Controversies Surrounding Clostridium difficile Infection in Infants and Young Children

Challenges for Clinical Development of Vaccines for Prevention of Hospital-Acquired Bacterial Infections

Increasing antibiotic resistance in bacteria causing endogenous infections has entailed a need for innovative approaches to therapy and prophylaxis of these infections and raised a new interest in vaccines for prevention of colonization and infection by typically antibiotic resistant pathogens. Nevertheless, there has been a long history of failures in late stage clinical development of this type of vaccines, which remains not fully understood. This article provides an overview on present and past vaccine developments targeting nosocomial bacterial pathogens; it further highlights the specific challenges associated with demonstrating clinical efficacy of these vaccines and the facts to be considered in future study designs. Notably, these vaccines are mainly applied to subjects with preexistent immunity to the target pathogen, transient or chronic immunosuppression and ill-defined microbiome status. Unpredictable attack rates and changing epidemiology as well as highly variable genetic and immunological strain characteristics complicate the development. In views of the clinical need, re-thinking of the study designs and expectations seems warranted: first of all, vaccine development needs to be footed on a clear rationale for choosing the immunological mechanism of action and the optimal time point for vaccination, e.g., (1) prevention (or reduction) of colonization vs. prevention of infection and (2) boosting of a preexistent immune response vs. altering the quality of the immune response. Furthermore, there are different, probably redundant, immunological and microbiological defense mechanisms that provide protection from infection. Their interplay is not well-understood but as a consequence their effect might superimpose vaccine-mediated resolution of infection and lead to failure to demonstrate efficacy. This implies that improved characterization of patient subpopulations within the trial population should be obtained by pro- and retrospective analyses of trial data on subject level. Statistical and systems biology approaches could help to define immune and microbiological biomarkers that discern populations that benefit from vaccination from those where vaccines might not be effective.

Epidemiological Features of Clostridium difficile Colonizing the Intestine of Jordanian Infants

Clostridium difficile is commonly found in the intestine of infants without causing any disease. This study investigated the most important epidemiological features of C. difficile strains colonizing intestine of Jordanian infants. A total of 287 fecal samples were collected from infants admitted to the Jordan University Hospital (JUH) over the period of 2015. Samples were cultured for C. difficile and their growth was identified using microbiological culture and PCR. The overall C. difficile colonization rate among hospitalized and nonhospitalized infants was 37/287 (12.9%). Neonates were less colonized than other infants (8.7% verses 19.5%). Colonization of the infants with C. difficile toxigenic strains (TcdA and TcdB) was observed in 54% of the isolates, whereas those colonized with nontoxigenic strains were 46% and only one isolate was positive for binary toxin. Breast feeding of infants is a significant factor associated with decreased colonization with C. difficile. All C. difficile strains were susceptible to vancomycin and metronidazole, while high resistance rate to ciprofloxacin (78.4%) and less resistance rate to erythromycin (29.7%) were detected among the isolates. The results showed that 40.5% of the isolates carried mutated gyrA and gyrB genes which have cross-resistance to ciprofloxacin and moxifloxacin. This study represents useful epidemiological features about C. difficile colonizing intestine of infants living in a developing country.

High-resolution profiling of the gut microbiome reveals the extent of Clostridium difficile burden

Microbiome profiling through 16S rRNA gene sequence analysis has proven to be a useful research tool in the study of C. difficile infection (CDI); however, CDI microbiome studies typically report results at the genus level or higher, thus precluding identification of this pathogen relative to other members of the gut microbiota. Accurate identification of C. difficile relative to the overall gut microbiome may be useful in assessments of colonization in research studies or as a prognostic indicator for patients with CDI. To investigate the burden of C. difficile at the species level relative to the overall gut microbiome, we applied a high-resolution method for 16S rRNA sequence assignment to previously published gut microbiome studies of CDI and other patient populations. We identified C. difficile in 131 of 156 index cases of CDI (average abundance 1.78%), and 18 of 211 healthy controls (average abundance 0.008%). We further detected substantial levels of C. difficile in a subset of infants that persisted over the first two to 12 months of life. Correlation analysis of C. difficile burden compared to other detected species demonstrated consistent negative associations with C. scindens and multiple Blautia species. These analyses contribute insight into the relative burden of C. difficile in the gut microbiome for multiple patient populations, and indicate that high-resolution 16S rRNA gene sequence analysis may prove useful in the development and evaluation of new therapies for CDI.

Nosocomial Clostridium difficile-associated diarrhoea in Assiut University Children's Hospital, Egypt

BACKGROUND

There are no large epidemiological studies of Clostridium difficile-associated disease (CDAD) in hospitalised children.

AIM

To describe the frequency, demography, clinical features and outcome of nosocomial CDAD in children admitted to Assiut University Children's Hospital, Egypt.

PATIENTS AND METHODS

In this descriptive cross-sectional study, 72 children developed nosocomial diarrhoea between April 2010 and March 2011. A medical history, clinical assessment and culture for Clostridium difficile and direct toxin detection from stool samples by enzyme immuno-assay were undertaken in all patients.

RESULTS

CDAD was diagnosed in 17 (23·6%) patients. Those aged ≤12 months were the most commonly affected (eight, 47%). The main cause of admission was respiratory disorders (eight, 47% of cases), followed by surgical problems (three, 17·7%). Ten patients (58·8%) had severe symptoms. There were no statistically significant differences between any of the demographic or laboratory data for children with CDAD and children with other causes of nosocomial diarrhoea. None of the patients developed complications. Seven children with CDAD (41·2%) had recurrence.

CONCLUSION

CDAD is an important cause of nosocomial diarrhoea in children in Assiut University Children's Hospital. Established guidelines should be followed in all hospitals to minimise exposure to the pathogen. Physicians can do much to reduce the risk of a severe outcome in children by early identification and rapid management. Further research should be undertaken to identify the risk factors for recurrence.