Identification and resistance characteristics of CAMP-negative Streptococcus agalactiae

Acta Universitatis Medicinalis Anhui 2025 01 v.60 142-146     font:big middle small

Found programs: National Natural Science Foundation of China (No. 82102460);Research Project of Anhui Medical University (No. 2021xkj050);Research Project of Anhui Provincial Institute of Translational Medicine(No. 2021zhyx-C47)

Authors:Wang Xiu; Leng Guiyun; Tang Wei; Zhou Qiang

Keywords:Streptococcus agalactiae;MALDI-TOF MS;CAMP assay;16S rDNA;qPCR;cfb

DOI:10.19405/j.cnki.issn1000-1492.2025.01.020

〔Abstract〕 Objective To explore identification and resistance characteristics of CAMP-negativeStreptococcus agalactiae. Methods Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF MS) and the CAMP assay, 33 presumptive strains ofStreptococcus agalactiaewere identified. The CAMP-negative strains were further validated through 16S rDNA, while the CAMP factor encoding gene(cfb) was detected using real-time fluorescence quantitative polymerase chain reaction(qPCR). Antimicrobial susceptibility testing was conducted using the microbroth dilution method, and the resistance rates of CAMP-negative and CAMP-positive strains were compared. Results Based on MALDI-TOF MS identification, all 33 strains were classified asStreptococcus agalactiae. Among them, 7 strains tested negative for CAMP were subsequently confirmed asStreptococcus agalactiaethrough 16S rDNA. The qPCR results indicated that, only 1 strain showedcfbpresence. The CAMP-negative and CAMP-positive strains were sensitive to penicillin G, cefepime, cefotaxime, vancomycin, and linezolid. The resistance rates of the former to chloramphenicol and tetracycline(28.57%, 85.71%) were slightly higher than the latter(15.38%, 57.69%), while the resistance rates to moxifloxacin, levofloxacin, and erythromycin(14.29%, 14.29%, 42.86%) were slightly lower than the latter(34.62%, 34.62%, 57.69%), but was not significant. Conclusion Drug risistance of CAMP-negativeStreptococcus agalactiaeis the same as CAMP-positive strains, but traditional CAMP assay andcfb-targeted qPCR can result in missed detections. MALDI-TOF MS offers a quick, simple, and accurate identification method that merits wider adoption.