Detection and molecular characterization of staphylococci from eggs of household chickens

Authors: SYED, MUHAMMAD - University Of Haripur; Jackson, Charlene; RAMADAN, HAZEM - Mansoura University; AFRIDI, RIAZUDDIN - Hazara University; BANO, SHEHR - University Of Haripur; BIBI, SUMERA - University Of Haripur; FATIMA, BUSHRA - University Of Haripur; TABASSUM, SADIA - Hazara University; JAMIL, BUSHRA - National University Of Medical Sciences; KHAN, MUHAMMAD - Hazara University; Barrett, John; Woodley, Tiffanie

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2019
Publication Date: 4/19/2019
Citation: Syed, M., Jackson, C.R., Ramadan, H., Afridi, R., Bano, S., Bibi, S., Fatima, B., Tabassum, S., Jamil, B., Khan, M., Barrett, J.B., Woodley, T.A. 2019. Detection and molecular characterization of staphylococci from eggs of domesticated chickens. Foodborne Pathogens and Disease. https://doi.org/10.1089/fpd.2018.2585.
DOI: https://doi.org/10.1089/fpd.2018.2585

Interpretive Summary: Eggs are a healthy and nutritious food source, but may be contaminated by bacteria. Previous studies have reported the presence of staphylococci in eggs of farmed chickens, but no study has evaluated the staphylococcal population of eggs from domesticated chickens. In this study, staphylococci from eggs of domesticated chickens in Pakistan were isolated and characterized. Staphylococcus xylosus was the most frequently detected species; isolates were resistant to antimicrobials used in human medicine and harbored antimicrobial resistance genes. The isolates also produced an inhibitory substance capable of preventing the growth of a broad spectrum of bacteria including methicillin-susceptible and methicillin-resistant S. aureus, Salmonella enterica serotype Typhi, and Escherichia coli. Like table eggs, eggs of domesticated chickens also contain staphylococci that may be resistant to antimicrobials used to treat human infections. As consumption of eggs of domesticated chickens continues to gain in popularity worldwide, studies on these eggs are greatly needed to assess potential food safety concerns. Since S. xylosus is a documented opportunistic human pathogen and is also used in food production, this information is useful for consumers and personnel who handle eggs as safe handling and cooking methods should be followed to avoid colonization and infection with these resistant bacteria. This information is also useful for scientists as they develop prevention and control strategies.

Technical Abstract: Eggs are a healthy and nutritious food source, but may be contaminated by bacteria. Previous studies have reported the presence of staphylococci in eggs of farmed chickens, but no study has evaluated the staphylococcal population of eggs from domesticated chickens. In this study, staphylococci from eggs (n=275) of domesticated chickens collected from November 2016 to March 2017 from different villages of Khyber Pakhtunkhwa province, Pakistan were characterized. Seven species of staphylococci were identified from 65 eggs including the predominant species, Staphylococcus xylosus (49/275; 17.8%). S. xylosus isolates (n=73) were tested for antimicrobial susceptibility, presence of resistance genes, genetic relatedness and inhibitory activity against other bacteria. The majority of isolates were resistant to oxacillin (83.6%) and tetracycline (24.7%), but also exhibited resistance to daptomycin and linezolid (5.5% each). Of the ten resistance genes tested, isolates were only positive for mecA (35.6%; 26/73), mecC/C1 (2.7%; 2/73) and tet(K) (14/73; 19%). Using Pulsed-field Gel Electrophoresis (PFGE), nine clusters had identical PFGE patterns. Isolates produced inhibitory activity against a broad spectrum of bacteria; 20.5%, 19.2%, 17.8%, and 16.4% of S. xylosus were able to inhibit growth of Salmonella enterica serotype Typhi, methicillin-susceptible S. aureus, Escherichia coli and methicillin-resistant S. aureus, respectively. This study demonstrated the presence of genetically related antimicrobial resistant S. xylosus from eggs from domesticated chickens. Like table eggs, eggs of domesticated chickens also contain staphylococci that may be resistant to antimicrobials used to treat human infections. Further study of these egg types and their microbial composition is warranted.