European Journal of Clinical Microbiology最新文献

A method for typing Pseudomonas aeruginosa using antibiotic susceptibility patterns is presented, which allows recognition of clusters of the same strain among clinical isolates from different patients, thus indicating whether cross infection has occurred. An index of similarity (the euclidean or the oblique distance), which includes all the differences of disk zone sizes among isolates, is computed and then elaborated by a clustering algorithm that successively groups all the isolates in larger clusters. The results of clustering are presented as dendrograms, whose terminal branches are pruned down to a level below which differences are casual; isolates that still appear on a common branch are considered identical. The reliability of this technique for detecting nosocomial cross infections was assessed by comparing its results with that of serotyping and pyocin typing. Only 2 of 31 (6.4%) clusters detected by multivariate analysis were not confirmed, while 4 of 33 (12.1%) clusters were recognized by serotyping and pyocin typing, but not by multivariate analysis. In at least two instances the differences in susceptibility patterns were due to cytoplasmic R factors. The routine use of antibiogram data for typing purposes should be considered an essential part of nosocomial infection control.

A technique to determine the effects of combining antimycobacterial drugs in liquid medium employing the radiometric growth readings in the Bactec system was tested using 20 Mycobacterium avium complex strains. Ten of the strains had been isolated from children with lymphadenopathy and ten from adults with pulmonary disease. All isolates were resistant to streptomycin, rifampicin, isoniazid and ethambutol when tested with a conventional resistant ratio technique on Löwenstein-Jensen medium. Synergistic interactions were shown for the two-drug combinations streptomycin + ethambutol and ethambutol + rifampicin against all 20 strains. Good efficacy was also found for all three-drug combinations containing ethambutol. Thus, although most isolates of the Mycobacterium avium complex are resistant to first-line antituberculous drugs when tested individually, they are susceptible in vitro to certain combinations of these drugs. This rapid radiometric assay is an efficient means for detecting such synergy.

Optochin resistant Streptococcus pneumoniae having typical pneumococcal morphology in culture and Gram stain and giving clear agglutination with anti-pneumococcal polysaccharide antisera were isolated from primary cultures of blood and middle ear fluid. The isolated pneumococci were either fully sensitive to penicillin and other antimicrobial agents commonly used or relatively resistant to penicillin and resistant to cloxacillin, tetracycline, erythromycin, sulphatrimethoprim and clindamycin.

A 998 bp fragment of plasmid pBR322, comprising part of the TEM-1 beta-lactamase gene, was labelled with biotin-11-dUTP for use as a DNA probe in a rapid non-isotopic spot hybridisation test. Diluted broth cultures of bacteria producing different beta-lactamases were filtered onto nitrocellulose and lysed in situ. Following pre-hybridisation treatment with proteinase K, hybridisation with the labelled probe was demonstrated using a commercially available streptavidine/polyalkaline phosphatase-based detection system. The probe was highly specific, reacting only with strains producing either the TEM-1 or structurally similar TEM-2 enzyme. An inoculum of 3-4 X 10(6) cells gave optimum positive discrimination. When 90 recent ampicillin-resistant strains of Escherichia coli isolated from patients with urinary tract infections were screened using the system, 72% gave a positive hybridisation signal.

The clinical problems caused by inducible beta-lactamases in certain gram-negative bacteria are being recognized with increasing frequency. These problems include the rapid emergence of multiple beta-lactam resistance during therapy with many of the newer beta-lactam antibiotics. Such multiply resistant organisms are now spreading within the hospital and have become important nosocomial pathogens. This has been a particularly difficult problem for intensive care units, cystic fibrosis centers and burn units where there are clusters of patients who are highly susceptible to infections with organisms like Enterobacter spp., Serratia spp. and Pseudomonas aeruginosa, which possess inducible beta-lactamases. Only through an awareness of these problems, their cause, and restriction of the use of certain newer beta-lactam antibiotics can these problems be controlled.

The purpose of this investigation was to develop a serological procedure for rapid identification of the following five Bacteroides species: Bacteroides distasonis, Bacteroides fragilis, Bacteroides ovatus, Bacteroides uniformis, and Bacteroides vulgatus. The outer membrane fractions were assayed using SDS-polyacrylamide slab gel electrophoretic techniques. The species-specific protein band from each species as well as the group-specific protein were purified and used to develop an indirect enzyme-linked immunosorbent assay to detect the species-specific and group-specific protein from the outer membrane of five reference species. The sensitivity and specificity of the procedure were evaluated by indirect ELISA methodology using 506 clinical isolates of organisms in this group, ten other species of anaerobic gram-negative bacilli, and three species of aerobic gram-negative bacilli. Each species evaluated yielded unique outer membrane protein patterns, suggesting the potential for development of a rapid, species-specific diagnostic procedure.

Three commercial methods (enzyme immunoassay, fluoroimmunoassay and latex agglutination) and a complement fixation test were compared for detection of cytomegalovirus antibodies using a panel of 490 serum samples from blood and organ donors, from immunocompromised patients and paired sera from five patients with recent cytomegalovirus infection. An indirect immunofluorescence test for antibodies to cytomegalovirus was used for classifying samples giving discrepant results by any of the four methods. All methods showed high sensitivity and specificity, but the enzyme immunoassay and the latex agglutination tests had the highest sensitivity. Latex agglutination is recommended for large-scale screening of cytomegalovirus antibodies in blood and organ donors. Negative results obtained by latex agglutination should be confirmed by sensitive enzyme immunoassays.