Tuesday, August 23, 2011

Gram-negative bacteria Overview (Part 1)

null Gram-negative bacilli that belong to the family Enterobacteriaceae continue to be the most frequently recovered bacterial isolates from clinical specimens. Thirty named genera are recognized in the family. Although most clinically significant isolates belong to 20 or 25 species that have been well known for many years, new species are being continually discovered (Warren et al., 2000).

2.1.1 Enterobacter species:
Motile Gram-negative bacilli that conform to the definition of the enterobacteria. The genus Enterobacter is one of the members of the family Enterobacteriaceae and consists of 13 species. Among them, E. cloacae and
E. aerogenes are the most frequently isolated species, causing infections in
hospitalized and debilitated patients (Sanders et al., 1997).

E. cloacae and E. aerogenes are the two species of Enterobacter most frequently isolated from nosocomial infections. These species are members of normal intestinal flora and are opportunistic pathogens which colonize and critically ill patients (Ronveaux et al., 1999).

Enterobacter spp. are usually characterized by their high levels of resistance to ampicillin, amoxicillin-clavulanic acid, and expanded-spectrum
cephalosporins or imipenem (Pitout et al., 1997).

The increased endemic prevalence of Enterobacter species producing class 1 β-lactamases is probably due to high level of β-lactamases antibiotics
usage, such as amoxicillin, and second and third generation cephalosporins (Hanberger et al., 2001).

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