2.2 BACTERIAL STRAINS
Collected samples were inoculated into blood agar plates supplemented with colistin nalidixic acid and incubated for 18-24 h at 37°C in a candle jar enriched with 5% Carbon-dioxide. All greyish, smooth, small and non-pigmented colonies with a visible zone of beta hemolysis appearing 24 h after incubation were isolated, further incubation and their reactivity to catalase evaluated. Colonies with a negative catalase reactivity after further incubation were then isolated and used for the confirmatory diagnosis using the Pastorex strep kit (BIO-RAD). Colonies which agglutinated with the GBS latex reagent were considered positive.
The resulting isolates were then used for antibiotic susceptibility testing by the Kirby Bauer disc difusion method. The antibiotics was tested and their respective diameters of inhibitions were measure and compare to those of the French microbiology society as of 2018 (SFM ; EUCAST)
2.3 ANTIMICROBIAL SUSCEPTIBILITY TESTING
Antimicrobial susceptibility testing was performed according to Clinical and Laboratory Standard Institute Guidelines (CLSI, 2014) by disk diffusion 14. A suspension of the test organism was prepared by removing 3-5 colonies from a pure culture plate by emulsifying in 3 ml of sterile physiological saline and was diluted with saline until the turbidity of the suspension become matched with turbidity standard equivalent to 0.5 McFarland and inoculated on Muller-Hinton agar (MHA, Oxoid, England) with 5% sheep’s blood. After the excess suspension was removed by gentle rotation of the swab against the surface of the tube, the swab was then used to distribute the bacteria evenly over the entire surface of MHA supplemented with 5% sheep blood. The inoculated plates were left at room temperature to dry for 3-5 minutes and a set of 6 antibiotic discs in each plate were placed with the concentration of penicillin G (10µg), gentamicin (CN) (10 µg), erythromycin (E) (15µg), clindamycin (DA) (2µg), tetracyclin (10 µg), norfloxacin (10 µg), Chloramphenicol (C) (30µg), pristicin (10 µg), steptomycin (10 µg), rifampicin (10 µg) and incubated at 35-37 °C with 5% CO2 atmosphere by candle jar for 18-24 hours. The zone of growth inhibition was measured using rulers. The sizes of the inhibition zones were graded according to the CLSI 2014 and interpreted as susceptible, intermediate or resistant14 (All of the antibiotics used in the investigation are product of Oxoid, England and HIMEDIA).