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Bacterial structure and functions
Bacillus anthracis (Anthrax)
Bacillus cereus (Food poisoning)
Corynebacterium diphtheriae (Diphtheria)
Clostridium botulinum (Botulism)
Clostridium difficile (Pseudomembranous colitis)
Clostridium tetani (Tetanus)
Streptococcus agalactiae (Group B Strep)
Streptococcus pyogenes (Group A Strep)
Bartonella henselae (Cat-scratch disease and Bacillary angiomatosis)
Legionella pneumophila (Legionnaires disease and Pontiac fever)
Salmonella typhi (typhoid fever)
Yersinia pestis (Plague)
Vibrio cholerae (Cholera)
Bordetella pertussis (Whooping cough)
Francisella tularensis (Tularemia)
Haemophilus ducreyi (Chancroid)
Mycobacterium tuberculosis (Tuberculosis)
Mycobacterium avium complex (NORD)
Gardnerella vaginalis (Bacterial vaginosis)
Coxiella burnetii (Q fever)
Ehrlichia and Anaplasma
Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species
Borrelia burgdorferi (Lyme disease)
Borrelia species (Relapsing fever)
Treponema pallidum (Syphilis)
0 / 1 complete
0 / 2 complete
Enterococci p. 135
enterococci p. 135
penicillins for p. 185
vancomycin p. 187
vancomycin-resistant (VRE) p. 135
Gram-positive algorithm p. 132
UTIs p. 179
enterococci as cause p. 135
With Enterococcus, entero- refers to the intestines, while -coccus means round shape.
So Enterococcus is a genus of round bacteria that commonly colonizes the gut of humans and animals.
Enterococcus is also called Group D streptococcus in Lancefield classification developed by an American microbiologist Rebecca Lancefield.
There are two species that can cause infections in humans and these are Enterococcus faecalis, amounting for the majority of infections, and Enterococcus faecium, which causes disease more rarely.
Now, looking at an individual bacterium, Enterococcus has a thick peptidoglycan cell wall, which takes in purple dye when Gram stained - so this is a gram-positive bacteria.
When there’s more of them, Enterococci grow in short chains, usually in pairs.
They’re non-spore forming, facultative anaerobes, meaning that they can survive in both aerobic and anaerobic environments and catalase negative, which means they don’t produce an enzyme called catalase.
Enterococci also can tolerate extreme environmental conditions including high sodium chloride concentrations, high pH and even high temperatures.
They can survive at 60 degrees Celsius for up to 30 minutes!
Ok, now, enterococcus is pyrrolidonyl arylamidase positive, because it makes an enzyme called L-pyrrolidonyl arylamidase.
To test for this, a small sample is taken from a suspected bacterial colony, and then inoculated to a disk pad that’s embedded with pyrrolidonyl beta naphthylamide - another joy of a word.
With Enterococcus, pyrrolidonyl arylamidase hydrolyzes pyrrolidonyl beta-naphthylamide to produce beta-naphthylamide.
Try saying that 3 times fast! Finally, another reagent called N-methylamino-cinnamaldehyde is added to the disk, and it reacts with beta-naphthylamide, resulting in a bright red color that confirms Enterococcus is pyrrolidonyl arylamidase positive.
Now, most commonly, Enterococci are gamma hemolytic which means that when cultivated on blood agar they don’t induce hemolysis, so the agar under and around the colony remains unchanged.
But sometimes, they can induce alpha hemolysis, also called partial hemolysis, which means that the agar under the colony turns dark and greenish.
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