What are the common antibiotics and the organisms they cover?

From the Guidelines

Common antibiotics are classified based on their mechanisms of action and the organisms they effectively target, with the most recent guidelines recommending specific antibiotics for various infections, such as penicillins, cephalosporins, macrolides, fluoroquinolones, tetracyclines, aminoglycosides, and carbapenems.

• Penicillins like amoxicillin (250-500mg three times daily for 7-10 days) are effective against many gram-positive bacteria including streptococci and some gram-negative organisms 1.
• Cephalosporins such as cefazolin (1-2g every 8 hours IV) cover similar organisms but with enhanced gram-negative coverage 1.
• Macrolides like azithromycin (500mg on day 1, then 250mg daily for 4 days) target atypical pathogens including Mycoplasma and Chlamydia 1.
• Fluoroquinolones such as ciprofloxacin (500mg twice daily for 7-14 days) provide broad coverage against gram-negative bacteria including Pseudomonas 1.
• Tetracyclines like doxycycline (100mg twice daily) are effective against a wide range of bacteria including intracellular organisms 1.
• Aminoglycosides such as gentamicin (5-7mg/kg daily IV) target gram-negative bacteria including Pseudomonas 1.
• Carbapenems like meropenem (1g every 8 hours IV) offer the broadest spectrum, covering most gram-positive and gram-negative bacteria including many resistant strains 1. These antibiotics work by different mechanisms - inhibiting cell wall synthesis, protein synthesis, or DNA replication - which explains their effectiveness against specific bacterial groups. Appropriate antibiotic selection should consider the likely pathogen, infection site, patient factors, and local resistance patterns, as recommended by the most recent guidelines from reputable sources such as the Infectious Diseases Society of America (IDSA) and the American College of Physicians (ACP) 1.

From the FDA Drug Label

Ciprofloxacin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections... Aerobic gram-positive microorganisms Enterococcus faecalis Staphylococcus saprophyticus Streptococcus pneumoniae (penicillin-susceptible strains only) Streptococcus pyogenes Aerobic gram-negative microorganisms Campylobacter jejuni Proteus mirabilis Citrobacter diversus Proteus vulgaris Citrobacter freundii Providencia rettgeri Enterobacter cloacae Providencia stuartii Escherichia coli Pseudomonas aeruginosa Haemophilus influenzae Salmonella typhi Haemophilus parainfluenzae Serratia marcescens Klebsiella pneumoniae Shigella boydii Moraxella catarrhalis Shigella dysenteriae Morganella morganii Shigella flexneri Neisseria gonorrhoeae Shigella sonnei

The tetracyclines, including doxycycline, have a similar antimicrobial spectrum of activity against a wide range of gram-positive and gram-negative organisms. Calymmatobacterium granulomatis Haemophilus ducreyi Haemophilus influenzae Yersinia pestis (formerly Pasteurella pestis) Francisella tularensis (formerly Pasteurella tularensis) Vibrio cholerae (formerly Vibrio comma) Bartonella bacilliformis Brucella species Escherichia coli Klebsiella species Enterobacter aerogenes Shigella species Acinetobacter species (formerly Mima species and Herellea species) Bacteroides species Streptococcus pyogenes Streptococcus pneumoniae Enterococcus group (Streptococcus faecalis and Streptococcus faecium) Alpha-hemolytic streptococci (viridans group) Rickettsiae Chlamydia psittaci Chlamydia trachomatis Mycoplasma pneumoniae Ureaplasma urealyticum Borrelia recurrentis Treponema pallidum Treponema pertenue Clostridium species Fusobacterium fusiforme Actinomyces species Bacillus anthracis Propionibacterium acnes Entamoeba species Balantidium coli Plasmodium falciparum

Common Antibiotics and Organisms They Cover:

• Ciprofloxacin: effective against a wide range of gram-positive and gram-negative microorganisms, including:

