Download Enterobacter aerogenes

Enterobacter
aerogenes
Enterobacter sp.
Enterobacter sp.
•
Species:
•
•
•
•
•
•
•
Enterobacter aerogenes
Enterobacter agglomerans
Enterobacter cloacae – causes UTI, enterotoxigenic
Often found in the normal intestinal flora, soil and water
Differentiated from other enterobacteriaceae based on
biochemical characteristics
Causes nosocomial infections esp. of urinary tract, surgical
wounds, bacteremia and septicemia
Produces beta-lactamase  inactivates penicillins and 1st-gen.
cephalosporins
Enterobacter
– NF of GI tract
– TSI, LIA, and urea give variable results
depending upon species
– Citrate +
– Clinical significance
•
•
•
•
• Nosocomial infections
• Bacteremia in burn patients
Enterobacter aerogenus
Capsulated
Free living in the intestine
Cause UTI and sepsis.
As part of the Enterobacteriaceae family,
Enterobacter aerogenes is related to E. coli
and salmonella. In terms of size, E.
aerogenes is smaller than many of its
microbial cousins, but its occurrence in
hospitals and resistance to antibiotics have
made it of particular importance. As E.
aerogenes continues to evolve new strains,
it will continue to pose challenges to the
biomedical community.
Bacteriology
E. aerogenes is a rod-shaped
bacteria, or a "bacillus" in
scientific lingo. As a facultative
anaerobe, it thrives in
environments with little or no
oxygen, such as soil, sewage
and feces.
Illnesses
E. aerogenes causes a wide range of
illnesses, depending on which part of
the body it invades. Common illnesses
include bacteremia, osteomyelitis,
pneumonia and septicemia. However,
E. aerogenes also causes infections in
the gastrointestinal tract, the respiratory
tract, the urinary tract and skin.
Risk Factors
E. aerogenes is an opportunistic
pathogen. This means that it infects a
host that has already been weakened.
E. aerogenes is also a nosocomial
bacteria, which means that it commonly
resides in hospitals. Consequently, its
risk factors include hospital stays that
last 2 weeks or longer, invasive
surgery, intensive care visits and use of
antibiotics.
Predilections
Like other Enterobacter bacteria, E. aerogenes
has no predilection for race. However, it does
occur more frequently among newborns, toddlers
and the elderly, particularly among males.
Treament
E. aerogenes is resistant to most antibiotics,
including chloramphenicol, quinolones and
tetracycline. As a result, the use of "old" drugs--that is, drugs that were commonly prescribed in
past decades---is growing in popularity. Another
popular treatment is using a combination of drugs
such as imipenem and gentamicin.
Enterobacter aerogenes is a Gram-negative, oxidase negative,
catalase positive, citrate positive, indole negative, rod-shaped
bacterium.
E. aerogenes is a nosocomial and pathogenic bacterium that causes
opportunistic infections including most types of infections. The majority
are sensitive to most antibiotics designed for this bacteria class, but this
is complicated by their inducible resistance mechanisms, particularly
lactamase which means that they quickly become resistant to standard
antibiotics during treatment, requiring change in antibiotic to avoid
worsening of the sepsis.
Some of the infections caused by E. aerogenes result from specific
antibiotic treatments, venous catheter insertions, and/or surgical
procedures. E. aerogenes is generally found in the human
gastrointestinal tract and does not generally cause disease in healthy
individuals. It has been found to live in various wastes, hygienic
chemicals, and soil. The bacterium also has some commercial
significance – the hydrogen gas produced during fermentation has
been experimented with using molasses as the substrate.
It may spoil maple sap and syrup.
E. coli is seen on the left and E. aerogenes on the right
Biochemical Characteristics of
Enterobacter Aerosinosa
TSI
Lactose
ONPG
Indole
Methyl red
VP
Citrate
Lysine
Motility
H2S (TSI)
Ornithine
Arginine
PDA
A/Ag
+
+
–
–
+
+
+
+
–
+
–
–