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present in a cow’s udder or equipment may get into raw milk. Although the number of
microorganisms required to cause disease is not known, it is suspected to be very
small. Colonies of the bacteria are flat, grayish and with irregular edges, and tend
with time to spread on the surface of the agar. Its cultures have a characteristic odor
and a metallic sheen, which are both useful characters for identification. Variants
may not have these characters; but they may appear upon sub-cultivation (Willey et
al. 2008).
4.3.3 Klebsiella pneumoniae.
Klebsiella pneumonia is a Gram-negative, non-sporulating, facultative, aerobic rod
that is normally found in the human gastro-intestinal tract. It is nitrogen-fixing
bacteria. An adhesion to a mucosal surface is often the first step in the development
of an infection. Adhesins are often also hemmaglutinins and may or may not be
located on fimbriae which protrude from the surface of the bacterial cells. Strains of
Klebsiella oxytoca may produce thick channeled fimbriae associated with mannose-
sensitive hemaglutination. These strains may also produce thin non-channelled (type
3) fimbriae associated with the mannose-resistant hemaglutinins. These type-3
fimbriae can be coated with type-3 antiserum against Klebsiella oxytoca (K70/1) and
are antigenically related to those of Enterobacter gergoviae. Strains of Klebsiella
oxytoca that have not acquired any resistant determinants are naturally resistant to
aminopenicillin (ampicillin) and carboxypenicillin (carbenicillin) and susceptible to
other beta-lactam antibiotics. This is due to the production of a chromosomal
penicillinase which is inhibited by clavulanic acid. A small zone of inhibition around
100 µg carbenicillin discs is typical of this phenotype. Acquired resistance often
arises from the production of a plasmid-determined penicillinase. The strains show a
higher resistance to carbenicillin and resistance to ureidopenicillins, cefalothin,
cefamandole, and cefuroxime (Willey et al. 2008).
Klebsiella species may be found in human feces. A survey of the presence of
Klebsiella in urban residents, hospital personnel, and newly admitted patients
showed that 30-37% of individuals carried Klebsiella, including a 29-35% fecal
carriage and a three-to-four-percent throat carriage. There was a slight increase in
prevalence among long-term patients. Klebsiella species can cause human diseases
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