Microbiology, Empiric regimens – Common Bacterial species

Anaerobes (gram positive and negative):

Empiric drug regimens listed for the various bacterial strains are for ADULT patients with normal renal function. Review the relevant package insert for additional prescribing information.

Anaerobic Gram-Negative Bacilli
>Bacteroides fragilis (most important clinically)
[Other Bacteroides species  – less common clinically:  (B. acidifaciens, B. gracilis,
B. oris, B. ovatus,  B. pyogenes , B. stercoris, B. vulgatus)]
>Bacteroides melaninogenicus (reclassified and split into Prevotella melaninogenica
and Prevotella intermedia.)
>Fusobacterium necrophorum
>Porphyromonas gingivalis

Anaerobic Gram-Negative cocci
-Veillonella parvula

Anaerobic Gram-positive cocci
Peptostreptococcus species

Anaerobic Gram-positive bacilli
1] Gram-positive spore-forming:
>Clostridium species

2]  Gram-positive nonspore-forming bacilli:
>Bifidobacterium species



  • Anaerobic bacteria do not grow on solid media in room air (0.04% carbon dioxide and 21% oxygen).
  • Facultative anaerobic bacteria can grow in the presence as well as in the absence of air.
  • Microaerophilic bacteria do not grow at all aerobically or grow poorly, but grow better under 10% carbon dioxide or anaerobically.
  • Anaerobic bacteria can be divided into strict anaerobes that can not grow in the presence of more than 0.5% oxygen and moderate anaerobic bacteria that are able of growing between 2 to 8% oxygen.
  • Anaerobic bacteria usually do not possess catalase, but some can generate superoxide dismutase which protects them from oxygen.
  • The clinically important anaerobes in decreasing frequency are:
    • 1. Six genera of Gram-negative rods (Bacteroides, Prevotella, Porphyromonas, Fusobacterium, Bilophila and Sutterella spp.);
    • 2. Gram-positive cocci (primarily Peptostreptococcus spp.);
    • 3. Gram-positive spore-forming (Clostridium spp.) and nonspore-forming bacilli (Actinomyces, Propionibacterium, Eubacterium, Lactobacillus and Bi?dobacterium spp.); and
    • 4. Gram-negative cocci (mainly Veillonella spp.) .
  • Because of their fastidious nature, anaerobes are hard to isolate and are often not recovered from infected sites.

Microbiology Bacteria Bacterial Pathogens  Pathogenic Bacteria



  1. Achromobacter xylosoxidans
  2. Acinetobacter baumannii
  3. Actinomyces
  4. Actinomyces israelii
  5. Aeromonas species
  6. Anaerobes
  7. Atypical Organisms
  8. Bacillus species
  9. Bacteroides fragilis
  10. Bacteroides melaninogenicus
  11. Bartonella species
  12. Bordetella pertussis
  13. Borrelia species
  14. Brucella species
  15. Burkholderia species
  16. Campylobacter
  17. Capnocytophaga species
  18. Chlamydophila pneumoniae
  19. Chlamydophila psittaci
  20. Citrobacter species
  21. Clostridium species
  22. Corynebacterium species
  23. Coxiella burnetii
  24. Ehrlichia species
  25. Eikenella corrodens
  26. Enterobacter species
  27. Enterobacteriaceae
  28. Enterococcus faecalis
  29. Enterococcus faecium
  30. Escherichia coli
  31. Francisella tularensis
  32. Fusobacterium necrophorum
  33. Gardnerella vaginalis
  34. Gram Negative Bacteria
  35. Gram Positive Bacteria
  36. Haemophilus species
  37. Helicobacter Pylori
  38. Klebsiella species
  39. Lactobacillus species
  40. Legionella species
  41. Leptospira species
  42. Listeria monocytogenes
  43. Miscellaneous Bacteria
  44. Moraxella catarrhalis
  45. Morganella species
  46. Mycoplasma pneumonia
  47. Neisseria species
  48. Nocardia species
  49. Pasteurella multocida
  50. Peptostreptococcus species
  51. Porphyromonas gingivalis
  52. Propionibacterium acnes
  53. Proteus species
  54. Providencia species
  55. Pseudomonas aeruginosa
  56. Rickettsia
  57. Salmonella species
  58. Serratia marcescens
  59. Shigella species
  60. Spirochetes
  61. Staph epidermidis
  62. Staph hominis
  63. Staph. haemolyticus
  64. Staphylococcus aureus
  65. Staphylococcus saprophyticus
  66. Stenotrophomonas maltophilia
  67. Streptococcus agalactiae
  68. Streptococcus anginosus group
  69. Streptococcus pneumoniae
  70. Streptococcus pyogenes (Groups A, B, C, G, F)
  71. Treponema pallidum
  72. Vibrio species
Bacteroides fragilis