MIC and MBC of Honey and Gold Nanoparticles against methicillin-resistant (MRSA) and vancomycin-resistant (VRSA) coagulase-positive S. aureus isolated from contagious bovine clinical mastitis

Abstract

Staphylococcus aureus is one of the major causative agents of the bovine clinical mastitis. This study aimed to isolate and identify S. aureus from cases of bovine clinical mastitis followed by phenotypic detection of MRSA and VRSA. The genotypic detection of MRSA was done through PCR detection of the resistance mecA gene. Furthermore, this study aimed to investigate the in vitro MIC and MBC of the Dodonaea angustifolia plant extract, Honey, and AuNPs against the clinically isolated MRSA and VRSA. Of 93 mastitis milk samples examined, 54 (58.1%) S. aureus were isolated and identified {CP S. aureus = 46 (85.2%) and CN S. aureus = 8 (14.8%)}. The whole MRSA, VRSA, MSSA, and VSSA detected were 19 (35.2%), 7 (13%), 35 (65%), and 47 (87%) respectively. The mean counts of S. aureus were between 8.6 × 104 ± 3.5 × 105 CFU/ml. The oxacillin and vancomycin MICs against MRSA and VRSA respectively, were >256 µg/ml. AuNPs sized 30 nm produce observable in vitro anti-MRSA and anti-VRSA activities. Imtenan® citrus blossom honey has also antibacterial activities against MRSA and VRSA with general MBC and MIC range values were observed at a concentration of 0.625, 1.25, 2.5, and 5 (%v/v). In the present study, the most significant result obtained when AuNPs was mixed with Imtenan® citrus blossom honey (1:1 = v:v) with the best MBC was observed at the concentration of 0.56 × 109:0.3 (NP/ml: honey %v/v).

Minimum bactericidal concentration of chemically synthesized silver nanoparticles against pathogenic Salmonella and Shigella strains isolated from layer poultry farms

“…Multidrug-Resistant (MDR) strains were also determined. Any isolate resistant to ≥ 3 is defined as multidrug-resistant pathogen (Magiorakos et al, 2012;Omara et al, 2014).…”

“…The broth was then incubated with shaking at 37°C for overnight. Then the concentrations of these suspensions were adjusted to be equal to 5×10 5 CFU/ml using sterile saline (Omara, 2017).…”

“…Antimicrobial activities of the chemically synthesized AgNPs against the clinically isolated antibiotic-resistant Salmonella and Shigella isolates were analyzed through determination of the minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), and MBC/MIC ratio values using a broth microdilution method in the 96-well microtiter plates (Omara, 2017). To each well, 50 μl of the adjusted bacterial inoculum (5 × 10 5 CFU/ml) were added horizontally, while 50 μl of the AgNPs dilution were added vertically.…”

“…After MIC determination, aliquots of 100 μl from each well, which showed no bacterial growth after incubation was seeded in BHI agar plates, which are not supplemented with AgNPs, then were incubated at 37 °C for 20 hours. The lowest concentration of the AgNPs that kills 100% of the initial bacterial population showing no colony on the MH agar after 20 hours of incubation at 37°C was recorded as the MBC (CLSI, 2013;Omara, 2017).…”

“…Salmonella is a serious threat facing poultry industries as it has the ability to infect chickens causing diarrhea (Hsu et al, 2016). In the last few years, consumption of contaminated poultry, eggs, and their products become the most common sources of foodborne human salmonellosis (Mahmoud et al, 2015;Park et al, 2015;Kalupahana et al, 2017). On the other hand, Shigella has the ability to infect chickens, which consequently could infect human causing shigellosis (Xu et al, 2004;.…”