Microbiology Demystified

• Pasteurella-Haemophilus. Pasteurella-Haemophilus are very small faculta-
  tively anaerobic gram-negative, rod shaped bacteria, that are named for
  Louis Pasteur. Examples include:
  
  
  • Pasteurella causes blood poisoning (septicemia) in cattle, chickens
    (fowl cholera) and pneumonia in various animals.
  
  
  • P. multocida,the species which was identified by Louis Pasteur, is
    transmitted to humans by a dog or cat bite.
  
  
  • Haemophilus.The genus Haemophilus(which means “blood loving”)
    are bacteria that live in mucous membranes of the upper respiratory
    tract, mouth, intestinal tract and vagina.
  
  
  • H. ducreyi, the species of Haemophilusbacterium that causes chan-
    croid, which is an infectious venereal ulcer.
  
  
  • H. aegyptiusisthe species that causes acute conjunctivitis or pink eye.
  
  
  
  

Anaerobic Gram-Negative Cocci and Rods

Anaerobic gram-negative cocci and rods can live in anaerobic conditions and are

non-motile. They do not form endospores, which are small spores that developed

inside the bacteria as a resistant survival form of the bacteria.

Anaerobic gram-negative cocciare spherically shaped and form a single

chain or are clustered. Veillonellaare common anaerobic gram-negative cocci

that are found between teeth and on gums. Veillonellais the cause of abscesses

of teeth and gums.

Anaerobic gram-negative rodsare called Bacteroidesand are members of the

Bacteriodaceaefamily of bacteria that live in the intestinal tract of humans.

Bacteroides can cause peritonitis, which is inflammation of the peritoneum due

to infection. Another kind of anaerobic gram-negative rod is Fusobacterium.

These are long slender rods that live in the gingival crevices of teeth and cause

gingivitis, which is a gum infection.

Rickettsias and Chlamydias

Rickettsias and Chlamydias are intracellular parasites that need a host in order

to reproduce and therefore enter the cell of a host. These bacteria were once

(^158) CHAPTER 10 The Prokaryotes