Biomedical subjects

C Thornsberry

Publications and source records attributed to C Thornsberry.

At least 145 records · Page 8Linked to original sources

PubMed1985

Proposed disk diffusion susceptibility criteria for ofloxacin.

Disk diffusion zone diameter breakpoint criteria for ofloxacin were tentatively established by correlating MICs with 1-, 3-, and 5-micrograms disk inhibitory zone diameters for 638 bacterial isolates representing 36 species. We recommend use of 5-micrograms disks with the following breakpoints: susceptible (MIC, less than or equal to 2.0 micrograms/ml), greater than or equal to 16 mm; intermediate (MIC, 4.0 micrograms/ml), 13 to 15 mm; and resistant (MIC, greater than or equal to 8.0 micrograms/ml), less than or equal to 12 mm.

Anti-Bacterial Agents↗

PubMed1985

Interpretive standards and quality control guidelines for cefpiramide disk susceptibility tests.

Disk susceptibility tests with 30- and 75-micrograms cefpiramide disks were evaluated with 614 bacterial isolates. Quality control parameters were also evaluated, and control limits for disk tests are recommended. Tests with 75-micrograms disks are recommended, with zone size standards of greater than or equal to 19 mm for susceptible (MIC, less than or equal to 32 micrograms/ml) and less than or equal to 15 mm for resistant (MIC, greater than or equal to 128 micrograms/ml).

Cephalosporins↗

PubMed1985

Evaluation of the BIOGRAM antimicrobial susceptibility test system.

BIOGRAM is an antimicrobial susceptibility test system for the determination of MICs from the standard disk diffusion test zone diameters. The system was challenged with 511 recent clinical isolates of members of the family Enterobacteriaceae, nonfermentative gram-negative bacteria, staphylococci, and enterococci. Results were compared with those obtained with the broth microdilution method. Appropriate control organisms were included with each test series. A total of 10,085 organism-drug combinations were evaluated. BIOGRAM demonstrated an overall correlation of 95.9% with the reference broth microdilution method.

Anti-Bacterial Agents↗

PubMed1985

Cefotiam susceptibility testing criteria.

Interpretive zone size breakpoints for diffusion tests with 30-micrograms cefotiam disks are diameters of greater than or equal to 18 mm for susceptible and less than or equal to 14 mm for resistant strains. The standard control strains Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 should both give zones 27 to 33 mm in diameter. Tests with 579 clinical isolates yielded an unacceptably high rate of very major discrepancies between disk tests and microdilution tests; such discrepancies were especially common among Enterobacter spp. Additional studies support the concept that standard microdilution tests and standard disk diffusion tests may fail to detect a potential for resistance among some microorganisms.

Cefotaxime↗

PubMed1985

Nosocomial Pseudomonas pickettii colonization associated with a contaminated respiratory therapy solution in a special care nursery.

Pseudomonas pickettii caused respiratory tract colonization in five infants in the special care nursery of a Chicago hospital. All organisms had the same antimicrobial susceptibilities. Endotracheal suctioning with saline from 5-ml unit-dose vials was identified by epidemiologic investigation as a risk factor for colonization. The vials of saline were contaminated with a strain of P. pickettii having the same antimicrobial susceptibility pattern as the isolates from patients. As part of an investigation of the manufacturing plant where the saline solution was produced, P. pickettii was recovered from deionized water used to make the product and from several sites in the processing line. Bypassing of a 180 degrees F (ca. 82 degrees C) water-holding tank appeared to be temporally related to product contamination. The ability of P. pickettii to survive and grow in this solution has been demonstrated in the laboratory. This outbreak demonstrates that, despite pertinent Food and Drug Administration regulations and company programs for identifying such contamination, intrinsically contaminated solutions can occasionally reach the bedside of the patient.

Cross Infection↗

PubMed1984

3-0-demethyl fortimicin A: in vitro activity and interpretive zone standards for disk diffusion susceptibility tests.

