Basic Bacteriology: Stains, Culture, Metabolics, Special Characteristics Flashcards
Name the bugs that stain poorly.
(HINT: Acronym!)
These Microbes May Lack Real Color
Treponema: Too thin to be visualized: Use dark-field microscopy and fluorescent antibody staining.
Mycobacteria: High lipid content in cell wall, detected by carbolfuchsin in acid-fast stain
Mycoplasma (no cell wall)
Legionella pneumophila (primarily intracellular) — USE SILVER STAIN!
Rickettsia (intracellular)
Chlamydia (intracellular, lacks muramic acid in cell wall)
Name the bacteria that stain with Giemsa
(HINT: Acronym)
Certain Bugs Really Try my Patience
Chlamydia
Borrelia
Rickettsiae
Trypanosomes
Plasmodium
What does PAS (periodic acid-Schiff) stain?
What do you use it to diagnose?
Acronym: PAS the sugar
Stains glycogen, mucopolysaccharides
Use to diagnose Whipple disease (Tropheryma whipplei)
What does Ziehl-Neelsen stain?
AKA Carbol fuchsin.
Acid-fast organisms: Nocardia, Mycobacterium.
What does India Ink stain?
Cryptococcus neoformans (Note: mucicarmine can also be used to stain thick polysaccharide capsule red.)
What can silver be used to stain for?
Fungi (e.g., Pneumocystis), Legionella, Helicobacter pylori
What special media is required to culture H. influenzae?
Haemophilus Influenzae:
Chocolate agar with factors V (NAD+) and X (hematin)
What special media is required to grow the neisseria species N. gonorrhoeae and N. meningitidis?
Acronym: “To connect to Neisseria, please use your VPN client.”
Thayer-Martin (or VPN) media.
Vancomycin: Inhibit gram-positive organisms
Polymixin: Inhibit gram negatives except Neisseria
Nystatin: Inhibit fungi
What media is used to isolate B. pertussis?
Bordet-Gengou (potato) agar
Acronym: Bordet for Bordetella
What media is used for isolation of C. diphtheriae?
Tellurite agar, Loffler medium.
Corynebacterium diphtheriae
What media is used to isolate M. tuberculosis?
Lowenstein-Jensen agar
What media is used to isolate M. pneumoniae?
Eaton agar, requires cholesterol
What media is used to isolate Lactose-fermenting enterics?
Pink colonies on MacConkey agar (fermentation produces acid, turning colony pink).
E. coli grown on eosin-methylene blue (EMB) agar as colonies with green metallic sheen.
What media is used to isolate Legionella?
Charcoal yeast extract agar buffered with cysteine and iron.
What media is used to isolate fungi?
Sabouraud agar
Acronym: Sab’s a fun guy!”
What is an acronym to remember obligate aerobes?
Nagging Pests Must Breathe
Nocardia, Pseudomonas aeruginosa, and MycoBacterium tuberculosis.
Note: Reactivated M. tuberculosis (immunocompromise or TNF-alpha use) go to apices of lung, highest PO2.
P. aeruginosa is an aerobe seen in burn wounds, complications of diabetes, nosocomial pneumonia, and pneumonias in cystic fibrosis patients.
What’s an acronym to remember obligate anaerobes?
What class of antibiotics cannot be used for these infections?
Anaerobes Can’t Breathe Air
Clostridium, Bacteroides, and Actinomyces. Lack catalase and/or superoxide dismutase, susceptible to oxidative damage. Foul smelling (short chain fatty acids), difficult to culture, produce gas in tissue.
Normal GI flora, pathogenic elsewhere.
AminO2glycosides ineffective becasue these antibiotics require O2 to enter the cell.
What are the obligate intracellular bugs?
Rickettsia, Chlamydia. Can’t make their own ATP.
Stay inside (cells) when it’s Really Cold.
What are the facultative intracellular bacteria?
Some Nasty Bugs May Live FacultativeLY
_S_almonella, _N_eisseria, _B_rucella, _M_ycobacterium, _L_isteria, _F_rancisella, _L_egionella, _Y_ersinia pestis.
What are some encapsulated bacteria?
Who is at risk for infection with them?
Acronym: SHiNE SKiS
_S_treptococcus pneumoniae, _H_aemophilus _i_nfluenzae type B, _N_eisseria meningitidis, _E_scherichia coli, _S_almonella, _K_lebsiella pneumoniae, and group B Strep.
Capsules are an antiphagocytic virulence factor. Bacteria must be opsonized and then cleared by spleen.
Asplenics at risk for severe infections - give S. pneumoniae, H. influenzae, and N. meningitidis vaccines. Vaccine = capsule + protein conjugate.
What are some catalase-positive organisms?
Who is at risk for infection with them?
Acronym: You need PLACESS for your cats.
Pseudomonas, Listeria, Aspergillus, Candida, E. coli, S. Aureus, Serratia.
Catalase degrades H2O2 before it can be converted to microbicidal products by the enzyme myeloperoxidase.
Patients with chronic granulomatous disease (NADPH oxidase deficiency) have recurrent infections with catalase positive organisms.
Name some encapsulated bacteria vaccines.
What is the importance of “conjugating” a vaccine?
Some vaccines with polysaccharide capsule antigens are conjugated to a carrier protein - this enhances immunogenicity by promoting T-cell activation and class switching. Polysaccharide antigen alone cannot be presented to T-cells.
Pneumococcal vaccine: PCV (pneumococcal conjugate vaccine, i.e., Prevnar)
PPSV (pneumococcal vaccine with no conjugated protein. i.e., Pneumovax)
H. influenzae type B (conjugate vaccine)
Meningococcal vaccine (conjugate vaccine)
What are the urease positive bugs?
CHuck Norris hates PUNKSS
Cryptococcus, H. pylori, Proteus, Ureaplasma, Nocardia, Klebsiella, S. epidermidis, S. saprophyticus.
Bacterium that produces yellow “sulfur” granules.
Actinomyces _israel_ii
Acronym: Israel has yellow sand.