• Aerobic gram-positive microorganisms: Enterococcus faecalis, Staphylococcus saprophyticus, Streptococcus pneumoniae (penicillin-susceptible strains only), Streptococcus pyogenes
• Aerobic gram-negative microorganisms: Campylobacter jejuni, Proteus mirabilis, Citrobacter diversus, Proteus vulgaris, Citrobacter freundii, Providencia rettgeri, Enterobacter cloacae, Providencia stuartii, Escherichia coli, Pseudomonas aeruginosa, Haemophilus influenzae, Salmonella typhi, Haemophilus parainfluenzae, Serratia marcescens, Klebsiella pneumoniae, Shigella boydii, Moraxella catarrhalis, Shigella dysenteriae, Morganella morganii, Shigella flexneri, Neisseria gonorrhoeae, Shigella sonnei

• Doxycycline: effective against a wide range of gram-positive and gram-negative microorganisms, including:

• Calymmatobacterium granulomatis, Haemophilus ducreyi, Haemophilus influenzae, Yersinia pestis (formerly Pasteurella pestis), Francisella tularensis (formerly Pasteurella tularensis), Vibrio cholerae (formerly Vibrio comma), Bartonella bacilliformis, Brucella species
• Escherichia coli, Klebsiella species, Enterobacter aerogenes, Shigella species, Acinetobacter species (formerly Mima species and Herellea species), Bacteroides species
• Streptococcus pyogenes, Streptococcus pneumoniae, Enterococcus group (Streptococcus faecalis and Streptococcus faecium), Alpha-hemolytic streptococci (viridans group)
• Rickettsiae, Chlamydia psittaci, Chlamydia trachomatis, Mycoplasma pneumoniae, Ureaplasma urealyticum, Borrelia recurrentis, Treponema pallidum, Treponema pertenue, Clostridium species, Fusobacterium fusiforme, Actinomyces species, Bacillus anthracis, Propionibacterium acnes, Entamoeba species, Balantidium coli, Plasmodium falciparum 2 3

From the Research

Common Antibiotics and Organisms They Cover

• Broad-spectrum antibiotics are used to treat various infections, including those caused by:
  • Escherichia coli (E. coli) 4
  • Staphylococcus aureus (S. aureus) 5, 6
  • Pseudomonas aeruginosa (P. aeruginosa) 6, 7
  • Enterococcus spp. 6
  • Haemophilus influenzae (H. influenzae) 6
  • Streptococcus pneumoniae (S. pneumoniae) 6
  • Bacteroides fragilis (B. fragilis) 6
• Specific antibiotics and their coverage:
  • Ampicillin: effective against E. coli, but resistance rates are high (55.1%) 4
  • Cephalexin: effective against E. coli, but inferior to trimethoprim in treating symptomatic domiciliary infections 8
  • Co-trimoxazole (TMP-SMX): effective against E. coli, but resistance rates are increasing (41.1%) 4
  • Fluoroquinolones (FQ): commonly prescribed for urinary tract infections, but empirical use should be discouraged due to increasing resistance rates (25.2%) 4
  • Gentamicin: effective against E. coli, with low resistance rates (6.1%) 4
  • Trimethoprim: effective against E. coli, with low resistance rates and fewer side effects compared to other antibiotics 8

Organism-Specific Antibiotic Coverage

• Urinary tract infections (UTIs):
  • E. coli: ampicillin, cephalexin, co-trimoxazole, fluoroquinolones, gentamicin, trimethoprim 4, 8
  • Enterococcus spp.: co-trimoxazole, gentamicin 6
• Respiratory tract infections (RTIs):
  • H. influenzae: ampicillin, cephalexin, co-trimoxazole, fluoroquinolones 6
  • S. pneumoniae: ampicillin, cephalexin, co-trimoxazole, fluoroquinolones 6
  • P. aeruginosa: fluoroquinolones, gentamicin 6, 7
• Anaerobic infections:
  • B. fragilis: co-trimoxazole, metronidazole 6