parts of the body (for example, through the ingestion of water that is
contaminated with fecal matter.)- Shigella. Shigella causes bacillary dysentery or shigellosis, more com-
monly known as traveler’s diarrhea. - Salmonella. Salmonellais a group (genera) of enteric bacteria that has
members that can infect humans. Species include Salmonella typhi,
which causes typhoid fever and Salmonella choleraesuis and
Salmonella enteritidesboth of which are food-borne pathogens that
cause salmonellosis, a type of food poisoning. - Klebsiella.The genera Klebsiellais a bacterium that cause bacterial
pneumonia.
•Erwinia. Erwiniais a bacterium that infects plants and causes what is
commonly called soft root rot. - Enterobacter.The genus enterobacterconsists of the species Enterobacter
cloaceand Enterobacter aerogenes. Both of these organisms cause uri-
nary tract infections and nosocomial (hospital) infections in individuals
with a weakened immune system. - Serratia marcescens, Serratia marcescensbacteria are found on catheters
and instruments that are allegedly sterile; this bacterium causes urinary
and respiratory infections.
•Yersinia pestis. Yersinia pestis, also known as Y.pestis, caused the
bubonic or black plague, which ravaged Europe during the Middle
Ages. It begins by causing abscesses of lymph nodes and then produces
pneumonia-like symptoms when it reaches the lungs, which is called
pneumonia plague. - Vibrios. Vibrios are facultative anaerobic gram-negative, comma-shaped
bacteria that inhibit aquatic environments and some also live in the intes-
tinal tracts of animals and humans. There are two important species of vib-
rios bacteria. These are:
•Vibrio cholerae. Vibrio choleraeis the bacteria that cause cholera, signs
and symptoms are abdominal pain and watery diarrhea.
•Vibrio parahaemolyticus. Vibrio parahaemolyticusis the bacterium
that causes inflammation and irritation of the stomach and intestine—
better known as gastroenteritis—when contaminated shellfish is ingested
raw or undercooked.
CHAPTER 10 The Prokaryotes^157