Salmonella enterica Frequency in Ground Meats By: Laurel Kovach

Salmonella enterica Frequency in Ground MeatsBy: Laurel Kovach White, D., S. Zhao, R. Sudler, S. Ayers, S. Friedman, S. Chen, P. McDermott, S. McDermott, D. Wagner, and J. Meng. 2001. The isolation of antibiotic- resistant salmonella from retail ground meats. New England Journal of Medicine 345:16:1147-1154.

Background • Salmonella is known to cause gastroenteritis and enteric fever. • It can be caused by the ingestion of any contaminated meat, vegetable, or liquid. • There are many forms of Salmonella, some of which are multidrug resistant. • It is important to find other ways to control Salmonella.

gastroenteritis • inflammation of the lining of the stomach and intestines

Pathway of Salmonella enterica • Small intestine • Specialized M cells of the Peyers Patches • Regional nodes • Liver • Spleen

M cells • Folds along the intestinal wall believed to be responsible for phagocytizing the invasive bacteria

How does Salmonella gain access to the small intestine? • The most critical step for Salmonella is the ability to invade the small intestine. • First, the cellular membrane rearranges to form actin (M cells) ruffles. • The actin ruffles phagocytize the bacteria.

Purpose of Study • Test antimicrobial susceptibility/resistance • Frequency in Ground meats

Cause of Resistance • Believed to be from the use of antibiotics in animals raised for food purposes.

Materials • 200 meat samples • 51 chicken • 50 beef • 50 turkey • 49 pork

Place of purchace • 3 retail stores in Washington D.C. area (Between June and September of 1998) • 98 at store 1 • 54 at store 2 • 48 at store 3

Gel Electrophoresis • Needed to isolate similar strains of bacteria to use in the experiment • Used to separate fragments of DNA resulting from digestion of restriction enzymes

Guidelines • DNA patterns could not differ from each other by more than 30% • Patterns of the same size and the same number of bands were considered to be the same strain • Patterns that differed by less than three bands were considered to be of the same subgroup

Frequency of Salmonella • 41 of 200 meat samples contained Salmonella isolates • Out of 4 samples each yielded two strains • Salmonella was more commonly found in poultry than pork.

Results for serotyping • Among the 45 isolates 13 different serotypes were identified • Istanbul (28%)- Chicken • Agona (22%)- All four types • Typhimurium- 4 pork, 4 chicken

Chart focus • Frequency in different meats • PFGE patterns • pulse field gel electrophoresis

Table 1

Antimicrobial Suceptibility • Tested for susceptibility to 17 different antibiotics • Used minimal inhibitory concentrations

Results • 84% were resistant to at least one antibiotic • 54% were resistant to at least three

Most Common Antibiotics for Resistance • Streptomycin • Sufamethoxazole • Tetracycline

Resistance • The 10 Agona isolates were resistant to nine antibiotics • All 13 Istanbul isolates were resistant to Tetracycline and Streptomycin • Six of these 13 were also resistant to Sulfamethoxazole • 7 of the eight Typhimurium isolates were resistant to five antibiotics

Don’t Worry • All strains of Salmonella were susceptible to the following - amikacin - apramycin - ciprofloxacin - nalidixic acid

Order of resistance to antibiotics • Tetracycline • Streptomycin • Sulfamethoxazole • Ampicillin

Resistance • Keep food frozen until ready to be cooked • Cook thoroughly before eating • refrigerate leftovers

Conclusion • 20% of ground meat samples were contaminated with 13 serotypes • Typhimurium causes the most illness and is resistant to many drugs • It is possible that resistance may be caused by the use of antibiotics in animals raised by food

Salmonella enterica Frequency in Ground Meats By: Laurel Kovach