The glucosyltransferase activity of C. difficile Toxin B is required for disease pathogenesis

Enzymatic inactivation of Rho-family GTPases by the glucosyltransferase domain of Clostridioides difficile Toxin B (TcdB) gives rise to various pathogenic effects in cells that are classically thought to be responsible for the disease symptoms associated with C. difficile infection (CDI). Recent in vitro studies have shown that TcdB can, under certain circumstances, induce cellular toxicities that are independent of glucosyltransferase (GT) activity, calling into question the precise role of GT activity. Here, to establish the importance of GT activity in CDI disease pathogenesis, we generated the first described mutant strain of C. difficile producing glucosyltransferase-defective (GT-defective) toxin. Using allelic exchange (AE) technology, we first deleted tcdA in C. difficile 630Δerm and subsequently introduced a deactivating D270N substitution in the GT domain of TcdB. To examine the role of GT activity in vivo, we tested each strain in two different animal models of CDI pathogenesis. In the non-lethal murine model of infection, the GT-defective mutant induced minimal pathology in host tissues as compared to the profound caecal inflammation seen in the wild-type and 630ΔermΔtcdA (ΔtcdA) strains. In the more sensitive hamster model of CDI, whereas hamsters in the wild-type or ΔtcdA groups succumbed to fulminant infection within 4 days, all hamsters infected with the GT-defective mutant survived the 10-day infection period without primary symptoms of CDI or evidence of caecal inflammation. These data demonstrate that GT activity is indispensable for disease pathogenesis and reaffirm its central role in disease and its importance as a therapeutic target for small-molecule inhibition.

More than 50% of Clostridium difficile Isolates from Pet Dogs in Flagstaff, USA, Carry Toxigenic Genotypes

Nosocomial acquisition of Clostridium difficile is well documented, yet recent studies have highlighted the importance of community acquired infections and identified community associated reservoirs for this pathogen. Multiple studies have implicated companion pets and farm animals as possible sources of community acquired C. difficile infections in humans. To explore the potential role of pet dogs in human C. difficile infections we systematically collected canine fecal samples (n = 197) in Flagstaff, AZ. Additionally, nineteen fecal samples were collected at a local veterinary clinic from diarrheic dogs. We used these combined samples to investigate important questions regarding C. difficile colonization in pet canines: 1) What is the prevalence and diversity of C. difficile in this companion pet population, and 2) Do C. difficile isolates collected from canines genetically overlap with isolates that cause disease in humans? We used a two-step sequence typing approach, including multilocus sequence typing to determine the overall genetic diversity of C. difficile present in Flagstaff canines, and whole-genome sequencing to assess the fine-scale diversity patterns within identical multilocus sequence types from isolates obtained within and among multiple canine hosts. We detected C. difficile in 17% of the canine fecal samples with 10% containing toxigenic strains that are known to cause human disease. Sequencing analyses revealed similar genotypes in dogs and humans. These findings suggest that companion pets are a potential source of community acquired C. difficile infections in humans.

[A NOVEL APPROACH TO GENOTYPING OF HOSPITAL ISOLATES OF CLOSTRIDIUM DIFFICILE]

AIM

Development of a novel approach in genotyping of Clostridium difficile and its testing on the example of 140 hospital isolates.

MATERIALS AND METHODS

The approach is based on an idea of double digest and selective label (DDSL), used previously during genotyping of other bacterial pathogens. Selection of optimal enzymes for restriction of MluI and Mph1103I was carried out, condition of DDSL reaction execution were optimized.

RESULTS

Genotyping of C. difficile hospital isolates was carried out, index of strain discrimination was calculated, conclusions regarding possibilities of the method in elucidation of spread pathways and identification of infection sources were made.

CONCLUSION

The developed method of genotyping has a number of advantages over the existing method and can be used to'address issues in epidemiology of infections caused by C. difficile.

