Utility of serial rectal swab cultures for detection of ceftazidime- and imipenem-resistant gram-negative bacilli from patients in the intensive care unit.

Forty-four patients receiving intensive care were studied prospectively to assess the utility of serial rectal swab cultures and clinical correlates of resistance for Pseudomonas aeruginosa, Enterobacter spp., Citrobacter spp., Morganella morganii, and Serratia marcescens strains resistant to ceftazidime or imipenem. Strains of Pseudomonas aeruginosa, Enterobacter spp., Citrobacter spp., or Morganella morganii were found in 26 of 44 (59%) patients: 17 (65%) in clinical sites (11 with concomitant rectal isolates) and nine (35%) in a rectal site only. Of 49 total isolates, 13 (26.5%) were resistant: 10 (20.4%) to ceftazidime and three (6.1%) to imipenem. Surveillance rectal swabs from 27 patients without a clinical isolate identified two patients with resistant organisms (15% of all resistant isolates). The majority of resistance to ceftazidime or imipenem among Pseudomonas or Enterobacter can be detected by the use of clinical specimens alone.

Predicting Clostridium difficile stool cytotoxin results in hospitalized patients with diarrhea.

OBJECTIVE: To validate a model for the prediction of Clostridium difficile cytotoxin assay results, and to identify a subgroup of patients with a very low likelihood of C. difficile-associated disease in whom the yield of routine cytotoxin testing is low. DESIGN: Prospective cohort study. Relevant clinical symptoms, signs, and antibiotic exposure were recorded before reporting of assay results. Each predictor was assigned a score based on regression coefficients, and patients were stratified according to their total score. SETTING: Two urban, tertiary care, university hospitals. PATIENTS: A total of 609 consecutive adult inpatients who received testing for C. difficile cytotoxin during a 3-month period in 1994. MEASUREMENTS AND MAIN RESULTS: The prevalence of positive cytotoxin assays was 8% in the validation set, compared with 14% in the derivation set. Defining patients without both prior antibiotic use and at least one symptom predictor (significant diarrhea or abdominal pain) as a low-risk subgroup, the misclassification rate was 2.8% (5/177) for assay results; of the five misclassified cases patients, only one was judged to have C. difficile-associated disease. Use of this rule to identify low-risk patients could have potentially averted 29% of all cytotoxin assays. CONCLUSIONS: Patients without a history of antibiotic use and either significant diarrhea or abdominal pain are unlikely to have positive C. difficile cytotoxin assays and may not require cytotoxin testing.

Risk factors leading to clinical failure in the treatment of intra-abdominal or skin/soft tissue infections.

A study of determinants of outcome in adult patients with intra-abdominal or skin/soft tissue infections treated with cefotetan, cefoxitin, or ampicillin/sulbactam monotherapy was undertaken. Patients were matched for principal infectious process, surgery performed for the management of the infection, year of hospital admission, age, and sex. The criteria for inclusion, exclusion, and matching of patients and assignment of clinical and microbiological outcome were based on the 1992 Infectious Diseases Society of America/Federal Drug Administration guidelines for the evaluation of anti-infective drug products. One hundred and thirty-seven cases of intra-abdominal or skin and soft tissue infections treated with cefotetan (n = 47), cefoxitin (n = 43), or ampicillin/sulbactam (n = 47) monotherapy were selected without knowledge of outcome and analyzed using a single blinded analysis. The baseline characteristics did not differ between the treatment groups, nor did the rates of clinical or microbiological failure. A multivariate analysis showed that isolation of an organism resistant to the treatment regimen, including Pseudomonas spp., [odds ratio (OR) = 14.9, p = 0.001], being on antibiotic therapy at the time of admission (OR = 4.5, p = 0.007), and diagnosis of a complicated intra-abdominal infection (OR = 3.5, p = 0.014) were independently associated with clinical failure. These data support the assertion that antibiotic resistant organisms in mixed anaerobic/aerobic infections are associated with clinical failure and suggest that the antibiotic regimen should be modified to include Pseudomonas spp. in its spectrum when this organism is isolated from patients with such infections.