The in vitro activity of 3-0-demethyl fortimicin A was compared to that of amikacin and tobramycin against 5,230 clinical isolates in four institutions. Amikacin and tobramycin were more active than 3-0-demethyl fortimicin A against Pseudomonas aeruginosa and Acinetobacter spp., but all three drugs had similar activity against the Enterobacteriaceae and Staphylococcus aureus. Additional tests with 335 representative gram-negative bacilli compared five different aminoglycosides, demonstrating differences with some isolates. Standardized disk diffusion tests were also performed with 30 micrograms 3-0-demethyl fortimicin A disks, according to the National Committee for Clinical Laboratory Standards. The following interpretive breakpoints are proposed: less than or equal to 11 mm for resistant (MIC greater than or equal to 32 micrograms/ml) and greater than or equal to 15 mm for susceptible (MIC less than or equal to 16 micrograms/ml).

Acinetobacter↗

PubMed1984

Temocillin: in vitro activity against 734 selected clinical isolates, including beta-lactamase-producing strains.

The in vitro activity of temocillin against 734 clinical isolates was tested by broth microdilution. Good activity was demonstrated against Enterobacteriaceae and both beta-lactamase-positive and -negative strains of Haemophilus influenzae and Neisseria gonorrhoeae. There was little to no activity against gram-positive cocci and nonfermenting gram-negative bacilli. Bactericidal activity and effect of inoculum size on temocillin activity were comparable to that of ticarcillin. Temocillin was stable to commonly encountered beta-lactamases and significantly inhibited Richmond-Sykes type 1 enzymes of Enterobacter cloacae.

Bacteria↗

PubMed1984

A nursery outbreak of multiple-aminoglycoside-resistant Escherichia coli.

In the neonatal intensive care unit (NICU) of one hospital, 16 infants became colonized or infected with multiply-resistant Escherichia coli (MR-E.coli) over an 8-month period. Isolates were obtained from blood, urine, and sputum of three patients and from rectal surveillance cultures of 13 patients. The one patient with the blood isolate died. A matched case-control study identified continuous feeding (nine of 16 cases vs. one of 16 controls, p less than or equal to 0.001) and receipt of aminoglycosides (p less than or equal to 0.03) as risk factors. For case-babies not exposed to continuous feeding, duration of bolus feeding was significantly greater than for their controls (cases, 22 days; controls, 7 days; p less than or equal to 0.02). All 16 isolates were the same serotype and were resistant to amikacin, tobramycin, kanamycin, and gentamicin. The epidemiologic investigation suggested that MR-E. coli may have spread from person-to-person on the hands of personnel and that MR-E. coli persisted in the NICU for 8 months until effective control measures were instituted.

Aminoglycosides↗

PubMed1984

Nosocomial meningitis due to Citrobacter diversus in neonates: new aspects of the epidemiology.

Two term neonates born within four days of each other at a small hospital developed sepsis and meningitis caused by a unique strain of Citrobacter diversus not previously reported to cause meningitis. Eleven (27.5%) of 40 other infants admitted to the nursery during the epidemic period developed rectal or umbilical colonization by C. diversus. Contact soon after birth with either of two nurses was more common among infected or colonized infants than among infants who were not infected or colonized. Hand cultures of both nurses and a rectal culture of one of the nurses yielded the epidemic strain. C. diversus may have been introduced into the nursery by the rectal carrier and spread person to person. Six weeks later continued surveillance identified a second cluster (of four colonized infants) associated with a mother who was a carrier of C. diversus and whose newborn infant became colonized at birth. The outbreak ended after strict control measures were used.

Carrier State↗

PubMed1984

In vitro activity of ticarcillin plus clavulanic acid against 632 clinical isolates.

A total of 632 clinical bacterial isolates were tested for susceptibility to twofold dilutions of ticarcillin alone and in combination with 1, 2, and 4 micrograms of clavulanic acid (CA) (Timentin) per ml by a reference microdilution method. With the addition of CA, ticarcillin MICs were reduced eightfold or greater with 54 of 59 (92%) strains of the family Enterobacteriaceae with ticarcillin MICs of greater than or equal to 64 micrograms/ml. The inhibitory effect of CA on pseudomonads was minimal. Ticarcillin MICs for beta-lactamase-producing Haemophilus influenzae, Neisseria gonorrhoeae, and most Staphylococcus aureus were reduced to less than or equal to 0.5 micrograms/ml when CA was added. For dilution susceptibility testing of ticarcillin-clavulanic acid, dilutions of ticarcillin combined with 2 micrograms of CA per ml is suggested.

