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Microbiology > Gram Negatives I > Flashcards

Gram Negatives I Flashcards

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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
Q

What are the characteristics of Brucella (Brucellosis)?

A

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
Q

How many species of Brucella are there?

A

Three;

B. abortus - Cattle reservoir

B. suis - Swine (Pigs)

B. melitensis - Goats

27
Q

What are the virulence factors for Brucella?

A

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
Q

What disease does Brucella species cause?

A

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
Q

How can Brucellosis be prevented?

A

Pasteurization of milk

Treatment with doxycycline and one other drug (Gentamicin, streptomycin, or rifampin)

Immunize cattle with an attenuated strain of Brucella abortus

30
Q

What is the capsule used for in Brucella species?

A

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
Q

What are the characteristics of Francisella tularensis?

A

Gram - rod

Non-spore forming

Has an antiphagocytic capsule

Non-motile

Obligate aerobe that requires cystine; also facultatively anaerobic

Facultative intracellular parasite

32
Q

How can Francisella tularensis be diagnosed?

A

Culture with systenin in blood agar media

Skin test

Measure IgG titer

33
Q

What are virulence factors for Francisella tularensis?

A

LPS endotoxin

Antiphagocytic cell wall components

34
Q

What are the reservoirs for Francisella tularensis?

A

Rabbits and squirrels

Ticks

Infection results from direct contact with infected tissues through skin cuts/abrasions or the ingestion of undercooked meats

35
Q

What are the symptoms of Tularemia?

A

The symptoms mimic plague

Lymph node involvement

Septicemia or pneumonia

Typhoidal involvmenet of the GI tract

36
Q

How can Tularemia be treated?

A

Streptomycin or Tetracycline

Attenuated vaccine

37
Q

What are the characteristics of Yersinia pestis?

A

Gram -pleomorphic rod

Facultative anaerobe

Facultative intracellular parasite

Encapsulated

Non-motile

Can induce apoptosis in host cells

38
Q

What is the reservoir of Yersinia pestis?

A

Wild rodents

City rats

Squirrels

Prairie dogs

Fleas

39
Q

What are the two types of plague that Yersinia pestis responsible for?

A

Urban plague and Sylvanic plague

40
Q

How is Yersinia pestis spread?

A

Flea bite

Contact with infected tissue

Inhaled aerosolized spray

41
Q

What form of plague is present when the disease is endemic within a population?

A

Pneumonic plague

42
Q

What are the three forms of plague?

A

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
Q

What are the virulence factors of Yersinia pestis?

A

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
Q

What type of secretion system does Yersinia pestis have?

A

Type III

45
Q

What is the Type III secretion system?

A

In pathogenic bacteria, the needle-like structure is used as a sensory probe to detect the presence of eukaryotic organisms and secrete proteins that help the bacteria infect them.

46
Q

What stains are used to diagnos Yersinia pestis?

A

Stain sputum or lymph node (bubo) aspirate

Bipolar staining with Wayson’s Stain (This is methylene blue and carbol fuchsin)

Biopolar staining

47
Q

How is Yersinia pestis treated?

A

Streptomycin and tetracycline

Chloramphenicol is also used

Control rodent population

Insecticides for fleas

Formalin-killed bacillus vaccine

48
Q

What are the characteristics of Pseudomonas aeruginosa?

A

Gram - bacillus

Encapsulated

Motile; polar flagella

Aerobic, opportunistic pathogen

Non-lactose fermenter

Oxidase positive

49
Q

What are the virulence factors?

A

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
Q

What is the epidemiology of Pseudomonas aeruginosa?

A

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
Q

What conditions of clinical significance can Pseudomonas aeruginosa cause?

A

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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