Mycobacterium, Enterics, Pseudomonas

Question 1

What are two major acid-fast organisms?

Answer 1

1. Myocbacteria
2. Nocardia

Question 2

What is the one class of lipid that only acid-fast organisms have? What factors does it have that gives it virulence? (4)

Answer 2

Mycosides

1. glycolipid - mycolic acid bound to a carb (clumps bacteria)
2. Cord factor -increases TNF-alpha, contains immune system, toxic to luekocytes
3. Sulfatides - allow bacteria to survive inside macrophage, prevent phagolysozome fusion
4. capture iron - survival inside phagocyte

Question 3

Ghon complex

Answer 3

• Lesion seen in the lung, caused by TB
• has a calcified tubercle of infection and lymph node

Question 4

When you hear granulomas, you should think of what disease?

Answer 4

Mycobacterium Tuberculosis

• macrophages destroy the bacteria in the lung, causing necrosis of lung tissue
• caseous necrosis = granular creamy cheese
• surrounded by macrophages, multinucleated giant cells, fibroblasts, collagen deposits, calcification
• granuloma of the bacteria

Question 5

When might you get a false positive PPD Skin test? (PPD = purified protein derivative)

Answer 5

-if you’ve had BCG vaccine (bacillus calmette-guerin)

Question 6

Most adult cases of tuberculosis occur after the bacteria have been dormant for some time. What type of TB is this called?

Answer 6

Reactivation or secondary tuberculosis

Question 7

What is the most common site of reactivation tuberculosis?

Answer 7

Pulmonary

• occurs around clavicles (apically)

Question 8

Big picture of Tuberculosis

Answer 8

• chronic disease
• slow weight loss, low-grade fever
• organ systems infected (lung, pleural/pericardial, lymph node, kidney, skeletal, joines, CNS, miliary TB

Question 9

It is impossible to grow this bacterium on articial media; it is only grown on these guys

Answer 9

Mycobacterium leprae

-armadillos!

Question 10

Clinically, leprosy is broken up into these two main subdivisions based on the level of cell-mediated immunity. Describe them

Answer 10

1. Lepromatous leprosy

• Failure of Th1 response, need Th 2 (helper cells) ==>adaptive immnune response
• raised skin lesions all over body (extensor surfaces)
• lionine facies (face thickens, looks like lion)
• saddlenose deformity
• symmetric glove and stocking neuropathy

2. Tuberculoid leprosy

• can mount a cell-mediated defense against bacteria (Th1)
• milder disease, fewer skin damages
• strongly positive Lepromin skin test (good cell mediated response)

Question 11

What is the most common cause of Non-tuberculosis mycobacteria? (NTM)

Answer 11

Mycobacerium avium-complex (MAC)

Presents in two ways:

1. upper cavitary disease (in male smokers)

2. lower + middle lung involement with bronchiectasis and nodular infiltrates in middle aged non smoking women

-common in AIDS patients: disseminated infection with fever, weight loss, hepatitis, and diarrhea

-lymmphadenitis, common in children

-

Question 12

Of all the enterics, which one can ferment lactose? (and convert it into gas and acid)

Answer 12

E. Coli, Enterobacter cloacae, Serratia marcescens, and Klebsiella pneumoniae

Question 13

Which important enterics do NOT ferment lactose?

Answer 13

Shigella, Salmonella, and Pseudomonas aeruginosa

Question 14

Lactose fermenters develop a pink-purple coloration on this agar

Answer 14

MacConkey agar

Question 15

What is the H antigen associated with? Which enterics have it?

Answer 15

H antigen makes up subunits of the bacterial flagella, so only motil bacteria will have it (i.e. salmonella)

Question 16

Which enterics exhibit “No cell invasion?” Describe what this is.

Answer 16

• bacteria bind to intestinal epithelial cells, but do NOT enter the cell
• released exotoxins (enterotoxins) cause the watery diarrhea –> fluid + electrolyte loss
• Ex. E. coli and Vibrio cholera

Question 17

Which enterics exhibit “invasion of the intestinal epithelial cells?” Explain this.

Answer 17

• bacteria’s virulence factors allow them to bind and invade cell
• release toxins to detroy the cells
• results in systemic immune response with bloody stool and fever
• Ex. Enteroinvasive E. coli (Enterotoxigenic= ETEC), Shigella, and Campylobacteri jejuni

Question 18

What are some examples of noscomial gram-negative enterics? (hospital acquistion)

Answer 18

1. E. Coli
2. Klebsiella, Serratia, Enterobacter cloacae
3. Pseudomonas aeruginosa

Question 19

What organism is the most common cause of duodenal ulcers? (and chornic gastritis)

Answer 19

Helicopbacter pylori

Question 20

E. coli normally resides in the colon without causing disease. However, when it acquires virulence, it can cause disease. What are some of its virulence factors? (5)

Answer 20

Structural:

1. capsule
2. fimbria/pilli for mucosal adherence

Toxins:

3. LPS endotoxin (lipid A portion)
4. shiga-like toxin (EHEC)
5. heat labile and heat stabile toxin (ETEC)

Question 21

What is the #1 cause of gram (-) sepsis?

Answer 21

LPS endotoxin on outer cell membrane of E. coli

Question 22

List the diseases caused by E. coli and list what’s specific to EHEC and ETEC

Answer 22

Commonalities:

1. diarrhea
2. neonatal meningitis
3. urinary tract infection
4. Sepsis

Enterohemorrhagic:

• bloody stool/diarrhea
• can cause hemolytic-uremic syndrome (HUS)

Enterotoxigenic:

-traveler’s diarrhea (watery)

Question 23

What bacteria is the #1 cause of UTIs?

Answer 23

E. Coli

Question 24

What are ETECs two toxins? What are their effects?

Answer 24

• Heat labile toxin (increases cAMP)
• Heat stabile toxin (increases cGMP)
• inhibits Na and Cl reabsorption and stimulates their secretion
• leads to electrolyte and fluid loss
• watery diarrhea, similar to cholera’s rice water diarrhea

Question 25

Which two bacteria’s toxins both inhibit the 60S ribosome?

Answer 25

Shigella toxin and Shiga-like toxin of Enterohemorrhagic E. Coli (EHEC)

Question 26

Which two enteric bacteria are never consdiered part of the normal intestinal flora?

Answer 26

Shigella and Salmonella

Question 27

What is the #1 cause of sepsis in a patient with sickle cell anemia?

Answer 27

Salmonella. Prone to bone infection because spleen isnt as strong clearing encapsulated bacteria