7,789views
00:00 / 00:00
de completadas
2024
2023
2022
2021
lactose fermentation p. 142
nosocomial infection p. 182
taxonomy p. 122
Enterobacter is a genus of Gram-negative rod-shaped bacteria which belongs to a family of bacteria called the Enterobacteriaceae.
There are several species which cause infection in humans and the most important are Enterobacter cloacae and Enterobacter aerogenes.
It’s an opportunistic pathogen, which can be normally found in the intestinal flora and causes a wide variety of hospital-acquired infections, mainly respiratory and urinary infections.
Now, a little bit of microbe anatomy and physiology. First, Enterobacter has a thin peptidoglycan layer, so it doesn’t retain the crystal violet dye during Gram staining.
Instead, like any other Gram-negative bacteria, it stains pink with safranin dye.
And since it’s a Gram-negative bacillus, it looks like a little pink rod under the microscope.
Enterobacter is motile, non-spore forming, facultative anaerobic which means it can survive in both aerobic and anaerobic environments and oxidase negative which means it doesn’t produce an enzyme called oxidase.
Alright, now Enterobacter is urease positive which means it can produce an enzyme called urease that dissociates urea into carbon dioxide and ammonia.
This can be tested by transferring a pure sample of bacteria from the culture to a sterile tube containing a mixture of “urea agar” broth and phenol red. Then, the mixture is incubated.
So, with Enterobacter, urease makes urea dissociate into carbon dioxide and ammonia.
Ammonia then makes the mixture change color from orange-yellow to bright pink.
Finally, Enterobacter grows well on MacConkey agar which is a medium that contains a pH sensitive dye and lactose.
This medium helps identify whether Gram-negative bacteria are lactose fermenters or not.
Some Enterobacteriaceae, like Enterobacter, Klebsiella and Escherichia coli, can ferment lactose, which results in the production of acid, that makes the pH sensitive dye turn pink - so their colonies will be pink, while others, like Salmonella and Shigella, can’t ferment lactose so their colonies will be colorless.
Now, Enterobacter has very few notable virulence factors such as fimbriae, which help it attach to host cells, and they secrete hemolysins, which cause formation of tiny holes in the cell membrane, leading to cell damage.
So, an infection with Enterobacter can be acquired in two ways - endogenous and exogenous.
Enterobacter is a Gram-negative bacillus, facultative anaerobic, oxidase negative, and lactose fermenting bacteria that's known to cause nosocomial infections affecting the urinary tract, lungs, and other parts of the body. It's usually treated with antibiotics. It's diagnosed bia bacteria culture, of the blood, urine, or sputum, and treated with antibiotics.
Copyright © 2024 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.