MMSC 428 FINAL EXAM | QUESTIONS AND ANSWERS |
WITH COMPLETE SOLUTION
Staphylococcus aureus Answer - -gram positive cocci in clusters
-facultative aerobe (prefers O2)
-halotonic
-ferment mannitol (yellow on MSA plate)
-catalase +
-*coagulase +*
-clumping factor +
-medium sized b-hemolytic white colonies
-serological tests for TSST-1 and DNA probes are the best diagnosis methods
-most clinically significant staphylococcus
-important cause of nosocomial infection
staphylococcus aureus virulence mechanisms Answer - -protein A: virulent cell
wall protein that binds to IgG antibodies and prevents them from being active
-hemolysins: produce B-hemolysis of RBCs
-exfoliatin: causes epidermal layer of skin to peel off
-pyrogenic toxin: causes fever
-toxic shock syndrome toxin 1 (TSST-1): super antigen over stimulates the T
cells and produces cytokine storm
-panton valentine leukocidin (PVL): lyses WBCs, platelets and RBCs
-staphycoagulase: activates fibrin to cause clotting and prevent WBCs from
reaching the bacteria
,-hyaluronidase: breaks down hyaluronic acid in tissue to spread bacteria
-lipases & proteases: destroy host tissues and spread bacteria
staphylococcus aureus clinical manifestations Answer - -furuncle: large raised
suppurative dome shaped boil due to infection of oil gland or hail follicle
-carbuncle: a furuncle that progresses and infects a deeper level of the skin,
infection causes systemic symptoms of fever and chills
-impetigo: bullous (>5 mm) domed fluid filled pustules surrounded by zone of
erythema, mainly seen in children
-cellulitis: inflammatory infection of connective tissue
-staphylococcal scalded skin syndrome (SSS): release of exfoliatin exotoxin
causes exfoliative dermatitis with red peeling skin that resembles a burn,
mainly in children and newborns
-toxic shock syndrome (TSS): release of TSST-1 and enterotoxin B cause
systemic symptoms including fever, liver and kidney damage, vomiting,
diarrhea, muscle aches and rash, menstrual and non-menstrual forms
-endocarditis
-intoxication food poisoning: food is contaminated with enterotoxins (no actual
bacteria) and causes vomiting and diarrhea
-nosocomial infections: wound infections, osteomyelitis, biofilm on body
implants
-childhood infections: SIDS, head and neck infection
staphylococcus aureus drug resistance Answer - -penicillin resistant due to
acquiring beta-lactamase genes
-MRSA: methicillin resistant staphylococcus aureus
-VISA: vancomycin intermediate staphylococcus aureus
-VRSA: vancomycin resistance staphylococcus aureus
,staphylococcus epidermidis Answer - -gram positive cocci in clusters
-nonmotile
-facultative anaerobe (prefer O2)
-smooth, round, non-hemolytic white colonies on BSA
-staphycoagulase - (indicated by the fact that it is nonhemolytic)
-clumping factor -
-PYR -
-ODC d+
-is part of the normal biota, only causes opportunistic infections
-hospital acquired infections: biofilms, septicemia, osteomyelitis, catheter
associated UTI
staphylococcus lugdunensis Answer - -gram positive cocci in clusters
-staphycoagulase -
-clumping factor d+
-PYR +
-*ODC +* (very strong and fast)
-mannitol -
-nonhemolytic
-oxacillin resistant (mecA gene)
-highly virulent
-equally clinically significant as Staphylococcus aureus, just isolated less
frequently
-community and hospital acquired infections: skin abscess, meningitis,
septicemia, septic shock, UTI
-endocarditis: very aggressive and fatal
, staphylococci characteristics Answer - -gram positive cocci that grow in clusters
-*catalase +* (good to differentiate from streptococcus)
-non-motile, lack flagella
-facultative anaerobes (prefer O2)
-lysostaphin sensitive
-glucose fermentation +
-modified oxidase test -
-bacitracin resistant
-produce a sticky glycocolyx that allow them to establish a biofilm
-important causes of hospital acquired infections
micrococcus Answer - -gram positive cocci in pairs, tetrads or clumps
-related to staphylococci, but less clinically significant
-*lysostaphin resistant* (would only be able to lyse staphylococcus cells)
-glucose fermentation -
-modified oxidase (cytochrome C oxidase) +
-bacitracin sensitive
streptococcus pyogenes (group A strep) Answer - -gram positive cocci in chains
-lancefield group A cell wall antigens
-aerotolerant anaerobe (fermentation only)
-modified oxidase test -
-catalase -
-*PYR +* (the only B-hemolytic strep that is)
-B-hemolytic
