Reagents
This reagent test differentiates Staphylococcus (positive) from Streptococcus (negative) by detecting the presence of an enzyme that breaks down hydrogen peroxide into water and oxygen.
What is the catalase test?
This Enterobacteriaceae member is lactose-fermenting, indole-positive, and typically produces metallic green sheen on EMB agar.
What is Escherichia coli?
This organism produces beta-hemolytic, small, translucent colonies and is known for its bacitracin sensitivity, helping identify it as the cause of streptococcal pharyngitis.
What is Streptococcus pyogenes (Group A Strep)?
This organism often produces a grape-like or leather-like odor when grown on culture media.
What is Pseudomonas aeruginosa?
This class of antibiotics inhibits cell wall synthesis by binding to penicillin-binding proteins, preventing peptidoglycan cross-linking.
What are β-lactams (penicillins, cephalosporins, carbapenems)?
This test identifies the ability of bacteria—particularly Staphylococcus aureus—to clot plasma through the production of a specific enzyme.
What is the coagulase test?
This genus shows swarming motility on blood agar, is urease-positive, and produces H₂S on TSI or KIA agar, and indole negative.
What is Proteus mirabilis?
These colonies appear large, mucoid, and pink on MacConkey agar due to strong lactose fermentation and a prominent capsule.
What is Klebsiella spp.?
This organism is known for its “mousy” or “bleach-like” odor.
What is Haemophilus influenzae?
This antibiotic class inhibits protein synthesis by binding to the 30S ribosomal subunit, causing misreading of mRNA.
What are aminoglycosides?
A positive result for this test produces a bright cherry-red color, helping to identify Streptococcus pyogenes and Enterococcus species.
What is the PYR test?
This organism is lactose-positive, urease-positive, non-motile, and often produces large, mucoid colonies due to its capsule.
What is Klebsiella species?
This organism produces metallic blue-green pigment and often smells like grapes or tortillas on culture plates.
What is Pseudomonas aeruginosa?
This gram-negative rod produces a strong, putrid odor and is sometimes described as burnt chocolate.
What is Proteus species?
This drug blocks DNA gyrase and topoisomerase IV, preventing DNA replication and transcription.
What are fluoroquinolones?
This agar slant detects glucose, lactose, and sucrose fermentation, gas production, and hydrogen sulfide, and is commonly used for identifying Enterobacterales.
What is the TSI (Triple Sugar Iron) agar test?
This pathogen is H₂S-positive, lactose-negative, lysine decarboxylase–positive, and commonly associated with foodborne illness from poultry or eggs.
What is Salmonella?
This gram-positive organism forms white to golden, round, convex colonies with beta-hemolysis on blood agar and is DNase- and coagulase-positive.
What is Staphylococcus aureus?
This organism, part of the Streptococcus anginosus (milleri) group, is known for producing a butterscotch or caramel-like odor on culture.
What is Streptococcus anginosus group?
This class inhibits folate synthesis by blocking sequential steps in the folic acid pathway—specifically dihydropteroate synthase and dihydrofolate reductase.
What are sulfonamides and trimethoprim (TMP-SMX)?
This reagent test identifies bacteria capable of producing cytochrome c oxidase, with a positive reaction turning the reagent dark purple within seconds.
What is the oxidase test?
This Enterobacteriaceae member is urease-positive, non-H₂S-producing, shows a “safety pin” appearance on staining, and may grow best at room temperature for biochemical reactions.
What is Yersinia species?
These colonies are small, gray, translucent, and produce alpha hemolysis, giving a characteristic “greenish” discoloration on blood agar.
What is Streptococcus pneumoniae?
This organism has been noted to give an odor of fresh or green apples.
What is alcaligenes faecalis
This antibiotic binds to the 50S ribosomal subunit, inhibiting translocation, and is commonly used for atypical pathogens like Mycoplasma, Chlamydia, and Legionella.
What are macrolides (e.g., azithromycin, erythromycin)?