Carvacrol Essential Oil: A Natural Antibiotic against Zoonotic Multidrug-Resistant <i>Staphylococcus</i> Species Isolated from Diseased Livestock and Humans

• Main Authors: Ahmed H. Abed (Author), Esraa F. Hegazy (Author), Sherif A. Omar (Author), Rehab M. Abd El-Baky (Author), Ahmed A. El-Beih (Author), Ahmed Al-Emam (Author), Ahmed M. S. Menshawy (Author), Eman Khalifa (Author)
• Format: Book
• Published: MDPI AG, 2021-10-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 10.3390/antibiotics10111328; 2079-6382
• Keywords: <i>Staphylococci</i>; <i>S. aureus</i>; antimicrobial resistance; MRSA; VRSA; haemolysis; Therapeutics. Pharmacology; RM1-950
• Source: Antibiotics, Vol 10, Iss 11, p 1328 (2021)

<i>Staphylococcus</i> species cause diseases in animals and humans. The prevalence and antimicrobial profiles of <i>Staphylococcus</i> spp. in animals and human samples in the Minya Governorate, Egypt, were determined, and resistance- and virulence-associated genes were observed in multidrug-resistant (MDR) isolates. Moreover, the antibacterial effect of carvacrol essential oil (EO) on the MDR isolates was studied. A total of 216 samples were aseptically collected from subclinically mastitic cow's milk (<i>n</i> = 100), sheep abscesses (<i>n</i> = 25) and humans (<i>n</i> = 91). Out of 216 samples, a total of 154 single <i>Staphylococcus</i> species (71.3%) were isolated. The most frequent bacterial isolates were <i>S. aureus</i> (43%), followed by <i>S. schleiferi</i> (25%), <i>S. intermedius</i> (12%), <i>S. xylosus</i> (12%), <i>S. haemolyticus</i> (4.5%), S. <i>epidermidis</i> (2%) and <i>S. aurecularis</i> (1%). Haemolytic activity and biofilm production were detected in 77 and 47% of isolates, respectively. Antimicrobial susceptibility testing showed a high degree of resistance to the most commonly used antimicrobials in human and veterinary practices. The <i>mec</i>A, <i>van</i>A, <i>van</i>C1 and <i>erm</i>C resistance genes were detected in 93, 42, 83 and 13% of isolates, respectively. Moreover, <i>hla</i>, <i>ica</i>A and <i>ica</i>D virulence genes were detected in 50, 75 and 78% of isolates, respectively. Carvacrol effectively inhibited the growth of all tested isolates at concentrations of 0.1, 0.05 and 0.04% while a concentration of 0.03% inhibited 75% of isolates. Interestingly, some phenotypic changes were observed upon treatment with a carvacrol oil concentration of 0.03%. All the treated MDR <i>Staphylococcus</i> isolates changed from multidrug resistant to either susceptible or intermediately susceptible to 2-3 antimicrobials more than parental bacterial isolates. Real-time PCR was applied for the detection of the differential expression of <i>mec</i>A and <i>van</i>C1 genes before and after treatment with carvacrol which revealed a mild reduction in both genes' expression after treatment. <i>Staphylococcus</i> spp. Containing MDR genes are more likely to spread between humans and animals. From these results, carvacrol EO is a promising natural alternative to conventional antimicrobials for pathogens impacting human health and agriculture due to its potential antimicrobial effect on MDR pathogens; even in sub-lethal doses, carvacrol EO can affect their phenotypic properties and genes' expression.