Acinetobacter baumannii is a multidrug-resistant nosocomial opportunistic pathogen that is becoming a major health threat worldwide. In this study, we have focused on the A. baumannii DSM30011 strain, an environmental isolate that retains many virulence-associated traits. We found that its genome contains two loci encoding for contact-dependent growth inhibition (CDI) systems. These systems serve to kill or inhibit the growth of non-sibling bacteria by delivering toxins into the cytoplasm of target cells, thereby conferring the host strain a significant competitive advantage. We show that one of the two toxins functions as a DNA-damaging enzyme, capable of inducing DNA double-stranded breaks to the chromosome of Escherichia coli strain. The second toxin has unknown catalytic activity but stops the growth of E. coli without bactericidal effect. In our conditions, only one of the CDI systems was highly expressed in the A. baumannii DSM30011 strain and was found to mediate interbacterial competition. Surprisingly, the absence of this CDI system promotes adhesion of A. baumannii DSM30011 to both abiotic and biotic surfaces, a phenotype that differs from previously described CDI systems. Our results suggest that a specific regulation mediated by this A. baumannii DSM30011 CDI system may result in changes in bacterial physiology that repress host cell adhesion and biofilm formation.
Tampons recovered from a cohort of 737 healthy women (median age 32 years) were analyzed for the presence of Staphylococcus aureus. A total of 198 tampons (27%) were colonized by S. aureus, and 28 (4%) was by a strain producing toxic shock syndrome toxin 1 (TSST-1). S. aureus was detected more frequently in tampons that did not require an applicator for their insertion (74/233 [32%] versus 90/381 [24%]; OR=1.51 [95% CI 1.04-2.17]) and in women who used an intrauterine device for contraception (53/155 [34%] versus 145/572 [27%]; OR =1.53 [95% CI 1.05-2.24]). The S. aureus strains isolated from tampons belonged to 22 different clonal complexes (CCs). The most prevalent CC was CC398 agr1 (n=57, 27%), a clone that does not produce superantigenic toxins, followed by CC30 agr 3 (n=27, 13%) producing TSST-1 (24/27 [89%]), the principal clone of S. aureus involved in menstrual toxic shock syndrome. IMPORTANCE Menstrual toxic shock syndrome (MTSS) is an uncommon severe acute disease that occurs in healthy menstruating women colonized by TSST-1-producing S. aureus who use intravaginal protection, such as tampons and menstrual cups. The catamenial product collected by the protection serves as a growth medium for S. aureus and allows TSST-1 production. Previous studies evaluated the prevalence of genital colonization by S. aureus by vaginal swabbing, but they did not examine tampon colonization. This study demonstrates a high prevalence of tampon colonization by S. aureus, and the presence of the CC30 TSST-1 S. aureus clone responsible for MTSS in tampons from healthy women. The results support the vaginal carriage of this lineage in healthy women. In addition, the higher prevalence of S. aureus within tampons that do not require an applicator indicates a crucial role of hand-washing before tampon handling to decrease the risk of tampon contamination.
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