Systems Flashcards
Normal flora of tissues
Skin - S. epidermidis
Nose - S. epidermidis; colonized by S. aureus
Oropharynx - Viridans group strep
Dental plaque - S. mutans
Colon - B. fragilis > E. coli
Vagina - Lactobacillus; colonized by E. coli/GBS
C-section babies have no flora, colonized after birth
Bugs causing food poisoning:
- Reheat rice
- Canned food/honey
- Reheated meat
- Undercooked meat
- Poultry/eggs
- Meats/mayo/custard
- Shellfish/wounds from water or shellfish
- B. cereus - reheated rice
- C. botulinum - improperly canned foods (bulging can) = preformed toxin; honey spores
- C. perfringens - reheated meat dishes
- EHEC (O157:H7) - undercooked meat
- Salmonella - poultry, meat, eggs
- S. aureus - Meats, mayo, custard; performed toxin
- V. parahaemolyticus/V. vulnificus - contaminated seafood (shellfish) or wounds from water/shellfish
Bugs causing diarrhea: bloody vs. watery
Bloody diarrhea (ChEEESSY)
- Campylobacter
- E. histolytica
- EHEC (enterohemorrhagic)
- EIEC (enteroinvasive)
- Salmonella
- Shigella
- Y. enterocolitica
Watery diarrhea (CCEPVV)
- C. difficile
- C. perfringens
- ETEC (enterotoxigenic)
- Protozoa
- V. cholerae
- Viruses
Causes of bloody diarrhea
“ChEEESSY”
- Campylobacter - oxidase +, comma-shaped, grows at 42C
- E. histolytica - protozoan, amebic dysentery, liver abscess
- EHEC (enterohemorrhagic) - O157:H7 mutation, makes Shiga-like toxin (inhibit 60S subunit on ribosome = cell death); can cause HUS
- EIEC (enteroinvasive) - invades colonic mucosa
- Salmonella - lactose neg, oxidase neg, flagellar motility (animal reservoir; poultry/eggs)
- Shigella - lactose neg, oxidase neg, very low ID50 –> makes shiga-toxin
- Y. enterocolitica - day-care breakout, pseudoappendicitis
Causes of water diarrhea
“CCEPVV”
- Clostridium difficile - pseudomembranous colitis, caused by abx. Sometimes bloody diarrhea
- Clostridium perfringens - myonecrosis and gas gangrene
- ETEC (enterotoxogenic) - Traveler’s diarrhea; heat-labile (HL) and heat-stable (ST) toxins
- Protozoa - Giardia, cryptosporidium (in immunocompromised)
- V. cholerae - comma-shaped gram neg, grows in alkaline environment (sensitive to pH); rice-water diarrhea, often from infected seafood
- Viruses - rotavirus, norovirus
Causes of pneumoniae by age
- Neonates (<4wks): GBS, E. coli (think vagina)
- Kids (4wk-18yo): Viruses (RSV), Mycoplasma, C. trachomatis (0-3yo), C. pneumoniae (school-aged), S. pneumoniae
- Runts May Cough Chunky Sputum
- Adults (18-40yo): mycoplasma, C. pneumoniae, S. pneumoniae
- Adults (40-65yo): S. pneumoniae, H. influenzae, Anaerobes, Viruses, Mycoplasma
- Elderly: S. pnuemoniae, Influenza virus, Anaerobes, H. influenzae, Gram-neg
Special groups of pneumoniae
- Alcoholic/IV drug user
- Aspiration
- Atypical
- CF
- Immunocompromised
- Nosocomial
- Postviral
- Alcoholic/IV drug user - S. pneumoniae, Klebsiella, Staph
- Aspiration - anerobes
- Atypical - mycoplasma, legionella, chlamydia
- CF - pseudomonas, S. aureus, S. pneumoniae
- Immunocompromised - Staph, enteric gram-neg rods, fungi, viruses, PCP (HIV)
- Nosocomial - Staph, pseudomonas, enteric gram-neg rods
- Postviral - staph, H. influenzae, S. pneumoniae
Common causes of meningitis by age
- Newborn (0-6mo): GBS, E. Coli (think vagina), Listeria
- Kids (6mo-6yr): S. pnuemoniae, N. meningiditis, HiB, Enterovirus
- 6-60yo: S. pneumoniae, N. meningitidis (#1teens), enterovirus, HSV
- > 60yo: S. pneumoniae, Gram-neg rods, Listeria
- HiB meningitis much lower since vaccine introduction!
