Bacteriology Flashcards
Strep A: strep pyogenes
G+, catalase -, bacitracin sensitive, strep throat, impetigo, M protein helps it evade phagocytosis, beta-hemolytic
Strep B: strep agalactiae
GI&GU (UTI during pregnancy), Bacterial meningitis (neonatal), Beta-hemolytic, Calatase -, Bacitracin resistant
Staph aureus
Superficial lesions, pneumonia, food poisoning, fast bacterial diarrhea, Catalase +, Coagulase +, post-viral pneumonia (#1), VZV superinfection
Streptococus pneumoniae
“Pneumococcal”, optochin sensitive, otitis media, rusty sputum, bacterial meningitis, #1 cause of URI in adults
Haemophilus influenzae
2 cause of URI, bacterial meningitis, buccal cellulitis, exacerbation of chronic bronchitis
Bacterial meningitis, young children
H. Influenzae (vaccine), Non-polio Enterococcus
Which GI bacteria release preformed toxins?
Staph aureus, B. cereus
Which GI bacteria produce toxins in vivo?
C. perfringens, V. cholerae, EHEC, ETEC, C. difficile, and B. cereus
Which GI bacteria invade tissue?
C. jejuni, Salmonella, Shigella, EIEC
What organisms cause bloody/mucoid diarrhea (inflammatory, aka dysentery)?
C. jejnui (think undercooked poultry), Shigella, Salmonella S. typhi, Entamoeba histolytica
What organisms would cause abrupt, watery, secretory diarrhea?
S. aureus and Bacillus cereus
What organisms cause watery, secretory diarrhea 8-16 hrs after exposure?
Clostridium perfringens (think meat, poultry dishes)
What organisms cause watery, secretor ydiarrhea 48 h later?
E. coli (ETEC) and V. cholera
Diarrhea & water parks
Cryptosporidium parvum
Diarrhea & pet turtles, dairy products
Salmonella enteritidis
Very sever diarrhea in patient with AIDS
cryptosporidium parvum
Non-inflammatory diarrhea with nausea and vomiting.
S. aureus
Fatty diarrhea
Giardia lamblia (smiley face)
What organisms would lead to inflammatory diarrhea?
C. jejuni, Salmonella typhi, Shigella, EHEC, EIEC, EPEC, Entamoeba histolytica
What two organisms are the most common transmitters of y. pestis?
[Y. pestis = plague] Humans and fleas
Who is most likely to have a strep pneumonia infection? 15 mo. baby, 24 y.o. girl, or 55 y.o. male?
Babies and old people: biphasic prevalence
What organism causes syphilis and what is the name of the special lesion associated with it? What do you treat syphilis with?
Treponema pallidum. Condylomata lata. Penicillin G.
What organism causes Lyme disease? What do you treat it with?
Borrelia burgdorferi, treat with doxycycline
What bacteria are beta-hemolytic? gamma-hemolytic? alpha-hemolytic?
Strep A and B are beta-hemolytic. Enterococcus is gamma-hemolytic. Strep pneumonia is alpha-hemolytic.
What should you think about if you see a TB patient with negative PPD?
Immuno-compromised! HIV
What bacteria causes hemolytic uremic syndrome?
EHEC
How would you describe the toxin produced by V. cholera?
Has A and B subunits
You suspect a chancre, so you do what test…?
…Darkfield microscopy to look for a spirochete.
How do you run a serologic test for syphilis?
Assay for anti-cardiolipin antibodies since T pallidum has lots of cardiolipin in its membrane.
What process involves a sex pilus and transfer of plasmids?
Conjugation. (Transformation when it takes up DNA from dead bacteria, Transduction from phages)
With a latent TB infection, would a patient be contagious? Have positive PPD? Need to be treated? Have a primary TB infection?
With a LTBI, patients are not contagious, have +PPD, show no evidence of active tb on chest xray. They should be treated.
What are the two major non-infectious sequelae of Strep A infrection?
Rheumatic fever and acute glomerulonephritis.
What would cause high fever, malaise, headache, confusion, and nausea in three-day cycles as well as thrombocytopenia, tachycardia, splenomegaly, hemoglobinuria, and anemia?
Plasmodium falciparum
What form of plasmodium falciparum is most often transmitted during biting?
Sporozite. (Sporozites mature into merozites, infest RBCs and go to ring stage then trophozoite.
WHat are the major G- cocci we covered?
Neisseriae meningitidis and Neisseriae gonorrhoeae
What are the major G+ cocci we covered?
Strep (Group A, B, and Pneumo), Staph (aureus and epidermis), and Enterococcus
What are the major G+ rods we covered?
C. difficile, B. cereus, Listeria, and Clostridia perfringens
A 25 y.o. man has non-bloody urethral discharge. G stain reveals numerous neutrophils but no bacteria. What’s the most likely culprit?
Chlamydia trachomatis.
A patient presenting with diffuse, erythematous rash, fever, low blood pressure, and a sterile blood culture might have which of the following? What are the two major causes of this?
Toxic shock syndrome, most often caused by Strep A or Staph aureus
Because vancomycin is a large molecule that cannot penetrate a membrane to access its D-ala-D-ala target on the cell wall, you would NOT consider it for which of the following agents? Enterococcus faecium, Chlamydia trachomatis, Staph aureus, Strep pneumoniae.
Chlamydia trachomatis, since al lthe other organisms are G+. Not oly is C. trachomatis a G-, it is also an intracellular pathogen. Vancomycin is not effective against gram negatives, let alone gram negatives that reside within cells.
What is the most likely body site on which to find Staph aureus?
Nose!
Your patient is a 27 year old woman who was treated with oral ampicillin for Streptococcus pyogenes cellulitis. She now has bloody diarrhea, and you suspect pseudomembranous colitis. The causative organism:
A. Is an anaerobic gram-positive rod that produces exotoxins
B. It is a comma-shaped gram negative rod that grows best at 41°C
A.) C. dificile.
B.) describes camplybacter and Vibrio cholera
How does staph become methicillin resistant?
It expresses mecA gene and makes a different penicillin binding protein.
What is caseous necrosis?
Granulomatous inflammation with central necrosis.
What does acute inflammation look like?
Cells filled with segmented nuclei (neutrophils!)
What does chronic inflammation look like?
Distention with mononuclear cells, common for viral pneumonia where the inflammatory cells are monocytes.
What would cause bloody diarrhea following a course of antibiotics? Stool culture negative.
C. difficile. Remember it’s not cultured. Rather, you detect the toxin (TcdA) in stool.
Bloody diarrhea and fever 3 days after the summer reunion picnic. Blood culture growing a non-lactose fermenting gram-negative rod? How does it cause bacteremia? Should it be treated?
Salmonella (E coli and Klebsiella are lactose fermentors.) It can cross M cells and epithelial cells, taken up by macrophages where it modifies the vacuole containing it so it can survive. Usually not treated (treatment can actually prolong shedding).
A 5 year old with renal failure and a recent history of bloody diarrhea following a visit to Taco Bell. Blood smear shows fragmented RBCs and low platelets. What is the agent? What causes the tissue damage? How is it treated?
EHEC presenting with hemolytic uremic syndrome. Shiga toxin acts on blood vessels, kidney, platelets. Treated with supportive therapy. Abx not useful!
A school-aged child presents with small macules that progress to pustules and crust over. What is the agent?
Impetigo. Usually caused by Staph aureus though Strep A can also cause it. Better hygeine can prevent.
Patient presents with erythema migarns and flue-like symptoms. What is the agent? How do you diagnose? What are the complications? What is the treatment?
Borrelia burdorferi (a spirochete!). Causes Lyme disease. Diagnose with serollogy, ELISA followed by western blot. Complications include Bell’s palsy (facial paralysis), CNS involvement. Treated with doxycycline (amoxicillin a second choice).
Sexually active male with flu-like symptoms and the generalized, macular-papular rash covering the entire body. What ist he agent? How do you diagnose? What happens if it’s not treated?
Treponema pallidum (syphillis). This is secondary syphillis (primary has the painless ulcer (chancre)). DIagnose with darkfield examination of skin exudate and serologies. Tertiary syphilis will follow if not treater: granulomatous lesions virtually everywhere.
Where do you get Rickettsia rickettsii from? How do you culture the organism? How do you treat?
A bit from infected tick. Don’t culture it (it’s intracellular). Diagnose w/ fluorescently labeled antibodies. Treat with tetracyclies; chloramphenicol, fluoroquinolones.
A sexually active male with pain on urination and a non-purulent urethral exudate. Gram-stain and culture negative. What are complication? How do you treat?
For women, pelvic inflammatory disease, sterility.
Chlamydia: one dose of azithromycin; doxycycline for 7 days; or a fluoroquinolone
Neisseria: third generation cephalosporin like Ceftriaxone; always treat for chlamydia as well unless if you have ruled it out.
Infection of burned skin in a patient on empiric broad-spectrum antibiotic therapy. Gram-stain showing gram-negative rods. Agent? How do you treat?
Pseudomonas aeruginosa. Treatment is difficult – pipericillin and gentamicin.
How do you treat Staph epidermis?
If methicillin sensitive, use oxacillin or naficillin. If methicillin resistant, use vancomycin
A 2 year old presents with pain and fever associated with tugging at her right ear. On exam the right tympanic membrane is red and bulging. Likely agent(s)? Where did the organism come from? Is resistance an issue? Is this vaccine-preventable?
H. influenzae and Strep pneumo. Colonizes UR tract. Some resistance to penicillins, so augmentin used (has beta-lactamase inhibitor). Yes-ish for both.
7-month old not up to date on vaccines taken abroad presents with fever and a stiff neck. You suspect meningitis caused by what organisms? Where do they come from? how do you differentiate them w/ G stain and culture?
H. influenzae, Strep pneumonia, N. meningitidis. H. flu most common, usually follows URI. All three colonize upper respiratory tract. H. flu is G- coccobacillus, S. pneumo is G+ diplococcus, N. meningitidis is G- diplococcus.
Bacterial meningitis, teenagers
Pneumococcus, N. meningiditis
Flaccid paralysis in infants
Infant botulism. Clostridium botulinum is a heterogeneous group of anaerobic rods. Infant botulism is the most common form of botulism in the US; the toxin is produced in the gut by C. botulinum that colonizes; obtained from contaminated soil. Affects the very young.
Toxin promotes transmission by elevating intracellular cAMP levels increasing secretions?
Cholera, pertussis, ETEC
An abscess developed following abdominal surgery on an elderly woman. Nothing grew on blood, nutrient or EMB agar. Abscess fluid plated on blood, nutrient and EMB agar grew no colonies. The specimen showed the presence of coccobacilli. Identical media did produce colonies when incubated in a candle jar.
B. fragilis
A retired army sergeant contracted pneumonia a week after a visit to Pennsylvania. Microabscesses and inflammatory exudates developed as the disease progressed. Bronchial lavages showed a few pleomorphic thin rods, but cultivation on most media failed to produce any colonies.
Legionella pneumophilia
What are the four worms, and what are the treatments for each?
Schistasoma mansoni: praziquantel, Entorobius vermicularis (pinworm) and Ascaris (roundworm): mebendazol, Taenia solium: praziquantel
