Biomedical subjects

S Mirrett

Publications and source records attributed to S Mirrett.

67 records · Page 4Linked to original sources

PubMed1982

Comparative evaluation of supplemented peptone broth with sodium polyanetholesulfonate and trypticase soy broth with sodium amylosulfate for detection of septicemia.

We compared the yield and speed of detection of clinically important microorganisms from 10,156 paired 5-ml samples of blood cultured in supplemented peptone broth (SPB) with 0.03% sodium polyanetholesulfonate (SPS) or Trypticase soy broth (TSB) with 0.5% sodium amylosulfate (SAS). The atmosphere of incubation (open venting units) and ratio of blood to broth (1:10) were the same for both samples. Only cultures with adequate blood samples (greater than or equal to 80% of stated volume) were compared statistically. Overall, SPB/SPS outperformed TSB/SAS. Bacteroidaceae and Eubacterium were found more often (P less than 0.05) and viridans streptococci were found sooner (P less than 10(-4)) in SPB/SPS than in TSB/SAS. Most importantly, staphylococci were found both more often (P less than 0.03) and sooner (P less than 10(-7)) in SPB/SPS than in TSB/SAS. In a separate experiment, SAS slowed the growth of a clinical strain of Staphylococcus aureus in TSB. Unless important advantages can be confirmed for SAS in controlled clinical trials, SAS cannot be recommended for routine use as an anticoagulant in blood culture media.

Amylopectin↗

PubMed1982

Controlled evaluation of the effect of atmosphere of incubation on detection of bacteremia and fungemia in supplemented peptone broth.

To evaluate the role of atmosphere of incubation in the detection of clinically important bacteremia and fungemia in adults, we compared the yield of microorganisms from 10,541 paired 5-ml samples of blood incubated aerobically and anaerobically. The medium, supplemented peptone broth (SPB) with 0.03% sodium polyanetholesulfonate, and the ratio of blood to broth (1:10) were the same for all cultures. Only cultures with adequate blood samples (greater than or equal to 80% of stated volume) were compared statistically. More fungi (P less than 10(-7) ) grew in continuously vented bottles of SPB. Aerobic incubation also favored (P less than 0.01) isolation of Neisseria gonorrhoeae and Eubacterium; more than 80% of these bacterial organisms were detected only in vented bottles. Anaerobic incubation (plugged venting units) did not significantly favor the isolation of any genus of microorganisms, although an estimated 11% more Bacteroidaceae grew in the unvented bottle of SPB. By comparison of our data with published results for other media, we conclude that the need for both aerobic and anaerobic incubation of blood cultures is dependent upon the medium used and the microorganisms likely to be encountered. Vented incubation of blood cultured in SPB is crucial for detection of fungi and some bacteria. Routine use of an unvented bottle of SPB may not be worthwhile for patients in whom Bacteroidaceae cause bacteremia infrequently. However, when Bacteroidaceae are suspected as the cause of sepsis, use of an unvented bottle of SPB is prudent.

Bacteria↗

PubMed1982

Controlled evaluation of hypertonic sucrose medium for detection of bacteremia and fungemia in supplemented peptone broth.

Because the value of hypertonic media in detection of bacteremia and fungemia is controversial, we evaluated supplemented peptone broth (SPB) with 0.03% sodium polyanetholsulfonate with and without 10% sucrose in 5,439 paired blood cultures from adult patients. The aerobic atmosphere, 1:10 ratio of blood to broth, and methods for processing blood cultures were identical. Only cultures with adequate blood samples (greater than or equal to 4 ml) were compared statistically. More clinically important bacteria were recovered from SPB with sucrose (P less than or equal to 0.001), including Staphylococcus epidermidis, Enterobacteriaceae, and Bacteroidaceae. However, only one of nine isolates of Neisseria gonorrhoeae grew in SPB with sucrose. Staphylococci (P less than 0.001), Enterobacteriaceae (P less than 0.01), Pseudomonas aeruginosa (P less than 0.01), and yeasts (P less than 0.05) were detected 1 or more days earlier in SPB with sucrose. The effect of sucrose on blood cultures appears to be medium dependent, based on comparisons of our results with those of published reports.

Bacteria↗

PubMed1981

Neisseria gonorrhoeae strains inhibited by vancomycin in selective media and correlation with auxotype.

