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Biomedical subjects

R Lannigan

Publications and source records attributed to R Lannigan.

At least 19 recordsLinked to original sources
PubMed2000

Correlation of oxacillin MIC with mecA gene carriage in coagulase-negative staphylococci.

The National Committee for Clinical Laboratory Standards has recently changed the oxacillin breakpoint from >/=4 mg/liter to >/=0. 5 mg/liter to detect methicillin-resistant coagulase-negative staphylococci (CoNS) because the previous breakpoint lacked sensitivity. To determine the correlation between the new oxacillin breakpoint and the presence of the mecA gene, 493 CoNS of 11 species were tested. The presence of the mecA gene was determined by PCR, and oxacillin susceptibility was determined by the agar dilution method with Mueller-Hinton agar containing 2% NaCl and oxacillin (0. 125 to 4.0 mg/liter). The new breakpoint correctly classified all CoNS strains with mecA as methicillin resistant and strains of Staphylococcus epidermidis, S. haemolyticus, and S. hominis without mecA as methicillin susceptible. The breakpoint of >/=0.5 mg/liter was not specific for S. cohnii, S. lugdunensis, S. saprophyticus, S. warneri, and S. xylosus, in that it categorized 70 of 74 strains of these species without mecA (94.6%) as methicillin resistant. The results of this study indicate that the new oxacillin breakpoint accurately identifies strains of CoNS with mecA but is not specific for strains of certain species of CoNS without mecA.

Coagulase↗
PubMed2000

Rapid detection of mecA-positive and mecA-negative coagulase-negative staphylococci by an anti-penicillin binding protein 2a slide latex agglutination test.

A rapid slide latex agglutination (LA) test, MRSA-Screen (Denka Seiken Co., Niigata, Japan), which detects PBP 2a, was tested for its ability to differentiate between mecA-positive and -negative coagulase-negative staphylococci. A total of 463 isolates from 13 species were included in the study. The mecA gene was detected by PCR, and the oxacillin MIC was determined by the agar dilution method according to the guidelines of the National Committee for Clinical Laboratory Standards (NCCLS). The LA test was performed with oxacillin-induced isolates. The true-positive and true-negative results were defined on the basis of the presence or the absence of the mecA gene. By PCR, 251 isolates were mecA positive and 212 were mecA negative. The sensitivities, specificities, and positive and negative predictive values for the LA test compared to the NCCLS breakpoint for oxacillin resistance (>/=0.5 mg/liter) were as follows: for the LA test, 100, 99.5, 99.6, and 100%, respectively; for the NCCLS breakpoint, 100, 60.8, 75.1, and 100%, respectively. One hundred twenty-five mecA-positive isolates were also tested by the LA test without induction of PBP 2a; only 72 (57.6%) gave a positive result and required 3 to 15 min for reaction. With induction, all 251 isolates were positive within 3 min. The LA test was reliable in classifying mecA-negative isolates, but it classified isolates for which the oxacillin MIC was >/=0.5 mg/liter as oxacillin susceptible. For the reliable detection of oxacillin resistance by the MRSA-Screen in coagulase-negative staphylococci, induction of the mecA gene appears to be necessary.

Bacterial Proteins↗
PubMed1998

Evaluation of screening and commercial methods for detection of methicillin resistance in coagulase-negative staphylococci.

The National Committee for Clinical Laboratory Standards recommends 48 h of incubation by the oxacillin salt agar screen (OSAS) method for the detection of methicillin-resistant coagulase-negative staphylococci (CoNS). An earlier identification of methicillin resistance is desirable. The time to detection of the mecA gene by PCR was compared with the times to detection by OSAS, by the oxacillin disk diffusion (ODD) method, and with MicroScan Gram Positive Combo type 6 panels (MicroScan Inc. Sacramento, Calif.) and Vitek GPS-SA cards (bioMérieux Vitek Inc., Hazelwood, Mo.). The combination of the Vitek card and the ODD method detected 92 of 99 methicillin-resistant strains of CoNS at 24 h; however, 6 mecA-positive strains were phenotypically methicillin susceptible. We conclude that most methicillin-resistant CoNS can be detected and the results can be reported after overnight incubation by a combination of methods.

