Common Bacterial Pathogens 2 Flashcards
Name the most common gram + rods
Clostridium
Clostridium are:
- aerobic or anaerobic? - spore or non-spore?
Strict anaerobes
Spore formers
Why do we worry about C. difficile?
- Because its hospital-acquired (nosocomial) infection!
- diarrhea
- Pseudomembranous colitis - Because it is relatively resistant to most common antibiotics
- Spores not killed by alcohol-based hand sanitizers
T/F: C. difficile is caused by antibiotic treatment
True
Believed to result from depletion of the intestinal flora by antibiotic treatment, and resulting overgrowth of C. difficile from own patient or hospital staff/others
Again, what are the signs of a C. diff case? What would you do? (include medications)
A patient will go to hospital > get treated with antibiotics > get worse > do a culture and C.diff toxin ELISA > treat with metronidazole or ORAL vancomycin > gets better > four days later you get positive C. diff culture > take meds for two weeks to limit recurrence
How does Clostridium tetani cause spastic paralysis?
i.e. where does it come from, what/how does it target
Spores from soil and animals >
Local anaerobic infection and toxin production >
Retrograde transport of toxin to CNS >
Blocks inhibitory interneurons in CNS
T/F: C. botulinum grows spores inside the host
False
The spores grow in contaminated food under anaerobic conditions (ie: home canned foods) and is ingested
How is C. botulinum different from C. tetani?
Botulinum toxin blocks acetylcholine transmission at neuro-muscular junctions; results in “flacid paralysis”
Both can cause respiratory failure
Compare/ contrast food infections from Staph, Labile toxin, C. botulinum
Staph + Botulism: eating preformed toxin
Labile toxin: e. coli (like while in mexico)
-ingesting organisms that adhere and grow
What are microbio characteristics of C. perfringens? (shape, gram appearance, etc.)
- Endospore-forming
- obligate anaerobes
- Gram (+) bacilli (rods) **like all Clostridium
What kind of wound causes C. perfringens and explain pathophysiology
Wound infections: crushing type injuries → compromised blood flow→ low O2 environment → devitalized tissue → anaerobic perfringens growth
What are the types of wound infections in C. perfringens and what is the major toxin used?
-Ranges from cellulitis, to fasciitis, to myonecrosis (gas gangrene
=Alpha toxin: Kills phagocytic cells and muscle tissue
How can C. perfringens also cause Clostridial food poisoning?
Enterotoxin: disrupts tight junctions between endothelial cells in ilium → dysregulation of fluid transport
Name the two gram negative rods
E. Coli
Pseudomonas aeruginosa
What is ETEC?
Enterotoxigenic E. coli : traveler’s diarrhea
- Typically from contaminated food and water
- Also uses enterotoxin (remember which other one does..? —— C dif)
What urinary problems can E. coli cause?
UTI
-isolates from GI tract access the UT via urethra > bladder > kidney
-“Special” strains getting into the “wrong” place
Adhere to bladder epithelium, are hemolytic to RBCs
Similar to UTI’s, what other infections can E. coli cause?
Abdominal infections
-Release/escape of contents of colon to peritoneal cavity and adjacent tissues, e.g., Surgical wounds, traumatic wounds, etc
What traumatic injury would uniquely cause Pseudomonas aeruginosa infections?
BURNS! If there was a fire in the Louvre, you would need to make a Pseudo “mona lisa” or psuedomona
P. Aeruginosa can also be caused by traumatic injuries, surgical wounds
Let’s review, do you remember what gram stain/ shape are P. aeruginosa?
Gram (-) rods
*just like E. coli
What CHRONIC injury (disease) would uniquely cause P. aeruginosa infections?
Cystic Fibrosis (nearly all C.F patients between 15-20)
Lung infection: produce copious, viscous bronchial secretions → stasis in the lungs (predisposes the patient to infection) → Within the lungs, bacteria produces mucoid exopolysaccharide → protected from phagocytosis → produces toxins → progressive damage to the lungs due to the action of the toxins and the host immune response → death
So again, why is P. aeruginosa considered an opportunistic pathogen?