Regulation of Clostridium difficile Spore Formation by the SpoIIQ and SpoIIIA Proteins

Sporulation is an ancient developmental process that involves the formation of a highly resistant endospore within a larger mother cell. In the model organism Bacillus subtilis, sporulation-specific sigma factors activate compartment-specific transcriptional programs that drive spore morphogenesis. σ^G activity in the forespore depends on the formation of a secretion complex, known as the “feeding tube,” that bridges the mother cell and forespore and maintains forespore integrity. Even though these channel components are conserved in all spore formers, recent studies in the major nosocomial pathogen Clostridium difficile suggested that these components are dispensable for σ^G activity. In this study, we investigated the requirements of the SpoIIQ and SpoIIIA proteins during C. difficile sporulation. C. difficile spoIIQ, spoIIIA, and spoIIIAH mutants exhibited defects in engulfment, tethering of coat to the forespore, and heat-resistant spore formation, even though they activate σ^G at wildtype levels. Although the spoIIQ, spoIIIA, and spoIIIAH mutants were defective in engulfment, metabolic labeling studies revealed that they nevertheless actively transformed the peptidoglycan at the leading edge of engulfment. In vitro pull-down assays further demonstrated that C. difficile SpoIIQ directly interacts with SpoIIIAH. Interestingly, mutation of the conserved Walker A ATP binding motif, but not the Walker B ATP hydrolysis motif, disrupted SpoIIIAA function during C. difficile spore formation. This finding contrasts with B. subtilis, which requires both Walker A and B motifs for SpoIIIAA function. Taken together, our findings suggest that inhibiting SpoIIQ, SpoIIIAA, or SpoIIIAH function could prevent the formation of infectious C. difficile spores and thus disease transmission.

The bacterial spore-forming pathogen Clostridium difficile is a leading cause of nosocomial infections in the United States and represents a significant threat to healthcare systems around the world. As an obligate anaerobe, C. difficile must form spores in order to survive exit from the gastrointestinal tract. Accordingly, spore formation is essential for C. difficile disease transmission. Since the mechanisms controlling this process remain poorly characterized, we analyzed the importance of highly conserved secretion channel components during C. difficile sporulation. In the model organism Bacillus subtilis, this channel had previously been shown to function as a “feeding tube” that allows the mother cell to nurture the developing forespore and sustain transcription in the forespore. We show here that conserved components of this structure in C. difficile are dispensable for forespore transcription, although they are important for completing forespore engulfment and retaining the protective spore coat around the forespore, in contrast with B. subtilis. The results of our study suggest that targeting these conserved proteins could prevent C. difficile spore formation and thus disease transmission.

Interleukin-22 and CD160 play additive roles in the host mucosal response to Clostridium difficile infection in mice

Our previous work has shown the significant up-regulation of Il22 and increased phosphorylation of signal transducer and activator of transcription 3 (STAT3) as part of the mucosal inflammatory response to Clostridium difficile infection in mice. Others have shown that phosphorylation of STAT3 at mucosal surfaces includes interleukin-22 (IL-22) and CD160-mediated components. The current study sought to determine the potential role(s) of IL-22 and/or CD160 in the mucosal response to C. difficile infection. Clostridium difficile-infected mice treated with anti-IL-22, anti-CD160 or a combination of the two showed significantly reduced STAT3 phosphorylation in comparison to C. difficile-infected mice that had not received either antibody. In addition, C. difficile-infected mice treated with anti-IL-22/CD160 induced a smaller set of genes, and at significantly lower levels than the untreated C. difficile-infected mice. The affected genes included pro-inflammatory chemokines and cytokines, and anti-microbial peptides. Furthermore, histopathological and flow cytometric assessments both showed a significantly reduced influx of neutrophils in C. difficile-infected mice treated with anti-IL-22/CD160. These data demonstrate that IL-22 and CD160 are together responsible for a significant fraction of the colonic STAT3 phosphorylation in C. difficile infection. They also underscore the additive effects of IL-22 and CD160 in mediating both the pro-inflammatory and pro-survival aspects of the host mucosal response in this infection.

Clostridium difficile infection aggravates colitis in interleukin 10-deficient mice

AIM: To investigate the effect of Clostridium difficile (C. difficile) infection in an interleukin 10-deficient (IL-10^-/-) mouse model of inflammatory bowel disease.

