Adult patients who presented to an urban emergency room complaining of a sore throat had cultures and clinical information recorded. Models were constructed, using logistic regression analysis, of both a positive culture for Group A beta streptococcus and a positive guess by a resident. The model of a positive culture consisted of four variables--tonsillar exudates, swollen tender anterior cervical nodes, lack of a cough, and history of fever. Patients with all 4 variables had a 56% probability of a positive culture; 3 variables, 32%; 2 variables, 15%; 1 variable, 6.5%; and 0 variables, 2.5%. The model of a positive guess by a resident demonstrated an over-reliance on physical exam and an underuse of history. The model of a positive culture allows stratification of patients to assist clinicians in the management strategies.

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To determine risk factors for infection of hyperalimentation catheters, we prospectively studied 169 catheter systems (88 patients) by using a semiquantitative culture technique. Infection occurred in 24 (14%) catheters (16 patients), was inversely proportional to the number of previous catheters inserted by the operator (P less than .02), and was proportional to the interval between admission and catheter insertion (P less than .0005). Catheter replacement over a guidewire was no more likely to be associated with infection than was a de novo percutaneous insertion at another site (P = .6). Using a proportional hazards model, we estimated the risk of infection per day to be 1.3 times greater for a catheter if the patient had been hospitalized 50 days instead of seven days, and 3.8 times greater if the patient had a Swan-Ganz catheter at the time of insertion.

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An in-use study was done to determine the effect of transportation delay on the microflora of clinical specimens collected for microbiological analysis in a 1,000-bed university hospital. Portions of wound, respiratory, and urine specimens were planted for bacterial isolation on the wards immediately after collection. The remainder of each specimen was kept at room temperature without or without holding medium until it was picked up by messengers and taken to the bacteriology laboratory. The results of immediate planting on the ward were compared with those obtained by planting in the laboratory. Alterations in microflora were observed in all three types of specimens after averages of 2 to 4 hours of delay in planting.

Few studies evaluating susceptibility testing of methicillin-resistant staphylococci have included isolates of Siaphylococcus epidermnidis, a known pathogen in many types of serious infections. We tested 175 S. epidermidis and 95 Staphylococcus aureus isolates to determine the most sensitive procedures for detecting methicillinresistant staphylococci. Reference procedures included agar dilution with methicillin and 4% NaCl in the agar and broth microdilution with methicillin and 2% NaCI in cation-supplemented Mueller-Hinton broth. After 24 h of incubation, the results from both methods correlated well and were within 1 log2 dilution for all isolates tested. Only one-half of all resistant isolates (92 of 183) were detected at 18 h by using the standard disk diffusion technique with 5-,ig methicillin disks, and even fewer were detected with 10-,lg methicillin disks and newly recommended zone-size criteria. However, the standard disk diffusion method with 4% NaCl in the agar increased the sensitivity and specificity for identification of the proper phenotype to greater than 92%. The spread plate aild new spot techniques, both using agar with 4% NaCl, were also sensitive methods. Of 47 S. epidermidis isolates tested against oxacillin, 6 (13%) were oxacillin susceptible but methicillin resistant. Two automated systems, the Automicrobic system (Vitek Systems) and MicroScan (American MicroScan), as well as two broth screening systems available from Remel and Austin Biological Laboratories, failed to detect several resistant isolates, depending on the species.