House-style Bacterial Clin Stuff Flashcards
Staph bacteria are catalase positive, what does that mean? (picture staff with cats)
* catalase is an enzyme that converts H2O2-> H20 + O2
that is, Staph aureus, etc can convert hydrogen peroxide into water and oxygen (bubbles appear when staph present)
What are alpha, beta and gamma hemolytic bacteria?
Bacterial description:
beta - can fully lyse RBCs (they are cultured on sheep blood agar, so leave white spots as RBCs get killed, with red aroung)
alpha - can partially lyse RBCs, greenish colour on agar
gamma - cannot lyse RBCs
What can group A Strep do?
Can cause strep throat (pharyngitis), skin infections, glomerulonephritis, Toxic Shock Syndrome
Can also cause delayed antibody response diseases: scarlet fever (pyogenes class), rheumatic fever.
think PHaryingitis can also lead to glomerulonePHritis and rheumatic PHever
Group A - beta hemolytic (can kill sheep RBCs on agar completely)
So why does Group A Strep cause delayed antibody responses?
scarlet fever (pyogenes class), rheumatic fever
Also has pyrogenic exotoxin - can cause scarlet fever, superantigen - directly stimulates a sea of T cells -> massive cytokine rlease -> toxic shock syndrome
- scarlet fever: extensive rash on trunk and neck, spares face; skin may peel off in fine scale (happens due to exotoxin that Strep produces)
- toxic shock syndrome - (Strep or Staph), mediated by release of pyogenic toxin, need high dose of penicillin and clindamycin to stop toxin synthesis (blocks protein synthesis by blocking bacterial ribosomes)
Testing for Strep pharyngitis?
exudative pharyngitis common, swab tonsils and send for a rapid antigen detection test (RADT), in minutes, highly specific for Strep pyogenes, but can be misleading in kids (get throat culture in them as backup, b/c get strep often but results can be negative).
Skin infections in Strep?
- folliculitis: infection of hair follicles
- cellulitis: deep infection of skin cells, producing red, swollen skin hot to touch
- impetigo: vesicular (volcanic-lava like), blistered, skin with crusty yellow tops, frequent around mouth (can also be S. aureus); frequently pyoderma (=pus on skin) = impetigo contagiosa
- erysipelas - step infection of the superficial skin (dermis), raised, bright red rash with a sharp border that advances from the initial site of infection (S.aureus rare)
- necrotizing fasciitis : flesh eating streptococcus - swelling, heat, redness day one, then colour changes to purple to blue in a day and large blisteres (bullae form). then skin dies and msucle may also be infected (myositis). in this case fascia has to be surgically removed and rapid antibiotic therapy is crucial. add clindamycin to penicilin G treatent to shut down toxin production. also can be caused by Staphylococcus, Clostridium, etc
- scarlet fever: extensive rash on trunk an dneck, spares face; skin may peel off in fine scale (happens due to exotoxin that Strep produces)
image up front is erysipelas
on this page, impetigo
- necrotizing fasciitis
usually fo
Risk of untreated pharyngitis?
Rheumatic fever
usually in 5-15 years old, often follows untreated pharyngitis by Group A Strep
Think JONES
J for Joints: joitn swelling, arthritis
O for heart <3 (can’t type it) : myocarditis
N for nodules: subcutaneous nodules = rubbery nodules just under skin
E is for erythema marginatum: red margin rash that spreads from centre
(erythema is like red and marginatum like margins)
S is for St. Vitus dance = uncontrolled dance-like movements of the extremities
antibody-mediated, risk of developing arrythmias and heart failure, after recurrent infections heart can become permanently damaged, but takes many years for valves to show problems after initial myocarditis (rheumatic valvular disease develops). most often mitral valve.
remember CLIN: causes for valvular disease are #1 rheumatic, #2 rheumatic, #3 rheumatic
give prophylactic penicillin, b/c patients susceptible to repeats.
no permanent injury to the joints though
Antibody mediated diseases from Strep?
- rheumatic fever
-post-streptococcal glomerulonephritis
about 1 week after infection of either the pharynx or skin by nephritogenic (strains that can cause glomerulonephritis) strains of group A strep. antigen-antibody complexes travel to kidneys, get stuck in glomerular basement memgrane, activate complement cascade leading to glomerular destricution
1) puffy face (b/c retaining fluid)
2) dark pea (b/c blood in urine = hematuria)
3) high BP secondary to hypervolemia due to impaired kindey function
ASK ABOUT SORE THROAT A WEEK OR SO AGO
What do Group B Strep do?
B for baby
25% of women have these bugs vaginally, so baby can acquire during delivery, can cause neonatal meningitis, pneumonia and sepsis (<3 months old)
nonspecific signs: fever, vomiting, irritability, poor feeding.
act rapidly: diagnose by lumbar puncture, start antibiotics as soon as suspected, not when diagnosis confirmed.
Most common causes of meningitis in neonates: Strep Group B, E.Coli and Listeria = cover for all.
BABY brain saved by the BEL (saved from meningitis knowing it could be group B strep, E.Coli or Listeria)
Group B can cause pneumonia and sepsis in immunocompromised (diabetes, malignancy, renal failure, etc or elderly)
Criteria for SIRS?
SIRS = systemic inflammatory response syndrome
diagnosis is made if two+ of the following present:
- HR > 90 BPM
- RR > 20 breaths/min
- WBC <4,000 cu/mm or >12,000cu/mm or > 10% bands
- temperature <36 C or > 38C
Possible complications from otitis media?
- *1. Vertigo
2. Tinnitus
3. Facial paralysis
4. Mastoiditis
5. Meningitis**
What predisposes someone to accute sinusitis?
