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Pulsed-field gel electrophoresis (PFGE) is widely used for epidemic investigations of methicillin-resistant Staphylococcus aureus (MRSA). In the present study, we evaluated its use in a long-term epidemiological setting (years to few decades, country to continent level). The clustering obtained from PFGE patterns after SmaI digestion of the DNA of 20 strains was compared to that obtained using a phylogenetic typing method (multiprimer RAPD). The results showed that the analysis of small PFGE bands (10-85kb) correlates better with multiprimer RAPD than the analysis of large PFGE bands (>85-700kb), suggesting that the analysis of small bands would be more suitable for the investigation of long-term epidemiological setting. However, given the technical difficulties to obtain a good resolution of these bands and the putative presence of plasmids among them, PFGE does not appear to be a method of choice for the long-term epidemiology analysis of MRSA.

Staphylococcus epidermidis and S. aureus are the most common causes of bacterial endophthalmitis. A study of the penetration of selected antistaphylococcal antibiotics into human vitreous was undertaken in 58 patients. After 2-g intravenous doses of cephalothin, cefazolin, methicillin, oxacillin, or nafcillin were given to patients about to undergo vitreous surgery, mean vitreous levels for each antibiotic were as follows: cephalothin, 0.97 microgram/ml in diabetics and 0.69 microgram/ml in nondiabetics; cefazolin, 0.84 microgram/ml in diabetics and 1.6 microgram/ml in nondiabetics; methicillin, 2.56 micrograms/ml in diabetics and 2.64 micrograms/ml in nondiabetics; oxacillin, 0.62 microgram/ml in diabetics and 0.34 microgram/ml in nondiabetics; and nafcillin, 0.73 microgram/ml in diabetics and 0.75 microgram/ml in nondiabetics. Only cefazolin produced vitreous concentrations consistently above its minimum inhibitory concentration for 90% of S. epidermidis isolates. Staphylococcus aureus isolates were not similarly covered. There was a trend toward higher vitreous antibiotic concentrations in patients with proliferative vitreoretinopathy and rubeosis.