Screening Protocols for Group B Streptococcus: Are TransportMedia Appropriate?

[摘要] Objective:To evaluate group B streptococcus (GBS) detection in anin vitrosetting, using a low and controlledinoculum from swabs directly inoculated into a selective medium, as compared to delayed inoculation followinga period in a commercial Amies transport medium with charcoal (Venturi Transystem™Copan, Italy).Study design:Clinical isolates of GBS (n= 103), were inoculated into the Amies transport medium with charcoalin a concentration of 100 colony-forming units (cfu)/ml (10 cfu/swab). Swabs were then transferred to anenrichment broth (NPC) at time intervals of 0, 2, 4, 6 and 24 hours. Broths were then incubated for 18–24 hoursat 35C°in air, before being transferred to New Granada Medium Modified (NGM) for GBS detection and incubatedfor a further 18–24 hours at 35C°in air. If the characteristic orange pigmented colonies were observed afterthis period, the specimen was recorded as + (1–10 colonies) or ++ (more than 10 colonies).Results:Overall 92.2% (95/103) of isolates were detected in all tubes and at all times. An additional two isolateswere non-hemolytic, non-pigment forming GBS. Of note, 3.9% (4/103) were negative until 2 hours delayedinoculation and 1.9% (2/103) gave inconsistent results, likely due to the low inoculum used.Conclusion:Delayed inoculation into selective enrichment broth following a period in transport medium,even with a low inoculum, gave a similar and acceptable GBS detection rate to direct inoculation. Hence,Amies transport medium with charcoal is an appropriate transport medium to use, where it is not practical forclinical specimens to be directly inoculated into selective enrichment broth and as endorsed in the Centersfor Diseases Control (CDC) Guidelines, 2002.

[学科分类] 妇产科学