Vincent B. Young

Decreased Diversity of the Fecal Microbiome in Recurrent Clostridium difficile—Associated Diarrhea

Antibiotic-associated diarrhea due to Clostridium difficile (CDAD) is thought to reflect colonization of a disrupted microbial community by the pathogen. We profiled the fecal microbiota of patients with CDAD (both initial and recurrent episodes) by culture-independent phylogenetic analysis of 16S rRNA-encoding gene sequences. Compared with those from control subjects and patients with an initial episode, the fecal communities in patients with recurrent CDAD were highly variable in bacterial composition and were characterized by markedly decreased diversity. Preservation and restoration of the microbial diversity could represent novel strategies for prevention and treatment of recurrent CDAD, which is often recalcitrant to existing therapies.

Antibiotic-Associated Diarrhea Accompanied by Large-Scale Alterations in the Composition of the Fecal Microbiota

ABSTRACT Alterations in the diversity of the gut microbiota are believed to underlie the development of antibiotic-associated diarrhea (AAD). A molecular phylogenetic analysis was performed to document temporal changes in the diversity of fecal bacteria of a patient who developed AAD. Antibiotic administration was associated with distinct changes in the diversity of the gut microbiota, including a marked decrease in the prevalence of butyrate-producing bacteria. Following the discontinuation of the antibiotic, resolution of diarrhea was accompanied by a reversal of these changes, providing the first direct evidence linking changes in the community structure of the gastrointestinal bacteria with the development of AAD.

C57BL/6 and Congenic Interleukin-10-Deficient Mice Can Serve as Models of Campylobacter jejuni Colonization and Enteritis

ABSTRACT Campylobacter jejuni is a globally distributed cause of human food-borne enteritis and has been linked to chronic joint and neurological diseases. We hypothesized that C. jejuni 11168 colonizes the gastrointestinal tract of both C57BL/6 mice and congenic C57BL/6 interleukin-10-deficient (IL-10−/−) mice and that C57BL/6 IL-10−/− mice experience C. jejuni 11168-mediated clinical signs and pathology. Individually housed mice were challenged orally with C. jejuni 11168, and the course of infection was monitored by clinical examination, bacterial culture, C. jejuni-specific PCR, gross pathology, histopathology, immunohistochemistry, and anti-C. jejuni-specific serology. Ceca of C. jejuni 11168-infected mice were colonized at high rates: ceca of 50/50 wild-type mice and 168/170 IL-10−/− mice were colonized. In a range from 2 to 35 days after infection with C. jejuni 11168, C57BL/6 IL-10−/− mice developed severe typhlocolitis best evaluated at the ileocecocolic junction. Rates of colonization and enteritis did not differ between male and female mice. A dose-response experiment showed that as little as 106 CFU produced significant disease and pathological lesions similar to responses seen in humans. Immunohistochemical staining demonstrated C. jejuni antigens within gastrointestinal tissues of infected mice. Significant anti-C. jejuni plasma immunoglobulin levels developed by day 28 after infection in both wild-type and IL-10-deficient animals; antibodies were predominantly T-helper-cell 1 (Th1)-associated subtypes. These results indicate that the colonization of the mouse gastrointestinal tract by C. jejuni 11168 is necessary but not sufficient for the development of enteritis and that C57BL/6 IL-10−/− mice can serve as models for the study of C. jejuni enteritis in humans.

Colonization of the Cecal Mucosa by Helicobacter hepaticus Impacts the Diversity of the Indigenous Microbiota

ABSTRACT Establishment of mucosal and/or luminal colonization is the first step in the pathogenesis of many gastrointestinal bacterial pathogens. The pathogen must be able to establish itself in the face of competition from the complex microbial community that is already in place. We used culture-independent methods to monitor the colonization of the cecal mucosa of Helicobacter-free mice following experimental infection with the pathogen Helicobacter hepaticus. Two days after infection, H. hepaticus comprised a minor component of the mucosa-associated microbiota, but within 14 days, it became the dominant member of the community. Colonization of the mucosa by H. hepaticus was associated with a decrease in the overall diversity of the microbial community, in large part due to changes in evenness resulting from the relative dominance of H. hepaticus as a member of the community. Our results demonstrate that invasion of the complex gastrointestinal microbial community by a pathogenic microorganism causes reproducible and significant disturbances in the community structure. The use of non-culture-based methods to monitor these changes should lead to a greater understanding of the ecological principles that govern pathogen invasion and may lead to novel methods for the prevention and control of gastrointestinal pathogens.

