Beta hemolysin gene of Staphylococcus phage 3AJ_2017 genome is a suitable molecular marker for identification and characterization of pathogenic Staphylococcus aureus

Background: Staphylococcus aureus cause diseases both in humans and animals. These diseases range from mild to fatal infections thus necessitating development of a specific molecular method for detection of pathogenic S. aureus. Objectives: To identify and analyze genetic profile of pathogenic S. aureus using bacteriophage based genetic biomarkers. Methods: Using culture and biochemical methods, 148 S. aureus (87 %) were isolated from 170 raw milk samples taken from 10 dairy farms in Marsabit and Isiolo counties in Northern Kenya between June 2016 and February 2017. The samples were collected directly from dairy lactating cows previously diagnosed with S. aureus in a follow-up study. The isolates were analyzed by PCR and sequencing of beta hemolysin (hlb) gene. The genetic relationship between five Kenyan S. aureus isolates and five isolates previously identified was inferred. Results: From the 96 isolates screened for hlb gene, 75 (78.1%) tested positive. Some of the positive isolates yielded a band size of 975 bp, while others 1100 bp. Through Basic Local Alignment Search Tool (BLAST) search analysis, the two different band sizes (975 bp and 1100 bp) were both confirmed to be hlb gene from S. aureus isolates indicating that the difference in band size may have been due to deletions that were detected in the 975 bp hlb gene. Some S. aureus isolates from Kenya appeared to be closely related to isolates from other parts of the world, while some showed a distant relationship. Conclusions: Phage-derived hlb gene is a suitable molecular marker for detection of pathogenic S. aureus.