Glossary of Lab Objectives 14-16

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Lab 14
Name an infection commonly caused by Streptococcus bovis.
Lab 14
State the gram reaction and morphology of the enterococci.
Gram-positive cocci in chains.
Lab 14
Identify an organism as an Enterococcus and state the reasons why when it is seen growing in SF broth and on Bile Esculin agar.
SF: sodium azide inhibits most other growth, will turn indicator yellow-brown indicating fermentation of dextrose.
Bile Esculin: bile salts inhibit most other growth, black agar indicates esculin hydrolysis.
Lab 14
State the genus and species of the pneumococcus.
Streptococcus pneumoniae
Lab 14
State the gram reaction and morphology of Streptococcus pneumoniae.
It is a gram-positive diplococcus.
Lab 14
Recognize alpha hemolysis on Blood agar.
Appears as a zone of partial hemolysis surrounding the colony, often accompanied by a greenish discoloration of the agar.
Lab 14
State the natural habitat of Streptococcus pneumoniae and name four infections it may cause in humans.
Pneumococci are frequently found as normal flora of the nasopharynx of healthy carriers. Pneumonia, sinusitis, bacteremia, and meningitis.
Lab 14
Identify an organism as Streptococcus pneumoniae and state the reasons why when it is seen growing on a Blood agar plate with a Taxo P® disc containing optochin.
Large, translucent colonies with alpha hemolysis; is inhibited by Taxo P disc.
Lab 14
State the normal habitat of the viridans streptococci and name three infections they may cause in humans.
They are the dominant normal flora in the upper respiratory tract. Bacteremia, deep wound infections, dental abscesses, and bacterial endocarditis.
Lab 15
State the sources and the portal of entry for most Staphylococcus aureus infections.
The portal of entry is usually the skin. The source of the organism is either the healthy nasal carrier or contact with an abscess.
Lab 14
State the Lancefield group of streptococcus that is the most common cause of acute streptococcal infections in humans and name five other Lancefield groups that frequently cause human infections.
Group A is the most common cause of infections. B,C,D,F, and G also commonly infect humans.
Lab 14
State what the term "group A beta" means when referring to streptococci.
It is in the A serologic group of Lancefield typing and shows beta pattern hemolysis.
Lab 14
State the genus and species of the group A beta streptococci.
Streptococcus pyogenes
Lab 14
State the most common infection caused by Streptococcus pyogenes and name six other infections it may cause.
The most common infection is pharyngitis. The streptococci sometimes spread to other areas resulting in laryngitis, bronchitis, pneumonia, and otitis media, septicemia, and meningitis.
Lab 14
State the normal habitat of the group B streptococci, name three infections they may cause in newborns, and describe how the infants become colonized.
Found in genital and intestinal tracts of healthy adults. Colonized babies will develop pneumonia, septicemia, and/or meningitis. They become infected at birth if it is present in the birth canal.
Lab 14
State why Blood agar is usually stabbed during streaking when isolating beta streptococci.
One of the streptococcal hemolysins is inactivated by O; stabbing the agar will place some of the bacteria in an O free environment, activating the hemolysin and making hemolysis more visible.
Lab 14
Identify an organism as a group A beta streptococcus (or Streptococcus pyogenes) and state the reasons why when it is seen growing on a Blood agar plate with a Taxo A® disc containing bacitracin.
Hemolysis will be complete causing clear ring around colonies and it will be sensitive to Taxo A disc.
Lab 15
Name and describe three types of abscesses caused by Staphylococcus aureus.
Pustule (an infected hair follicle), a furuncle or boil (if it spreads from the hair follicle to adjacent subcutaneous tissue), or a carbuncle (multiple infection sites involving deeper connective tissue).
Lab 15
Name the infection normally caused by Staphylococcus saprophyticus.
S. saprophyticus is a relatively common cause of urinary tract infections.
Lab 15
Name the types of infections most commonly caused by coagulase-negative staphylococci other than Staphylococcus saprophyticus.
Infections associated with intravascular devices and shunts. Also infections of prosthetic joints, wound infections, osteomyelitis, and endocarditis.
Lab 15
State the gram reaction and morphology of all staphylococci.
All staphylococci appear as gram-positive cocci, usually in irregular, often grape-like clusters.
Lab 15
Recognize an organism as Staphylococcus aureus and state the reasons why after seeing the results of the following:
a. a Blood agar plate with a novobiocin disc
b. a Mannitol Salt agar plate
c. a DNase agar plate
d. a
a. Beta hemolysis, gold colonies, and sensitve to N disc.
b. Manitol fermetation (yellow, acid).
c. DNase positive (clear zone around colonies indication DNA catabolism).
d. Coagulase positive (plasma gels).
e. Coagulase or protein A positive (latex clumps).
Lab 16
State the gram reaction and the morphology of the neisseriae.
Gram-negative cocci usually occurring in pairs.
Lab 16
Describe how symptoms of gonorrhea differ in the male and in the female.
