Vitamin D supplementation in pregnancy and early infancy in relation to gut microbiota composition and C. difficile colonization: implications for viral respiratory infections

ABSTRACT

In Canada and the US, the infant diet is supplemented with vitamin D via supplement drops or formula. Pregnant and nursing mothers often take vitamin D supplements. Since little is known about the impact of this supplementation on infant gut microbiota, we undertook a study to determine the association between maternal and infant vitamin D supplementation, infant gut microbiota composition and Clostridioides difficile colonization in 1,157 mother-infant pairs of the CHILD (Canadian Healthy Infant Longitudinal Development) Cohort Study over 2009–2012. Logistic and MaAsLin regression were employed to assess associations between vitamin D supplementation, and C. difficile colonization, or other gut microbiota, respectively. Sixty-five percent of infants received a vitamin D supplement. Among all infants, infant vitamin D supplementation was associated with a lower abundance of genus Megamonas (q = 0.01) in gut microbiota. Among those exclusively breastfed, maternal prenatal supplementation was associated with lower abundance of Bilophila (q = 0.01) and of Lachnospiraceae (q = 0.02) but higher abundance of Haemophilus (q = 0.02). There were no differences in microbiota composition with vitamin D supplementation among partially and not breastfed infants. Neither infant nor maternal vitamin D supplementation were associated with C. difficile colonization, after adjusting for breastfeeding status and other factors. However, maternal consumption of vitamin-D fortified milk reduced the likelihood of C. difficile colonization in infants (adjustedOR: 0.40, 95% CI: 0.19–0.82). The impact of this compositional difference on later childhood health, especially defense against viral respiratory infection, may go beyond the expected effects of vitamin D supplements and remains to be ascertained.     

A Highly Specific Holin-Mediated Mechanism Facilitates the Secretion of Lethal Toxin TcsL in Paeniclostridium sordellii

Protein secretion is generally mediated by a series of distinct pathways in bacteria. Recently, evidence of a novel bacterial secretion pathway involving a bacteriophage-related protein has emerged. TcdE, a holin-like protein encoded by toxigenic isolates of Clostridioides difficile, mediates the release of the large clostridial glucosylating toxins (LCGTs), TcdA and TcdB, and TpeL from C. perfringens uses another holin-like protein, TpeE, for its secretion; however, it is not yet known if TcdE or TpeE secretion is specific to these proteins. It is also unknown if other members of the LCGT-producing clostridia, including Paeniclostridium sordellii (previously Clostridium sordellii), use a similar toxin-release mechanism. Here, we confirm that each of the LCGT-producing clostridia encode functional holin-like proteins in close proximity to the toxin genes. To characterise the respective roles of these holin-like proteins in the release of the LCGTs, P. sordellii and its lethal toxin, TcsL, were used as a model. Construction and analysis of mutants of the P. sordellii tcsE (holin-like) gene demonstrated that TcsE plays a significant role in TcsL release. Proteomic analysis of the secretome from the tcsE mutant confirmed that TcsE is required for efficient TcsL secretion. Unexpectedly, comparative sample analysis showed that TcsL was the only protein significantly altered in its release, suggesting that this holin-like protein has specifically evolved to function in the release of this important virulence factor. This specificity has, to our knowledge, not been previously shown and suggests that this protein may function as part of a specific mechanism for the release of all LCGTs.     

Measuring the severity of Clostridium difficile infection: implications for management and drug development

The appropriate management of Clostridum difficile infection (CDI) has become a growing clinical and economic issue, as a new epidemic strain with enhanced virulence is causing increased morbidity and mortality. Presently, only two antibiotics (metronidazole and vancomycin) are routinely used to treat CDI. Both increasing disease severity and recurrent infections have been an impetus not only to develop new agents, but also to better recognize which patients are at highest risk for treatment failure and/or recurrence so that treatments can be optimized from the outset. The availability of a standardized and validated system for stratifying CDI severity could improve patient management and potentially accelerate the development of new treatment agents.     

Detection of virulence genes of Clostridium difficile by multiplex PCR

Antikainen J, Pasanen T, Mero S, Tarkka E, Kirveskari J, Kotila S, Mentula S, Könönen E, Virolainen‐Julkunen A‐R, Vaara M, Tissari P. Detection of virulence genes of Clostridium difficile by multiplex PCR. APMIS 2009; 117: 607–13. Clostridium difficile strains belonging to the PCR ribotype 027, pulse‐field gel electrophoresis (PFGE) type NAP1, toxinotype III and restriction endonuclease analysis group BI harbouring mutations in the tcdC gene and possessing binary toxin components A and B have been described to cause epidemics with increased morbidity and mortality. In the present study we developed a conventional multiplex PCR designed to detect selected virulence associated markers of the hypervirulent C. difficile PCR ribotype 027. The multiplex PCR assay detected the major toxins A and B, binary toxin components A and B as well as a possible deletion in the tcdC gene: a characteristic pattern of amplification products for the PCR ribotype 027 strains was detected. This rather simple method was specific for the screening of this hypervirulent C. difficile strain. The correlation between the multiplex PCR and PCR ribotyping methods was excellent. The sensitivity and specificity were 100% in our epidemiological situation. In conclusion, this multiplex PCR was found useful in the preliminary screening for the hypervirulent C. difficile PCR ribotype 027.     

抗生素相关性腹泻治疗现状评价

目的:对抗生素相关性腹泻的病因、机制、危险因素及诊治现状进行评价。方法:收集国内外相关文献进行整理归纳。结果及结论:抗生素相关性腹泻诱因主要为抗生素的应用,常由肠道正常菌群遭到破坏、胃肠蠕动加快、肠道黏膜损害等引发。一经确诊应立即停用相关抗生素,轻症患者停用后多能自愈,重症患者需用针对艰难梭菌的抗生素治疗。合理使用抗生素是预防AAD的关键。     

Resistance determinants in strains of Clostridium difficile from two geographically distinct populations

Ninety-three clinical isolates of Clostridium difficile, comprising 65 from Royal Gwent Hospital, Newport and 28 from Southmead Hospital, Bristol were examined to determine the prevalence of genes coding for macrolide resistance and to explore differences in susceptibility patterns. Antibiogram testing produced similar results for both sets of strains with respect to amoxicillin, tetracycline, erythromycin and cefotaxime. Results differed for rifampicin, where 53% of the Bristol isolates were resistant, compared with 3% of the Newport isolates. Clindamycin disc susceptibility testing produced similar resistance rates. However, clindamycin MIC determinations revealed that 53% of the Bristol strains exhibited high-level resistance (MIC > 256 mg/L), whereas strains from Newport had clindamycin MICs ranging from 0.25 to 3 mg/L. erm (B) was present in 15 of the strains from Bristol and in none of the Newport strains. erm (F) and erm (Q) were not detected in either population. The two geographically distinct populations of C. difficile differed considerably in their susceptibility to antibiotics. The possibility that C. difficile may serve as a conservator for resistant determinants subsequent to exposure to antimicrobial agents, has important implications for infection control.