Doxycycline calcium microbiology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohamed Moubarak, M.D. [2]
Microbiology
Doxycycline inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit. Doxycycline has bacteriostatic activity against a broad range of Gram-positive and Gram-negative bacteria. Cross resistance with other tetracyclines is common.
Doxycycline has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section of the package insert for VIBRAMYCIN.
- Gram-Negative Bacteria
Acinetobacter species Bartonella bacilliformis Brucella species Calymmatobacterium granulomatis Campylobacter fetus Enterobacter aerogenes Escherichia coli Francisella tularensis Haemophilus ducreyi Haemophilus influenzae Klebsiella species Neisseria gonorrhoeae Shigella species Vibrio cholerae Yersinia pestis
- Gram-Positive Bacteria
Bacillus anthracis Streptococcus pneumoniae
- Anaerobic Bacteria
Clostridium species Fusobacterium fusiforme Propionibacterium acnes
- Other Bacteria
Nocardiae and other aerobic Actinomyces species Borrelia recurrentis Chlamydophila psittaci Chlamydia trachomatis Mycoplasma pneumoniae Rickettsiae Treponema pallidum Treponema pertenue Ureaplasma urealyticum
- Parasites
Balantidium coli Entamoeba species Plasmodium falciparum1
Doxycycline has been found to be active against the asexual erythrocytic forms of Plasmodium falciparum, but not against the gametocytes of P. falciparum. The precise mechanism of action of the drug is not known.
Susceptibility Testing Methods
When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antimicrobial drugs used in resident hospitals to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting the most effective antimicrobial.
Dilution techniques
Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized test method1,2,4 (broth or agar). The MIC values should be interpreted according to criteria provided in Table 1.
Diffusion techniques
Quantitative methods that require measurement of zone diameters can also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The zone size provides an estimate of the susceptibility of bacteria to antimicrobial compounds. The zone size should be determined using a standardized test method1,3,4. This procedure uses paper disks impregnated with 30-μg doxycycline to test the susceptibility of microorganisms to doxycycline. The disk diffusion interpretive criteria are provided in Table 1.
Anaerobic Techniques
For anaerobic bacteria, the susceptibility to doxycycline can be determined by a standardized test method5. The MIC values obtained should be interpreted according to the criteria provided in Table 1.