Gnococcus typically invades the anterior urethra of males, usually producing a purulent discharge, pain upon urination, and frequent urination (1/3 asymtomatic). In females organism invades the cervix, the urethra, and frequently the rectum (majority are asymtomatic).
Lab 16
Give the normal habitat for Neisseria meningitidis and briefly describe how it reaches the meninges.
Nasopharynx is the normal habitat, mild infections there can allow it to invade the blood, cross the blood-brain barrier and into the meniges.
Lab 16
Identify a positive GC smear and state how you can tell it is positive.
Gram-negative diplococci associated with white blood cells.
Lab 16
Discuss one characteristic common to the genus Mycobacterium which allows us to distinguish this organism from most other genera of bacteria.
The acid-fast cell wall is almost exclusive mycobacterium and will not be decolorized by alcohol and will retain red stain.
Lab 16
State the significance of Mycobacterium avium-intracellulare complex (MAC).
Frequently causes systemic infections in people with HIV/AIDS.
Lab 16
Describe the appearance of a positive acid-fast stain for tuberculosis.
M tuberculosis are red bacilli.
Lab 16
Recognize granuloma when shown a slide of a tuberculoid organ.
Lab 16
Name the most common obligate anaerobe to cause infections in humans, state its normal habitat, and name the most common type of infections it causes.
Bacteroides fragilis resides in intesinal tract. It causes anaerobic wound infections.
Lab 16
State the normal habitat of Clostridium perfringens and name an infection it may cause.
Normal flora of intestinal tract; causes gas gangrene.
Lab 16
Describe the appearance of C. perfringens when it is anaerobically-grown on Blood agar and in Litmus Milk.
On the blood agar was white to gray with alpha and beta hemolysis. In Litmus Milk turned lavander and showed stormy fermetation.
Lab 14
Name four infections commonly caused by Enterococcus faecalis.
Urinary tract infections, kidney infections, prostate infections, and endocarditis.
Lab 14
State the gram reaction and morphology of the streptococci.
They are gram-positive cocci in pairs or chains.
Lab 15
State the significance of Staphylococcus aureus enterotoxin, the exotoxin TSST-1, and the exotoxin exfoliatin.
Some strains produce TSST-1 and cause toxic shock syndrome, others produce exfoliatin, that causes scalded skin syndrome. Enterotoxin can cause staphylococcal food poisoning.
Lab 16
State the results of N. gonorrhoeae and N. meningitidis for the oxidase test and for the fermentation of carbohydrates in CTA glucose, CTA maltose, and CTA sucrose media.
Both are oxidase-positive. N. meningitidis ferments glucose and maltose. N. gonorrhoeae ferments only glucose.
Lab 16
List two pathogenic species of Mycobacterium and name the infection that each causes.
M. tuberculosis, the causative organism of tuberculosis, and M. leprae, the causative agent of leprosy.
Lab 15
Name four systemic Staphylococcus aureus infections.
Septicemia, septic arthritis, endocarditis, meningitis, and osteomyelitis.
Lab 14
Name two autoimmune diseases associated with the group A beta streptococci.
Rheumatic fever and acute glomerulonephritis.
Lab 14
Describe alpha hemolysis, beta hemolysis, and gamma reaction on Blood agar plates.
1. Beta hemolysis: refers to a clear zone around a colony indicating complete lysis of blood cells.
2. Alpha hemolysis: refers to a zone of green around colony indicating partial hemolysis.
3. Gamma reaction: no hemolysis on the agar.
4. Double-zone hemolysis: refers to both a beta and an alpha zone of hemolysis.
Lab 16
State the possible urogenital complications of gonorrhea in the male and in the female.
In males, infection can travel to prostate, vas deferens, epididymis, and testes, resulting scar tissue can cause sterility. In females, infection travels to fallopian tubes (PID) resulting in scar tissue and sterility or ectopic pregnancies.
Lab 16
State the correct scientific names for the gonococcus and the meningococcus and indicate what disease each causes.
Neisseria gonorrhoeae (the gonococcus)causes gonorrhea, and Neisseria meningitidis (the meningococcus)causes meningococcal (epidemic) meningitis.
Lab 16
State how a diagnosis of active tuberculosis is confirmed.
By culturing the sputum.
Lab 16
Identify an organism as N. gonorrhoeae or N. meningitidis and state the reasons why when it is seen growing on MTM Chocolate agar with a Taxo N® (oxidase) disc and in CTA glucose, CTA maltose, and CTA sucrose media.
Growth on Chocolate agar indicates Neisseria, the oxidase positive colonies apear black because of N-disc.
N. gonorrheae is only glucose positive (phenol is yellow , acid), N. menigitidis ferments glucose and maltose (both are yellow, acid).
Lab 15
Name three common clinically important species of Staphylococcus and state which is most pathogenic.
Staphylococcus aureus, S. epidermidis, S. saprophyticus. Staph aureus is most pathogenic

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