From the Guidelines
Doxycycline is effective against a wide range of bacteria, including Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus (MSSA and MRSA), and others, as recommended by the British Thoracic Society guideline for bronchiectasis in adults 1.
Bacteria that Improve with Doxycycline
The following bacteria have been shown to improve with doxycycline treatment:
- Streptococcus pneumoniae: Doxycycline is recommended as a second-line treatment for Streptococcus pneumoniae infections, with a dosage of 100 mg twice daily for 14 days 1.
- Haemophilus influenzae: Doxycycline is recommended as a second-line treatment for Haemophilus influenzae infections, with a dosage of 100 mg twice daily for 14 days 1.
- Moraxella catarrhalis: Doxycycline is recommended as a second-line treatment for Moraxella catarrhalis infections, with a dosage of 100 mg twice daily for 14 days 1.
- Staphylococcus aureus (MSSA and MRSA): Doxycycline is recommended as a second-line treatment for Staphylococcus aureus (MSSA) infections, with a dosage of 100 mg twice daily for 14 days, and as a first-line treatment for Staphylococcus aureus (MRSA) infections, with a dosage of 100 mg twice daily for 14 days 1.
Dosage and Administration
The typical adult dosage of doxycycline is 100 mg twice daily on the first day, followed by 100 mg once daily for 7-14 days depending on the infection, as recommended by the Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults 1.
Mechanism of Action
Doxycycline works by inhibiting bacterial protein synthesis by binding to the 30S ribosomal subunit, preventing the attachment of aminoacyl-tRNA to the mRNA-ribosome complex, which stops bacterial growth and allows the immune system to clear the infection 1.
Additional Considerations
It's worth noting that doxycycline is also effective against atypical bacteria such as Mycoplasma pneumoniae, Chlamydia species, Rickettsia, and Coxiella burnetii, as well as spirochetes like Borrelia burgdorferi (Lyme disease) and Treponema pallidum (syphilis) 1. However, the primary consideration should be the most recent and highest quality study, which in this case is the British Thoracic Society guideline for bronchiectasis in adults 1.
From the FDA Drug Label
Doxycycline is indicated for the treatment of the following infections: Rocky Mountain spotted fever, typhus fever and the typhus group, Q fever, rickettsialpox, and tick fevers caused by Rickettsiae. Respiratory tract infections caused by Mycoplasma pneumoniae. Lymphogranuloma venereum caused by Chlamydia trachomatis. Psittacosis (ornithosis) caused by Chlamydia psittaci. Trachoma caused by Chlamydia trachomatis, Inclusion conjunctivitis caused by Chlamydia trachomatis. Uncomplicated urethral, endocervical, or rectal infections in adults caused by Chlamydia trachomatis. Nongonococcal urethritis caused by Ureaplasma urealyticum. Relapsing fever due to Borrelia recurrentis. Doxycycline is also indicated for the treatment of infections caused by the following gram-negative microorganisms: Chancroid caused by Haemophilus ducreyi. Plague due to Yersinia pestis (formerly Pasteurella pestis). Tularemia due to Francisella tularensis (formerly Pasteurella tularensis). Cholera caused by Vibrio cholerae (formerly Vibrio comma). Campylobacter fetus infections caused by Campylobacter fetus (formerly Vibrio fetus). Brucellosis due to Brucella species (in conjunction with streptomycin). Bartonellosis due to Bartonella bacilliformis. Granuloma inguinale caused by Calymmatobacterium granulomatis. Doxycycline is indicated for treatment of infections caused by the following gram- negative microorganisms, when bacteriologic testing indicates appropriate susceptibility to the drug: Escherichia coli. Enterobacter aerogenes (formerly Aerobacter aerogenes). Shigella species. Acinetobacter species (formerly Mima species and Herellea species). Respiratory tract infections caused by Haemophilus influenzae. Respiratory tract and urinary tract infections caused by Klebsiella species. Doxycycline is indicated for treatment of infections caused by the following gram-positive microorganisms when bacteriologic testing indicates appropriate susceptibility to the drug: Upper respiratory infections caused by Streptococcus pneumoniae (formerly Diplococcus pneumoniae) Anthrax due to Bacillus anthracis, including inhalational anthrax (post-exposure): to reduce the incidence or progression of disease following exposure to aerosolized Bacillus anthracis. When penicillin is contraindicated, doxycycline is an alternative drug in the treatment of the following infections: Uncomplicated gonorrhea caused by Neisseria gonorrhoeae. Syphilis caused by Treponema pallidum. Yaws caused by Treponema pertenue. Listeriosis due to Listeria monocytogenes. Vincent’s infection caused by Fusobacterium fusiforme. Actinomycosis caused by Actinomyces israelii. Infections caused by Clostridium species.
The bacteria that improve with doxycycline are:
- Gram-negative bacteria:
- Haemophilus ducreyi
- Yersinia pestis
- Francisella tularensis
- Vibrio cholerae
- Campylobacter fetus
- Brucella species
- Bartonella bacilliformis
- Calymmatobacterium granulomatis
- Escherichia coli
- Enterobacter aerogenes
- Shigella species
- Acinetobacter species
- Haemophilus influenzae
- Klebsiella species
- Neisseria gonorrhoeae
- Gram-positive bacteria:
- Streptococcus pneumoniae
- Bacillus anthracis
- Treponema pallidum
- Treponema pertenue
- Listeria monocytogenes
- Fusobacterium fusiforme
- Actinomyces israelii
- Clostridium species
- Other bacteria:
- Rickettsiae
- Mycoplasma pneumoniae
- Chlamydia trachomatis
- Chlamydia psittaci
- Ureaplasma urealyticum
- Borrelia recurrentis 2
From the Research
Bacteria Susceptible to Doxycycline
- Rickettsia, Borrelia, Ehrlichia, and Plasmodium falciparum are susceptible to doxycycline, as stated in the study 3
- Doxycycline displays excellent activity against gram-positive and gram-negative aerobic and anaerobic pathogens, including those that cause respiratory tract infections, skin and soft tissue infections, genitourinary infections, and intraabdominal infections, as reported in the study 4
- Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis are also susceptible to doxycycline, although the susceptibility rates vary, with 80.4% of S pneumoniae isolates, 25.1% of H influenzae isolates, and most M catarrhalis isolates being resistant to doxycycline, as found in the study 5
Specific Bacterial Infections Treated with Doxycycline
- Respiratory tract infections, including atypical pneumonias, as mentioned in the study 4
- Skin and soft tissue infections, as reported in the study 4
- Genitourinary infections, including gonorrhea, syphilis, nonspecific urethritis, and prostatitis, as stated in the study 4
- Intraabdominal infections due to trauma, sepsis, or surgery, as mentioned in the study 4
- Cholera, as reported in the study 4
- Legionnaires' disease, as suggested in the study 4
- Traveler's diarrhea, as found in the study 4