METHODS: Bone marrow-derived dendritic cells isolated from wild type (WT) and IL-10^-/-mice were stimulated for 4 h with C. difficile toxin A (200 μg/mL), and gene expression of interferon (IFN)-γ, IL-12 and IL-23 was determined by real-time reverse transcription polymerase chain reaction. WT and IL-10^-/- mice (n = 20 each) were exposed to an antibiotic cocktail for three days and then were injected with clindamycin (i.p.). Mice (n = 10 WT, 10 IL-10^-/-) were then challenged with oral administration of C. difficile (1 × 10⁵ colony forming units of strain VPI 10463). Animals were monitored daily for 7 d for signs of colitis. Colonic tissue samples were evaluated for cytokine gene expression and histopathologic analysis.

RESULTS: C. difficile toxin A treatment induced IFN-γ gene expression to a level that was significantly higher in BDMCs from IL-10^-/- compared to those from WT mice (P < 0.05). However, expression of IL-12 and IL-23 was not different among the groups. Following C. difficile administration, mice developed diarrhea and lost weight within 2-3 d. Weight loss was significantly greater in IL-10^-/- compared to WT mice (P < 0.05). C. difficile infection induced histopathologic features typical of colitis in both IL-10^-/- and WT mice. The histopathologic severity score was significantly higher in the IL-10^-/- than in WT mice (mean ± standard error; 5.50 ± 0.53 vs 2.44 ± 0.46; P < 0.05). This was accompanied by a significantly greater increase in IFN-γ gene expression in colonic tissues from IL-10^-/- than from WT mice challenged with C. difficile (P < 0.05).

CONCLUSION: These results indicate that colitis is more severe after C. difficile infection in IL-10^-/-mice, and that IFN-γ expression is involved in this process.

Differential stress transcriptome landscape of historic and recently emerged hypervirulent strains of Clostridium difficile strains determined using RNA-seq

C. difficile is the most common cause of nosocomial diarrhea in North America and Europe. Genomes of individual strains of C. difficile are highly divergent. To determine how divergent strains respond to environmental changes, the transcriptomes of two historic and two recently isolated hypervirulent strains were analyzed following nutrient shift and osmotic shock. Illumina based RNA-seq was used to sequence these transcriptomes. Our results reveal that although C. difficile strains contain a large number of shared and strain specific genes, the majority of the differentially expressed genes were core genes. We also detected a number of transcriptionally active regions that were not part of the primary genome annotation. Some of these are likely to be small regulatory RNAs.

Acute infection of mice with Clostridium difficile leads to eIF2α phosphorylation and pro-survival signalling as part of the mucosal inflammatory response

The current study sought to delineate the gene expression profile of the host response in the caecum and colon during acute infection with Clostridium difficile in a mouse model of infection, and to investigate the nature of the unfolded protein response in this process. The infected mice displayed a significant up-regulation in the expression of chemokines (Cxcl1, Cxcl2 and Ccl2), numerous pro-inflammatory cytokines (Ifng, Il1b, Il6, and Il17f), as well as Il22 and a number of anti-microbial peptides (Defa1, Defa28, Defb1, Slpi and Reg3g) at the site(s) of infection. This was accompanied by a significant influx of neutrophils, dendritic cells, cells of the monocyte/macrophage lineage and all major subsets of lymphocytes to these site(s). However, CD4 T cells of the untreated and C. difficile-infected mice expressed similar levels of CD69 and CD25. Neither tissue had up-regulated levels of Tbx21, Gata3 or Rorc. The caeca and colons of the infected mice showed a significant increase in eukaryotic initiation factor 2α (eIF2α) phosphorylation, but neither the splicing of Xbp1 nor the up-regulation of endoplasmic reticulum chaperones, casting doubt on the full-fledged induction of the unfolded protein response by C. difficile. They also displayed significantly higher phosphorylation of AKT and signal transducer and activator of transcription 3 (STAT3), an indication of pro-survival signalling. These data underscore the local, innate, pro-inflammatory nature of the response to C. difficile and highlight eIF2α phosphorylation and the interleukin-22-pSTAT3-RegIIIγ axis as two of the pathways that could be used to contain and counteract the damage inflicted on the intestinal epithelium.

