tailieunhanh - Chapter 129. Staphylococcal Infections (Part 10)

Diagnosis While the detection of CoNS at sites of infection or in the bloodstream is not difficult by standard microbiologic culture methods, interpretation of these results is frequently problematic. Since these organisms are present in large numbers on the skin, they often contaminate cultures. It has been estimated that only 10–25% of blood cultures positive for CoNS reflect true bacteremia. Similar problems arise with cultures of other sites. Among the clinical findings suggestive of true bacteremia are fever, evidence of local infection (., erythema or purulent drainage at the IV catheter site), leukocytosis, and systemic signs of sepsis. . | Chapter 129. Staphylococcal Infections Part 10 Diagnosis While the detection of CoNS at sites of infection or in the bloodstream is not difficult by standard microbiologic culture methods interpretation of these results is frequently problematic. Since these organisms are present in large numbers on the skin they often contaminate cultures. It has been estimated that only 10-25 of blood cultures positive for CoNS reflect true bacteremia. Similar problems arise with cultures of other sites. Among the clinical findings suggestive of true bacteremia are fever evidence of local infection . erythema or purulent drainage at the IV catheter site leukocytosis and systemic signs of sepsis. Laboratory findings suggestive of true bacteremia include multiple isolations of the same strain . the same species with the same antibiogram or a closely related DNA fingerprint from separate cultures growth of the strain within 48 h and bacterial growth in both aerobic and anaerobic bottles. Clinical Syndromes CoNS cause diverse prosthetic device-related infections including those that involve prosthetic cardiac valves and joints vascular grafts intravascular devices and CNS shunts. In all of these settings the clinical presentation is similar. The signs of localized infection are often subtle the rate of disease progression is slow and the systemic findings are often limited. Signs of infection such as purulent drainage pain at the site or loosening of prosthetic implants are sometimes evident. Fever is frequently but not always present and there may be mild leukocytosis. Infections that are not associated with prosthetic devices are infrequent although native-valve endocarditis due to CoNS has accounted for 5 of cases in some reviews. S. lugdunensis appears to be a more aggressive pathogen in this setting causing greater mortality and rapid valvular destruction with abscess formation. Staphylococcal Infections Treatment General Principles of Therapy Surgical incision and .