Bacterial Disease Testing Flashcards
What are some reasons a culture is performed?
- confirm a dx
- exclude a dx
- screening
- monitor course of disease
- monitor response of therapy
- stage the severity of the disease
- provide a prognosis
What are some factors that may alter culture results?
improper technique/collection method, transport, or patient factors (medications)
What is the cutoff of growth to consider it an infection?
contaminant?
considered infection if >10^5
contaminant if
What would you expect to receive a preliminary report for most cultures?
usually issued within 24 hours
Skin Flora
normal
pathogenic
normal- staph epidermidis, *S. aureus, micrococcus, few gram neg bacilli moist skin, corynebacterium, propionibacterium
pathogenic- strep pyogens, pseudomonas, proteus
Mouth Flora
pathogenic
strep pneumoniae, strep pyogenes, neisseria meningitidis, haemophilus influenza, neisseria gonorrheae
Oropharynx Flora
Potential pathogens
Pathogens
PP- mycoplasma, bordatella pertussis, many others
pathogens- staph aureus, pseudomonas
Conjunctiva Flora
normal
pathogens
normal- cornyebacterium, neisseria, moraxellae, staph and strep, occasional haemophilus and parainfluenza
pathogens- pneumococcus, pseudomanas (contacts!), strep
GI tract Flora
pathogens
C. diff, salmonella, toxic strains E. coli, helicobacter pylori (in duodenum)
Anterior Urethra Flora
Pathogens
chlamydia, gonorrhea, syphilis
Vagina Flora
Normal
pathogens
normal flora varies with hormonal state
Pathogens- candida, trichomonas
Do you obtain a specimen before or after administration of antibiotics/?
BEFORE!!!
*specimens should be transported as quickly as possible
How long do blood cultures take?
How long do most routine cultures take?
how about anaerobes?
blood cultures take 48-96 hours
routine cultures (urine, throat, sputum) take 24-48 hours
Anaerobes- 48-72 hours
*almost always get gram stain with culture in most settings
Who selects the appropriate culture media?
What is the routine agar?
The LAB! (so why is this a slide??)
routine- blood agar
thioglycollate media- a liquid media used to supplement plated media
Wound culture
Usually pus present, try to get the good stuff from the middle
Abscess/boil/furuncle culture approach
- incised and any fluid or material swabbed out with culture swab and sent to lab
- important to get pus/exudate from deep in the wound to avoid surface contamination
Eye- conjunctiva culture
- gently swab to collect drainage
- place in appropriate container and send to lab at 25 degrees C
Throat culture
- generally obtained to rule out what?
- inform lab if what?
- rule out strep pharyngitis
- inform lab if you’re trying to ID something else such as N.gonorrheae because it requires special medium
- avoid touching any other part of the mouth
- often indicated if the in office rapid strep is negative
Sputum culture
Indications
- hospital acquired pneumonia
- hospitalized patients with pneumonia (CAP) and any of the following criteria: ICU admission, failure of outpateint abx therapy, cavitary lesion, active alcohol use, pleural effusion
NOT indicated in:
- most outpatient CAPs
- Management of bronchitis
- initial management of acute exacerbations of COPD
What is a bronchoscopy?
sampling of the lower airway
-another potential diagnostic method
Sputum culture stuff
- may be inaccurate due to mouth flora (rinse out mouth, not eating 1-2 hours before collection)
- suspect a pathogen if WBCs are present along with an overabundance of one type of organism
- first morning sputum will represent a deeper pulmonary secretion
- induce cough with nebulizer, pulmonary PT, aspiration, bronchoscopy
- always get gram stain with culture
What will the sputum contain from an atypical pneumonias?
abundant polymorphonuclear cells and few or no organisms will be seen on the gram stain
What colors would appear on a sputum gram stain of strep pneumoniae?
Pink and purple
pink and purple
Blood culture
indications
- bacteremia
- septicemia
- unexplained post op shock
- unexpected fever of several days duration
- pneumonia
- chills and fever in patients with: infected burns or UTIs, rapidly progressing tissue infections, postop wound sepsis, indwelling venous/arterial cath
- debilitated patients receiving: antibiotics, corticosteroids, immunosuppressives, parenteral hyperalimentation
What are blood cultures used to detect?
bacteremia (septicemia)
What can a urine dipstick test?
pH specific gravity bilirubin protein glucose ketones blood nitrite (indicates the presence of enerobacteriaceae that converts nitrate to nitrite) leukocyte esterase (if positive, likely indicates pyuria)
*if negative but positive for sx of UTI, still want urine culture
What would you expect to find in a microscopic analysis of urine sediment from spun urine?
Normals RBC: 0-5 HPF WBC: 0-5 HPF Bacteria: absent casts: 0-4 hyaline LPF crystals
Lumbar puncture
indications
collection and transport
- to look for blood (possible subarachnoid hemorrhage)
- to find the organism causing the meningitis or brain abscess
collect 1-5 ml of CSF, transport at 25 degrees C
4 tubes: 1. cell count, 2. glucose and protein, 3. gram stain and culture, 4. cell cound to compare to tube 1
Pleural fluid collection (thoracentesis)
Therapeutic indication
diagnostic indication
therapeutic- relieves dyspnea
diagnostic- to test the fuild for TB, fungus, CEA level (tumor marker), cytology, culture, gram stain, pH
*go over the top of the rib because vessels and nerves go under the ribs
Synovial Fulid evaluation
indications
swollen joint (is it infection? inflammation? what?)
*medications should not be administered therapeutically at the same time
Swab of the cervix would be to test what?
Female urethra?
cervix- gonorrhea, chlamydia, other organisms and PID
urethra- chlamydia
What is a Wet Mount helpful in evaluating?
vaginitis/ bacterial vaginosis
trichomonads
can reveal multiple PMNs
KOH (potassium hydroxide) wet mount can reveal candida organisms
Urethral culture
- usually on male/female?
- culture for what?
- media?
- usually on male/female? Males
- culture for what? GC (gonorrhea), chlamydia
- media? thayer martin/ new york media
Stool culture
indications
- routine culture for those with prolonged diarrhea or haven’t been on abx or hospitalized
- test of choice to check for the C. diff toxin
