Abstract
To assess biofilm formation ability and identify differences in the prevalence of genes involved in biofilm formation among Staphylococcus aureus strains isolated from different food samples, the ability of biofilm formation among 97 S. aureus strains was evaluated using a colorimetric microtiter plate assay. Thirteen genes encoding microbial surface components recognizing adhesive matrix molecules, and the intracellular adhesion genes were detected by PCR using specific primers. Approximately 72% of the isolates produced biofilms. Among these isolates, 54.64% were weak biofilm producers, while 14.43% and 3.09% produced moderate and strong biofilms, respectively. The icaADBC, clfA/B, cidA, and fib genes were detected in all the S. aureus strains, whereas the bap gene was not present in any of the strains. The occurrence of other adhesin genes varied greatly between biofilm‐producing and nonbiofilm‐producing strains. However, a significant difference was observed between these two groups with respect to the fnbpB, cna, ebps, and sdrC genes. No obvious evidence was found to support the link between PFGE strain typing and the capacity for biofilm formation. Considerable variation in biofilm formation ability was observed among S. aureus strains isolated from food samples. The prevalence of adhesin‐encoding genes also varied greatly within strains. This study highlights the importance of biofilm formation and the adhesins of S. aureus strains in food samples.
Highlights
Staphylococcus aureus is a major foodborne pathogen that causes food poisoning due to the ingestion of heat‐stable staphylococcal enterotoxins (Balaban & Rasooly, 2000; Le Loir, Baron, & Gautier, 2003)
Biofilms are considered a part of the normal life cycle of S. aureus in the environment (Otto, 2008), where planktonic cells attach them‐ selves to solid surfaces and subsequently proliferate and accumulate in multilayer cell clusters embedded in special three‐dimensional structures as mushrooms or towers separated by fluid‐filled chan‐ nels (Azara, Longheu, Sanna, & Tola, 2017)
Pulsed‐field gel electrophoresis (PFGE) of the S. aureus isolates was performed in a CHEF Mapper system (Bio‐Rad Laboratories) using chromosomal DNA digested with SmaI (New England Biolabs Inc.) according to the conditions described previously by Chung, Jeon, Sung, Kim, and Hong (2008), with some modifications
Summary
Staphylococcus aureus is a major foodborne pathogen that causes food poisoning due to the ingestion of heat‐stable staphylococcal enterotoxins (Balaban & Rasooly, 2000; Le Loir, Baron, & Gautier, 2003). Biofilms can protect this microbe from the action of antibiotic drugs, proteases released by host defense cells and environmental stress factors (Singh, Ray, Das, & Sharma, 2010). This protection may contribute to the per‐ sistence of S. aureus in food processing environments, increasing cross‐contamination risks and subsequent economic loss due to recalls of contaminated food products (Vazquez‐Sanchez et al, 2013). Clones isolated from different food sources can differ in their ability to form biofilms. It is unclear whether all MSCRAMMs play important roles in this process. We investigated biofilm production and evaluated the biofilm‐related genes of S. aureus strains isolated from different types of food in markets in Hangzhou
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