Bacterial Proteins↗
PubMed1996

Quality improvement of diagnostic microbiology through a peer-group proficiency assessment program. A 20-year experience in Ontario. The Microbiology Committee.

OBJECTIVE: To evaluate the microbiology laboratory performance in Ontario over a 20-year period of participation in a quality assessment program and to assess the impact of quality improvement strategies. DESIGN: Longitudinal review of isolation, identification, and antimicrobial susceptibility testing of bacteria from lyophilized, simulated patient samples. SETTING: Ontario medical laboratories, licensed by the Ministry of Health, have been subjected to mandatory testing by the Laboratory Proficiency Testing Program of the Ontario Medical Association since 1974. Survey reports, information bulletins, correspondence, on-site consultations, educational assistance tutorials, and teleconference education are used as quality improvement strategies. PARTICIPANTS AND INTERVENTIONS: Laboratories were subjected annually to 20 external quality assessment challenges. Performance was assessed against consensus reference values. Single survey and cumulative profiles were reviewed by a peer-group panel for acceptable or unacceptable performance. Specific interventions are used to improve collective and individual laboratory performance. RESULTS: The number of microbiology laboratories declined from 335 in 1974 to 190 in 1994. Twenty-one percent failed expected performance standards on initial review. One hundred forty-two on-site consultations and 61 educational assistance tutorials have been provided. Twenty-five laboratories were declared nonproficient. Since 1989, 50% of the laboratories have scored at or above 80% for isolation and identification, but 25% have scored at or below 50% on susceptibility testing, and 10% or fewer have scored at or above 80%. Poor susceptibility testing performance is due to inappropriate agent selection, not testing errors. CONCLUSIONS: The emphasis of the Laboratory Proficiency Testing Program is on quality improvement, not punishment. Performance has improved, but poor performers have the same characteristics as in 1974. Identification to species is common owing to the use of commercial systems. Automated susceptibility testing has increased to 45% of participants.

Bacterial Infections↗
PubMed1995

Evidence that the National Committee for Clinical Laboratory Standards disk test is less sensitive than the screen plate for detection of low-expression-class methicillin-resistant Staphylococcus aureus.

A low-expression-class methicillin-resistant Staphylococcus aureus strain (strain 9302-2) was sent to 207 laboratories as part of the bacteriology component of the Laboratory Proficiency Testing Program of Ontario. An incorrect (susceptible) result was reported by 16 of 76 (21%) of laboratories that used the National Committee for Clinical Laboratory standards disk test, whereas 1 of 104 laboratories that used other methods reported an incorrect result (P < 0.05). Experiments showed discrepancies in the disk test results given by Mueller-Hinton agars from three manufacturers. We advise that laboratories should use a low expression-class methicillin-resistant S. aureus isolate as a control for the National Committee for Clinical Laboratory Standards disk test.

Humans↗
PubMed1994

Gas-liquid chromatography of cellular fatty acids for identification of staphylococci.

A commercially available, computer-assisted microbial identification system (MIS) employs gas-liquid chromatographic analyses of bacterial fatty acids. The MIS was used to identify 470 isolates of Staphylococcus species. The accuracy of the MIS was compared with the accuracies of conventional methods. There was a complete agreement between the MIS and conventional methods in the identification of 413 (87.8%) strains. For 36 of 45 misidentified strains, the correct identification was listed by the MIS as a choice but not as the first choice. Twelve strains could not be matched. All strains of Staphylococcus cohnii, S. epidermidis, S. intermedius, S. lugdunensis, S. schleiferi, S. sciuri, S. simulans, and S. xylosus were correctly identified. Two species, S. hominis and S. saprophyticus, accounted for 52.6% (30 of 57) of the misidentifications. Seventy-eight organisms were retested. Identification of 73 organisms remained unchanged, and for five organisms, the second choice became first and vice versa. The overall performance of the MIS is acceptable, and the system can be used as an alternate identification method for staphylococci.