Strains of Neisseria gonorrhoeae that failed to grow on Thayer-Martin (T-M) and Martin-Lewis (M-L) media accounted for 2.0% of isolates at the University of Colorado Hospital and its Venereal Disease Clinic. A total of 31 inhibited and 31 control strains were compared by agar dilution testing for their susceptibilities to 13 antimicrobial agents used for treatment or in selective media. All 62 isolates were resistant to lincomycin, colistin, nystatin, amphotericin B, trimethoprim lactate, polymyxin B, and anisomycin. Vancomycin was the inhibitory antibiotic for N. gonorrhoeae in both T-M and M-L media. The vancomycin-inhibited strains were also significantly more sensitive to penicillin and ampicillin than were the control strains (P less than 0.001). The presence of the other antibiotics in selective media did not affect the minimum inhibitory concentrations of vancomycin for gonococci. All 31 inhibited strains were sensitive to 8.0 micrograms of vancomycin per ml, and 26 of these were sensitive to 2.0 microgram/ml. Decreasing the size of inoculum of gonococci results in greater inhibition by any given concentration of vancomycin. The vancomycin-sensitive strains contained significantly more arginine- hypoxanthine-, and uracil-requiring auxotypes (28 out of 31) than did the control strains (9 out of 31). As with T-M medium, some strains of gonococci will be missed when M-L medium with 4.0 micrograms of vancomycin per ml is the only medium used for the diagnosis of gonorrhea. This may be of particular importance in the confirmation of disseminated infection with Arg- Hyx- Ura- auxotypes of N. gonorrhoeae when cultures of blood, joint fluid, or skin lesions are negative.

Anti-Bacterial Agents↗

PubMed1981

Comparison of acridine orange and Gram stains for detection of microorganisms in cerebrospinal fluid and other clinical specimens.

Acridine orange, a fluorochrome strain, is potentially superior to the Gram stain in the direct microscopic examination of clinical specimens because it gives striking differential staining between bacteria and background cells and debris. Its value in clinical laboratories was evaluated by testing 209 cerebrospinal fluids and 288 other body fluids, tissues, and exudates by both techniques. Smears were made in duplicate, fixed with methanol, stained, and examined without knowledge of the result of the companion smear or culture. Overall, acridine orange was slightly more sensitive than the Gram stain (acridine orange, 59.9%; Gram stain, 55.8%) and equally specific in detecting microorganisms. One smear was falsely positive by the Gram stain; none was falsely positive by the acridine orange stain. We conclude that acridine orange staining is a sensitive method for screening clinical specimens and reviewing selected specimens that are purulent, but negative by the Gram stain. Bloody fluids, thick exudates, and other normally difficult-to-read specimens were easily and quickly examined. We recommend, however, that positive smears be reexamined with the Gram stain to confirm the result and determine the Gram reaction of the microorganisms.

Acridine Orange↗

PubMed1980

Comparison of in vitro activity of moxalactam (LY127935) with cefazolin, amikacin, tobramycin, carbenicillin, piperacillin, and ticarcillin against 420 blood culture isolates.

To compare the in vitro activity of moxalactam (LY127935), a new broad-spectrum antimicrobial agent, with cefazolin, amikacin, tobramycin, carbenicillin, piperacillin, and ticarcillin, each drug was tested against 420 bacterial isolates from the blood of septic patients. Standard broth dilution methods were used to determine minimum inhibitory and bactericidal concentrations. LY127935 was as active as the aminoglycosides against aerobic gram-negative organisms, including Pseudomonas aeruginosa, and was at least 10-fold more active than the other beta-lactam agents against these bacteria. LY127935 was the most active agent tested against Bacteroides fragilis; its activity against all other anaerobic bacteria and Staphylococcus aureus was similar to those of the other agents tested. All streptococci, however, grew at higher concentrations of LY127935 than any other drug, and Streptococcus faecalis and Listeria monocytogenes were not inhibited at the highest concentration tested (minimum inhibitory concentration, > 64 microgram/ml). Although a greater proportion of blood culture isolates were susceptible to LY127935 than to any other drug tested, LY127935 does not have a sufficiently broad spectrum of in vitro activity to be recommended safely alone for empirical treatment of sepsis of unknown etiology.

Amikacin↗

PubMed1980

Activity of cefamandole, cefoxitin, ampicillin and gentamicin against 419 bacteria isolated from blood of patients with sepsis.

To compare the in vitro activity of cefamandole with ampicillin, cefoxitin, and gentamicin, each antimicrobial was tested against 419 bacteria isolated from the blood of patients with proved sepsis. Cefamandole was active against all gram-positive cocci except the enterococci. Most Enterobacteriaceae were inhibited by both cefamandole and cefoxitin. Cefamandole showed an activity similar to ampicillin against Haemophilus influenzae. The percent of blood culture isolated considered susceptible to the drugs tested were as follows: cefamandole 79%, cefoxitin 78%, ampicillin 55% and gentamicin 81%. None of the drugs tested would be adequate alone for treatment of sepsis of unknown etiology based on in vitro susceptibility data.

Ampicillin↗

PubMed1979

False-positive Gram-stained smears.

The rate per 1,000 smears showing nonviable Gram-negative bacilli (false-positive smears) increased from a baseline of 10.8 to 38.5 following purchase of new culture-collection devices; the rate decreased to 8.0 following replacement of contaminated culture sets. False-positive reports led to changes in therapy for five patients. In addition to being sterile, commercial culture-collection devices should be certified by the manufacturer as being free of stainable microorganisms or as unsuitable for preparation of Gram-stained smears.

