Rotazyme assay in neonates without diarrhea. Results of screening survey and preliminary analysis of false positive specimens.

One hundred forty-seven stool specimens from 93 infants younger than four months of age in a Neonatal Intensive Care Unit were tested for rotavirus by the Rotazyme ELISA method (Abbott Laboratories, North Chicago, IL). None of the infants had diarrhea at the time of the testing. Ten of 147 (6.8%) specimens were either low or suspect positive. None had rotavirus by electron microscopy. Excluding the suspect positives, which were negative on retesting, the false positive rate was only 6 of 147 (4.1%). Of five specimens with sufficient material and repeatedly positive tests, heat to 56 degrees C for one-half hour eliminated the binding to the Rotazyme bead but had no effect on the rotavirus positive control. One patient was found to have an extremely high positive Rotazyme test, independently of the survey. No virus was found in this specimen by electron microscopy, and the material responsible for the false positive result was not removed by centrifugation (100,000 X g for one hour), heating to 56 degrees C for one-half hour, trypsin, ether/beta-mercaptoethanol, or dialysis. Thus, false positives were encountered, but the overall rate was acceptably low. Such false positives are likely to result from more than one cause and, depending on results of further study, may be confirmed as false positives by loss of reactivity at 56 degrees C for one-half hour and perhaps lack of binding to a control bead.

Synergy between penicillins and low concentrations of gentamicin in the killing of group B streptococci.

Antimicrobial sensitivity, synergy, and timed-killing assays were determined for 20 strains of group B streptococci isolated from cultures of blood and cerebrospinal fluid (CSF) of infected neonates. The mean minimal inhibitory concentrations by the tube-dilution method were as follows: penicillin, 0.02 microgram/ml; ampicillin, 0.05 microgram/ml; and gentamicin, 4.5 micrograms/ml. No synergy was detected with any combination of penicillin or ampicillin and gentamicin by the checkerboard titration method. Killing kinetics were determined for combinations of penicillin or ampicillin and gentamicin at low concentrations of these antibiotics comparable to those attained in the CSF following systemic administration of these antibiotics. Addition of 0.1 microgram and 0.5 microgram of gentamicin/ml to penicillin or ampicillin significantly accelerated the killing of group B streptococci. Despite the "poor" permeation of gentamicin into the CSF, the accelerated killing of streptococci at low concentrations of this antibiotic provides a rationale for the initial use of a combination of penicillin or ampicillin and gentamicin in the treatment of group B streptococcal meningitis.

New approach to management of unilateral tension pulmonary interstitial emphysema in premature infants.

Conservative management of unilateral tension pulmonary interstitial emphysema is reported. Treatment consisted of (1) positioning the infant on his or her side with the emphysematous lung dependent, (2) minimal chest physiotherapy and endotracheal suctioning, and (3) appropriate ventilator management. Conservative therapy is effective and appears to be safer than selective bronchial intubation or surgical therapy.