Unit 3: Moraxella, Alcaligenes, Neisseria Flashcards
What does Moraxella bovis cause and in what species?
infectious bovine keratoconjunctivitis in cattle
What other bacteria is commonly associated with infectious bovine keratoconjunctivitis?
M. bovoculi
What does Moraxella bovis look like on gram stain?
gram negative short rods or cocci - found in pairs or short chains
What do colonies of Moraxella bovis look like?
1 mm colonies on BAP at 48 hours - they are hemolytic, flat, small, and tend to corrode the agar
In regards to oxygen, what type of organism is Moraxella bovis?
it is a strict aerobe
Is Moraxella bovis oxidase positive or negative?
positive
What does Moraxella bovis due to litmus milk?
it alkalinizes it
What is the function of fimbriae in Moraxella bovis infection?
to attach to the corneal epithelium
What toxins does Moraxella bovis release?
RTX toxin
What is the function of the RTX toxin of Moraxella bovis?
it lyses corneal epithelial cells, neutrophils, and RBCs
The neutrophils release their degradative enzymes onto the surface of the cornea and can cause extensive damage
What enzymes does Moraxella bovis release?
hyaluronidase, fibrinolysin, aminopeptidase, phosphoamidase, phosphatase
What is the functions of the enzymes that Moraxella bovis releases?
to break down the junctions between corneal epithelial cells and initiate an inflammatory response
What is the natural habitat of Moraxella bovis?
conjunctiva of cattle
When is infectious bovine keratoconjunctivitis common?
in summer and fall
What is infectious bovine keratoconjunctivitis associated with (environment)?
dust, UV light, face flies, and long, stemmy pastures
What is thought to initiate infectious bovine keratoconjunctivitis?
dubtle damage to the corneal epithelium that initiates the disease
What is the pathogenesis of infectious bovine keratoconjunctivitis?
Mycoplasma bovoculi infects the areas of subtle damage to create additional damage. Moraxella bovis takes over and creates a mild to severe inflammatory response. The cornea becomes opaque and may ulcerate, leading to blindness
During acute disease of infectious bovine keratoconjunctivitis what clinical signs are seen?
inappetence and poor weight gain
Do cattle get better immunity against Moraxella bovis when they recover from it?
no - they can just get reinfected with another fimbrial type
What is used to reduce the severity of a Moraxella bovis infection?
fimbrial bacterins
What treatments are useful for Moraxella bovis infection?
steroids, tylosin, long-acting tetracyclines, subconjunctival injections of penicillin and steroids, florfenicol, eye patches, various eye ointments, dyes, powders, and salt
NONE OF THESE ARE TECHNICALLY ALLOWED
What is Moraxella ovis typically isolated from?
pinkeye infections in sheep and cattle
What used to be the cause of pinkeye in humans but is isolated only rarely now?
Moraxella lacunata
What are some other species of Moraxella been recognized as the cause of?
oititis media in children and respiratory infections in adults
What does Alcaligenes look on gram stain?
they are gram negative rods
In regards oxygen, what type of organisms are Alcaligenes?
obligate aerobes
Is the genus Alcaligenes urease positive or negative?
negative
Is the genus Alcaligenes oxidase positive or negative?
positive
What is the natural habitat of the genus Alcaligenes?
water, soil, intestinal tract of vertebrates as a saprophyte
What clinical materials is the genus Alcaligenes typically isolated from?
blood, sputum, urine, ears, spinal fluid, wounds, IV solutions, and catheters
What are the two important species of the genus Neisseria?
Neisseria meningitidis and Neisseria gonorrhoeae
What is Neisseria meningitidis and Neisseria gonorrhoeae the cause of?
meningococcal meningitis (N. meningitidis) and gonorrhea in humans (N. gonorrhoeae)
What do Neisseria meningitidis and Neisseria gonorrhoeae look like on gram stain?
gram-negative cocci
What other Neisseria species is associated from bite wounds?
Neisseria canis
What do the major Neisseria species require for growth?
iron-containing media as well as starch, cholesterol, or albumin (to neutralize the effect fatty acids that inhibit growth of the organisms)
Are the major Neisseria species oxidase positive or negative?
positive
What is Neisseria meningitidis the cause of?
20% of the meningitis seen in humans
What is the natural habitat of Neisseria meningitidis?
the nasopharynx of a large percentage of humans
What serogroup of Neisseria meningitidis causes the majority of meningitis cases in the United States?
serogroup B
What is the role of IgA in the pathogenesis of Neisseria meningitidis?
IgAs that bind to N. meningitidis are very poor at opsonizing and fixing complement. IgA binding to these organisms blocks the adherence of specific opsonizing IgM and IgG. In the abscence of opsonization by IgM or IgG, these organisms are not readily killed by phagocytic cells. Disseminated disease has been linked to the presence of blocking IgA in the serum of affected patients
What does severe disease caused by Neisseria meningitidis look like?
fever, prostration, DIC, gram-negative shock, and a characteristic petechial eruption on the skin due to vascular thrombosis
What organism is responsible for the most common venereal disease in humans?
Neisseria gonorrhoeae
What are the three important virulence factors released by Neisseria gonorrhoeae?
lipooligosaccharide, peptidoglycan monomers, and IgA protease
What is the role of lipooligosaccharide that is released by Neisseria gonorrhoeae?
It damages host cells. It causes a loss of ciliary activity and sloughing of ciliated epithelium
What is the role of peptidoglycan monomers released by Neisseria gonorrhoeae?
these damage ciliated epithelial cells, activate complement, and modulate mononuclear cell proliferation
What is the pathogenesis of Neisseria gonorrhoeae?
Colonization occurs on the mucosal surfaces line with columnar epithelial cells. Initial attachment is via fimbriae and subsequently solidified by outer membrane proteins. Invasion and intracellular residence occurs in the mucosae of the cervix or urethra and the organism is transcytosed to the basal surface of these cells
