A report of Susceptible (S) indicates that the antimicrobial is likely to inhibit growth of the pathogen if the antimicrobial compound reaches the concentrations at the infection site necessary to inhibit growth of the pathogen. A report of Intermediate (I) indicates that the result should be considered equivocal, and, if the bacteria is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug product is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone that prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of Resistant (R) indicates that the antimicrobial is not likely to inhibit growth of the pathogen if the antimicrobial compound reaches the concentrations usually achievable at the infection site; other therapy should be selected.

Quality Control
Standardized susceptibility test procedures require the use of laboratory controls to monitor and ensure the accuracy and precision of the supplies and reagents used in the assay, and the techniques of the individuals performing the test1,2,3,4,5,6,7. Standard doxycycline and tetracycline powders should provide the following range of MIC values noted in Table 2. For the diffusion technique using the 30 mcg doxycycline disk the criteria noted in Table 2 should be achieved.
Table 2: Acceptable Quality Control Ranges for Susceptibility Testing for Doxycycline and Tetracycline  QC Strain Minimal Inhibitory Concentration
(mcg/mL) Zone Diameter
(mm) Agar Dilution
(mcg/mL)
Enterococcus faecalis ATCC 29212   
  Doxycycline 2 – 8 - -
  Tetracycline 8 – 32 - -
Escherichia coli ATCC 25922   
  Doxycycline 0.5 – 2 18 – 24 -
  Tetracycline 0.5 – 2 18 – 25 -
Haemophilus influenzae ATCC 49247   
  Tetracycline 4 – 32 14 – 22 -
Neisseria gonorrhoeae ATCC 49226   
  Tetracycline - 30 – 42 0.25 – 1
Staphylococcus aureus ATCC 25923   
  Doxycycline - 23 – 29 -
  Tetracycline - 24 – 30 -
Staphylococcus aureus ATCC 29213   
  Doxycycline 0.12 –0.5 - -
  Tetracycline 0.12 – 1 - -
Streptococcus pneumoniae ATCC 49619   
  Doxycycline 0.015 – 0.12 25 – 34 -
  Tetracycline 0.06 – 0.5 27 – 31 -
Bacteroides fragilis ATCC 25285   
  Tetracycline - - 0.12 – 0.5
Bacteroides thetaiotaomicron ATCC 29741   
  Tetracycline - - 8 – 32
Mycoplasma pneumoniae ATCC 29342   
  Tetracycline 0.06–0.5 - 0.06–0.5
Ureaplasma urealyticum ATCC 33175   
  Tetracycline - - ≥8

INDICATIONS AND USAGE
To reduce the development of drug-resistant bacteria and maintain effectiveness of Vibramycin and other antibacterial drugs, Vibramycin should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacter