Discrepancy between favourable in vitro microbiological data and a severe clinical course of a staphylococcal knee and soft tissue infection responsive to oxazolidinone linezolid only after failure of all other therapeutic attempts
Abstract number: p1609
Manfredi R., Sabbatani S., Chiodo F.
To offer therapeutic alternatives for the emerging, multiresistant, serious Gram-positive infections, novel molecules (quinupristin/dalfopristin, linezolid, daptomycin) were introduced and are made available when multiresistant Gram-positive cocci are documented as no more susceptible to all available drugs including glycopeptides. However, inezolid encompasses unique tissue penetration and diffusion features (regarding soft tissues, lungs, joints and central nervous system) which make this last drug extremely promising in all circumstances where the penetration rate into infectious foci becomes critical.
Clinical experience: A very intriguing case report of a severe, staphylococcal knee arthtiris associated to an extensive local cellulitis/fasciitis and haematogenous dissemination occurring after a surgical curettage was characterized by a complete lack of response to a prolonged vancomycin/teicoplanin plus rifampicin therapy based on the apparently favourable in vitro sensitivity assays of methicllin-resistant Staphylococci, but rapidly responded to i.v. (followed by oral) linezolid administration. The complete lack of clinical activity of a 2-week glycopeptide-rifampicin administration cannot be explained by the in vitro measured MIC90 values of isolated pathogens which showed complete sensitivity of Staphylococcus aureus against vancomycina/teicoplanin and rifampicin and susceptibility of a concurrent hematogenous S. epidermidis strain to glycopeptides-rifampicin. Since an abscess formation and an underlying osteomyelitis were carefully excluded by adequate instrumental examinations, from a theoretical point of view the active glycopeptide-rifampicin molecules should have been provided appropriate cure. On the other hand, from a strictly clinical issue, only a 2-week administration of i.v. linezolid followed by one more week of oral linezolid allowed to obtain a complete clinical-bacteriological cure and a complete function recovery without any sequelae after a 1.5-year follow-up.
When the management of severe, multiresistant Gram-positive infections is of concern, the in vitro activity of single drugs and therapeutic classes should be carefully evaluated in relation with the expected penetration and diffusion rates of these drugs into the relevant organs and tissues involved by the ongoing infectious localizations. Otherwise, apparently unexplained failures may occur also when in vitro studies point out a complete activity of the tested compounds.
|Session name:||XXIst ISTH Congress|
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