Diagnosing toxigenic Clostridium difficile: new confidence bounds show culturing increases sensitivity of the toxin A/B enzyme immunoassay and refute gold standards.

OBJECTIVE: To scrutinize published sensitivity estimates obtained using questionable gold standards by comparing sensitivities of culturing Clostridium difficile in commercially available media followed by enzyme immunoassay (EIA) toxin A or B detection (culture test) with applying the EIA to stool samples alone (direct test). METHODS: In 2008, consecutive stool samples were cultured on C. difficile selective culture media: (1) medium I: Clostridium difficile-selective agar (CDSA; Becton Dickinson); (2) medium II: CLO agar (BioMérieux); (3) medium III: C. difficile agar according to Brazier (Oxoid). In addition, a direct test was performed (Ridascreen, r-Biopharm), which was also used to confirm toxin A or B production in the cultured C. difficile. New confidence bounds for sensitivities were applied, without assuming any perfect reference test or any conditional independence of the tests compared. RESULTS: Of 256 liquid stool samples, 18.4% were diagnosed as positive by at least 1 of the 4 tests; 12.8% were positive with culture medium I, 16.4% with medium II, and 13.6% with medium III, and 10.1% were positive by the direct test. Assuming culture tests to be at least as specific as the direct test yields an upper bound of 61% (upper 95% confidence bound (CB) 81%) for the sensitivity of the direct test. Assuming a prevalence of 15% yields sensitivity gains of the culture tests of at least 18% (lower 95% CB--4%) for medium I, 40% (lower 95% CB 21%) for medium II, and 23% (lower 95% CB 2%) for medium III. CONCLUSIONS: Published high sensitivities of direct toxin A/B EIAs, up to 96%, and the correctness of the cytotoxicity test assumed for their estimation are doubtful. With culture medium II, sensitivity gains of at least about 20% are obtainable. Direct toxin A/B EIAs alone are insufficiently sensitive for the clinical diagnosis of C. difficile infections.

Associations between the drill (Mandrillus leucophaeus) and sympatric monkeys in Korup National Park, Cameroon.

Studies of polyspecific associations among African forest primates have primarily focused on arboreal Cercopithecus and Procolobus/Colobus species. We examined the association frequency of the terrestrial drill (Mandrillus leucophaeus) with six sympatric monkey species in Korup National Park, Cameroon, testing reports that Mandrillus associations are infrequent and transient. We conducted 3,284 km of trail walks for 12 months (February-June 2006; July 2007 to January 2008), recording species composition in 612 primate clusters. Using a Markov chain Monte Carlo test, we compared the observed frequency of dyadic associations against null models of "no association." A novel conservative statistical approach which addresses possible dependence of observations close in time was also used, further strengthening confidence in our findings. Drills associated with all monkeys throughout the study period, and were with at least one other species (range 1-5) in half of the encounters. The association frequency of drills with red-capped mangabeys (Cercocebus torquatus) was greater than expected by chance, which is interesting given the morphological adaptation of the Mandrillus-Cercocebus clade for the exploitation of the same dietary niche, hard seeds. The difference we observed in the use of forest strata by drills and mangabeys may reflect a strategy to reduce food competition while in association. The nature and duration of observed drill associations varied. Although some associations seemed to be chance encounters, others lasted for hours with the involved species foraging together.

Thoracic organ transplantation may not increase the risk of bacterial transmission in intensive care units.

A transmission study was performed to investigate whether organ recipients suffer more transmissions of bacteria than do non-transplanted patients. We chose enterococci for molecular typing because of their high prevalence, transmissibility, and predominance in causing nosocomial infections. Patients staying longer than 48h in a cardiovascular surgery intensive care unit (ICU) were included in our one-year prospective cohort study. Enterococci identified from clinical or surveillance isolates were collected and typed by PFGE. Episodes of transmission were defined by the identification of genetically indistinguishable isolates in two or more patients who were treated during overlapping intervals or within a 9-day window period in the same ICU. Risk factor analysis was performed. Out of 585 patients microbiological specimens were cultured from 336 patients. From 187 of these, enterococci were isolated. From 81 patients 186 enterococci isolates were typed. Out of 105 different enterococci strains, 16 cluster strains were detected and 30 episodes of transmissions occurred. The transmission rate was 7.8 per 1000 patient days. No significant association was found between "being cluster member "and "patient organ transplanted" (OR 1.5, CI(95%) 0.58; 3.98, p=0.38) or "patient treated in a single-room only" (OR 1.06, CI(95%) 0.36;3, 12, p=0.91), respectively. In contrast, "being cluster member" was associated with a prolonged length of stay (OR per additional days of stay 1.05, CI(95%) 1.01-1.09, p<0.01). Thoracic organ transplantation was not found to be a risk factor for bacterial transmission, but transmission was associated with a prolonged length of stay.

Evaluation of the impact of the source (patient versus staff) on nosocomial norovirus outbreak severity.

OBJECTIVE: To study the dependence of infection risk and outbreak size on the type of index case (i.e., patient or staff). METHODS: Nosocomial outbreaks were reviewed and categorized into those started by patients and those started by staff. Infection risks and outbreak sizes were evaluated taking into account the index case category. RESULTS: Of the 30 nosocomial outbreaks of norovirus with person-to-person transmission, 20 (67%) involved patients as the index cases. Patient-indexed outbreaks affected significantly more patients than did staff-indexed outbreaks (difference in means, 16.25; 95% confidence interval [CI95], 5.1 to 27.0). For the numbers of affected staff, no dependence on the index case category was detectable (difference in means, -1.05; CI95, -9.0 to 6.9). For patients exposed during patient-indexed outbreaks, the risk of acquiring a norovirus infection was approximately 4.8 times as high as the corresponding risk for patients exposed during staff-indexed outbreaks (odds ratio [OR], 4.79; CI95, 1.82 to 8.28). The infection risk for exposed staff during patient-indexed outbreaks was approximately 1.5 times as high as the corresponding risk during staff-indexed outbreaks (OR, 1.51; CI95, 0.92 to 2.49). CONCLUSIONS: Patient-indexed norovirus outbreaks generally affect more patients than do staff-indexed outbreaks. Staff appear to be similarly affected by both outbreak index category groups. This study demonstrates the importance of obtaining complete outbreak data, including the index case classification as staff or patient, during norovirus outbreak investigations. Such information may be useful for further targeting prevention measures