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Gram Negatives I Flashcards

1
Q

What is an endotoxin?

A

Endotoxins are heat stable, LPS components of the outter membrane of Gram - bacteria. They are released into the host circulation following bacterial cell lysis.

LPS consists of O antigen which protrudes from the exterior cell surface and Lipid A which is integrated into the outter membrane.

Lipid A is responsible for the toxic effects of the endotoxin.

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2
Q

What are the physiologic effects of endotoxin?

A

Fever

SHock

Hypotension

Thrombosis

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3
Q

How does LPS interact with CD14 and Toll-like receptors?

A

LPS binds to lectin binding mannose protein. This complex binds to CD14.

TLR 2 and 4 then bind to CD14 and this in turn activates an intracellylar signalling cascade that ultimatley leads to the activation of NF kappa B, TNF alpha, and IL8.

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4
Q

What is TNF alpha responsible for?

A

Hypotension

Disseminated intravascular coagulation

Inflammation

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5
Q

What are the characteristics of Haemaphilus influenza?

A

Gram - rod

Encapsulated

Can be cultured on blood agar (Chocolate agar) placed in high CO2

Quelling test can identify capsule

Requires X factor (Hematin) and V factor (NAD+) for growth.

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6
Q

What is the clinical significance of H. influenzae?

A

Primarly causes severe pediatric disease:

Meningitis - Caused by B-type capsule and the complications include mental retardation, seizures, deafness, and death.

Acute epiglottitis

Septic arthritis

Sepisis

Pneumonia

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7
Q

What are the virulence factors for H. influenzae?

A

Capsule - Six types, a thru f and b is the most virulent. This is also anti-phagocytic.

Attachment pili

IgA protease - Degrades IgA antibody

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8
Q

What are the toxins released by H. influenzae?

A

Endotoxins - Cytolethal distending toxin (CDT) and Hemolysin

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9
Q

What other encapsulated Gram - rods cause meningitis, fever, headache, and stiff neck in children?

A

Meningococcus and pneumoccocus

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10
Q

What do non-encapsulated strains of H. influenzae cause?

A

Upper respiratory tract infections such as otitis media and sinusitis.

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11
Q

How is H. influenzae spread and what is its reservoir?

A

Humans are the reservoir and the bacteriam is spread via the inhalation route via droplets.

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12
Q

What is the Type B capsule of H. influenzae made of?

A

Polyribosyl phosphate

Type B capsules cause meningitis and sepsis

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13
Q

What are the symptoms for sinusitis and otitis media?

A

Pain in affected area, opacification of sinus, swelling and redness of tympanic membrane.

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14
Q

In adults with COPD, what infection can H. influenzae cause?

A

Pneumonia

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15
Q

How is H. influenzae treated?

A

Vaccination is the first line of defense

Cefotaxime and Rifampin

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16
Q

What is the H. influenzae vaccine made from?

A

Hib capsular polysaccharide (PRP) conjugated to protein

Has a 90% efficacy in protecting infacts from Hib

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17
Q

What are the charateristics of Bordetella pertussis?

A

Gram - rod / coccobacilli

Encapsulated

Humans are the reservoir

Transmitted via respiratory route

Does not invade boddy tissues; multiplies on mucus membranes

Toxins cause local tissue damage

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18
Q

How can B. pertussis be diagnosed?

A

Bordet-Gengou media - Made up of potatoes, blood & glycerol agar

ELISA

PCR

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19
Q

What are the virulence factors of B. pertussis?

A

Capsule

Beta-lactamase

Filamentous hemagglutinin rod - A pili for attachment

Exotoxins

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20
Q

What are the toxins of B. pertussis?

A

Exotoxins -

a) Pertussis toxin - Activates G proteins that increase cAMP
b) Tracheal cytotoxin (Heat-labile toxin) - Kills ciliated epithelial cells
c) adenylate cyclase toxin

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21
Q

What diseases of clinical significance are caused by B. pertussis?

A

Whopping cough (Paroxysmal cough)

Encephalopathy

Lymphocytosis

Bronchopneumonia (Infrequent)

22
Q

What is the pathogenesis of B. pertussis?

A

After colonization of the upper respiratory tract:

1) Fever and cough after 10 day incubation
2) Catarrhal stage - Fever, sneezing, anorexia (2 weeks)
3) Paroxysmal stage - Toxemic; characteristic inspiratory gasp (Whooping cough, lasts 2-4 weeks)
4) Convalescent stage - Lasts 3-4 weeks; pneumonia, seizures are common

23
Q

What is the treatment for B. pertussis?

A

Erythromycin

24
Q

How is B. pertussis prevented?

