Molecular detection of serratia marcescens isolated from dairy products and study of the inhibition effect of some plant extracts (garlic and ginger) compared to antimicrobial agents

Abstract

Milk and dairy products are essential and basic food nutritional factor in the diet of human with high value as a portion of healthy food, and one of the most important causes of food poisoning is contamination of milk and milk products with micro-organisms. Therefore, this study was prepared to detect the contamination of dairy products with serratia marcescens that produce prodiginine pigment in milk and dairy products, Samples of (pasteurized milk, fermented milk drink, and cheeses with high moisture) obtained from various common establishments, such as supermarkets, dairies, and bakeries, from city of Baghdad during 2019 and examined for the presence of s. marcescens, From a total of 60 isolates, thirteen (21.6%) Isolates that presenting pinkish or reddish color were identified by MicrogenTM GnA+B-ID System then confirmed with PCR using 16SrRNA gene with 1500-bp. Seventeen antibiotics belonging to 11 classes, were used to determination of antimicrobial resistance profile, all isolates demonstrated at least one antibiotic resistance from the 17 tested. The most frequently observed resistance was to Cephalothin, was observed in 100% of the isolates. The antibacterial activity of both aqueous plant extracts for garlic and ginger inhibited the growth of the tested isolates. The largest inhibition zone diameter was 42 mm that watched with ginger with concentration of 1000%, compared with garlic that given 38mm. While the lowest inhibition haloes diameter against S. marcescens with concentration of 250% was 23mm with ginger and 22mm with garlic and the MIC was 12.5 mg/mL.