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[Is methicillin better than cloxacillin in serious infections caused by strong penicillinase-producing staphylococci
A H Siboni1, K T Jensen, V T Rosdahl
1Medicinsk afdeling, Esbjerg Centralsygehus.
Abstract:
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.
Insights
Cloxacillin failed to eradicate Staphylococcus aureus in a patient with severe infection. Switching to methicillin successfully cleared the bacteria, suggesting its superior efficacy for specific phage types.
Area of Science:
- Infectious Diseases
- Microbiology
- Pharmacology
Background:
- A patient with intravenous drug use presented with Staphylococcus aureus septicemia, pneumonia, and suspected endocarditis.
- Initial treatment involved cloxacillin and rifampicin for severe Staphylococcus aureus infection.
Observation:
- Despite prolonged cloxacillin and rifampicin therapy, Staphylococcus aureus persisted in blood and sputum.
- The patient's Staphylococcus aureus strain was identified as phage type 94/96, known for high penicillinase production.
Findings:
- Staphylococcus aureus isolates exhibited high penicillinase activity (304-362 units/mg), indicating resistance to cloxacillin.
- Switching treatment to methicillin resulted in the rapid clearance of Staphylococcus aureus from sputum and blood.
Implications:
- Methicillin demonstrated superior clinical efficacy compared to cloxacillin for severe infections caused by high penicillinase-producing Staphylococcus aureus phage type 94/96.
- This highlights the importance of antibiotic selection based on specific bacterial phage types and resistance mechanisms.