Gram-Positive and Negative Bacteria Master Summary

Flashcards covering key Gram-positive and Gram-negative bacteria, organized by classification, virulence traits, and diseases.

What color do Gram-positive bacteria stain and why?

Purple, due to their thick peptidoglycan layer.

How are Gram-positive bacteria further differentiated?

By shape (cocci vs bacilli) and catalase test (Staph + vs Strep -).

What are the key characteristics of Staphylococcus spp. regarding the catalase test?

Catalase-positive.

What is the mnemonic for remembering Staphylococcus properties?

Staph Clumps and Coags.

Name three species of Staphylococcus

S. aureus, S. pseudintermedius, and S. hyicus.

Which Staphylococcus species is most associated with humans and virulence?

S. aureus.

Which Staphylococcus species is most associated with dogs?

S. pseudintermedius.

Which Staphylococcus species is associated with greasy pig disease?

S. hyicus.

What is CNS and what type of staphylococcus is it related to?

Coagulase-negative staphylococci, like S. epidermidis.

Name three key tests used to identify Staphylococcus spp.

Coagulase test, growth on Mannitol Salt Agar and Hemolysis.

Describe the function of alpha-toxin, a virulence factor of

Causes hemolysis & necrosis.

Describe the function of beta-toxin, a virulence factor of Staphylococcus.

Sphingomyelinase.

Describe the function of Protein A, a virulence factor of Staphylococcus.

Binds IgG Fc (immune evasion).

Describe the function of TSST-1, a virulence factor of Staphylococcus.

Toxic shock.

Describe the function of PVL, a virulence factor of Staphylococcus.

Leukocyte lysis; necrotizing pneumonia.

What are the key characteristics of Streptococcus spp. regarding the catalase test?

Catalase-negative.

What is the mnemonic for remembering Streptococcus properties?

“Strep Strings & Groups”

How are Streptococcus spp. grouped?

Based on hemolysis and Lancefield Grouping (A-G).

What are the three types of hemolysis observed in Streptococcus spp. and how are they differentiated?

Alpha (α): Partial/green. Beta (β): Complete. Gamma (γ): None.

What is Lancefield grouping based on?

Carbohydrate antigens (A-G).

What disease is caused by S. pyogenes?

Strep throat, necrotizing fasciitis.

What disease is caused by S. agalactiae?

Bovine mastitis, neonatal sepsis.

What disease is caused by S. equi

Strangles

What disease in pigs and zoonotic cases is caused by S. suis?

Meningitis

What disease in canines is caused by S. canis

Respiratory disease

Name five virulence factors associated with Streptococcus spp.

Streptolysin O & S, M protein, Hyaluronic acid capsule, Streptokinase, C5a peptidase

What are the two types of Gram-positive bacilli based on spore formation?

Spore-forming and Non-spore-forming

Name two spore-forming Gram-positive bacilli genera.

Bacillus spp. (aerobic) and Clostridium spp. (anaerobic).

What are key characteristics of Listeria monocytogenes?

Zoonotic, survives in fridge.

What diseases are associated with Listeria monocytogenes?

Septicemia, abortion, CNS signs in ruminants.

What is the mnemonic to remember Listeria?

“Listeria Likes Low Temps & Lives in Cells

What diseases are associated with Erysipelothrix rhusiopathiae?

Erysipelas – diamond skin lesions, arthritis, endocarditis.

What is the mnemonic to remember Erysipelothrix?

“Rhomboid Rash = Rhusiopathiae”

What diseases are associated with Trueperella pyogenes?

Abscesses, summer mastitis (flies).

What is the mnemonic to remember Trueperella pyogenes?

“True Pyogenic Pus-Maker”

What diseases are associated with Corynebacterium spp?

C. pseudotuberculosis causes caseous lymphadenitis (sheep/goat) and ulcerative lymphangitis (horses), C. renale group causes bovine pyelonephritis.

What is the mnemonic to remember Corynebacterium spp?

Coryne = Caseous or Cystitis

What diseases are associated with Rhodococcus equi?

Pneumonia with nodules in foals <3 months.

What is the mnemonic to remember Rhodococcus equi?

Red Dust Rider = Rhodococcus

What diseases are associated with Actinomyces spp?

A. bovis causes ‘lumpy jaw’ in cattle, A. viscosus causes thoracic lesions in dogs.

What is the mnemonic to remember Actinomyces spp?

