The Abstract of
PHYSIOLOGICAL STUDY OF ENTEROTOXIGENIC Staphylococcus aureus ISOLATED FROM RAW AND ROASTED RED MINCED MEAT IN KIRKUK CITY
By Ali Namiq Sediq
March, 2016
“Total of 200 samples of minced raw and roastedred meat were randomly collected from different restaurants, unlicensed hawkers and food stalls in the center of Kirkuk city from the 1st of January 2015 to the end of May 2015 by 50 per samples of raw kebab, roastedkebab, raw meat burger and roastedmeat burger. The samples were subjected for determination of the aerobic bacterial counts, isolation, enumeration, and identification of Staphylococcus aureus and screening for Enterotoxigenic Staphylococcus aureus and studying the effect of some physiological factors on its growth.Samples collection and preparation were done according to the chapter one of Bacteriological Analytical Manual (BAM) (FDA, 2011).
The study showed that, 100%, 68%, 54%, and14% of rawkebab, raw meat burger, roasted kebab, and roasted meat burger samples respectively were contaminated with aerobic bacteria. The statistical analysis showed that the mean of total aerobic bacteria count in raw kebab was higher than the raw meat burger and in roasted kebab higher than the roasted meat burger while it was in raw meat samples higher than the roasted meat samples.
The Staphylococcus aureus isolates on Baired Parker (B.P.) media were identified microscopically and biochemically and the results shows that; (10%) Out of 200 samples contained Staphylococcus aureus, raw kebab isolates were the most frequent forming 7.5%, while raw meat burger formed 2%, then the roasted kebab were 0.5%, finally no isolate from roasted meat burger was obtained (0%).
The antimicrobial susceptibility test showed that (10%) of the twenty isolates were methicillin resistance (MRSA) and eighteen (90%) were sensitive (MSSA), seven (35%) of the twenty isolates were multidrug resistance S. aureus, however all the twenty isolates (100%) were resistant to Ampicillin, while all the twenty isolates were 100% sensitive to Ciprofloxacin, Trimethoprim sulfamethoxazole, and Vancomycin
The isolates were subjected to Revers Passive Latex Agglutination (RPLA) assay for detection of enterotoxins production from culture filtrates; six out of twenty isolates (30%) were Enterotoxigenic S.aureus, however 4 isolates produced only S.aureus Enterotoxin A (SEA) (20%), and two of them produced SEs (A+B) (10%).All the Enterotoxigenic isolates were obtained from raw meat samples. All the six Enterotoxigenic isolates were 100% positive for all biochemical testes (Coagulase, Catalase, Lecithinase, Lipase, Thermonuclease, Urease, DNase, Glucose fermentation, alkaline phosphatase, and ? hemolysis test).
The Physiological study of the Enterotoxigenic isolates showed that:
1- The inhibitory effect of NaCl concentration increased with increasing the incubation time .The inhibition percentage was significantly observed after 1hour with 47.3%, 91.5%, and 95.7%; while after 6 hours was 82.3%, 95.7% and 98.9% and finally it reached 94.3%, 99.99%, and 100% after12 hours for all of the six Enterotoxigenic isolates at 16%, 20%, and 22% NaCl concentrations respectively.
2- At 37?C there was no significant effect on Enterotoxigenic isolates growth at pH 5, 6, and 9after 12 hours, while there was a significant effect at 4 and 10.5 pH values with inhibitory percentage of 52.5%, and 99.8% respectively. The inhibitory effect of Alkaline and Acidic environments increased at 4?C with inhibitory percentage of 97.6%, 52.9, and 99.9% at 4, 9, and 10.5 pH values respectively.
3-The best growth temperature was at 37?C, while at 60 ?C 42.3% of the viable Enterotoxigenic isolates count had been reduced after 20 minutes, and 96.6% were eliminated at 70 ?C after the same period. 80 ?C were the lethal temperature after 20 minutes of heat treatment at pH 7.
4- The temperature of 4 ?C had a significant inhibitory effect on all of the Enterotoxigenic isolates after 168 hours (7days) at pH 7 with an inhibitory percentage of 99.8%. Meanwhile freezing at -18 had a significant inhibitory effect on the Enterotoxigenic isolates at pH 7 with an inhibitory percentage of 99.99%.”