A

Acellular pertussis vaccine

25
What are the characteristics of Brucella (Brucellosis)?
Gram - Obligate aerobe No capsule Non-motile Can be detected by culture on blood, bone marrow, liver, or lymph nodes. Serologic testing and skin testing can also be used to diagnosed. Facultive intracellular parasite
26
How many species of Brucella are there?
Three; B. abortus - Cattle reservoir B. suis - Swine (Pigs) B. melitensis - Goats
27
What are the virulence factors for Brucella?
Capsule - LPS endotoxin Cell wall antigens - A and M antigens. B. abortus has a high concentration of A antigen and B. melintensis has a high concentration of M antigen. Non-motility Tropism for erythritol, a sugar found in animal placentas
28
What disease does Brucella species cause?
Brucellosis This is an undulating fever that peaks in the evening and returns to normal by the morning Symptoms are weakness, loss of appetite, CNS symptoms, and spontaneous abortion induction
29
How can Brucellosis be prevented?
Pasteurization of milk Treatment with doxycycline and one other drug (Gentamicin, streptomycin, or rifampin) Immunize cattle with an attenuated strain of Brucella abortus
30
What is the capsule used for in Brucella species?
The capsule is used to prevent phagocytosis. All phagocytes except for PMN's will phagocytize Bacteria will form granulomas in which intracellular growth is favored; 3 days to 3 months
31
What are the characteristics of *Francisella tularensis*?
Gram - rod Non-spore forming Has an antiphagocytic capsule Non-motile Obligate aerobe that requires cystine; also facultatively anaerobic Facultative intracellular parasite
32
How can *Francisella tularensis* be diagnosed?
Culture with systenin in blood agar media Skin test Measure IgG titer
33
What are virulence factors for *Francisella tularensis*?
LPS endotoxin Antiphagocytic cell wall components
34
What are the reservoirs for *Francisella tularensis*?
Rabbits and squirrels Ticks Infection results from direct contact with infected tissues through skin cuts/abrasions or the ingestion of undercooked meats
35
What are the symptoms of Tularemia?
The symptoms mimic plague Lymph node involvement Septicemia or pneumonia Typhoidal involvmenet of the GI tract
36
How can Tularemia be treated?
Streptomycin or Tetracycline Attenuated vaccine
37
What are the characteristics of *Yersinia pestis*?
Gram -pleomorphic rod Facultative anaerobe Facultative intracellular parasite Encapsulated Non-motile Can induce apoptosis in host cells
38
What is the reservoir of *Yersinia pestis*?
Wild rodents City rats Squirrels Prairie dogs Fleas
39
What are the two types of plague that Yersinia pestis responsible for?
Urban plague and Sylvanic plague
40
How is Yersinia pestis spread?
Flea bite Contact with infected tissue Inhaled aerosolized spray
41
What form of plague is present when the disease is endemic within a population?
Pneumonic plague
42
What are the three forms of plague?
Bubonic - Lymph nodes. High fever and conjunctivitis. Sepsis - Bacteria survive in macrophages and spread to blood and organs. Pneumonic plague - Most fatal if left untreated. Bacteria are spread from person-to-person.
43
What are the virulence factors of *Yersinia pestis*?
Fraction 1 - Capusle; antiphagocytic V and W proteins - Prevents intracellular destruction once phagocytocyzed; these antigens are only produced at 37oC Coagulase - Causes coagulation disturbances, shock, and death Pesticin - Kills other bacteria Intracellular murine toxin LPS Fibrinolysin - Breaks down clots
44
What type of secretion system does Yersinia pestis have?
Type III
45
What is the Type III secretion system?
In pathogenic bacteria, the needle-like structure is used as a sensory probe to detect the presence of [eukaryotic](http://en.wikipedia.org/wiki/Eukaryotic "Eukaryotic") [organisms](http://en.wikipedia.org/wiki/Organism "Organism") and [secrete](http://en.wikipedia.org/wiki/Secretion "Secretion") proteins that help the bacteria [infect](http://en.wikipedia.org/wiki/Infection "Infection") them.
46
What stains are used to diagnos *Yersinia pestis*?
Stain sputum or lymph node (bubo) aspirate Bipolar staining with Wayson's Stain (This is methylene blue and carbol fuchsin) Biopolar staining
47
How is Yersinia pestis treated?
Streptomycin and tetracycline Chloramphenicol is also used Control rodent population Insecticides for fleas Formalin-killed bacillus vaccine
48
What are the characteristics of *Pseudomonas aeruginosa*?
Gram - bacillus Encapsulated Motile; polar flagella Aerobic, opportunistic pathogen Non-lactose fermenter Oxidase positive
49
What are the virulence factors?
Exotoxin A - Inhibits protein synthesis by ADP ribosylating EF-2. Immunosuppressive and not good for burn victims. Structure is similar to diptheria toxin. Exoenzyme S & T - ADP-ribosylates G-proteins including p21 RAS and interferes with host cell growth Collagenase Elastase and Alkaline protease - Destroys elastin containing tissues Fibrinolysin Phospholipase C - Heat labile hemolysin. Breaks down lipids and lecithin and causes tissue destruction. Stimulates an inflammatory response. DNAse LPS - Inhibits antibiotic killing and suppresses neutrophil and lymphocyte activity Pyocyanin - Impairs cillary function, mediates tissue damage via the production of oxygen radicals Adherence proteins and pili Alginate slime layer - Protects from antibiotics, complement, and phagocytosis
50
What is the epidemiology of Pseudomonas aeruginosa?
Hospiatl as well as naturally acquired No seasonal incidence Can colonize respiratory and GI tract of hospitalized patients Minimal nutritional requirements and can tolerate broad temperatures Resistant to many antibiotics
51
What conditions of clinical significance can Pseudomonas aeruginosa cause?
Pulmonary infections Burn wound infections UTI's External otitis Eye infections and corneal ulcerations Endocarditis Ecthyma gangrenosum - Cutaneous manifestation of severe, invasive infection that is usually seen in immunocompromised, burn patients

Microbiology (16 decks)

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