Chromatography, Gas↗
PubMed1993

Comparison of the E-test and reference agar dilution method for susceptibility of gram-negative anaerobic organisms.

Minimal inhibitory concentrations (MICs) of clindamycin, cefoxitin, imipenem, and metronidazole were determined by the E-Test and a reference agar dilution method for 92 gram-negative anaerobic organisms. For 335 MIC pairs, the agreement between the two systems was 80.1%; 60 (17.9%) differed by two or more twofold dilutions. The best agreement was observed with imipenem (91.7%) and the poorest with cefoxitin (67%). With the E-Test (PDM Epsilometer for antimicrobial susceptibility testing [AB Bodisk, Solna, Sweden]), MICs for individual organisms are simple to achieve, although for certain antibiotics discrepancies with the reference method are unacceptable.

Anti-Bacterial Agents↗
PubMed1993

Wound isolate of Salmonella typhimurium that became chlorate resistant after exposure to Dakin's solution: concomitant loss of hydrogen sulfide production, gas production, and nitrate reduction.

A strain of Salmonella typhimurium isolated from a decubitus ulcer that was being treated topically with half-strength Dakin's solution became H2S negative, nitrate negative, and unable to produce gas from glucose. Experimental data suggested that these effects were associated with the development of chlorate resistance. Thirty-five other strains of Salmonella spp. that were made chlorate resistant also became negative for these three tests.

Chlorates↗
PubMed1992

Evaluation of MicroScan Rapid Pos Combo panels for identification of staphylococci.

MicroScan Rapid Pos Combo panels (Baxter Diagnostics, Inc., MicroScan, West Sacramento, Calif.) contain substrates conjugated with fluorophores and substrates with a fluorescent pH indicator. AutoSCAn W/A, an automated panel processor equipped with a fluorometer, reads the panels after 2 h of incubation and can identify staphylococci to the species level. We tested 239 strains belonging to 17 species of staphylococci. All the strains were identified by conventional methods (W.E. Kloos and K.H. Schleifer, J. Clin. Microbiol. 1:82-88, 1975) and by the MicroScan Rapid ID system. The system correctly identified 219 (91.6%) strains; nine (3.8%) identification results were probably correct, and six (2.5%) results were incorrect. The system designated five (2.1%) strains as rare biotypes. The automated MicroScan Rapid ID system is useful and reliable in identifying most human isolates of staphylococci encountered in the clinical laboratory.

Bacterial Typing Techniques↗
PubMed1991

Gas-liquid chromatographic analysis of cellular fatty acids for identification of gram-negative anaerobic bacilli.

A commercially available, computer-assisted microbial identification system (MIS) employs gas-liquid chromatographic analysis of cellular fatty acids for bacterial identification. MIS was compared with conventional identification systems. Of 225 gram-negative anaerobes tested, MIS identified 72.4% of the strains to the species level, 88.9% to the appropriate group, and 93.3% to the correct genus.

Bacteriological Techniques↗
PubMed1990

Accuracy and reproducibility of the MicroScan rapid anaerobe identification system with an automated reader.

Rapid anaerobe identification (MicroScan) panels (4 h) were evaluated both visually and by the AutoScan-4, a computer-controlled microplate reader. The results of both reading methods were compared with identifications obtained by the conventional (Virginia Polytechnic Institute) method. In total, 237 anaerobes were tested. Correct identifications were obtained for 166 strains (70%) by visual reading and 157 strains (66.2%) by the AutoScan-4. Supplementary tests resulted in 80.1 and 76.7% total correct identifications, respectively. Comparison of the two reading methods revealed complete agreement for 169 strains. Differences between the two reading methods were due to difficulties in reading specific reactions. This was especially true with the clostridial species. The performance of the MicroScan system in the identification of anaerobic bacteria appears comparable to that of other 4-h identification systems for anaerobes, but this system shows significant variance from the conventional system. Improvements in the trays and data base are required before the system can be recommended for routine use.

Autoanalysis↗
PubMed1989

Immunoregulation in Heymann nephritis. I. Cell marker studies.

