isolated from
!fish towards chlortetracycline (CTC) at 5 ppm and 20 ppm levels
lhas been determined on two solid media, viz; sea water agar (SW A)
and a distilled water based medium consisting of peptone, beef
extract, glucose and NaCI (PBGA). The cultures employed consisted
of (i) gram-negative rods of marine origin viz; Achromobacler,
Pseudomonas, Vibrio and Flavobacterium and (ii) gram positive orga·
nisms viz; Micrococci and Corynebacterium. Depending on the
inhibition zone diameter, the order of CTC sensitivity was found
to be Pseudomonas < Vibrio < Achromoba.cter as determined on
PBGA at CTC levels of 5 and 20 ppm. The SWA enhanced the
development of resistance in majority of the cultures as compared
to PBGA. PBG broth containing CTC at less than 10 ppm
exerted a bacteriostatic effect only while that containing 10 ppm
or more exerted a bactericidal effect on Achromobacter, Pseudomonas
and Micrococci cuhures. The significance of these results in fish
preservation by CTC is discussed.