The following statement(s) is/are true concerning initial microbiologic diagnostic techniques

a. Appropriate expeditious transport of specimens to the microbiology laboratory is essential for obtaining accurate clinical information

c. Antibiotic sensitivity is determined by exposing the specific microorganism to varying amounts of antibiotic with the concentration of the antibiotic inhibiting growth referred to as the MIC (minimal inhibitory concentration)

d. Serum levels of antimicrobial agents should achieve in excess of a 4-to 8-fold increase over the MIC to be considered clinically efficacious

Because most surgical infections are polymicrobial, specimens should be cultured for aerobic and anaerobic bacteria, as well as fungi. Although aerobic and aerotolerant microorganisms often do not require special transport media, a delay in specimen processing may markedly reduce the yield, and anaerobic transport media have been demonstrated to markedly increase the cultural yield of this type of organism. The initial piece of information gained concerning potential infection may come from simple staining of a specimen. Gram stain, which will identify the staining characteristics of the organisms, as well as their number should be performed on all specimens. Potassium hydroxide is useful in that it will lyse bacteria and other cellular elements within a preparation and allow observation of yeast or mycelial elements. Initial culture results may solely indicate that microorganisms are growing and full characterization may take two to three days. Once a specific microorganism is identified, a sample is inoculated during the log phase into broth containing varying amounts of an antibiotic. After an 18-to 24-hour period, the tube or well that exhibits no visible growth is then noted, and the reciprocal of this dilution is termed the minimal inhibitory concentration (MIC). This value may be compared to either measured or known achievable serum levels for a particular antibiotic. In general, antimicrobial agents that achieve in excess of a 4-to 8-fold increase over MIC during the peak serum level have been demonstrated to be clinically efficacious.