Document Actions
2008: ANTIMICROBIAL SUSCEPTIBILITY TESTING
by
mike_rogers
—
last modified
August 10, 2009 02:09 PM
|
UNC Hospitals McLendon Clinical Laboratories 101 Manning Drive Chapel Hill, NC 27514 |
Click here for 2008 antibiograms
2008: ANTIMICROBIAL SUSCEPTIBILITY TESTING
Important: Please Read Fully
| It is imperative that these data be used in the appropriate clinical context. These data are not intended to be used as the sole determinant of antimicrobial therapy, nor are they intended for clinical use outside of the UNC Hospitals. UNC Hospitals and the McLendon Clinical Laboratories are not responsible for misuse of these data. |
For assistance in interpreting these data, or for additional information, please contact the Clinical Microbiology Laboratory at 6-4053.
Table 1 lists the antimicrobial susceptibility of frequently encountered aerobic bacterial isolates recovered from specimens submitted to the University of North Carolina Hospitals Clinical Microbiology Laboratory between 1 January 2008 and 31 December 2008. Most of the data are presented as percent of strains tested that were found to be susceptible by in vitro testing. Strains yielding intermediate or "I" results together with resistant or "R" results account for the balance of the strains.
| These data, while of interest to many, refer only to bacteria recovered from cultures obtained from patients seen at the University of North Carolina Hospitals, and not to bacterial strains recovered from patients seen at other institutions. |
Routine susceptibility testing of anaerobic isolates is no longer performed because of the many agents available to the physician such as metronidazole, imipenem, ampicillin/sulbactam, and ticarcillin/clavulanic acid which offer excellent coverage against these organisms.
Table 2 lists commonly used antimicrobial drugs with dosages, attainable drug levels in various body fluids, and correlation values between disk diffusion susceptibility results and minimal inhibitory concentrations (MIC) values. Correlation values may be useful in interpreting what a report of susceptible or resistant means with respect to a particular antimicrobial agent.
It should be clearly understood that, with the exception of Nitrofurantoin, the interpretive reporting terms "S" (susceptible), "I" (intermediate or indeterminate), or "R" (resistant) are based on blood levels which are achieved with the usually recommended drug dosage, and are not based upon antibiotic levels which may be reached in urine or other body fluids. (Nitrofurantion interpretations are based on achievable urinary tract levels.)
- An "S" result indicates that the organism is susceptible and therefore inhibited by concentrations of the antimicrobial that are achieved in serum with routine dosage.
- An "R" result indicates that the organism is resistant to the antimicrobial and is not inhibited even when increased dosages are given.
- An "I" result indicates that the susceptibility of the bacteria to the antimicrobial is intermediate, being between susceptible and resistant levels. Some investigators prefer to term "I" results "indeterminate" since both susceptible and resistant strains will occasionally yield an "I" result. If consideration is given to treating a patient with an antibiotic to which the causative organism demonstrates an "I" susceptibility result, it is wise to request Minimum Inhibitory Concentration (MIC) tests on the organism to better assess the susceptibility of the bacterial isolate to the antibiotic.