MICR102A - MIDTERM (PART 1)

What is the Gram reaction of Staphylococcus?

Gram-positive cocci

What is the shape of Staphylococcus cells?

Perfectly spherical

What is the size range of Staphylococcus cells?

0.5–1 µm in diameter

How do Staphylococcus cells grow?

In clusters like a bunch of grapes

What colony color is typical of S. aureus?

Golden yellow

What colony color is typical of S. epidermidis/S. albus?

White

Where is S. aureus commonly found?

Nasal passages, skin, oral cavity, intestinal tract

Where is S. epidermidis commonly found?

Normal inhabitant of the skin

Which Staphylococcus proteins promote colonization and attachment to host tissues?

Surface proteins

Which host proteins are bound by Staphylococcus laminin & fibronectin binding factors?

Laminin and fibronectin

What is the function of fibrinogen/fibrin-binding (clumping factor)?

Attachment to blood clots and traumatized tissues

Which infections are associated with collagen-binding factor in S. aureus?

Indwelling medical devices like IV catheters, prosthetic joints, heart valves

What happens to fibrinogen and fibronectin during prolonged device implantation?

Fibrinogen degraded, fibronectin predominates for attachment

Which capsular polysaccharide serotypes inhibit phagocytosis in S. aureus?

Serotype 5 and 8

What is the role of Protein A in S. aureus?

Binds IgG in a non-immune way, disrupts opsonization and phagocytosis, fixes complement

Which leukocytes are targeted by leukocidin?

Polymorphonuclear leukocytes (neutrophils)

What is the mechanism of alpha toxin in S. aureus?

Forms hexameric pores in cell membranes, causing leakage of cellular contents

Which toxin is a sphingomyelinase causing lysis of sheep RBCs?

Beta toxin

Which S. aureus toxin is a small peptide with phospholipase activity?

Delta toxin

Which two-component toxins include gamma toxin and leukocidin?

Gamma toxin & Leukocidin

Which S. aureus leukotoxin is potent and non-hemolytic?

Panton–Valentine (PV) Leukocidin

Which S. aureus toxins act as superantigens causing diarrhea and vomiting?

Enterotoxins (A, B, C, D, E, G)

Which toxin is responsible for toxic shock syndrome (TSS)?

TSST-1

Which S. aureus toxin causes scalded skin syndrome in neonates?

Epidermolytic (Exfoliative) Toxin (ETA, ETB)

What enzyme forms staphylothrombin and converts fibrinogen to fibrin?

Coagulase

Which S. aureus protein dissolves fibrin clots?

Staphylokinase

Which extracellular enzymes are produced by Staphylococcus?

Proteases, lipases, DNase, FAME

What is the function of FAME in abscesses?

Prolongs survival of bacteria

Which enzyme hydrolyzes hyaluronic acid to promote spread?

Hyaluronidase

Which Staphylococcus species is the most important coagulase-negative staphylococcus?

Staphylococcus epidermidis

Which infections are associated with S. epidermidis?

Infections related to prosthetic devices and catheters

What characteristic biofilm is produced by S. epidermidis?

Slime (biofilm)

Which coagulase/catalase reactions identify S. aureus?

Coagulase (+), Catalase (+)

Which coagulase/catalase reactions identify S. epidermidis?

Coagulase (–), Catalase (+)

Which Staphylococcus ferments mannitol?

S. aureus

Which Staphylococcus does not ferment mannitol?

S. epidermidis

Which method is used for epidemiological tracing of Staphylococcus?

Phage typing

Which disease in horses involves infected spermatic cord stump post-castration?

Botryomycosis

Which disease in cattle is caused by S. aureus colonization of teat tips?

Mastitis

Which disease in lambs involves septicemia with toxemia from S. aureus?

Tick pyemia

Which disease causes inflammatory skin lesions around the face and eyes in sheep?

Facial/periorbital eczema

Which S. aureus infection in poultry affects joints/feet?

Purulent synovitis/Bumble Foot

Which disease in rabbits is caused by cutaneous staphylococcosis?

Exudative dermatitis and subcutaneous abscesses

Which porcine S. aureus infection affects the uterus?

Necrotizing staphylococcal endometritis

Which Staphylococcus species is most prevalent in dogs and carnivores?

S. intermedius

Which Staphylococcus species causes exudative epidermitis in pigs?

S. hyicus subsp. hyicus

Which tests are used for Staphylococcus diagnosis?

Smears, Blood Agar Plate (BAP), Mannitol Salt Agar (MSA), Coagulase test, DNase test

Is there an effective vaccine against Staphylococcus?

