The effect of heat treatment, pH and osmotic pressure on viability of Pseudomonas aeruginosa isolated from raw dairy products in Baghdad. B.

In order to evaluate the effect of heat treatment, pH and osmotic pressure on viability of Pseudomonas aeruginosa isolated from some raw dairy products, a total of 73 samples of locally produced Cows raw milk (33 samples) and soft cheese (40 samples) were collected from different markets in Baghdad during February till August 2014, in which they processed (at Zoonoses Unit) according to standard and modified reference food and dairy microbiology procedures by using of gold standard, Cetrimide-Naldixic acid P. aeruginosa Chromogenic agar (CNP), rapid biochemical panel identification system (Microbact) and polyclonal latex agglutination kit. All isolates were subjected to pasteurization like treatments at 63 ©C for 30 minutes (low temperature long time protocol, LTLT) and at 72 ©C for 16 seconds (high temperature short time protocol, HTST), then exposed to acidified gradient environments at pH 2 & 5 and modified brine solutions (salty environments) at 3, 5 & 7 gradient concentrations and monitored for several hours to check their tolerance profiles. The results showed isolation of 47 isolates of P. aeruginosa out of 73 samples (64.38%): 17 (23.28%) isolates from raw milk samples, in which 5 (29.41%) isolates were resistant to HTST and all susceptible to LTLT, 2 (11.76%) isolates tolerate pH 5 and 1 (5.89%) isolate tolerate pH 2, 3 (11.76%) isolates tolerate salty environments (3 & 5%) and 1 (5.89%) isolate tolerate 7% brine solution; and 30 (41.1%) isolates from soft cheese samples, in which 12 (40%) isolates were resistant to HTST and all susceptible to LTLT, 7 (23.33%) isolates tolerate pH 5 and 3 (10%) isolates tolerate pH 2, 10 (23.33%) isolates tolerate 3% brine solution, 8 (10%) isolates tolerate 5% brine solution and 7 (23.33%) isolates tolerate 7% brine solution. These findings suggest indirectly presence of multi-stressors tolerance profiles among study isolates from Baghdad, thus recommend to monitoring these dairies periodically.