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Biomedical subjects

R M Brockett

Publications and source records attributed to R M Brockett.

9 recordsLinked to original sources
PubMed1999

Pseudo-outbreak of methicillin-resistant Staphylococcus aureus.

OBJECTIVE: To determine whether a high rate of methicillin-resistant Staphylococcus aureus at our institution was due to laboratory misclassification and to evaluate the effect of this misclassification. MATERIAL AND METHODS: We evaluated all S. aureus isolates identified at our institution during a 60-day period in 1997. Automated susceptibility test results (using the Vitek system) from our clinical microbiology laboratory and an independent laboratory were compared with oxacillin agar screen plate results at both laboratories. Isolates with discordant results for susceptibility to oxacillin were tested by broth microdilution minimal inhibitory concentrations and for the presence of the mecA gene. RESULTS: Eighteen (72%) of the 25 organisms (obtained from 17 patients) found to be resistant to oxacillin by the Vitek system at our institution were susceptible by the oxacillin agar screen. Discordant isolates tested by broth microdilution minimal inhibitory concentrations and for the mecA gene were found to be oxacillin susceptible and mecA gene negative. Thus, at our hospital, almost three fourths of the organisms initially identified as methicillin-resistant S. aureus by the Vitek system were actually susceptible to oxacillin. This misclassification resulted in needless infection control measures and unnecessary vancomycin use. CONCLUSION: Hospitals that use only automated susceptibility testing for S. aureus should periodically validate their results with additional testing.

Cross Infection↗
PubMed1996

Volume of blood required to detect common neonatal pathogens.

OBJECTIVE: To determine the minimum volume of blood and the absolute number of organisms required for detection of bacteremia and fungemia by an automated colorimetric blood culture system (BacT/Alert, Organon Teknika). DESIGN: Common neonatal pathogens, Escherichia coli, Streptococcus agalactiae (group B streptococcus (GBS): one American Type Culture Collection (ATCC) strain and one clinical isolate), Staphylococcus epidermidis, and Candida albicans, were seeded into blood to produce bacteremia or fungemia with low colony counts (1 to 3 colony-forming units (CFU) per milliliter) and ultra-low colony counts (<1 CFU/ml). For each organism, 96 culture bottles were inoculated with either 0.25, 0.5, 1.0, or 4.0 ml of the two seeded blood concentrations. Blood culture bottles were incubated in the BacT/Alert device for 5 days, and time to positivity was noted when applicable. All bottles were subcultured on plated media. DATA ANALYSIS: The Poisson statistic was used to calculate the probability of finding at least one viable CFU per inoculated culture bottle. The fraction of culture bottles with positive findings per group was divided by the probability of one or more organisms present to give the positivity index. RESULTS: Plated subculture identified no growth of organisms not detected by the colorimetric detection system. The false-positive rate for the automated device was less than 1%. The positivity index for the GBS clinical isolate was 1.13, for the GBS ATCC isolate 0.96, for S. epidermidis 0.94, for C. albicans 0.97, and for E. coli 0.95. There was a statistically significant difference with time to positivity and inocula volume (p <0.01), but the difference was not clinically important. CONCLUSIONS: If one or two viable colony-forming units are in the blood inoculated into culture media, the BacT/Alert system will detect growth rapidly. Because there appears to be a sizable subset of neonates who are at risk of sepsis with a colony count less than 4 CFU/ml, then a 0.5 ml inoculum of blood into the culture media is inadequate for sensitive and timely detection of bacteremia. One to two milliliters of blood should increase microorganism recovery in the face of low-colony-count sepsis.

Bacteremia↗
PubMed1979

Colonization and infection of newborn infants caused by bacteriophage-group II Staphylococcus aureus strains.

A staphylococcal strain which exhibited weak lytic reaction with group II phages was isolated from a newborn infant with a skin infection. Subsequent investigations established that this weakly reacting strain was responsible for an endemic level of infection and colonization within the hospital nursery. The use of consistently appearing weak lytic reactions in the evaluation of this episode is described.