- Dental infections
- Allergies
- Swimming
- Mechanical obstruction of nose
What bacterias commonly cause UTIs?
- Enterobacteria: E.coli, Klebsiella, Proteus
- Enterococcus spp (+ve but anaerobic, looks like strep)
- Staphylococcus sapprophyticus (#2 in young females)
- Strep. agalactiae (GBStrep)
Community:
E.coli (80%), Staph sapprophyticus, other Staph, enterococci, etc
Nosocomial:
E.coli (40%), Gram -ves (25%) = klebsiella, enterobacter, pseudomonas; then gram +ves, etc
Whats this Staph saprophyticus?
From Wikipedia:
In humans, S. saprophyticus is found in the normal flora of the female genital tract[3] and perineum.[4] It has been isolated from other sources too including meat and cheese products, vegetables, the environment, and human and animal gastrointestinal tracts.[4] S. saprophyticus causes 10-20% of urinary tract infections (UTIs). In females 17–27 years old, it is the second most common cause of community-acquired UTI, after Escherichia coli.[5] Sexual activity increases the risk of S. saprophyticus UTI because bacteria are displaced from the normal flora of the vagina and perineum into the urethra.[3] Most cases occur within 24 hours of sex,[3]earning this infection the nickname “honeymoon cystitis”.[6] S. saprophyticus has the capacity to selectively adhere to human urothelium. The adhesin for S. saprophyticus is a lactosamine structure. S. saprophyticus produces no exotoxins.[3]
Risk factors for UTI?
Anything to hold urine longer:
- Kidney infection
- Prostate problems (hypertrophy)
- short urethra in women
- catheters
- neurologic (bladder can have problems emptying)
- vesicoureteral reflux (urine travels up from bladder to ureter and kidneys (in kids, think reflux as going up)
Most likely cause of UTI in hospital?
Catheter - risk of UTI increases by 3% for every day with catheter
DO NOT FORGET about it , take it off patient as soon as you can
Make sure collection bag is below patient (use gravity to clean catheter!), intermittent catheter is better than continuous catheter
What is vesicoureteral reflux?
Vesicoureteral reflux (VUR) is an abnormal movement of urine from the bladder into ureters or kidneys. Urine normally travels from the kidneys via the ureters to the bladder. In vesicoureteral reflux the direction of urine flow is reversed (retrograde).
In healthy individuals the ureters enter the urinary bladder obliquely and run submucosally for some distance. This, in addition to the ureter’s muscular attachments, helps secure and support them posteriorly. Together these features produce a valvelike effect that occludes the ureteric opening during storage and voiding of urine. In people with VUR, failure of this mechanism occurs, with resultant retrograde flow of urine.
WIkipedia
Approach to UTI diagnosis:
- History and physical
- Urinalysis (urine test with electrolytes, proteins in urine, etc)
- Urine culture and susceptability (collect before starting antibiotics, dah)
Signs and symptoms of UTI?
- Dysuria (burning or discomfort when peeing)
- Fever
- Costovertebral angle tenderness (pyelonephritis)
- Frequency of urination changes
- Higher urgency of urination
- Hesitancy ?
- New onset incontinence in elderly
malodorous and cloudy urine is not a symptom of UTi
What sample of urine to collect?
* midstream urine (after you started peeing but before you finished to decrease chance of bacterial contamination, as first urine washes residual bacteria out)
* Foley catheter - ideally from newly inserted catheter, b/c those over 24 hrs will be colonzied, DO NOT collect from collection bag (usually there is bacteria there and overgrown)
* Suprapubic aspiration (needle over pubic bone)
* ileal conduit (piece of ileum used as bladder, always will be some bacteria in urine after that procedure)
* nephrostomy tube - conduit directly in kidneys
* cystoctomy tube - tube directly in bladder (cyst = bladder)
What is in urinalysis?
- test for leukocytes (leukocyte estarase + if WBC)
- test for nitrites (positive if there are bacteria that can transform nitrate to nitrite (NO3->NO2. think nitRITE is right, so NO2)
- Proteus, Klebsiella, E.Coli (enterobacters)
- WBC count = infection, cancer or catheters (can produce inflammation)
- RBC = infection, kidney disease, renal stones, urinary tract cancers, bleeding disorders, contamination
Urine culture
try mistream urine
> 10^5 bacteria in 1 ml = significant bacteriuria (for midstream urine only!)
if over 3 organisms found, likely contaminated sample instead
T or F?
Signs and symptoms, positive urinalysis and positive culture are required to assess for UTI
A positive quntitative urine culture alone just indicates bacteriuria (not UTI, could be asymptomatic)
A positive leukocyte esterase just indicates inflammation (not necessarily infection)
A positive nitrite just indicates the presence of bacteria that can reduce nitrate (Klebsiella, E.coli, proteus)
All true
When to get BLOOD culture when suspecting UTI?
- when presented with sepsis
- immunocompromised with fever, pyelonephritis and UTI symptoms (fear worse = bacterimia)
- all pediatric patients with fever (need to know what is goign on and can’t get all history, so resort to tests)
Commonly used UTI antibiotics?
TMP/SMX and ciprofloxacin have really good gram -ve coverage, were used empirically, but not anymore as develops resistance
nitrofurantoin and fosfomycin are good, for cystitis (bladder infection) but do not use in pyelonephritis
amoxicillin-clavulanate for gram +ves
Pregnancy: avoid TMP/SMX in first and third trimester, avoid nitrofurantoin and quinolones (ciprofloxacin)
IV: piperacillin+ tazobactram + gentamycin for broad spectrum
