[Is methicillin better than cloxacillin in serious infections caused by strong penicillinase-producing staphylococci (phage-type 94/96)?].

An intravenous drug addict was treated with cloxacillin for septicaemia with Staphylococcus aureus because of pneumonia and suspected endocarditis. After 51 days of treatment Staphylococcus aureus was still found in blood and expectorate despite continued treatment with intravenous cloxacillin 1 g three and later four times daily and oral rifampicin. The staphylococcal isolates were all of phage type 94/96. Investigations have shown that Staphylococci aurei of phage type 94/96 produce large amounts of penicillinase, and that methicillin is the most penicillinase-resistant of the penicillinase-resistant penicillins followed by dicloxacillin and cloxacillin. The penicillinase production of the patient's Staphylococcus aureus strain was 304-362 units per mg bacteria which is high compared to typical values of 50-200. After 50 days of cloxacillin treatment, the treatment was changed to methicillin 2 g four times daily. Within a week the staphylococci had disappeared from the expectorate, and were never again recovered from the blood. It is suggested that methicillin should have superior efficiency in serious infections with Staphylococcus aureus of phage type 94/96.