Detection of Streptococcus thoraltensis in Raw Milk with Special Reference to Their Antibiogram
Detection of Streptococcus thoraltensis in Raw Milk with Special Reference to Their Antibiogram
Hams M.A. Mohamed1, Mona A. El-Zamkan2*
ABSTRACT
The genus Streptococcus comprises a variety of pathogenic and commensal bacteria that show a surprising capacity for adaptation to new hosts and antimicrobial resistance, resulting in the spread of infection all over the world, leading to huge health loss. A total of 100 raw milk samples collected from small scale producers, farmers and markets at Qena city, Egypt, were examined for the presence of Streptococcus species. The preliminary identification was confirmed by using VITEK®2 system which revealed the presence of four isolates of S. thoraltensis. The antimicrobial susceptibility of the obtained isolates was detected phenotypically and genotypically, in addition to the ability of these isolates to produce biofilm and protease enzyme. All the isolates displayed resistance to penicillin and oxacillin, while, two isolates were resistant to vancomycin and erythromycin, and three isolates were resistant to linezolid. None of the isolates were resistant to tetracycline, chloramphenicol or clindamycin. B-lactams drug resistance encoded by pbp1A gene could be detected in all the isolates, while one isolate harbored vanA and optrA gene, and no isolate harbored ermB gene. Two isolates were biofilm producers, one of them possessed lmb gene while both lacked brpA gene. Only one isolate expressed a proteolytic activity. It was thought that S. thoraltensis is non-pathogenic in humans, however, recently, it was implicated in many infections and its isolation from raw milk represents a potential risk for human health. According to our best efforts of research, it is the first time to isolate S. thoraltensis from raw milk in Egypt.
Keywords | Raw milk, Streptococcus thoraltensis, Antimicrobial resistance, Biofilm production, Proteolytic activity
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