Risk factors of fecal toxigenic or non-toxigenic Clostridium difficile colonization: impact of Toll-like receptor polymorphisms and prior antibiotic exposure

BACKGROUND

This study is to investigate the significance and risk factors of fecal toxigenic (tCdC) or non-toxigenic Clostridium difficile colonization (ntCdC) among hospitalized patients.

METHODS

Adults admitted to medical wards in a district hospital between January 2011 and June 2012 were enrolled, and those with a history of colectomy, C. difficile fecal colonization or infection or receipt of either metronidazole or oral vancomycin within 3 months, were excluded. Stools collected within 48 hours after admission and every week during hospitalization were cultured for C. difficile.

FINDINGS

Among the 441 enrolled patients, 84 (20.0%) had CdC at initial screening, including 58 (13.2%) with tCdC and 26 (6.8%) with ntCdC. Among patients with initial negative fecal screening for CdC, it took an average of 70.6 days or 66.5 days to develop tCdC or ntCdC during the study period. Finally 78 (17.7%) had tCdC and 34 (7.7%) had ntCdC. During the follow-up period, the patients with tCdC had a higher risk of CDAD (11/79, 14.1%) than those without CdC (3/328, 0.9%) and those with ntCdC (0/34, 0%) (P<0.001). In multivariate analysis, the TLR4 rs1927914 polymorphism (GG genotype) (odds ratio [OR] 4.4, 95% confidence interval [CI] 1.6-11.8, P = 0.003) and recent cefepime therapy (OR 5.3, 95% CI 2.1-13.2, P<0.001) were independently associated with tCdC, whereas recent cefuroxime (OR 11.7, 95% CI 2.3-60.2, P = 0.003) and glycopeptide therapy (OR 10.9, CI: 2.1-57.2, P = 0.005) associated with ntCdC.

CONCLUSION

The incidence of CDAD is highest in patients with tCdC and lowest in patients with ntCdC, and the TLR4 rs1927914 polymorphism GG genotype and recent cefepime therapy were independently associated with tCdC.

Clostridium difficile Toxin B causes epithelial cell necrosis through an autoprocessing-independent mechanism

Clostridium difficile is the most common cause of antibiotic-associated nosocomial infection in the United States. C. difficile secretes two homologous toxins, TcdA and TcdB, which are responsible for the symptoms of C. difficile associated disease. The mechanism of toxin action includes an autoprocessing event where a cysteine protease domain (CPD) releases a glucosyltransferase domain (GTD) into the cytosol. The GTD acts to modify and inactivate Rho-family GTPases. The presumed importance of autoprocessing in toxicity, and the apparent specificity of the CPD active site make it, potentially, an attractive target for small molecule drug discovery. In the course of exploring this potential, we have discovered that both wild-type TcdB and TcdB mutants with impaired autoprocessing or glucosyltransferase activities are able to induce rapid, necrotic cell death in HeLa and Caco-2 epithelial cell lines. The concentrations required to induce this phenotype correlate with pathology in a porcine colonic explant model of epithelial damage. We conclude that autoprocessing and GTD release is not required for epithelial cell necrosis and that targeting the autoprocessing activity of TcdB for the development of novel therapeutics will not prevent the colonic tissue damage that occurs in C. difficile – associated disease.

Clostridium difficile is an anaerobic spore-forming bacterium that infects the human colon and causes diarrhea, pseudomembranous colitis, and toxic megacolon. Most people that develop disease symptoms have undergone antibiotic treatment, which alters the normal gut flora and allows C. difficile to flourish. C. difficile secretes two toxins, TcdA and TcdB, that are responsible for the fluid secretion, inflammation, and colonic tissue damage associated with disease. The emergence of hypervirulent strains of C. difficile that are linked to increased morbidity and mortality highlights the need for new therapeutic strategies. One strategy is to inhibit the function of the toxins, thereby decreasing damage to the colon while the patient clears the infection with antibiotics. Toxin function is thought to depend on an autoprocessing event that releases a catalytic ‘effector’ portion of the toxin into the host cell. In the course of trying to identify small molecules that would inhibit such a function, we found that TcdB induces a rapid necrosis in epithelial cells that is not dependent on autoprocessing. The physiological relevance of this observation is confirmed in colonic explants and suggests that inhibiting TcdB autoprocessing will not prevent the colonic tissue damage observed in C. difficile associated diseases.

