Shigella sonnei is a significant cause of gastroenteritis in both developing and industrialized countries. Definition of the diversity and antimicrobial susceptibility of S. sonnei isolates may be helpful in the management of individual cases and outbreaks. Antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE) were performed with 67 isolates of S. sonnei predominantly (n ‫؍‬ 59) from three counties in the west of Ireland. Phage typing (n ‫؍‬ 17), plasmid profiling (n ‫؍‬ 28), and integron analysis (n ‫؍‬ 24) were performed with subsets of strains. PFGE typing permitted recognition of two major clusters: PFGE type A (n ‫؍‬ 53) and PFGE type B (n ‫؍‬ 14). PFGE type A was associated with resistance to ampicillin, streptomycin, and sulfonamides (51 of 53 isolates), and those that were phage typed (n ‫؍‬ 6) were phage type 3. PFGE type B was associated with resistance to streptomycin, sulfonamides, tetracycline, and trimethoprim (11 of 14 isolates) and phage type 6 (9 of 11 isolates). Fifteen different plasmid profiles were identified among the 28 isolates analyzed. A class 2 integron was present in all 14 PFGE type B isolates. One of these isolates also contained a class 1 integron and showed a unique variant of the PFGE type B pattern. Sequence analysis of the gene cassette structures contained within these integrons identified distinct open reading frames that encoded determinants of resistance to trimethoprim, streptomycin, and streptothricin. Our data demonstrate two predominant PFGE types among S. sonnei isolates circulating in this region. The limited diversity of the S. sonnei isolates in this region means that detection of isolates indistinguishable by PFGE and according to their antibiograms in two or more patients is not persuasive evidence of a common-source food-or waterborne outbreak. Indistinguishable plasmid profiles in addition to indistinguishable PFGE and antibiogram types may be more suggestive of an epidemiologically relevant link between cases.

Clostridium difficile is the principal pathogen associated with hospital-acquired acute diarrheal disease. We have evaluated the performances of six approaches for diagnosis of C. difficile-associated diarrhea (CDAD). Consecutive stool specimens (n ‫؍‬ 200) from 133 patients were examined by cytotoxin assay, by culture of C. difficile on cycloserine-cefoxitin-fructose agar, and by toxin detection using four rapid immunoassay systems (Oxoid Toxin A test, ImmunoCard Toxin A test, TechLab Tox A/B II test, and Premier Toxins A&B test). A diagnosis of CDAD was established for 35 (27%) patients (representing 29% of specimens). The adjusted sensitivity and specificity of the methods were, respectively, 98 and 99% for the cytotoxin assay, 54 and 99% for ImmunoCard, 50 and 98% for Oxoid, 79 and 98% for TechLab, 80 and 98% for Premier, and 57 and 100% for culture. The TechLab and Premier assays are acceptable tests for diagnosis of CDAD but are not equivalent to the cytotoxin assay.Nosocomial infection with Clostridium difficile increases morbidity and mortality among hospitalized patients and places a significant economic burden on health services (3,7,18). Early diagnosis is associated with better prognosis (12); therefore; rapid laboratory diagnosis is highly desirable.The diagnosis of C. difficile-associated diarrhea (CDAD) is usually based on clinical features and detection of C. difficile toxin. Tissue culture assay is considered the "gold standard" for the demonstration of C. difficile toxins in specimens of feces. The technical complexity, slow turnaround time (24 to 48 h), and lack of standardization of the cytotoxin assay are significant limiting factors (11). As a result, a number of commercial products for rapid immunological detection of toxin have been developed. Some products are based on detection of only C. difficile toxin A, while others detect both toxin A and toxin B. The practical importance of detection of both toxins is unclear (4, 7). The impetus to detect both toxins may be supported if the suggestion that toxin A Ϫ B ϩ strains of C. difficile are emerging as significant pathogens is validated (1, 13).In this study, four rapid immunoassays were evaluated for the detection of C. difficile toxins in stool specimens and their performances were compared with that of the cytotoxin assay. The rapid assays consisted of two microwell-based enzyme immunoassays that detected both toxin A and toxin B and two chromatographic cassette-based immunoassays that detected toxin A only. The performances of six assay methods (the four immunoassays, the cytotoxin assay, and bacteriological culture) were evaluated with reference to clinical and biological criteria for diagnosis of CDAD. MATERIALS AND METHODSTwo hundred consecutive stool specimens (from 133 adult patients) received in the laboratory for routine investigation of C. difficile infection were included in the study. Stool specimens were cultured on the day of receipt. The study included specimens that were transported by routine road transport at room temper...

Volume 41, no. 5, p. 1919Volume 41, no. 5, p. -1924. In our paper, we described the characterization of a gene cassette-encoding region from a class 1 integron of Shigella sonnei isolate 1778 and identified a variable cassette region encoding sat-aadA genes. With reference to the letter of Partridge and Hall (J. Clin. Microbiol. 43:4298-4300, 2005), we have revised our sequence data and acknowledge that the sequence we originally identified as sat should be designated estX. Our GenBank entry (accession no. AY090896) has been modified accordingly. 4309on May 11, 2018 by guest