Bacteria↗

PubMed1984

Antibacterial activities of ciprofloxacin, norfloxacin, oxolinic acid, cinoxacin, and nalidixic acid.

In vitro studies were performed comparing ciprofloxacin (Bay o 9867) and norfloxacin with three related organic acids. Ciprofloxacin was two to eight times more active than norfloxacin against 658 bacterial isolates representing 30 species. For all species tested, ciprofloxacin MICs for 90% inhibition were less than or equal to 2.0 micrograms ml. Additional tests with 5,994 isolates detected only 37 (0.6%) strains resistant to 2.0 micrograms of ciprofloxacin per ml and 106 (1.8%) resistant to 1.0 micrograms/ml. Only 6 (0.1%) of the 5,994 strains were resistant to 16 micrograms of norfloxacin per ml, and 129 (2.1%) were resistant to 4.0 micrograms/ml. The majority of resistant strains were streptococci or Pseudomonas spp. Resistance among the Enterobacteriaceae was extremely rare (i.e., greater than 99.8% susceptible to both drugs.

Anti-Bacterial Agents↗

PubMed1984

In vitro evaluation of HR810, a new wide-spectrum aminothiazolyl alpha-methoxyimino cephalosporin.

HR810 (Hoechst-Roussel Pharmaceuticals Inc., Somerville, N.J.) is a new, cyclical-pyridinium cephalosporin that appeared superior to numerous comparison drugs against 658 strains of aerobic and facultative anaerobic bacteria. Seventeen Enterobacteriaceae spp. were tested by broth microdilution methods, and the 50% MICs (MIC50S) and 90% MICs (MIC90s) were 0.03 to 0.12 and 0.03 to 2.0 micrograms/ml, respectively. Only one strain had an MIC greater than 8.0 micrograms/ml (99.6% is considered susceptible). HR810 inhibited 98% of Pseudomonas aeruginosa isolates at less than or equal to 16 micrograms/ml, and the MIC90 for Acinetobacter spp. was 4.0 micrograms/ml. It was also very active against Pseudomonas spp. and Staphylococcus aureus (MIC90, 0.5 micrograms/ml) but marginally active against methicillin-resistant staphylococcal strains (MIC90, 16 micrograms/ml) and enterococcus (MIC90, 32 micrograms/ml). Non-enterococcal streptococci had MIC50s ranging from 0.008 micrograms/ml for Streptococcus pyogenes to 0.12 micrograms/ml for pneumococci. All MICs of HR810 against Haemophilus and Neisseria spp. were less than or equal to 0.03 micrograms/ml (MIC50, 0.002 to 0.008 micrograms/ml). HR810 poorly inhibited beta-lactamases and was very stable against 11 tested beta-lactamases of plasmid (TEM, OXA, SHV-1, and PSE) and chromosomal (K1, K14, P99) types.

Anti-Bacterial Agents↗

PubMed1984

Interpretive standards and quality control limits for susceptibility tests with ampicillin-sulbactam combination disks.

In vitro studies were performed to evaluate susceptibility tests with disks containing 10 micrograms of ampicillin plus 10 micrograms of sulbactam. Interpretive zone standards of less than or equal to 11 mm (resistant), 12 to 13 mm (intermediate), and greater than or equal to 14 mm (susceptible) are proposed. A nine-laboratory coordinated study was performed to establish tentative zone size limits for quality control of ampicillin-sulbactam disks. This included data with a new control strain selected to monitor performance of such combination disks.

Acinetobacter↗

PubMed1984

Modification of interpretive breakpoints for netilmicin disk susceptibility tests with Pseudomonas aeruginosa.

Regression analysis of data correlating 30-micrograms netilmicin disk zone diameters with microdilution MICs, obtained by testing close-interval dilution steps, was performed with 77 selected strains of Pseudomonas aeruginosa, each tested in three independent laboratories. A zone of greater than or equal to 15 mm correlated with an MIC of less than or equal to 12 micrograms/ml (susceptible), and a zone of less than or equal to 12 mm correlated with an MIC of greater than 16 micrograms/ml (resistant). Additional disk tests were performed with 256 strains having known resistance mechanisms and 280 susceptible strains: the majority were appropriately categorized by these interpretive zone standards. The previously recommended standards of greater than or equal to 17 mm (MIC, less than or equal to 8.0 micrograms/ml) for the susceptible category inappropriately placed a significant number of truly susceptible P. aeruginosa strains in the intermediate category.

