Clinical Bacteriology Micro Exam 2

alpha hemolysis

partial hemolysis

Beta hemolysis

complete hemolysis

gamma hemolysis

no hemolysis

hemolysis test

a laboratory test used to determine the type of bacterial hemolysis by assessing the degradation of red blood cells on blood agar.

useful for distinguishing streptococcal species

mannitol salt agar

high salt concentration inhibits most bacteria except for salt tolerant staphylococci

yellow for fermenters, red for non fermenters

composition: agar, mannitol, high salt concentration, pH indicator (usually phenol red)

MacConkey Agar

selects for gram negative bacteria, differentiates lactose fermenters from non fermenters

bile and crystal violet inhibit most gram positive bacteria

composition: agar, lactose, bile salts, neutral red (pH indicator), crystal violet

EMB Agar

Selects for gram negative bacteria, differentiates strong lactose fermenters from weak and non fermenters

Lactose fermenting colonies appear dark green, non lactose fermenters appear colorless or pink

composition: agar, Eosin Y and methylene ble dyes, lactose, peptone

gram positive cocci

staphylococcus, enterococcus, and streptococcus

non motile, non spore forming

major population responsible for cutaneous infections (SKIN INFECTIONS)

systemic infections include bacteremia, food poisoning, endocarditis, TSS, arthritis, osteomyelitis

staphylococci

facultative anaerobes

grape like cluster

catalase positive

can be coagulase positive or negative

staphylococcus aureus

coagulase positive

can cause pneumonia, skin infections, abscess formation,has been linked to TSS

toxins cause the skin to blister and peel, a condition known as staphylococcal scalded skin syndrome

streptococci

divided into 4 subgroups divided according to their hemolytic patterns

streptococcus pneumoniae

leading cause of pneumonia

alpha hemolytic bacteria

bacilli

areobic gram positive bacteria present in soil, water, and airborne dust

produces endospores

non motile and highly pathogenic

B cereus

motile

catalase positive, causes food poisoning and opportunistic infections.

B anthracis

nonhemolytic, nonmotile, catalase positive

causes anthraz

can cause edema and skin necrosis shock

lactobacillus

facultative anaerobe, nonmotile, nonspore forming

ferments lactose to lactic acid and releases CO2

used in dairy production

S aureus and S intermedius

only two staphylococci that are coagulase positive

enterococcus faecium

emerging drug resistant pathogen associated with bioflm formation

streptococcus pyogenes

streptococci that causes complete lysis of red blood cells, beta hemolytic

streptococcus pneumoniae

streptococci that causes partial lysis of red blood cells, alpha hemolytic

enzyme degradation

antibiotic resistance mechanism involves bacterial enzymes inactivating (breaking down) antibiotics

efflux pumps

antibiotic resistance mechanism that allows bacteria to expel antibiotics from their cells

Staphylococcus aureus

Which of the following bacteria produces an enzyme (or toxin) that can cause the scalded skin syndrome (blistering and peeling of the skin) for newborns?

streptococcus pyogenes

Which of the following infectious bacteria is a gram positive bacteria that tests negative for catalase and produces beta hemolysis? It is the main causative agent of strep throat.

horizontal gene transfer

allows bacteria to acquire new antibiotic-resistance genes.

Enterohemorrhagic e coli

Which bacterium is known to encode for Shiga-like toxin?

pseudomonas

causes respiratory distress and possible lung infection

often found in burn units in hospitals

ubiquitous, gram negative, oxidase positive

salmonella

oxidase negative

more

a lower LD50 meant that the pathogen is _____ dangerous

clostridium botulinum

produces a very potent neurotoxin that is a cause of botulism food poisoning and can develop into afebrile neurologic disorder

causes blurred vision, muscular weakness

immediate treatment with antitoxin required

vibrio cholerae

typically found in disaster zones and will cause severe diarrhea with rice water color and consistency

protein A

Among the adherence surface factors virulence. It binds to the Fc region of antibodies, to avoid opsonization and phagocytosis.

clostridium

anaerobic gram positive bacilli

spore forming rods, motile

produce exotoxins responsible for tetanus, botulism and gas gangrene

neisseria

gram negative cocci

aerobic, non spore forming

non motile, oxidase positive

veillonella

anaerobic counterpart of neisseria

enterobacteriaceae

family with members that are among the most pathogenic and commonly encountered organisms in microbiology

gram negative rods, oxidase negative

hemolytic patterns

streptococci of medical importance may be identified according to their _______ or according to antigenic differences in carbohydrates