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Background/purposes: The continuously increasing carbapenem resistance within Enterobacterales and Pseudomonas poses a threat to public health, nevertheless, the molecular characteristics of which in southern China still remain limited. And carbapenemase identification is a key factor in effective early therapy of carbapenem-resistant bacteria infections. We aimed to determine the molecular characteristics of these pathogens and compare commercial combined disc tests (CDTs) with the modified carbapenem inactivation method (mCIM) and EDTA-CIM (eCIM) in detecting and distinguishing carbapenemases using whole genome sequencing (WGS)., Methods: A total of 78 Enterobacterales , 30 Pseudomonas were obtained from two tertiary hospitals in southern China. Susceptibility tests were conducted using an automated VITEK2 compact system with confirmation via the Kirby-Bauer method. The WGS was conducted on all clinical isolates and the molecular characteristics were analyzed by screening the whole genome sequences. CDTs with or without cloxacillin, mCIM, and eCIM, were performed and compared by taking WGS results as the benchmark., Results: A total of 103 carbapenem non-susceptible and 5 carbapenem susceptible bacteria were determined, with Klebsiella pneumoniae (42.7%), Pseudomonas aeruginosa (23.3%) and Escherichia coli (18.4%) being most prevalent. Carbapenemase genes were detected in 58 (56.3%) of the 103 carbapenem-non-susceptible clinical isolates, including 46 NDM, 6 KPC, 3 IMP, 1 IPM+VIM,1NDM+KPC, and 1 OXA-181. Carbapenemase-producing isolates were detected more frequently in Enterobacterales (76.3%). Among K. pneumoniae , the major sequence types were st307 and st11, while among E. coli and P. aeruginosa , the most prevalent ones were st410 and st242 respectively. For carbapenemase detection in Enterobacterales , the mCIM method achieved 100.00% (95% CI, 92.13-100.00%) sensitivity and 94.44% (70.63-99.71%) specificity (kappa, 0.96); for Pseudomonas , detection sensitivity was 100% (5.46-100.00%), and 100% (84.50-100.00%) specificity (kappa, 0.65). Commercial CDT carbapenemase detection sensitivity for Enterobacterales was 96.49% (86.84-99.39%), and 95.24% (74.13-99.75%) specificity (kappa, 0.90); for Pseudomonas , carbapenemase detection sensitivity was 100.00% (5.46-100.00%) and 37.93% (21.30-57.64%) specificity (kappa, 0.04). When cloxacillin testing was added, CDT specificity reached 84.61% (64.27-94.95%)., Conclusion: The molecular epidemiology of carbapenem-non-susceptible isolates from pediatric patients in Southern China exhibited distinctive characteristics. Both the mCIM-eCIM combination and CDT methods effectively detected and differentiated carbapenemases among Enterobacterales isolates, and the former performed better than CDT among Pseudomonas ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Liang, Chen, Liang, Li, Cai, Lai, Zhong, Xie, Huang, Gao and Long.)

Maternal vaginal/rectal colonization of group B streptococcus (GBS) is a main risk for neonatal invasive infection. Efficient determination of GBS colonization in pregnant women is crucial. This study aimed to investigate the prevalence of GBS carriage and evaluate the diagnostic performance of six methodologies for GBS screening conducted in China, including blood agar plate, liquid chromogenic medium, and loop-mediated isothermal amplification (LAMP) without pre-enrichment, chromogenic agar plate with pre-enrichment, and GBS antigen detection without and with pre-enrichment in comparison with the standard reference method (Lim broth-enriched subculture with plating on 5% sheep blood agar). Vaginal/rectal swabs were collected from 1,281 pregnant women at 35-37 weeks of gestation. Of them, 309 were taken in triplicate, one for Lim broth-enriched subculture, one for blood agar plate, and the third for GBS antigen detection (Reagent W); 177 were acquired in duplicate, one for Lim broth-enriched subculture and the other for GBS antigen detection (Reagent H); 502 were obtained in duplicate, one for Lim broth-enriched subculture and the other for liquid chromogenic medium; 158 were collected in duplicate, one for Lim broth-enriched subculture and the other for LAMP; and 135 were inoculated in Lim broth-enriched for GBS antigen detection (Reagent W) and subculture with chromogenic agar plate and 5% blood agar plate. The overall prevalence of GBS carriage was 10.1% (130/1,281, 95% CI: 8.5-12.1%) according to the standard reference method. Compared with the standard reference method, the LAMP had excellent performance of sensitivity (100%, 95%CI: 83.4-100%), specificity (94%, 95%CI: 88.1-97.1%), and Yoden index (0.940); as well as the blood agar plate with sensitivity (81.5%, 95%CI: 61.3-93.0%), specificity (100%, 95%CI: 98.3-100.0%), and Yoden index (0.815). The other four methods were not sufficient to reach the threshold in terms of sensitivity or specificity compared to the standard reference method. Furthermore, for LAMP, results can be obtained within 0.5-1 h, while for blood agar plate, which needed 24-48 h, and further identification was required. Our data suggested that the performance of LAMP was highly comparable to the standard Lim broth-enriched subculture and LAMP is considered as an alternative for fast and accurate GBS screening., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Gao, Deng, Huang, Chang, Zhong, Xie, Guan and Liu.)