Bacteriophage Typing↗
PubMed1978

Prevalence of fungi during Skylab missions.

Samples for mycological analysis were collected from surfaces in the Skylab spacecraft before launch and during flight for each manned mission. Fungal contamination levels were low during the first two flights; however, the species recovered were different for each mission. On the third mission, widespread contamination of the Skylab spacecraft with Aspergillus and Pencillium spp. was detected. This contamination was traced to several contaminated space suit undergarments.

Aspergillus↗
PubMed1978

Epidemiologic features and phage types associated with nosocomial infections caused by Staphylococcus epidermidis.

An apparent problem with increased numbers of nosocomial infections caused by Staphylococcus epidermidis at a large hospital was studied in a clinical-epidemiological investigation. Thirty-six cases of S. epidermidis infection were confirmed on the thoracic surgery, general surgery, nursery and pediatric services during a 3-year period. Nine cases were fatal and six of these occurred in patients following cardiovascular surgery with implanted prothesis. The majority of cases (25/36) occurred following cardiovascular surgery. The median onset of infection was six days from the date of surgery, suggesting infection during the intraoperative period. Although the number of cases studied remains small, two phage types, 71/108/275a/459 and 407-2, did predominate among these clinical infections. Interestingly, during this same time interval these same types predominated among surgical staff members closely associated with these patients. Resistance to antimicrobials was high among isolates tested, with more than 50% of the strains resistant to six or more antimicrobial agents.

Adolescent↗
PubMed1978

Epidemiologic Surveillance for Staphylococcus epidermidis infections related to cardiopulmonary bypass.

Epidemiologic investigation of 20 Staphylococcus infections among valvular and aortocoronary bypass graft patients indicated a broad spectrum of clinical illness in these two groups. The highest infection rate (9.3%) and case specific mortality rate (54.5%) were noted among those patients undergoing cardiovalvular replacement surgery with protheses. The median onset of infection was 6 days suggesting infection during the intraoperative period. Using the epidemiologic data from this investigation, a transmission pattern was formulated and a series of control measures designed to interdict the routes of transmission were instituted wigh marked success. These measures significantly reduced the incidence of S. epidermidis infections among these high risk patients.

Bacteriophage Typing↗
PubMed1976

Epizootic staphylococcal infections in subhuman primates after surgical operation.

In late October, 1974, Staphylococcus aureus postoperative wound infection was recorded in a nonhuman primate (Macaca mulatta) which had recently undergone surgical operation. Infection in a second monkey appeared approximately 2 weeks later, and a clustering of 6 cases appeared over the next 3-week period. The clinical spectrum included septicemia in 2 monkeys and skin infection at the surgical incision site of several others. Investigation revealed a uniform and consistent association of a phage group II S aureus strain characterized as 3A/55/71. This strain was also found to be enzootic among other postoperative monkeys sharing or having shared a common postsurgical care unit with infected monkeys. Epizootiologic studies indicated that this unusually virulent S aureus strain probably was introduced by an infected monkey which underwent surgery earlier in the month and that additional monkeys became infected by animal-to-animal transmission. After appropriate control sanitary measures were instituted, no new infections occurred.

Animals↗
PubMed1975

Microbiological sampling of the spacecraft atmosphere during a simulated skylab mission.

A skylab Air Sampler (SAS) has been developed for the use during Skylab missions. The SAS was used in the Skylab Medical Experiments Altitude Test (SMEAT) to gather baseline data which could be directly compared to data obtained during actual Skylab missions. The results obtained in the SMEAT gave no evidence of consistent change in either concentration or types of microorganisms in the SMEAT atmosphere over the 56-d test. Microorganisms found included some potential pathogens but were largely normal human microflora. Few typical soil microorganisms were found. These findings are related to commonly anticipated effects of long-term spaceflights on environmental microflora and to other closed environment studies.

Aerospace Medicine↗