Background: The streptococcus agalactiae infectious leading to early neonatal morbidity and mortality,the streptococcus agalactiae screen became an important examination for pregnant women. The Centers for Disease Control and Prevention (CDC) recommends whole detection protocols of isolation and culture on streptococcus agalactiae.However, The essential factors including incubation time of agar plates, enrichment time of broth, and transport media storage conditions be ignored. This study was designed to understand above easy ignored point and to provide scientific proof for optimization detection method, revision of health standards and prevention and control of disease.
Methods: The transport medium without and with enrichment were directly inoculated onto Sheep blood agar plate for 24~48 hours. The positive detection rate of streptococcus agalactiae on different incubation time, with and without enrichment were compared,respectively. The transport medium with enrichment were inoculated for 24~48 hours.The positive detection rate of streptococcus agalactiae on different enrichment time were compared. The transport medium were respectively stored at 2℃~8℃ and 20℃~25℃. Interval 24 hours within 5 days, The recovery rate of streptococcus agalactiae on transport medium different storage temptature were compared. The growth of streptococcus agalactiae colonies were examined for pale pink to red, round and pearly colonies. The isolates colonies were identified by matrix assisted laser desorption ionization-time of flight mass spectrometry to confirm negative or positive.
Results: The overall results shown that the detection rate were significantly higher at 48 hours with directly culture methods (P＜0.01)or after enrichment culture methods (P＜0.05). The detection rate have no difference after enrichment for 24 hours or 48 hours (P＞0.05). The recovery rate of streptococcus agalactiae transport medium (stored at 2℃~8℃) were 100% within 4 days and 83.33% at 5th day. However, the recovery rate of streptococcus agalactiae transport medium (stored at 20℃~25℃) were 100% within 2 days,97.22% at 3th day, 52.78% at 4th day and 33.33% at 5th day, respectively.
Conclusions: In conclusion, the results suggested that the enrichment culture time was 24 hours, the transport media stable best time is 2 days stored at 20℃~25℃ or 4 days stored at 2℃~8℃, and the best incubation time is 48 hours for streptococcus agalactiae clinical testing in pregnant women.