-bacitracin sensitive
WITH COMPLETE SOLUTION
Staphylococcus aureus Answer - -gram positive cocci in clusters
-facultative aerobe (prefers O2)
-halotonic
-ferment mannitol (yellow on MSA plate)
-catalase +
-*coagulase +*
-clumping factor +
-medium sized b-hemolytic white colonies
-serological tests for TSST-1 and DNA probes are the best diagnosis methods
-most clinically significant staphylococcus
-important cause of nosocomial infection
staphylococcus aureus virulence mechanisms Answer - -protein A: virulent cell
wall protein that binds to IgG antibodies and prevents them from being active
-hemolysins: produce B-hemolysis of RBCs
-exfoliatin: causes epidermal layer of skin to peel off
-pyrogenic toxin: causes fever
-toxic shock syndrome toxin 1 (TSST-1): super antigen over stimulates the T
cells and produces cytokine storm
-panton valentine leukocidin (PVL): lyses WBCs, platelets and RBCs
-staphycoagulase: activates fibrin to cause clotting and prevent WBCs from
reaching the bacteria
,-hyaluronidase: breaks down hyaluronic acid in tissue to spread bacteria
-lipases & proteases: destroy host tissues and spread bacteria
staphylococcus aureus clinical manifestations Answer - -furuncle: large raised
suppurative dome shaped boil due to infection of oil gland or hail follicle
-carbuncle: a furuncle that progresses and infects a deeper level of the skin,
infection causes systemic symptoms of fever and chills
-impetigo: bullous (>5 mm) domed fluid filled pustules surrounded by zone of
erythema, mainly seen in children
-cellulitis: inflammatory infection of connective tissue
-staphylococcal scalded skin syndrome (SSS): release of exfoliatin exotoxin
causes exfoliative dermatitis with red peeling skin that resembles a burn,
mainly in children and newborns
-toxic shock syndrome (TSS): release of TSST-1 and enterotoxin B cause
systemic symptoms including fever, liver and kidney damage, vomiting,
diarrhea, muscle aches and rash, menstrual and non-menstrual forms
-endocarditis
-intoxication food poisoning: food is contaminated with enterotoxins (no actual
bacteria) and causes vomiting and diarrhea
-nosocomial infections: wound infections, osteomyelitis, biofilm on body
implants
-childhood infections: SIDS, head and neck infection
staphylococcus aureus drug resistance Answer - -penicillin resistant due to
acquiring beta-lactamase genes
-MRSA: methicillin resistant staphylococcus aureus
-VISA: vancomycin intermediate staphylococcus aureus
-VRSA: vancomycin resistance staphylococcus aureus
,staphylococcus epidermidis Answer - -gram positive cocci in clusters
-nonmotile
-facultative anaerobe (prefer O2)
-smooth, round, non-hemolytic white colonies on BSA
-staphycoagulase - (indicated by the fact that it is nonhemolytic)
-clumping factor -
-PYR -
-ODC d+
-is part of the normal biota, only causes opportunistic infections
-hospital acquired infections: biofilms, septicemia, osteomyelitis, catheter
associated UTI
staphylococcus lugdunensis Answer - -gram positive cocci in clusters
-staphycoagulase -
-clumping factor d+
-PYR +
-*ODC +* (very strong and fast)
-mannitol -
-nonhemolytic
-oxacillin resistant (mecA gene)
-highly virulent
-equally clinically significant as Staphylococcus aureus, just isolated less
frequently
-community and hospital acquired infections: skin abscess, meningitis,
septicemia, septic shock, UTI
-endocarditis: very aggressive and fatal
, staphylococci characteristics Answer - -gram positive cocci that grow in clusters
-*catalase +* (good to differentiate from streptococcus)
-non-motile, lack flagella
-facultative anaerobes (prefer O2)
-lysostaphin sensitive
-glucose fermentation +
-modified oxidase test -
-bacitracin resistant
-produce a sticky glycocolyx that allow them to establish a biofilm
-important causes of hospital acquired infections
micrococcus Answer - -gram positive cocci in pairs, tetrads or clumps
-related to staphylococci, but less clinically significant
-*lysostaphin resistant* (would only be able to lyse staphylococcus cells)
-glucose fermentation -
-modified oxidase (cytochrome C oxidase) +
-bacitracin sensitive
streptococcus pyogenes (group A strep) Answer - -gram positive cocci in chains
-lancefield group A cell wall antigens
-aerotolerant anaerobe (fermentation only)
-modified oxidase test -
-catalase -
-*PYR +* (the only B-hemolytic strep that is)
-B-hemolytic
-bacitracin sensitive