- Infections of traumatic injuries, surgical wounds, and especially BURNS
- Chronic lung infection of patients with Cystic fibrosis
- Hospital-acquired infections (UTIs, pneumonia, less frequently associated with intravascular catheter-related infections)
What is a gram (-) diplococci bacteria?
Neisseria gonorrhea
We know gonorrhea comes from sex, why else is it a concern?
Infected mothers can cause conjunctivitis and blindness in baby
So S. aureus has its super toxins, Group A strep has its M protein, and S. Pneumoniae has its antiphag capsule,
…. what does gonorrhea have?
PILI => adherence, interfers with neutrophil killing
-could keep getting it with different strains of pili
…Growth on mucosal surface incites robust inflammatory response, purulent discharge and local tissue invasion. Prolonged infection may lead to scarring and fibrosis
Do men or women usually have more symptoms with gonorrhea?
Men
-Males range from asymptomatic to urethritis.
-Females: More often asymptomatic than in males.
But can get infection of cervix, urethra, ascending infection including uterine tubes may result in fibrosis and infertility
Where are most anaerobic bacteria (besides clostridia) found in the body? and explain the typical infections?
Most anaerobic diseases are from normal flora from anaerobic nitches ie. Colon, Mouth (e.g., gums, tongue), Female genital tract and Skin
- Usually from bacteria getting into wrong place
- abscess is typical
- mixed infections: aerobic eat air so anaerobes can join party
You culture an anaerobic abscess from below the diaphragm, what is it?
Bacteroides fragilis
Although normally only 1-2% of normal gut flora, associated with more than 80% of intra-abdominal infections
What makes Bacteroides fragilis pack a punch? (give it virulence and make it not so “fragile”)
Tissue-destructive enzymes
Capsule
Superoxide dismutase
What’s the only obligate intracellular bacteria? (acts like virus)
Chlamydia trachomatis
Chlamydia is often seen with Gonorrhea, what are similar/ different concerns that you have with this infection? (besides sex)
Neonatal infections
-Infants born to mothers with C. trachomatis genital infection may become infected at birth→ neonatal conjunctivitis and neonatal pneumonia.
Different: Trachoma
=chronic infection of conjunctiva → scarring and blindness
Chlamydia exists as two stages, 1) what do you call the infectious particles? 2) what do you call the intracytoplasmic reproductive forms?
1) elementary bodies
2) reticulate bodies
What are the atypical bacteria without walls? Why is that unique?
Mycoplasma pneumoniae
-lack a rigid cell wall → shape is highly pleomorphic and penicillins are not effective
T/F: Mycoplasma pneumoniae causes pneumonia?
True
- Produces a common form of pneumonia (10%). “atypical pneumonia”
- Predilection for younger persons (5-20 yo)
T/F: M. pneumonia isn’t very infectious
False
- Occurs in any season, with outbreaks commonly occurring in families and closed communities.
- Long period of shedding and very low infectious dose
- Attack rate in families ~60% of susceptible individuals
T/F: M. pneumonia requires hospitalization?
What are symptoms?
False
- Disease generally mild (“Walking” pneumonia).
- Hospitalization is only very rarely required
- fever, headache, malaise for 2-4 days, followed by respiratory symptoms non-productive cough, chest and body aches, fatigue.
- Resolution and recovery occurs slowly over 1-4 weeks
T/F: M. pneumonia lab confirmation is through a gram stain
False
- culture doesn’t grow well
- Gram stain used primarily to rule-out other bacterial causes
- Laboratory diagnosis is often by serological tests
Where in your lungs does M. pneumonia infect?
Interstitium: the tissue around the air sacs of the lungs
-Alveoli are clear (hence, non-productive cough)
Mechanism: adheres to respiratory epithelial cells. Remains extracellular. Bacteria produce hydrogen peroxide and superoxide radicals, which damage host tissue.
