Isolation of L-form variants after antibiotic treatment in Staphylococcus aureus bovine mastitis.

An unstable L-form of Staphylococcus aureus was identified in milk samples from 3 quarters of 2 cows after treatment with cloxacillin. Milk samples incubated on standard 5% blood agar plates were culture-negative for 7 to 30 days after treatment, but S aureus was reisolated in 80% of 66 samples by additional culturing on enriched L-form media when incubated in 10% CO2 at 37 C. The organism was identified at various phases of reversion of L-form agar and was confirmed on transfer to blood agar plates.

Pathologic changes in the lungs of oxygen-adapted rats: a morphometric analysis.

Animals exposed to 85 per cent O2 for 5 or more days acquire the ability to survive for prolonged periods in 100 per cent O2. The basis of this acquired "tolerance" is poorly understood, but it has been proposed to be related to biochemical changes occurring in the lung cells. In order to quantify the structural changes that occur in the lungs of oxygen-adapted rats, rats were exposed to 85 per cent O2 for 7 days and then studied using morphometric techniques.