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Biomedical subjects

B A Forbes

Publications and source records attributed to B A Forbes.

28 records · Page 2Linked to original sources
PubMed1987

Recurrent Pseudomonas luteola (CDC group Ve-1) peritonitis in a patient undergoing continuous ambulatory peritoneal dialysis.

Recurrent Pseudomonas luteola (CDC group Ve-1) peritonitis occurred in a patient undergoing continuous ambulatory peritoneal dialysis. Catheter removal was required for cure despite therapy based on antibiotic susceptibilities. This is the third report in the English literature of severe P. luteola infection and the first report of peritonitis caused by this organism.

Adult↗
PubMed1986

Viral and bacterial organisms associated with acute pharyngitis in a school-aged population.

To investigate the causes and clinical characteristics of acute pharyngitis among school-aged children (4 to 18 years), we obtained throat cultures for respiratory viruses, Mycoplasma pneumoniae, group A streptococcus, and Chlamydia trachomatis from 320 patients with sore throat and 308 controls without respiratory complaints. The study was conducted from January to April 1985 in a private pediatric practice in central New York State. Sixty percent of the patients and 26% of the control subjects had positive cultures for at least one organism. Forty percent of patients had positive cultures for group A streptococcus, compared with 11.9% of the controls. Fifty (16%) patients had positive viral cultures, compared with eight (2.6%) controls; the predominant viral isolate was influenza A Philippines. Patients infected with influenza A were significantly more likely to complain of cough and hoarseness, and were less likely to have pharyngeal exudate or tender cervical adenopathy, than were patients who had positive cultures for group A streptococcus. Although 49 (15.8%) patients with acute pharyngitis had cultures positive for M. pneumoniae, 53 (17.6%) asymptomatic controls were also had M. pneumoniae-positive cultures. Thus detection of M. pneumoniae in the throat of school-aged children with pharyngitis may not be sufficient to establish a diagnosis of disease caused by this organism. C. trachomatis was not isolated from any patient or control.

Acute Disease↗
PubMed1986

Evaluation of a monoclonal antibody test to detect chlamydia in cervical and urethral specimens.

The MicroTrak Chlamydia trachomatis Direct Specimen Test (MT; Syva Co., Palo Alto, Calif.) was compared with cell culture in two patient populations. The sensitivity of the MT for a low-prevalence group was significantly lower (59.6%) than that for a high-prevalence group (84.4%). The results underscored the need to run the MT in parallel with culture initially if the prevalence of chlamydial infections is unknown and questioned the usefulness of the MT as a screening test for chlamydia in low-prevalence populations.

Antibodies, Bacterial↗
PubMed1985

Rapid method of MIC determinations utilizing tetrazolium reduction.

A rapid preliminary method of determining antibiotic susceptibilities of clinically isolated gram-negative fermentative organisms has been evaluated. The method utilizes tetrazolium dye reduction as a colorimetric indicator of bacterial growth. Tetrazolium dye reduction is incorporated into the standard Micro-Media MIC microdilution testing system and shortens the required incubation period from 15 to 18 hours to 4 hours. Parallel MIC determinations were made by the standard MIC method and by the rapid tetrazolium method. The test organisms included 218 gram-negative fermentative clinical isolates. The overall correlation between the standard and the rapid MIC methods was 93%. Of the 7% discordant results, 6.3% represented minor discrepancies and 0.7% represented major discrepancies. There were no very major discrepancies. The study concluded that the rapid tetrazolium MIC method is an accurate, low-cost, easily implemented method of preliminary antibiotic susceptibility testing for gram-negative fermentative organisms.

Anti-Bacterial Agents↗
PubMed1985

Conjugative R plasmids in antimicrobial resistance of Staphylococcus aureus causing nosocomial infections.

Increasing resistance to aminoglycoside antimicrobial agents in clinical isolates of Staphylococcus aureus was encountered in one hospital over a three-year period. Eleven of 16 isolates, selected to represent different time periods, transferred gentamicin resistance on filter membranes with transfer properties and restriction-enzyme analyses that were similar to pAM899-1, a self-transferable gentamicin plasmid previously isolated from Staphylococcus epidermidis within the same hospital. Self-transferable gentamicin R plasmids were demonstrated in isolates from six other nosocomial environments as early as 1974 and, though showing different restriction-enzyme digests, were highly related to pAM899-1 on the basis of Southern hybridization. These recently recognized, self-transferable plasmids seem to share a common evolutionary background and are important contributors to the increased resistance encountered in nosocomial staphylococci.

