CDAD usually responds to oral metronidazole or vancomycin but is nonetheless responsible for a high morbidity and occasional mortality in patients even when the diagnosis and treatment are pursued aggressively.

For 10 years the 700-bed Minneapolis Veterans Affairs Medical Center has conducted a policy of carefully controlled aminoglycoside usage and monitoring of resistance of over 25,000 aerobic and facultative gram-negative bacillary isolates to the aminoglycosides. On two occasions during the 1980s, our experience of introducing amikacin at a high level of usage was associated with a significant reduction in resistance to gentamicin and tobramycin among gram-negative bacilli. Rapid reintroduction of gentamicin usage in 1982 after the first amikacin period was associated with a significant and rapid increase in gentamicin and tobramycin resistance. However, in 1986, gentamicin was again reintroduced to this institution at an initially modest level, and the percentage of usage of gentamicin was gradually increased over a 15-month period without a significant change in resistance to gentamicin, tobramycin, or amikacin while maintaining an overall 68% gentamicin usage and 30% amikacin usage. Aminoglycoside usage (measured as patient days) rose steadily from under 2,000 patient days per quarter in 1980 and 1981 to over 3,000 days per quarter in 1985. Since 1985, usage has declined to under 2,500 patient days per quarter in 1990. This usage rise and fall occurred during a steadily declining daily patient census that was 590 in 1980 and 465 in 1989. A move to a new hospital building in June 1988 was associated with an additional significant decline in resistance to all aminoglycosides (P less than 0.05), continuing a trend that was evident for the year preceding the move. Resistance to aminoglycoside antibiotics is now at the lowest level in 10 years at this institution, with only one gram-negative organism, Pseudomonas aeruginosa, that exhibits more than 5% resistance to gentamicin and no gram-negative species that are more than 5% resistant to amikacin and tobramycin.

Bactericidal testing has been used for several decades as a guide for antimicrobial therapy of serious infections. Such testing is most frequently performed when bactericidal antimicrobial agent therapy is considered necessary (such as when treating infectious endocarditis or infection in an immunocompromised host). It has also been used to ensure that the infecting organism is killed by (not tolerant to) usually bactericidal compounds. However, few data are available to support the role of such tests in direct patient care. Several important variables affect the reproducibility of the test results; however, proposed reference methods are now available for performing the MBC test. With minor modifications, these can provide a standardized approach for laboratories that need to perform them. Currently, little evidence is available to support the routine use of such testing for the care of individual patients. However, testing of new (investigational) antimicrobial agents can be beneficial in determining their potential to provide bactericidal antimicrobial activity during clinical use. New methods to assess bactericidal activity are being developed, but as yet none have been rigorously tested in patient care settings; further, for most of these methods, little information is available as to which technical parameters affect their results. In clinical laboratories, all bactericidal tests must be performed with rigorously standardized techniques and adequate controls, bearing in mind the limitations of the currently available test procedures.

No abstract

CDAD usually responds to oral metronidazole or vancomycin but is nonetheless responsible for a high morbidity and occasional mortality in patients even when the diagnosis and treatment are pursued aggressively.