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Open Access Research article

Clinical and microbiologic characteristics of tcdA-negative variant clostridium difficile infections

Jieun Kim1, Hyunjoo Pai2*, Mi-ran Seo2 and Jung Oak Kang3

Author Affiliations

1 Department of Internal Medicine, Hanyang University College of Medicine, Guri, Korea

2 Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea

3 Department of Laboratory Medicine, Hanyang University College of Medicine, Guri, Korea

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BMC Infectious Diseases 2012, 12:109  doi:10.1186/1471-2334-12-109

Published: 9 May 2012



The tcdA-negative variant (A-B+) of Clostridium difficile is prevalent in East Asian countries. However, the risk factors and clinical characteristics of A-B+C. difficile infections (CDI) are not clearly documented. The objective of this study was to investigate these characteristics.


From September 2008 through January 2010, the clinical characteristics, medication history and treatment outcomes of CDI patients were recorded prospectively. Toxin characterization and antibiotic susceptibility tests were performed on stool isolates of C. difficile.


During the study period, we identified 22 cases of CDI caused by tcdA-negative tcdB-positive (A-B+) strains and 105 cases caused by tcdA-positive tcdB-positive (A+B+) strains. There was no significant difference in disease severity or clinical characteristics between the two groups. Previous use of clindamycin and young age were identified as significant risk factors for the acquisition of A-B+ CDI (OR = 4.738, 95% CI 1.48–15.157, p = 0.009 and OR = 0.966, 95% CI 0.935–0.998, p = 0.038, respectively) in logistic regression.

Rates of resistance to clindamycin were 100% and 69.6% in the A-B+ and A+B+ isolates, respectively (p = 0.006), and the ermB gene was identified in 17 of 21 A-B+ isolates (81%). Resistance to moxifloxacin was also more frequent in the A-B+ than in the A+B+ isolates (95.2% vs. 63.7%, p = 0.004).


The clinical course of A-B+ CDI is not different from that of A+B+ CDI. Clindamycin use is a significant risk factor for the acquisition of tcdA-negative variant strains.

Clostridium difficile infection; tcdA-negative variant strain; Clinical outcome; Risk factor; Antimicrobial susceptibility test; ermB gene