13医院感染及其防治.ppt

* * * * * * * The presence of some organisms, such as Propionibacterium acnes, in blood culture is unlikely to indicates true bacteremia, unless the patient is at special risk. The presence of some organisms, such as Staphylococcus aureus, should be assumed to indicate true bacteremia unless proven otherwise. Identification of coagulase-negative staphylococci in blood is one of the major reasons for vancomycin use in the United States, but most often these organisms are contaminants. The first step to interpret blood culture results when coagulase-negative staphylococci are identified is to assess the pre-test probability of true bacteremia. Some patients, including those with endovascular implants and other prosthetic devices, are at increased risk for coagulase-negative staphylococcal bacteremia. Likewise, neutropenic patients are at increased risk. Vascular catheters also increase the risk, but most coagulase-negative cultures in catheterized patients without other risk factors are contaminants. In patients who are critically ill, treatment is usually indicated until true bacteremia is excluded in the differential diagnosis. Additional information can help assess the post-test probability of true bacteremia. If more than one specimen is growing coagulase-negative staphylococci, then true bacteremia is more likely than when a single specimen is positive. If more than one culture is positive, comparing the antibiograms can help determine if they are similar (more likely to represent true bacteremia) or different (less likely). The best method for assessing true bacteremia is to compare genotypes of the suspect strains. This method is not widely available and results are usually not timely enough to guide therapy. * * * Ignaz Philipp Semmelweis (1818-65), a Hungarian obstetrician, introduced antiseptic hand hygiene techniques. Semmelweis noted that post-partum women examined by medical students who did not wash their hands after performing autopsies had high