agar and Phenylketonurias

The escalating number of blood specimens from late-fed premature or very sick newborns greatly increases the risk of missing the diagnosis of phenylketonuria (PKU). Babies receiving antibiotics have uninterpretable "clear-zone" results with the traditional Guthrie bacteriologic inhibition assay (BIA). For the past year the authors have reexamined the blood phenylalanine level on specimens giving the "clear-zone" effect by BIA by use of the McCaman-Robins chemical-fluorescent assay (CFA). Spuriously high blood phenylalanine levels occurred in four babies who were receiving ampicillin and whose specimens were collected on filter paper and autoclaved in preparation for the BIA. None of the babies proved to have PKU. The fluorescent interference caused by ampicillin resulted from the heat of autoclaving the specimen. The authors recommend that the blood specimen should not be autoclaved before analysis by either BIA or CFA.

Topics: Agar; Ampicillin; Bacillus subtilis; Diffusion; False Positive Reactions; Female; Fluorescence; Hot Temperature; Humans; Infant, Newborn; Infant, Premature; Male; Paper; Phenylalanine; Phenylketonurias

Faecal samples were taken from three diet-managed phenylketonuric children to determine effects of beta-2-thienylalanine (beta-2-t) on indigenous bacteria. From sample swabs, 127 anaerobes were identified and tested for beta-2-t inhibition on a phenylalanine (Phe)-free medium, Anaerobe Inhibition Test (AIT) agar. Of the isolates, 77.9% grew sufficiently to assay reactions on at least 25% of AIT plates. Using Phe-containing Columbia agar, 86.5% of the strains could be assayed. None of 28 Bacteroides cultures was inhibited by beta-2-t on AIT. Of the genera, Bifidobacterium, Eubacterium, Lactobacillus, Peptostreptococcus, and Propionibacterium, no isolates which would grow on AIT were inhibited. At least one isolate of each of the genera Peptococcus, Fusobacterium, and Clostridium was inhibited. Of 127 total isolates, only nine were inhibited by beta-2-t on AIT, and inhibition was abolished on Columbia agar. Thirty-nine "aerobes" were isolated from the same patients. Strains of the genera tested reacted similarly to previously tested strains from non-PKU sources. Also, anaerobically isolated Excherichia coli were inhibited, while Streptococcus faecalis cultures were not, confirming results on aerobically-isolated non-PKU cultures of the same species. These studies, the first dealing with beta-2-t and anaerobic bacteria, suggest that little change in intestinal bacterial populations might be expected during in vivo beta-2-t treatment.

Topics: Agar; Alanine; Anaerobiosis; Bacteria; Child; Culture Media; Feces; Humans; Infant; Male; Phenylketonurias; Species Specificity

Investigations were undertaken to discover the effect and importance of technical factors in the Guthrie test and to determine the most satisfactory materials available. These findings were used in setting up the screening service for phenylketonuria for the South West Metropolitan Region.

Topics: Agar; Bacillus subtilis; Biological Assay; Blood Specimen Collection; England; Humans; Infant; London; Mass Screening; Medical Records; Methods; Paper; Phenylalanine; Phenylketonurias

Topics: Agar; Bacteriological Techniques; Biological Assay; Blood Specimen Collection; False Positive Reactions; Filtration; Humans; Indicators and Reagents; Infant, Newborn; Methods; Paper; Phenylalanine; Phenylketonurias; Specimen Handling