Mycobacterium, Enterics, Pseudomonas Flashcards
What are two major acid-fast organisms?
- Myocbacteria
- Nocardia
What is the one class of lipid that only acid-fast organisms have? What factors does it have that gives it virulence? (4)
Mycosides
- glycolipid - mycolic acid bound to a carb (clumps bacteria)
- Cord factor -increases TNF-alpha, contains immune system, toxic to luekocytes
- Sulfatides - allow bacteria to survive inside macrophage, prevent phagolysozome fusion
- capture iron - survival inside phagocyte
Ghon complex
- Lesion seen in the lung, caused by TB
- has a calcified tubercle of infection and lymph node
When you hear granulomas, you should think of what disease?
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
When might you get a false positive PPD Skin test? (PPD = purified protein derivative)
-if you’ve had BCG vaccine (bacillus calmette-guerin)
Most adult cases of tuberculosis occur after the bacteria have been dormant for some time. What type of TB is this called?
Reactivation or secondary tuberculosis
What is the most common site of reactivation tuberculosis?
Pulmonary
- occurs around clavicles (apically)
Big picture of Tuberculosis
- chronic disease
- slow weight loss, low-grade fever
- organ systems infected (lung, pleural/pericardial, lymph node, kidney, skeletal, joines, CNS, miliary TB
It is impossible to grow this bacterium on articial media; it is only grown on these guys
Mycobacterium leprae
-armadillos!
Clinically, leprosy is broken up into these two main subdivisions based on the level of cell-mediated immunity. Describe them
- 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
- 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)
What is the most common cause of Non-tuberculosis mycobacteria? (NTM)
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
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Of all the enterics, which one can ferment lactose? (and convert it into gas and acid)
E. Coli, Enterobacter cloacae, Serratia marcescens, and Klebsiella pneumoniae
Which important enterics do NOT ferment lactose?
Shigella, Salmonella, and Pseudomonas aeruginosa
Lactose fermenters develop a pink-purple coloration on this agar
MacConkey agar
What is the H antigen associated with? Which enterics have it?
H antigen makes up subunits of the bacterial flagella, so only motil bacteria will have it (i.e. salmonella)
Which enterics exhibit “No cell invasion?” Describe what this is.
- 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
Which enterics exhibit “invasion of the intestinal epithelial cells?” Explain this.
- 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
What are some examples of noscomial gram-negative enterics? (hospital acquistion)
- E. Coli
- Klebsiella, Serratia, Enterobacter cloacae
- Pseudomonas aeruginosa
What organism is the most common cause of duodenal ulcers? (and chornic gastritis)
Helicopbacter pylori
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)
Structural:
- capsule
- fimbria/pilli for mucosal adherence
Toxins:
- LPS endotoxin (lipid A portion)
- shiga-like toxin (EHEC)
- heat labile and heat stabile toxin (ETEC)
What is the #1 cause of gram (-) sepsis?
LPS endotoxin on outer cell membrane of E. coli
List the diseases caused by E. coli and list what’s specific to EHEC and ETEC
Commonalities:
- diarrhea
- neonatal meningitis
- urinary tract infection
- Sepsis
Enterohemorrhagic:
- bloody stool/diarrhea
- can cause hemolytic-uremic syndrome (HUS)
Enterotoxigenic:
-traveler’s diarrhea (watery)
What bacteria is the #1 cause of UTIs?
E. Coli
What are ETECs two toxins? What are their effects?
- 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
Which two bacteria’s toxins both inhibit the 60S ribosome?
Shigella toxin and Shiga-like toxin of Enterohemorrhagic E. Coli (EHEC)
Which two enteric bacteria are never consdiered part of the normal intestinal flora?
Shigella and Salmonella
What is the #1 cause of sepsis in a patient with sickle cell anemia?
Salmonella. Prone to bone infection because spleen isnt as strong clearing encapsulated bacteria