The emergence of Clostridium difficile PCR ribotype 027 in Denmark--a possible link with the increased consumption of fluoroquinolones and cephalosporins?

Increasing rates of Clostridium difficile infection (CDI) with an unusual, severe course have been reported in several countries; this rise has partly been ascribed to the emergence of a virulent strain, C. difficile PCR ribotype 027 (CD027). An intriguing question is whether this could be related to increasing consumption of broadspectrum antibiotics. From 1997 to 2007, the number of hospital discharges in Denmark with the diagnosis enterocolitis caused by C. difficile increased from eight to 23 per 100,000 hospital discharges. This increase was proportional to a concomitant rise in the consumption of fluoroquinolones and cephalosporins. The first outbreak of CD027 in Denmark occurred from October 2006 to August 2007 and included 13 patients, most of them elderly, admitted to three hospitals in the same region. Most of the patients had overlapping periods of admission. All patients had been treated with broadspectrum antibiotics, in particular cephalosporins and fluoroquinolones, prior to positive culture of CD027. 30 days after confirmation of diagnosis, three of the 13 patients had died. Taken together, the data support the hypothesis that the increasing use of certain broadspectrum antibiotics may be related to a possible increase of C. difficile infection, and show that the specific contribution by CD027 in its emergence needs to be determined.

Association of interleukin-8 polymorphism and immunoglobulin G anti-toxin A in patients with Clostridium difficile-associated diarrhea

BACKGROUND & AIMS

Previous studies have shown that failure to produce serum antibodies to C. difficile (CD) toxin A is associated with more severe and recurrent C. difficile-associated diarrhea (CDAD); and that presence of AA genotype in the interleukin (IL)-8 gene promoter -251 position is associated with increased susceptibility to CDAD. This study examined the relationship between serum immunoglobulin G antibodies to CD toxin A and the presence of IL-8 AA genotype in hospitalized patients with CDAD.

METHODS

At enrollment, blood for host IL-8 genotype, serum for CD anti-toxin A antibody, and stool for IL-8 by enzyme-linked immunosorbent assay were obtained in CDAD patients and in CD-toxin-negative asymptomatic controls.

RESULTS

Nine of 24 (37.5%) CDAD and 3 of 20 (15%) controls were CD anti-toxin A positive (P = .095). Eleven of 24 (45.8%) CDAD subjects were positive for AA genotype compared with 5 of 20 (25.0%) controls (P = .0019). One of 11 (9.1%) CDAD with AA genotype were positive for anti-toxin A antibodies compared with 8 of 13 (61.5%) non-AA genotype CDAD (P < .0001). Fecal IL-8 concentration for the single antibody-positive CDAD subject with AA genotype was lower than the median level of 822 microg/mL seen in 10 anti-toxin A antibody-negative subjects with CDAD.

CONCLUSIONS

This study provided evidence that host susceptibility to C. difficile diarrhea is related both to a defective humoral immune response to CD toxin A and host IL-8 AA genotype.

Epidemiology of Clostridium difficile toxinotype III, PCR-ribotype 027 associated disease in Belgium, 2006

As a result of the reports of outbreaks of diarrhoea due to Clostridium difficile North American Pulse field type 1, PCR ribotype 027, toxinotype III in North America, United Kingdom, the Netherlands and Belgium, two different surveillance systems for C. difficile-associated diarrhoea were set up in Belgium

A common polymorphism in the interleukin 8 gene promoter is associated with Clostridium difficile diarrhea

OBJECTIVE

Mucosal interleukin 8 (IL-8) and neutrophil recruitment are central to the pathogenesis of Clostridium difficile (CD) toxin-induced diarrhea (CDD). We hypothesized that like other inflammatory mucosal infections, susceptibility to CDD would relate to genetically determined variations in the production of IL-8.