Conjugation, Genetic↗
PubMed1984

Subinhibitory concentrations of imipenem induce increased resistance to methicillin and imipenem in vitro in methicillin-resistant Staphylococcus aureus.

Methicillin-resistant (MR) Staphylococcus aureus that was susceptible to less than 0.75 micrograms of imipenem per ml demonstrated inducible resistance. MR S. aureus preincubated with 0.05 microgram of imipenem per ml grew in medium with an imipenem concentration of 32 micrograms/ml, and methicillin MICs increased 20-fold. Non-MR S. aureus exhibited no induction. Preincubation with methicillin produced no effect. Induction appeared to be a unique interaction of imipenem with MR S. aureus.

Enzyme Induction↗
PubMed1983

Transfer of resistance plasmids from Staphylococcus epidermidis to Staphylococcus aureus: evidence for conjugative exchange of resistance.

The ability of Staphylococcus epidermidis to transfer antimicrobial resistance to Staphylococcus aureus was tested by mixed culture on filter membranes. Two of six clinical isolates examined were able to transfer resistance to S. aureus strains 879R4RF, RN450RF, and UM1385RF. Subsequent S.aureus transconjugants resulting from matings with S. epidermidis donors were able to serve as donors to other S. aureus strains at similar frequencies. Cell-free and mitomycin C-induced filtrates of donors and transconjugants showed no plaque-forming ability. Addition of DNase I, citrate, EDTA, calcium chloride, and human sera to mating mixes and agar showed no effect on transfer. Nonviable donor cells were unable to transfer resistance and transfer did not occur at 4 degrees C. Cell-to-cell contact was required since transfer did not occur in broth or when filters of donor and recipient, respectively, were placed back-to-back so cells were not in direct contact. Analysis of DNA from S. epidermidis isolate UM899, its subsequent S. aureus transconjugants, and cured derivatives demonstrated that all resistance markers which transferred resided on plasmids. Mating experiments suggested a central role for the gentamicin plasmid pAM899-1 in the transfer process. It is concluded that our results are consistent with a conjugative transfer of resistance from S. epidermidis to S. aureus analogous to plasmid transfer demonstrated in streptococcal species for plasmids such as pAM beta 1. This represents a novel mechanism for gene exchange among staphylococci.

Conjugation, Genetic↗
PubMed1977

Guanine-plus-cytosine composition of five group B streptococcal serotypes.

The percent guanine-plus-cytosine content of deoxyribonucleic acid of each of the five serotypes of group B streptococci was determined by thermal denaturation. The range of guanine-plus-cytosine content was 35.1 to 36.9%, with a mean value of 35.9%. These values suggest a genetic homogeneity to the serotypes of the group B streptococci.

Cytosine↗
PubMedDate not supplied

Critical assessment of gene amplification approaches on the diagnosis of tuberculosis.

The resurgence of tuberculosis prompted the development of a number of new options for the rapid laboratory diagnosis of Mycobacterium tuberculosis (MTB). One of the most promising and exciting methodologies has been the introduction of assays employing amplification technology to detect MTB directly in clinical specimens. Although amplification assays hold significant promise to improve the laboratory diagnosis of tuberculosis, the decision to perform or not perform these assays is complicated. The performance of in-house polymerase chain reaction (PCR) assays and two commercially-prepared assays. GenProbe's AMTD test and Roche's AMPLICOR PCR assay are reviewed. Regardless of the amplification format, all assays have decreased sensitivity with specimens that are acidfast bacilli (AFB) stain-negative. Data from these studies and others indicate possible potential pitfalls of amplification assays, those being sampling errors, the presence of substances in clinical specimens that inhibit the amplification assay, and clinical utility. In light of these findings, the possible roles for these assays in the clinical microbiology laboratory are reviewed. In addition, factors such as cost, assay performance, etc. are discussed in order to facilitate the decision-making process concerning whether an amplification assay would be appropriate in a particular laboratory setting.

Humans↗