European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology · 2026
CAMP-negative group B Streptococcus in pregnant women: molecular and clinical features with implications for diagnostics and neonatal management.
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Huang Lianfen, Lin Zeying, Zhu Sufei, Fong Chengman, Tan Zengyu, Gao Kankan, Kang Manqiu, Liu Zimeng, Chen Xiaolan, Zhong Huamin, Xie Yongqiang, Liang Bingshao, Gao Fei, Long Yan
Аннотация
OBJECTIVES: The Christie-Atkins-Munch-Peterson (CAMP) test and cfb-targeted polymerase chain reaction (PCR) are widely used for identification of Streptococcus agalactiae (Group B Streptococcus, GBS). However, CAMP-negative strains may evade detection. This study aimed to characterize antimicrobial resistance, molecular profiles, and pregnancy outcomes associated with CAMP-negative GBS.
METHODS: 55 CAMP-negative GBS strains (45 from pregnant women and 10 from non-pregnant outpatients) were collected; the 10 non-pregnant isolates were included only for molecular characterization and antimicrobial resistance profiling, while clinical pregnancy outcomes were analyzed exclusively in the pregnant cohort. A total of 66 contemporaneous CAMP-positive controls were collected (2017–2021) at Guangzhou Medical University Affiliated Women and Children’s Medical Center. Isolates were identified by VITEK-2 (bioMérieux) or matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) followed by CAMP test. Pregnancy outcomes were retrieved. Antimicrobial susceptibility, multilocus sequence typing (MLST), capsular serotyping, and 11 virulence genes were analyzed.
RESULTS: Among 46,746 pregnant women screened, 6,108 (13.1%) were GBS-positive, including 45 (0.74%) CAMP-negative isolates. Adverse outcomes were observed in 42.2% (19/45), including premature rupture of membranes (11/45, 24.4%), low birth weight (6/45, 13.3%), and preterm delivery (2/45, 4.4%). All isolates were susceptible to β-lactams, vancomycin, linezolid, and levofloxacin, but resistant to erythromycin (18/55, 32.7%), clindamycin (31/55, 56.4%), and tetracycline (35/55, 63.6%). CAMP-negative isolates were predominantly of serotype III and sequence type (ST) 862 (50/55, 90.9%), compared with diverse types in controls. All lacked cfb and bac genes but harbored 9 remaining virulence genes.
CONCLUSIONS: Although CAMP-negative GBS is rare in clinical settings, it can escape detection by the CAMP test and single-target PCR assays targeting the cfb gene, leading to false negative results. Integrated diagnostic strategies combining culture-based screening with multiplex PCR are therefore essential to accurate detection of GBS in maternal GBS surveillance, which is critical for optimizing neonatal GBS disease prevention and management.
SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10096-026-05483-8.
METHODS: 55 CAMP-negative GBS strains (45 from pregnant women and 10 from non-pregnant outpatients) were collected; the 10 non-pregnant isolates were included only for molecular characterization and antimicrobial resistance profiling, while clinical pregnancy outcomes were analyzed exclusively in the pregnant cohort. A total of 66 contemporaneous CAMP-positive controls were collected (2017–2021) at Guangzhou Medical University Affiliated Women and Children’s Medical Center. Isolates were identified by VITEK-2 (bioMérieux) or matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) followed by CAMP test. Pregnancy outcomes were retrieved. Antimicrobial susceptibility, multilocus sequence typing (MLST), capsular serotyping, and 11 virulence genes were analyzed.
RESULTS: Among 46,746 pregnant women screened, 6,108 (13.1%) were GBS-positive, including 45 (0.74%) CAMP-negative isolates. Adverse outcomes were observed in 42.2% (19/45), including premature rupture of membranes (11/45, 24.4%), low birth weight (6/45, 13.3%), and preterm delivery (2/45, 4.4%). All isolates were susceptible to β-lactams, vancomycin, linezolid, and levofloxacin, but resistant to erythromycin (18/55, 32.7%), clindamycin (31/55, 56.4%), and tetracycline (35/55, 63.6%). CAMP-negative isolates were predominantly of serotype III and sequence type (ST) 862 (50/55, 90.9%), compared with diverse types in controls. All lacked cfb and bac genes but harbored 9 remaining virulence genes.
CONCLUSIONS: Although CAMP-negative GBS is rare in clinical settings, it can escape detection by the CAMP test and single-target PCR assays targeting the cfb gene, leading to false negative results. Integrated diagnostic strategies combining culture-based screening with multiplex PCR are therefore essential to accurate detection of GBS in maternal GBS surveillance, which is critical for optimizing neonatal GBS disease prevention and management.
SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10096-026-05483-8.