Actino = Abscesses, Anaerobe

What diseases are associated with Nocardia spp?

Pyogranulomas in immunocompromised animals.

What is the mnemonic to remember Nocardia spp?

Nocardia = Nasty Nodules, Needs Air

What diseases are associated with Dermatophilus congolensis?

‘Rain rot’ / ‘mud fever’ / ‘lumpy wool’ in cattle, sheep, horses.

What is the mnemonic to remember Dermatophilus congolensis?

D. congo = Dermatology Disasters

What is a unique characteristic of acid-fast bacilli?

Detection via Ziehl-Neelsen stain.

What diseases are associated with Mycobacterium spp.?

M. bovis causes Bovine TB (granulomas, chronic), M. avium paratuberculosis (MAP) causes Johne’s disease in cattle/sheep.

What is the mnemonic to remember Mycobacterium spp?

Myco = MACrophage Invader

What color do acid-fast bacteria stain with Ziehl-Neelsen stain?

Red

What does the Catalase test differentiate?

Staph (+) from Strep (–)

What does the Coagulase test identify?

Pathogenic staph

What does Hemolysis & Lancefield Grouping classify?

Streps

List five zoonotic gram-positive bacterial threats

Listeria, Erysipelothrix, Rhodococcus, Mycobacterium, Streptococcus suis

What are common traits of oxidase-negative Enterobacterales?

Glucose fermenters

Where is Escherichia coli (E. coli) normally found?

Large intestine

Name four virulence factors for Escherichia coli (E. coli)

Endotoxin (LPS), fimbriae, iron acquisition.

What diseases are caused by Salmonella enterica?

Diarrhoea, septicaemia

What is the transmission route for Salmonella enterica?

Faecal-oral.

Name three diseases caused by Yersinia spp.

Y. pestis (Bubonic plague), Y. pseudotuberculosis (Guinea pigs), Y. enterocolitica (Foodborne in humans).

Name three bacterium classifications that are oxidase positive and glucose fermenters

Pasteurella, Actinobacillus, Mannheimia.

Name three Pasteurella multocida related diseases

Fowl cholera, “Snuffles” (rabbits), atrophic rhinitis (pigs).

Which bacterium is sensitive to penicillin?

Pasteurella multocida

What disease is caused by Mannheimia haemolytica?

Shipping fever / pneumonic pasteurellosis in cattle.

What bacterium exhibits growth on Chocolate agar (NAD+)?

Actinobacillus spp.

What disease is caused by Glaesserella parasuis?

Glässer’s disease (pigs); polyserositis, joint infections, high mortality.

Name five Oxidase-positive, non-glucose fermenters (non-enteric) bacterium

Pseudomonas, Bordetella, Aeromonas, Brucella, Taylorella.

Which bacterium exhibits Metallic sheen, sweet smell, pyocyanin; grows on MacConkey.?

Pseudomonas aeruginosa

What disease is caused by Bordetella bronchiseptica?

Secondary cause of Canine Infectious Respiratory Disease (kennel cough).

Name two diseases in fish caused by Aeromonas spp.

A. hydrophila, A. salmonicida: furunculosis, septicaemia

Name three diseases caused by Brucella spp.

Repro tract (abortion, infertility), zoonotic (undulant fever).

What disease is caused by Taylorella equigenitalis?

Contagious equine metritis (infertility, abortion).

Name three Curved rods (oxidase-positive, motile) bacterium

Campylobacter, Helicobacter, Vibrio, Lawsonia.

Which bacterium disease transmission is poultry related?

C. jejuni: Poultry; zoonotic food poisoning

What disease is caused by Leptospira spp.?

Nephritis

What disease is caused by Anaplasma phagocytophilum?

Tick fever in cattle/sheep.

What disease is caused by Ehrlichia canis?

Canine ehrlichiosis (non-UK).

What disease is caused by Coxiella burnetii?

Q fever.

Name three Chlamydophila spp related diseases

C. felis: Feline conjunctivitis, C. abortus: Enzootic abortion in sheep, C. psittaci: Psittacosis (parrots) – zoonotic.

What are the different types of E. Coli?

Enterotoxigenic (ETEC) - neonatal scours

Enteropathogenic (EPEC) - colisepticaemia

Enterohemorrhagic (EHEC) - shiga-like toxin

Extraintestinal - UTI, mastitis, pyometra