METHODS

Fecal IL-8 production and single nucleotide polymorphism (SNP) frequency in the -251 region of the IL-8 gene were determined in hospitalized patients: 42 with CDD, 42 with CD-negative diarrhea, and 41 without diarrhea. Cases and controls were matched by age, length of hospital stay, comorbidity, and receipt of antibiotics.

RESULTS

An association was found between the IL-8 -251 A/A allele and occurrence of CDD, 39%versus 16% (OR = 3.26, 95% CI 1.09-9.17) and 17% (OR = 5.50, 95% CI 1.22-24.8) for the two control groups. Comparing results by IL-8 genotype for the CDD cases, median and mean fecal IL-8 levels were significantly higher for the -251 A/A genotype (p = 0.03 for median and 0.001 for mean).

CONCLUSIONS

These studies indicate a common SNP in the IL-8 gene is associated with increased susceptibility to CDD and with increased fecal IL-8 in diarrheal stools.

Reduced gene expression of intestinal alpha-defensins predicts diarrhea in a cohort of African adults

BACKGROUND

Human defensin (HD) 5 and HD6, both Paneth cell alpha-defensins, contribute to the antimicrobial barrier against intestinal infection. We have previously demonstrated that levels of both HD5 and HD6 mRNA were reduced in adults living in urban Zambia, compared with those in adults living in London. The aim of the present study was to determine, during 2 years of follow-up, whether alpha-defensin expression in Zambian adults is related to susceptibility to diarrhea.

METHODS

We analyzed intestinal biopsy samples from a longitudinal cohort study conducted in 83 Zambian adults by quantitative reverse-transcription polymerase chain reaction, Western blotting, immunohistochemistry, and in situ hybridization, and we measured the incidence of diarrhea.

RESULTS

Levels of HD5 and HD6 mRNA in Paneth cells varied between participants, over time, and seasonally and were strongly correlated with mucosal architecture. Gene expression was almost exclusively restricted to Paneth cells. The median (interquartile range) HD5 mRNA level was 6.0 (5.6-6.7) log10 transcripts/microg of total RNA among 18 participants who experienced diarrhea within 2 months after biopsy-sample collection, compared with 6.8 (6.2-7.3) log10 transcripts/microg of total RNA among 94 participants who did not (P=.006). A similar observation was made for HD6.

CONCLUSIONS

These data indicate that intestinal alpha-defensin expression is dynamic and seasonal and suggest that susceptibility to intestinal infection is related to alpha-defensin expression.

Essential involvement of IFN-gamma in Clostridium difficile toxin A-induced enteritis

Clostridium difficile has emerged as the important causative agent of antibiotics-associated pseudomembranous colitis; especially its toxin A is presumed to be responsible for the colitis. We examined the pathophysiological roles of IFN-gamma in toxin A-induced enteritis using IFN-gamma knockout (KO) mice. When toxin A of C. difficile was injected into the ileal loops of BALB/c wild-type (WT) mice, massive fluid secretion, disruption of intestinal epithelial structure, and massive neutrophil infiltration developed within 4 h after the injection. IFN-gamma protein was faintly detected in some CD3-positive lymphocytes in the lamina propria and submucosa of the ileum of untreated WT mice. On the contrary, at 2 and 4 h after toxin A injection, IFN-gamma protein was detected in infiltrating neutrophils and to a lesser degree in CD3-positive lymphocytes. In the ileum of WT mice, toxin A treatment markedly enhanced the gene expression of TNF-alpha, macrophage inflammatory protein-1alpha and -2, KC, and ICAM-1 >2 h after treatment. In contrast, the histopathological changes were marginal, without enhanced fluid secretion in the ileum of toxin A-treated IFN-gamma KO mice. Moreover, toxin A-induced gene expression of TNF-alpha, neutrophil chemotactic chemokines, and ICMA-1 was remarkably attenuated in IFN-gamma KO mice. Furthermore, pretreatment of WT mice with a neutralizing anti-IFN-gamma Ab prevented toxin A-induced enteritis. These observations indicate that IFN-gamma is the crucial mediator of toxin A-induced acute enteritis and suggest that IFN-gamma is an important molecular target for the control of C. difficile-associated pseudomembranous colitis.

