Minocycline hydrochloride microbiology

Microbiology

The tetracyclines are primarily bacteriostatic and are thought to exert their antimicrobial effect by the inhibition of protein synthesis. The tetracyclines, including minocycline, have a similar antimicrobial spectrum of activity against a wide range of gram-positive and gram-negative organisms. Cross-resistance of these organisms to tetracyclines is common.

Minocycline has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section:

AEROBIC GRAM-POSITIVE MICROORGANISMS

Because many strains of the following gram-positive microorganisms have been shown to be resistant to tetracyclines, culture and susceptibility testing are especially recommended. Tetracycline antibiotics should not be used for streptococcal diseases unless the organism has been demonstrated to be susceptible. Tetracyclines are not the drug of choice in the treatment of any type of staphylococcal infection.

Bacillus anthracis†

Listeria monocytogenes†

Staphylococcus aureus

Streptococcus pneumoniae

AEROBIC GRAM-NEGATIVE MICROORGANISMS

Bartonella bacilliformis

Brucella species

Calymmatobacterium granulomatis

Campylobacter fetus

Francisella tularensis

Haemophilus ducreyi

Vibrio cholerae

Yersinia pestis

Because many strains of the following groups of gram-negative microorganisms have been shown to be resistant to tetracyclines, culture and susceptibility tests are especially recommended:

Acinetobacter species

Enterobacter aerogenes

Escherichia coli

Haemophilus influenzae

Klebsiella species

Neisseria gonorrhoeae†

Neisseria meningitidis†

Shigella species

"OTHER" MICROORGANISMS

Actinomyces species†

Borrelia recurrentis

Chlamydia psittaci

Chlamydia trachomatis

Clostridium species†

Entamoeba species

Fusobacterium nucletum ssp. fusiforme†

Mycobacterium marinum

Mycoplasma pneumonia

Propionibacterium acnes

Rickettsiae

Treponema pallidum subspecies pallidum†

Treponema pallidum subspecies pertenue†

Ureaplasma urealyticum

†When penicillin is contraindicated, tetracyclines are alternative drugs in the treatment of infections caused by the cited microorganisms.

Susceptibility tests

Susceptibility testing should be performed with tetracycline since it predicts susceptibility to minocycline. However, certain organisms (e.g., some staphylococci, and Acinetobacter ssp.) may be more susceptible to minocycline and doxycycline than to tetracycline.

Dilution techniques

Quantitative methods are used to determine antimicrobial minimal inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized procedure. Standardized procedures are based on a dilution method1,3 (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of tetracycline powder. The MIC values should be interpreted according to the following criteria:

For testing aerobic gram-negative microorganisms (Enterobacteriaceae), Acinetobacter ssp. and Staphylococcus aureus.

References

Adapted from the FDA Package Insert.