Drug Resistance, Microbial↗

PubMed1984

Preparing inoculum for susceptibility testing of anaerobes.

We studied six methods for preparation of inoculum to use in susceptibility tests of anaerobic bacteria to determine viable counts of 15 different species of anaerobes. We counted viable bacteria for each method-organism combination. Methods studied included those used for the more routine tests (broth microdilution and broth-disk elution) and for the National Committee for Clinical Laboratory Standards standard reference agar method. Inocula prepared from broth suspensions of organisms from 24- and 48-h anaerobe blood agar plates and adjusted to the turbidity of a 0.5 McFarland standard gave the most consistent counts for all organisms and also the highest numbers. Counts from these suspensions were higher than those from overnight growth in thioglycolate or Schaedler broth when all were adjusted against the same turbidity standard. Preparing inoculum directly from agar plates may also speed up the sometimes lengthy process of susceptibility testing of anaerobes and thus make results more clinically useful.

Bacteria, Anaerobic↗

PubMed1984

New recommendations for disk diffusion antimicrobial susceptibility tests for methicillin-resistant (heteroresistant) staphylococci.

The agar disk diffusion susceptibility test was reevaluated for its ability to discriminate between susceptible and resistant Staphylococcus aureus (128 strains) and coagulase-negative staphylococci (19 strains) when tested with methicillin, oxacillin, and nafcillin. The results show that the current recommendations for disk potencies and interpretive zone diameters do not fit well with MIC correlates that we now recommend. Based on data from this study, we suggest that these parameters of the test be changed. For methicillin, we recommend a 10-micrograms disk with breakpoints of less than or equal to 11 mm (greater than or equal to 16 micrograms/ml) to indicate resistance and greater than or equal to 15 mm (less than or equal to 4 micrograms/ml) to indicate susceptibility. For oxacillin and nafcillin, we recommend 4-micrograms disks with breakpoints of less than or equal to 12 mm (greater than or equal to 8 micrograms/ml) to indicate resistance and greater than or equal to 16 mm (less than or equal to 2 micrograms/ml) to indicate susceptibility. MIC breakpoints were from a broth microdilution system which used a medium containing salt. If one of these three penicillins were to be selected for routine tests, we would recommend oxacillin, based on our data, but we recognize that this may depend upon the population of staphylococci within a particular hospital.

Cephalothin↗

PubMed1984

Disk diffusion susceptibility testing of ticarcillin plus clavulanic acid.

Disk diffusion susceptibility testing of ticarcillin plus the beta-lactamase inhibitor clavulanic acid was performed on 489 clinical isolates, and the results were compared with reference broth microdilution susceptibilities. Four different disks containing 75 micrograms of ticarcillin plus 2.5, 5, 10, and 15 micrograms of clavulanic acid were evaluated. Based on test performance and clavulanic acid stability, the 75-10-micrograms disk is recommended. Interpretive criteria for ticarcillin as published by the National Committee for Clinical Laboratory Standards appear to be satisfactory for the combination drug, but because the number of ticarcillin-clavulanic acid-resistant isolates was small, this proposal must be considered only tentative.

Bacteria↗

PubMed1984

Interpretive criteria and tentative quality control limits for apalcillin disk susceptibility tests.

In vitro studies with 661 bacterial isolates were performed to establish interpretive criteria. In addition, a nine-laboratory study was performed to establish quality control limits for tests with 100-micrograms apalcillin disks and to confirm testing criteria for tests with 100-micrograms piperacillin disks. The two drugs were very similar, and nearly identical criteria were recommended for interpretation and for control of the two types of disks. Neither disk is recommended for testing Staphylococcus spp. or Haemophilus spp.; with other microorganisms, zone size limits of less than or equal to 13 mm (resistant) and greater than or equal to 18 mm (susceptible) are proposed for tests with 100-micrograms apalcillin disks.

Ampicillin↗