Relapses or reinfections: analysis of a case of Clostridium difficile-associated colitis by two typing systems

Immunoblotting and pulsed-field gel electrophoresis of Clostridium difficile isolates were employed to differentiate reinfection by a newly acquired strain from relapse by an original strain in a 10-year-old patient with four episodes of C. difficile-associated colitis. Immunoblot typing demonstrated subserogroup K-1 of serogroup K for the first and second organisms, subserogroup A-1 of serogroup A for the third organism, and subserogroup G-4 of serogroup G for the fourth organism. PFGE analysis revealed consistent results with immunoblot analysis except that the strains from the fourth episode, whose DNA constantly degraded, were nontypable by this method. Five separate isolates of C. difficile from a specimen of each episode showed identical PFGE patterns, indicating that infections of multiple strains probably did not occur in this patient. These typing results suggested that the second episode after a 17-day course of vancomycin therapy represented a relapse by the strain causing the first episode, and that the third and fourth episodes after tapering vancomycin therapy were reinfections by other strains. Both immunoblot and PFGE typing systems are promising tools for analyzing recurrence of C. difficile infection.

Cellular localization of tumor necrosis factor (TNF)-alpha transcripts in normal bowel and in necrotizing enterocolitis. TNF gene expression by Paneth cells, intestinal eosinophils, and macrophages

Tumor necrosis factor-alpha (TNF) has been shown to induce intestinal necrosis in animals. Moreover, plasma TNF levels are elevated in patients with necrotizing enterocolitis. Thus, it is possible that TNF plays a role in the pathogenesis of NEC. In the present study we used in situ hybridization (with human TNF riboprobes) to localize TNF transcripts in the intestinal tissues from normal biopsies and NEC patients. We found that in normal intestine a small amount of TNF mRNA was present only in Paneth cells. In contrast, in the acute stage of NEC, a high amount of TNF transcripts was detected in Paneth cells as well as in infiltrating eosinophils. In one case that showed infiltrating macrophages, TNF mRNA was also detected in these cells. Resident macrophages in the lamina propria and other inflammatory cells were negative for TNF transcripts. Our results suggest that: 1) Paneth cells are the major source of TNF transcripts in normal intestine, and 2) there is a marked increase in TNF mRNA formation in Paneth cells, as well as in infiltrating eosinophils and macrophages in patients with NEC. TNF-containing cells may play an important role in the pathophysiology of NEC.

Twins and triplets with necrotizing enterocolitis

We reviewed 2856 multiple-gestation pregnancies from 1980 to 1985 to identify whether birth order or other features (eg, asphyxia) were significant risk factors for the development of necrotizing enterocolitis (NEC). There were 42 infants identified as having NEC from 30 pairs of twins and three sets of triplets. The firstborn was diagnosed with NEC in 19 (45%) of the cases, with the disorder occurring in the secondborn in 23 cases (55%). While infants A and B were simultaneously affected in nine cases, among the three sets of triplets, no thirdborn infants developed NEC. Although the secondborn infants had significantly lower one-minute Apgar scores and a more frequent need for resuscitation, they were no more prone to develop NEC than were firstborn infants. Multiple gestation, birth order, feeding practices, and a number of other features we evaluated were not associated with the development of NEC. Our findings support the contention that prematurity is the only consistent risk factor in the development of NEC.

[Pseudomembranous colitis after antibiotics therapy]

Pseudomembranous colitis may arise as a severe complication of chemotherapy with antibiotics. Lincomycin and clindamycin are especially incriminated, but the condition has also been reported after treatment with other broad-spectrum antibiotics. The endoscopic findings are suggestive, though not specific. Overall mortality is estimated to be 10--20%. There is an increased risk in patients with a previous history and pseudomembranous colitis in relatives of these patients.

Familial pseudomembranous colitis and its relation to lincomycin therapy

Severe pseudomembranous colitis was observed in 3 members of a single family: the father and 2 of his children. 2 of the affected family members received the antibiotic lincomycin prior to the onset of their symptoms. The findings in this family raise the possibility that antibiotic-induced pseudomembranous colitis in some patients may be the result of a pharmacogenetic interaction.