In vitro activity of thiamphenicol against multiresistant Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus in Italy.

Thiamphenicol is a derivative of chloramphenicol characterized by a spectrum comparable to that of the parent compound against multiresistant pathogens but showing satisfactory tolerability. The in vitro activity of thiamphenicol and of 11 comparative drugs against 397 recently isolated antibiotic-resistant and/or invasive pneumococci and 52 multiply-resistant MRSA including 2 VISA strains was determined. Bactericidal activity against Haemophilus influenzae and the post-antibiotic effect on Streptococcus pneumoniae, H. influenzae, Staphylococcus aureus and Escherichia coli were also assessed. Against invasive pneumococci, thiamphenicol and chloramphenicol were the most potent non-beta-lactam molecules together with vancomycin and rifampin. Against high-level penicillin-resistant strains phenicol activities were superior to those of cefotaxime, ceftriaxone and imipenem. Against MRSA thiamphenicol and chloramphenicol were second only to the glycopetides and also inhibited the VISA strains. Thiamphenicol showed a significant PAE (0.33 to 2.9h) on all pathogens studied and a powerful bactericidal effect against beta-lactamase-positive and -negative H. influenzae. These results indicate a good in vitro activity of thiamphenicol against difficult-to-treat multiply resistant pathogens.