LAB 15 – DIAGNOSTIC BACTERIOLOGY Flashcards
What should be present if a good sputum specimen was collected?
- minimal amounts of saliva/ epithelial cells
- presence of PMNs = acute bacterial infection of lower respiratory tract
PMN - polymorphonuclear neutrophils
You are tasked with doing controls at the beginning of shift. Which organisms would you use as a positive control for the following tests:
a. ALA
b. Oxidase
c. DNase
d. PYR
e. Catalase
f. Germ tube
g. Slide coagulase
h. Tube coagulase
i. Bile solubility
a. Haemophilus parainfluenzae
b. Pseudomonas aeruginosa, Pasteurella multocida, Neisseria sp., Campylobacter, Brucella sp., Moraxella catarrhalis
c. Staphylococcus aureus, Moraxella catarrhalis
d. Streptococcus pyogenes
e. Staphylococcus sp., Corynebacterium sp., Listeria monocytogenes, Pasteurella multocida, Brucella sp.,
f. Candida albicans
g. Staphylococcus aureus
h. Staphylococcus aureus
i. Streptococcus pneumoniae
What is the main pathogen we are looking for in a throat specimen? What plate and conditions would we use to best isolate this organism?
- Streptococcus pyogenes
- only BAP*
- anaerobic conditions enhance beta-hemolysis
What are 3+ pathogens that cause infection of the lower respiratory tract?
- S. pneumoniae and K. pneumoniae
- Haemophilus influenzae
- S. aureus
- Enterobacteriaceae
Name 5+ organisms that cause GIT infections.
- Salmonella sp.
- Shigella sp.
- Escherichia coli
- Campylobacter jejuni
- Vibrio cholerae
- Yersinia sp.
- Clostridium sp.
- S. aureus
Name 2+ pathogens commonly associated with UTI’s?
- Staphylococcus saprophyticus
- Enterobacteriaceae (especially E. coli)
- Pseudomonas aeruginosa
Name 3 bacterial or non-bacterial pathogens associated with genital tract infections.
Bacterial:
- Neisseria gonorrhea
- Gardnerella vaginalis
- Listeria monocytogenes
Non-bacterial:
- Trichomonas vaginalis
- Candida albicans
- Chlamydia sp.
How does E. coli O157 media differentiate O157 from other serotypes?
(SMAC) Supplemented MacConkey:
- Cefixime, potassium, tellurite, and vancomycin inhibits other gram -ve flora
- MAC: E. coli O157:H7 does not ferment sorbitol and forms opaque, colorless colonies on the medium (wh) , while other E. coli strains ferment sorbitol to form typical pink colonies (pk)
Describe 3 methods used for isolation of organisms for urine specimens
- midstream urine
- catheter collection
- suprapubic collection
You are tasked with doing controls at the beginning of shift. Which organisms would you
use as a negative control for the following tests:
a. ALA
b. Oxidase
c. DNase
d. PYR
e. Catalase
f. Germ tube
g. Slide coagulase
h. Tube coagulase
i. Bile solubility
a. Haemophilus influenzae
b. Enterobacteriaceae
c. Neisseria gonorrhoeae, Neisseria meningitidis
d. Streptococcus agalactiae, Non-enterococcus sp.
e. Streptococcus sp.
f. Candida sp.
g. CNS
h. CNS
i. Viridans
What are the appropriate plates for plating the following specimen types?
a. CSF
b. Blood culture
c. Urine
d. Sterile body fluids
e. Sputum
f. Genital tract specimen
g. Stool specimens
h. Skin and wounds
a. CSF = BAP (ss in CO2), CAP (CO2) and MAC
b. Blood culture = BAP (CO2), CAP (CO2) and MAC ?
c. Urine = BAP (CO2), CAP (CO2) and MAC ?
d. Sterile body fluids = BAP (CO2), CAP (CO2) and MAC ?
e. Sputum = BAP (ss in CO2), CAP (CO2) and MAC
f. Genital tract specimen = BAP (CO2), BAP (anaerobic), PHY, MAC
g. Stool specimens = HE, Shigella agar, CHROMagar
h. Skin and wounds = BAP, BAP (anaerobic), MAC
HE - Hektoen Enteric agar
Why is Thayer Martin agar with antibiotics used to recover Neisseria gonorrhoeae in specimens?
- It inhibits mixed micro flora from suppressing gonococci growth
- N. gonorrhoeae is fastidious; Thayer Martin agar contains hemin (X factor), v factors, vitamin, amino acids, and antimicrobics to promote its growth
Why is a direct smear not required for stool specimens?
Stool contains too many different species of bacteria
What does blood culture media contain?
- Growth factors: peptones, yeast extract, hemin, dextrose, vitamins, amino acids
- Penicillinase
- Sodium polyanethol sulfonate:
- an anticoagulant
- inhibits Bactericidal properties of blood (phagocytosis + complement)
- neutralizes Aminoglycosides
How does automated detection work for blood cultures?
- continuously incubated at 35°C
- bacteria growth = CO2 release = proportional fluorescence
- BACTEC instrument (pCO2 electrode) detects H+ via fluorescence photodetection
- Positive blood culture is noted by a blinking light and audible alarm
- Further isolation and identification is needed