Streptococcus intermedius causing infective endocarditis and abscesses: a report of three cases and review of the literature

BackgroundStreptococcus intermedius is a member of the Streptococcus anginosus group. Clinical disease with S. intermedius is characterized by abscess formation and rarely endocarditis. Identification of Streptococcus intermedius is difficult, leading to the development of molecular methods to more accurately identify and characterize this organism.Case presentationOver a period of 6 months we encountered three cases of invasive Streptococcus intermedius infection presenting as hepatic abscesses, brain abscess, and endocarditis. We confirmed our microbiologic diagnosis through 16S sequencing and found a common virulence gene in each case.ConclusionOur report illustrates three different clinical manifestations due to Streptococcus intermedius infection that can be encountered in healthy individuals in a community hospital setting. To our knowledge, this is the first case of Streptococcus intermedius endocarditis confirmed by 16S sequencing analysis. The use of molecular methods may allow a better understanding of the epidemiology and pathogenesis of this organism.

Spherules, hyphae, and air-crescent sign.

Coccidioidomycosis is endemic in the southwestern United States, resulting in 100,000 infections annually. The majority of these infections are asymptomatic or manifest as community-acquired pneumonia. In rare cases, patients can present with a mononuclear-cell predominant pyopneumothorax. The presence of spherules in tissue specimens is pathognomonic of this condition. A 72-year-old man born in Arizona with a heavy smoking history, presented with a 1-month history of weakness, night sweats, exertional dyspnea, and left pleuritic chest pain. The physical examination was remarkable for decreased breath sounds and dullness to percussion at the left lung base. His initial laboratory examination showed leukocytosis, eosinophilia, and elevated C-reactive protein. Computed tomography of the chest revealed a left lower lobe infiltrate, a cavity with air-crescent sign and hydropneumothorax. The pleural fluid was sampled and revealed an eosinophilic exudate with normal pH. Bacterial and fungal cultures of the pleural fluid were negative. Biopsy of the cavity wall showed chronic inflammation, fungal hyphae, and rare spherule-like structures. The surgical specimen culture grew Coccidioides immitis. Complement fixation for coccidioidomycosis performed on a serum sample was positive at a titer of 1:2 but a latex agglutinin test was negative. The patient was diagnosed with chronic fibrocavitary pneumonia with pyopneumothorax secondary to C. immitis infection and discharged on itraconazole for 1 year. Coccidioidomycosis can present in a variety of forms and should be part of the differential diagnosis in patients presenting with cavitation, air-crescent sign, eosinophilic pleural effusion, and hyphae and spherules on the tissue specimen. Chronic fibrocavitary pneumonia should be especially considered in patients who lived in endemic areas and have risk factors such as diabetes mellitus or pulmonary fibrosis related to smoking.

Treatment of clostridium difficile infection with tigecycline proof of concept study

BackgroundCases of tigecycline treatment, as single or adjacent therapy, have been reported in patients with Clostridium difficile infection (CDI). At present, there have not been any controlled investigations of tigecycline in this patient population. MethodsTen hospitalized adult patients with CDI were treated with standard doses of intravenous tigecycline and oral vancomycin or metronidazole therapy. Susceptibility testing and polymerase chain reaction ribotyping of C difficile isolates were performed on initial fecal specimens. Blood and fecal concentrations of tigecycline were determined on day 3 of treatment by high-performance liquid chromatography. The efficacy and safety of treatment was assessed each day of hospitalization and for 30 days after discharge. ResultsThe C difficile isolates cultured from these patients exhibited similar minimum inhibitory concentrations (range, 0.125–0.25 mg/L) to tigecycline irrespective of ribotype. The mean ± SD fecal concentration of tigecycline (17.8 ± 23.8 &mgr;g/g) on day 3 of treatment was almost 100 times higher than the corresponding mean ± SD serum level (0.18 ± 0.14 mg/L). No serious untoward events occurred during this study, but 2 patients had mild nausea associated with tigecycline administration. In general, these patients did well after hospital discharge, but one had recurrent CDI and was hospitalized during the follow-up period. ConclusionsThe results from this investigation support further study of intravenous tigecycline in patients with CDI.