No

Which resistance mechanisms are seen in Staphylococcus?

Beta-lactamase production, MRSA or multidrug resistance

Which Gram reaction describes Streptococcus?

Gram-positive cocci

Is Streptococcus motile or non-motile?

Non-motile

Does Streptococcus form spores?

Non-spore forming

How are Streptococcus cells arranged?

In pairs or chains

Is Streptococcus usually capsulated?

Yes, usually capsulated

What is the shape and size of Streptococcus cells?

Round to ovoid, 0.6–1.0 µm in diameter

Does Streptococcus produce catalase?

Catalase-negative

What type of oxygen requirement does Streptococcus have?

Facultative anaerobe

Where are Streptococcus saprophytes commonly found?

Milk

Which Streptococcus species are parasites of mucous membranes and intestines?

Parasitic species

Which classification categorizes Streptococcus into Pyogenic, Viridans, Lactic, and Enterococcus?

Sherman Classification

Which classification uses serologically active carbohydrate (C substance) to group Streptococcus?

Lancefield Classification

What were the original Lancefield groups?

A, B, C, D, E, N

Which additional groups are included in Lancefield classification?

F, G, H, K, L, M, O, P, Q, R, S, T, U, V

Where is the Lancefield carbohydrate/polysaccharide antigen located?

Cell wall and teichoic acid between wall and membrane

Are Streptococcus organisms fastidious?

Yes

What enrichment do Streptococcus colonies require?

Blood or serum

What is the colony appearance of Streptococcus?

Small, delicate, translucent colonies (~1 mm)

How does Streptococcus grow in milk?

Produces lactic acid

Which structural virulence factor interferes with phagocytosis?

Hyaluronic acid capsule

Which virulence factor provides type-specific immunity and inhibits phagocytosis?

Protein M

Which virulence factor mediates attachment to epithelial cells?

Lipoteichoic acid (Fimbriae)

Which Streptococcus hemolysins cause beta hemolysis?

Streptolysin O (SLO) and Streptolysin S (SLS)

Which hemolysin is oxygen-sensitive and antigenic?

Streptolysin O (SLO)

Which hemolysin is oxygen-stable and non-antigenic?

Streptolysin S (SLS)

Which hemolysins are toxic to neutrophils and macrophages?

Both SLO and SLS

Which Streptococcus enzyme converts plasminogen to plasmin?

Streptokinase

Which enzyme reduces viscosity of pus and aids bacterial growth?

DNases (A, B, C, D)/Streptodornase

Which enzyme promotes tissue spread of infection?

Hyaluronidase

Which toxins cause the rash in scarlet fever?

Erythrogenic toxins (A, B, C)

Which toxins are low-molecular-weight proteins?

Erythrogenic toxins

Which toxins kill phagocytes in Group A Streptococcus?

NADases

Which enzyme has broad substrate specificity and is produced by Group A?

Proteinase

Which Streptococcus species forms long chains in infected udder secretions?

Streptococcus agalactiae

What is the CAMP test used to detect?

Synergistic hemolysis with Staphylococcus aureus

CAMP test involves which interaction?

Staphylococcal Beta Toxin and Ceramide-binding factor of S. agalactiae

Which animals are affected by S. agalactiae mastitis?

Cows, sheep, goats

How is S. agalactiae transmitted?

Milker’s hands, contaminated machines, calves’ mouths

Through which anatomical structure does S. agalactiae enter?

Teats → mammary glands

What milk changes indicate S. agalactiae infection?

Alkaline pH, WBC >500,000/mL, thin watery milk

Is vaccination effective against S. agalactiae?

No

How is S. agalactiae diagnosed?

Direct smear, colony characteristics, biochemical tests

Which Streptococcus causes acute severe mastitis and belongs to Lancefield Group C?

Streptococcus dysgalactiae

Which Streptococcus is a normal commensal of horses?

Streptococcus zooepidemicus

Which infections are caused by S. zooepidemicus?

Wound infections in horses, secondary in foals, mastitis in cows, pleuritis, pericarditis, pneumonia in lambs

Which Streptococcus causes bovine mastitis but does not react with Lancefield grouping?

Streptococcus uberis

Which Streptococcus is most common cause of suppurative arthritis in pigs?

Streptococcus equisimilis

What clinical signs does S. equisimilis cause in pigs?

Lameness, joint swelling, necrosis

Which Streptococcus causes strangles in horses?

Streptococcus equi

Which Streptococcus produces “peach fuzz” protein coating?

Streptococcus equi

What type of colonies does S. equi produce?

Matt/ Mucoid colonies