Adolescent↗

PubMed1979

Evaluation of preservative fluid for urine collected for culture.

Immediate culture or refrigeration of urine is recommended, but not always practical. Therefore, we evaluated the Becton-Dickinson Urine Culture Kit containing a boric acid-glycerol-sodium formate preservative in a study of 1,000 clinical urine specimens. Each specimen was cultured a total of four times by the surface streak technique with a 0.001-ml calibrated loop. After an initial reference culture (culture 1), a portion of urine was poured into a clean nonsterile paper cup, aspirated into a urine transport tube, and recultured immediately (culture 2). The original specimen cup was refrigerated for 18 to 24 h (culture 3), and the urine transport tube was held at room temperature for 18 to 24 h (culture 4) before repeat cultures. Eighty-eight of the initial reference cultures were positive (pure growth of greater than 10(5) bacteria per ml). Eighty-two (93.2%) of the 88 specimens positive on the reference culture were also positive after refrigeration or holding at room temperature in the transport tube for 24 h. There was one false-positive culture from refrigerated urine but none from the transport tube. Mixing of urine in a nonsterile container did not introduce detectable contamination. We conclude that the Becton-Dickinson Urine Culture Kit maintains a stable bacterial population in urine for up to 24 h as reliably as refrigeration. Urine for culture may be collected in a nonsterile container if it is immediately aspirated into the transport tube so that contaminants are not allowed to multiply.

Bacteria↗

PubMed1979

Comparison of direct and standard antimicrobial disk susceptibility testing for bacteria isolated from blood.

To determine the reliability of early antimicrobial susceptibility testing, we compared the results of direct and standard single-disk diffusion methods for 581 positive blood cultures processed routinely by the clinical microbiology laboratory. The direct procedure differed from the standard one only in that the 0.5 McFarland inoculum was prepared from 1 ml of turbid broth rather than five isolated colonies from a subculture plate. A major discrepancy in results was defined as a change from susceptible to resistant or vice versa according to interpretive standards for zone diameters, whereas a minor discrepancy was defined as a shift to or from the intermediate category when paired direct and standard tests were compared. The overall agreement between the two methods was 94.6% of 2,308 comparisons. There were 119 minor (5.2%) and 6 major (0.3%) discrepancies. The major discrepancies were seen with three strains of Staphylococcus epidermidis and one strain each of S. aureus, Escherichia coli, and Enterobacter sp. Direct susceptibility testing of positive blood cultures that were pure by gram-stained smear provided reliable results 24 to 36 h earlier than conventional procedures; therefore, we recommended this procedure to guide early antimicrobial therapy in patients with bacterial sepsis.

Anti-Bacterial Agents↗

PubMed1975

Motility-indole-lysine medium for presumptive identification of enteric pathogens of Enterobacteriaceae.

Detection of lysine decarboxylase activity is a useful supplement to reactions on triple sugar-iron (TSI) and urea agars in the initial examination of suspected pathogenic isolates from fecal cultures. Owing to the added value of motility and indole production in the differentiation of enteric pathogens, we prepared and evaluated a motility-indole-lysine (MIL) medium. The following 890 organisms were tested: 264 Shigella, 2 Edwardsiella, 182 Salmonella enteritidis, 235 S. typhi, 3 Arizona, 32 Yersinia enterocolitica, and 172 other members of the family Enterobacteriaceae. With few exceptions the MIL medium gave the same results as the standard motility, indole, and lysine decarboxylase (Moeller) test media. All discrepancies were with the indole reaction, which was weak in 2 of 67 strains of Escherichia coli and falsely negative in 6 of 32 strains of Y. enterocolitica. When both TSI agar and lysine-iron agar (LIA) slants are used in the evaluation isolates from fecal cultures, detection of H2S is duplicated. Both LIA and MIL medium detect lysine decarboxylase and deaminase activity equally well. Because of its ability to detect motility and indole production, the MIL medium is more useful than LIA when used with TSI agar. The combination of TSI agar, MIL medium, and urea agar enables reliable initial recognition of enteric pathogens of the Enterobacteriaceae.

Carboxy-Lyases↗

PubMed1975

Motility-indole-lysine-sulfide medium.

A medium designed for the detection of motility, indole, lysine decarboxylase and deaminase reactions, and H2S production was devised and evaluated. Results, using 157 strains of enteric pathogens, were in agreement with reference methods. When 300 isolates from fecal cultures were screened using this medium, Shigella was easily differentiated from Escherichia and more of the Proteus species, especially P. morganii, could be eliminated from further study.

Agar↗

PubMedDate not supplied

Acridine orange stain.

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Acridine Orange↗