- Viral - enterococcus (Coxsackie), HSV2, HIV, West Nile, VZV
- In HIV - cryptococcus, CMV, toxo (brain absces), JC virus (PML)
Tx for meningitis
Ceftriaxone + vanc empirically
- Add ampicillin if suspect listeria (very old/young)
CSF findings in meningitis
Bacterial: incr openingP, high PMNs, incr protein, decr sugar
Fungal/TB: incr openingP, high lymphocytes, incr protein, decr sugar
Viral: normal/incr opening P, high lymphocytes, normal/incr protein, normal sugar
Osteomyelitis
*Most in kids, high CPR/ESR; subtle on XR, cavity on MRI
- S. aureus - most common
- Neisseria gonorrhea - rare, more often causes septic arthritis
- Pseudomonas, serratia –> DM/IV drug users
- Salmonella - sickle cell
- S. aureus/S. epidermidis - prosthetic jt replacement
- M. TB (Pott) - vertebral involvement
- Pasteurella - cat/dog bites
UTI = cystitis
Ascession of microbes from urethra to bladder
- Dysuria, frequency, urgency, suprapubic pain, WBCs (NOT WBC casts) in urine
- Males - infants with cong defects, vesicourethral reflex
- Elderly -enlarged prostate
- Females - 10x more common (short urethra w/ fecal flora)
Other risks: obstruction, kidney surgery, catheterization (pseudomonas), GU malformation, DM, pregnancy
Pyelonephritis
Accession of microbes from bladder to kidney
- Fever, chills, flank pain, CV tenderness, hematuria, WBC casts
UTI bugs
- E. coli - most common, green metallic sheen on EMB agar
- S. saphrophyticus - 2nd cause in sexually active women
- Klebsiella - 3rd cause, large mucoid capsule + viscous colonies
- Serratia m. - red pigment; nosocomial/drug-resistant
- Enterobacter - nosocomial/drug-resistant
- Proteus - motility –> “swarming” on agar, urease, struvite stones
- Pseudomonas aeruginosa - blue-green pig/fruity odor; nosocomial/drug-resistant
Labs with UTI
- WBC = UTI
- WBC casts = pyelonephritis
- LE+ = bacterial UTI
- Nitrate+ = gram-neg UTI
- Urease = urease-producing bugs (Proteus, Klebsiella, H. pylori)
Vaginal infections
Bacterial vaginosis - no inflammation, thin/white discharge with fishy odor
- Gardernella, clue cells, pH >4.5
- Tx = metronidazole
Trichomonas vaginalis - inflammation, frothy, grey-green, foul-smelling discharge
- Motile trichomonads, pH >4.5
- Tx = metronidazole; treat sexual ptnr
Candida vulvovaginitis - inflammation, thick, white, “cottage cheese” discharge
- Pseudohyphae, pH nl (4-4.5)
- Tx = -azoles
ToRCHeS infections
ToRCHeS
- Toxo
- Rubella
- CMV
- HIV
- HSV-2
- Syphilis
Congenital toxo
Get from cat feces/undercooked meat
- Maternal - asx, LAD rarely
- Neonatal - triad = chorioretinitis, hydrocephalus, intracranial calcifications
Congenital rubella
Respiratory droplets
- Maternal - rash, LAD, arthritis
- Neonatal - triad = PDA, cataracts, deafness +/- blueberry muffin rash
Congenital CMV
Sex, organ transplant
- Maternal - asx or mono-like illness
- Neonatal - hearing loss, sz, petechial rash, blueberry muffin rash
Congenital HIV
Sex, needle stick
- Maternal - depends on CD4
- Neonatal - recurrent infections, chronic diarrhea