Gram negative cocci Flashcards
What are the 3 infectious genus of Gram Negative cocci?
Neisseria
Moraexlla
Veillonellae
How are the Gram negative further subcategoriezed and what test are used?
Divided into Aerobic or Anaerobic by Oxidase test
Aerobic gram negative cocci: Neisseria or Moraxella
-Neisseria gonorrhoeae (aka gonococcus)
-Neisseria meningitidis (aka meningococcus)
-Moraxella catarrhalis
Anaerobic gram negative cocci: Veillonellae genus
oxidase test: smear some bacteria onto a paper strip with the cytochrome c like reagent onto it, and if the bacteria possesses a cytochrome c oxidase and can therefore perform oxidative electron transport (aerobic metabolism), the strip turns blue
Neisseria gonorrhoeae and Neisseria meningitidis
morphology
culture
biochemical ID tests
Both are gram negative, bean shaped diplococci - the concave edges facing eachother like the two are facing one another.
Culture: Demanding, sensitive bugs
riquires nutrient rich medium, chocolate agar and 5-10% CO2
They are sensitive to dessication, heat, disinfectants, and antibiotics.
Oxidase positive - means they both expresses cytochrome oxidase, and can generate a blue colored product it oxidizes the test substrate
Both have long Pili aka Fimbriae for cell attachment.
N. meningitidis produces acid (color change) from glucose (d-glucose aka dextrose) and maltose. Meningitids = Maltose
N. gonorrhoeae produces acid only from glucose and not maltose
BOTH are Lactose Negative
How are N gonorrhoeae and N meningitidis differentiated from other Neisseria (sicca sublfava flavescens the apathogenic species)?
Other Neisseria species (gram negative aerobic diplococci)
1) can be grown on simple agar
2) produce pigment
3) Produce acid from Lactose
4) can grow optimally at 22-37C instead of just 37C like gonorrhoeae and meningitidis.
What is the habitat of meningococcus?
Reservoir and transmission?
Humans are the only carriers
about 5% carriest it symptomless in the nasopharynx.
Others are actively sick.
Transmitted by respiratory droplet or direct contact of infected tissue.
Virulence factors of meningococcus (5)
The capsule (12 serotypes) - it may change expression of its capsule type.
Pili/Fimbriae - mediate cell attachment
IgA proteases
Outer Membrane Proteins
LOS proteins- LipoOligoSaccharides, envelope proteins. mimicry sialysation: serum resistance. These LOS envelope proteins are highly produced and bleb off in the blood exotoxins, causing a massive immune response.
LPS endotoxin
What diseases are caused by Neisseria meningitidis?
How is it diagnosed?
Diseases:
Pharyngitis
Purulent Meningitis, meningitis epidemica - Fever, headache, vomiting, confusion, delirium, convulsions, arched back spasms. May also result in Brain Hemorrhage.
Petechial and Pupural rashes on the skin, cornea, and mucous membranes.
Meningococcal septicemia, causes further problems ->
-Waterhouse-Friderichsen-syndrome** - acute adrenocortical insufficiency, **due to acute hemorrhage of the adrenal glands caused by the b acterial septicemia, exact mechanism/cause is unknown. Acute cortisol insufficiency is life threatening. Involves
-DIC (diffuse intravascular coagulation)
-Gangrene, caused by the loss of circulation due to DIC.
Diagnosis:
CSF sample, lumbar puncture
blood culture
biopsy of the petechiae or pupurae
nasopharyngeal swab to test for asymptomatic carriers during an outbreak.
Gram negative diplococci in the CSF, blood, and intracellularly in the meninges.
Glucose and Maltose acid tests are positive.
Lactose and Sucrose acid tests are negative.
Confirmed by Latex-agglutination of qPCR for bacteria DNA from blood or CSF.
How is meningococcus meningitis treated?
Prevented?
What is the meningitis belt?
Treatment:
High dose penicillin G for sepsis. Meningococcus is NOT a beta-lactamase producer.
Ceftriaxone for meningitis, because this passes the BBB
High dose corticosteroids and fluids given to counteract Waterhouse-Friederichsen syndrome
Prevention:
Active immunization by vaccine containing several meningococcal serotype polysaccharides
There is no vaccination against meningococcus B, therefore one must use Prophylactic Rifampin if in a high risk situation.
The meningitis belt: A geographic belt region of Subsaharan Africa, where the hot, dry climate with lots of dust causes nasal mucosa damage, and there is high incidence of Meningococcus infections.
Neisseria gonorrhoeae
Virulence factors (8)
Pili/Fimbriae
POR, OPA, and RMP proteins - variable expression of these genes causes antigen variation
Transferrin-binding proteins
Lactoferrin-binding proteins
Hemoglobin-binding proteins
LOS- lipooligosaccharide, an endotoxin, mimicry?
Cell-wall peptidoglycan endotoxin
IgA protease
Nisseria gonorrhea
Reservoir
Transmission
Diagnosis
Only found in humans,
Sexually transmitted
Neisseria gonorrhoeae
Clinical diseases
Diagnosis
Males: Pus filled urethral discharge and painful urination. Prostatitis.
Females: May be asymptomatic or may have purulent cervical discharge. Endometritis, Salpingitis
Infants: Ophthalmoblenorrhea neonatorum. If an infant gets its eye infected from the mother during birth, it causes this pus forming eye infection, with perforating corenal ulcers.
Stupid name for pus discharge: blenorrhea
“Alternative gential” infections
Anorectal infection
Pharyngitis
In severe dessiminated cases of both sexes:
fever, rashes,
tendosynovitis, arthritis,
sepsis,
meningitis
Diagnosis:
Testing a clinical specimen: the urethral/cervical discharge
Blood culture
Synovial fluid sample
CSF sample in meningitis
Will acidify medium from only glucose (dextrose), and not from lactose, maltose, or sucrose.
transparent, nonpigmented colonies, non-hemolytic. gram negative, catalase positive, oxidase positive.
Methylene blue stain: kidney bean shaped diplococci, 0.8 uM. Bacteria found bound to or intracellularly in PMN cells and lymphocytes in the acute stage.
Special culture: grows in Thayer martin medium after 24 hours incubation at 10% CO2.
Confirmation by direct labeling with FITC-labeled anti-gonococcus antibodies on a direct sample smear.
In chronic cases, can test patients sera for specific circulating antibodies, by complement fixation test. or by ELISA
qPCR measurement of patient samples.
Prevention of gonoccous infections
Post gonoccocal immunity
Physical barriers, condoms.
AgNO3, Oculogutta Crede
There are no vaccines or medical preventions
There is NO acquired immunity after an infection, due to antigenic variations of N gonorrheae infections, a person can be infected many times.
How is gonococcus treated?
antibiogram is essential
20% are penicillin resistant
Macrolide and Tetracycline resistant strains exist
Floroquinolone strains exist as well
Normal treatment:
Penicillin, and probenecid as a single dose, given a second dose if necessary
If penicillin allergy Macrolides or tetracycline
In life threatening infections 3rd generation Cephalosporin Ceftriaxone
What are the characteristics of the other Neisseria species (not gonococcus or meningococcus)
They are normal flora of the respiratory tract
Can rarely be opportunistic pathogens causing conjunctivitis
They grow on simple Agar, and the colonies are pigmented (gonococcus and meningococcus are not)