Immunoregulation was examined in rats with Heymann nephritis (HN), an established model of membranous glomerulonephropathy (MGN). There is little known of the cellular immune events for the induction and maintenance of the autoimmune response in HN. The cell marker studies utilized fluorescein (FITC)-labelled monoclonal antibodies directed to B cells (Mark-I), and T cell subsets: pan T (ER-I), helper/inducer T (ER-2) and suppressor/cytotoxic T (ER-3). Lymphoid subsets were compared in spleen, lymph nodes, peripheral blood and bone marrow, of normal and diseased rats. Animals were investigated during the induction and chronic phases of disease. The induction of HN was associated with an early, significant, but transient increase of the non-specific myeloid component of the defence system. Subsequently, a significant increase was seen in the number of cells of the B lymphocyte lineage in HN animals, which coincided well with the overall increased humoral immune responsiveness. No alterations in the T lymphocyte subsets were noted during the development of this experimental autoimmune disease.

Animals↗
PubMed1989

Immunoregulation in Heymann nephritis. II. Functional studies.

In this study, the functional properties of the cells involved in the immunoregulation of Heymann nephritis (HN) have been investigated. HN is a disease model in the rat where the pathology closely resembles membranous glomerulonephropathy (MGN) in man. This autoimmune model is induced by injection of renal tubular antigen (RTA) incorporated in Freund's complete adjuvant (FCA). The strong B cell and plasma cell response in the chronic phase of HN, as determined by cell marker analyses, is predominantly antigen-non-specific. The secondary response pattern found was not only to RTA upon repeated immunization, but also to non-related antigen (SRBC). Although cell marker studies have indicated no major quantitative changes in the T cell population throughout the development of HN, a severe deregulation of the cellular immune response is observed especially during the induction period of HN. This was shown by a strong decrease of the mitogen-induced proliferative response and IL-2 production. This phenomenon is caused by both defective cellular components and inhibitory serological factors. Finally, in the chronic phase, these aberrations gradually return to normal.

Animals↗
PubMed1988

Pulmonary cavitation due to Neisseria mucosa in a child with chronic neutropenia.

A case of spontaneous pulmonary abscess with cavitation caused by Neisseria mucosa in a chronically neutropenic child is reported. Neisseria mucosa was isolated as the sole pathogen from a percutaneous needle aspirate. It appears that the clinical course of the pulmonary lesion was indolent. Interestingly, a gallium scan was diagnostic for pulmonary abscess even though the child was neutropenic.

Adolescent↗
PubMed1988

Microbiological investigation of an outbreak of bacteraemia due to Streptococcus faecalis in an intensive care unit.

An increased incidence of bacteraemia due to Streptococcus faecalis in a Critical Care and Trauma Centre (CCTC) during November 1985 prompted investigation. During the epidemic 21 blood cultures from five CCTC patients were positive for S. faecalis. A point prevalence culture survey revealed two more strains from wounds from two of these five patients. Fifteen strains from blood cultures and the two strains from wound sites were further characterized by conventional biotyping methods and susceptibility patterns, but they could not be differentiated from 40 unrelated control strains by these methods. The API-20S and the API-ZYM systems, however, were able to distinguish the outbreak isolates from the control strains. This investigation supports the hypothesis that S. faecalis is capable of causing cross-infection, and it may be necessary to characterize enterococci beyond routine tests to identify an outbreak due to this organism.

Adult↗
PubMed1987

Comparison of RapID-ANA and Minitek with a conventional method for biochemical identification of anaerobes.

Two micromethods for the identification of anaerobes, one requiring growth (Minitek) and one nongrowth dependent (RapID-ANA), were compared with a conventional identification culture system. For 222 clinical isolates, RapID-ANA agreed with PRAS in 187 (84%) and Minitek agreed for only 170 strains (76%). Both systems identified common isolates well, but encountered some difficulty in identifying less common clostridia and Gram-negative bacilli. Although adequate for most strains, the results from both systems should be interpreted with caution, particularly for less frequently isolated species.

Bacteria, Anaerobic↗