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Staphylococcus species?

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Composed of gram-positive cocci arranged in irregular "grape-like" clusters
Ubiquitous
Important part of the bodies normal flora on skin, mucosal surfaces, and in the upper respiratory tract
Some types are pyogenic (pus forming)

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Staph infections?

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Infections normally occurs when the microbe becomes transplanted to a normally sterile part of the body
Easily transmitted from person to person
Once transmitted may become part of persons normal flora
Cause many nosocomial infections

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Staphlyococcus epidermidis

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Most often found as member of normal flora
Found on skin and mucus membranes
Not usually pathogenic

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Staphylococcus Aureus

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Most often cause of Stapylococcal infections
At least 20% of healthy individuals are carriers
Usually found as normal flora in the nose

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Mannitol Salt Agar (MSA)

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Both a selective and differential medium
It is selective for staphylococci
It differentiates pathogenic staphylococcus aureus
It contains mannitol (a sugar), 7.5% salt, and phenol red (pH indicator)
The salt only allows staphylococci species to grow
It differentiates different staph species based on whether they can ferment mannitol
The media will change color from red to yellow if pathogenic staph is present because of the acid formed during fermentation which changes the pH

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Test for pahtogenic staph

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Involves testing for the coagulase enzyme
Staph will form coagulase to protect itself from the bodies immune system
Performed by adding test organism to rabbit plasma. If clots form then organism is positive for pathogenic staph

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Streptococcus

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Gram-positive cocci normally arranged in chains
Many streptococcal species are found as part of the normal flora of the human body
Normally found in the upper respiratory tract

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Streptococcus pneumonia

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Found in the throat of a large percentage of healthy people
Oppututnistic pathogen
Most commonly infects lungs when hosts immune system is compromised

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Streptococcus Pyogenes

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Cause of "strep throat"
A true pathogen
Pus causing
Commonly transmitted via aerosol droplets from infected individuals

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Hemolysis patterns

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Three common patterns when grown on blood agar
Hemolysis: hemolysisn cause complete lysis of red blood cells. The result is a clear zone around colonies
Hemolysis: Hemolysin cause partial lysis of red blood cells. The result is a green zone around colonies
Hemolysis: no hemolysis. This results in no change in the blood agar

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Catalase

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Enzyme produced by staph species but not strep species
Can be used to differentiate between the two

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Bacitracin susceptability

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Can be used to differentiate between their susceptibility to antibiotics
Hemolytic streptocci are pathogenic and are referred to as Group A streptococci
Over 90% of streptococcal infections are caused by Streptococcus pyogenes

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Optochin susceptibility

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Can further differentiate hemolytic streptococci
Optochin hemolytic streptococci are considered nonpathogenic viridans streptocci

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What is occuring when the color of the Mannitol Salt Agar plate changes from red to yellow?

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Staph aureus is fermenting the mannitol in the medium which causes a pH change, which causes the color change from red to yellow.

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What is the definitive test for pathogenic staphylococci?

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Detection of the coagulase enzyme

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What antibiotics are used to show susceptibility for alpha and beta hemolytic strep?

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Bacitracin and Optochin

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MRSA

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Methicillin-resistant staphylococcus aureus
Occurs asymptomatically in the nose in 1-2% of the population
Very hard to kill

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Throat culture

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Used to determine if strep pyogenes is present

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What strep species is primarily responsible for cavities?

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Strep sanguis

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What is the scientific term for a cavity?

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Dental caries

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What is the main source of carbon and energy in the mouth for streptococcus species?

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Sucrose

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What types of Streptococcus inhabits the mouth?

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Streptococcus mutans
Streptococcus sanguis
Streptococcus salivarius

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Streptococcus sanguis

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Gram-positive facultative aerobic bacteria
Produces glistening colonies surrounded by an indentation of the agar surface

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Mitis Salivarius Bacitracin agar

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Medium which inhibits the growth of most oral bacteria except S. mutans
It also contains sucrose to promote capsule formation

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Streptococcus salivarius

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Spherical, gram-positivie bacteria
Part of the mouths normal flora
Produces large, raised, mucoid colonies

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Streptococcus mutans

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Gram-positive, coccus shaped, facultative anaerobe
Part of the mouths normal flora
Produces colonies that are small, light blue to black, raised and rough. Colonies resemble burnt sugar

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Neisseria gonorrhoeae

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A fastidious, gram-negative diplococcus that is an obligate human pathogen
Does not live outside the human body
One of the most common secually transmitted diseases
Can infect any of the mucus membranes
It is on the list of reportable diseases
Can be diagnosed at bedside with gram-staining

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What are common food pathogens?

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E. coli, Salmonella, Shigella, campylobacter, staph aureus, and C. botulinum

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What is food intoxication?

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Food which is contaminated has toxins inside of it produced by certain microbes which can cause illness if ingested

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Food infection

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Ingestion of certain microbes in infected food can cause fever and problems in the gastrointestinal tract

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What microbes cause food intoxication?

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S. aureus and C. botulinum

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Methylene Blue Reductase test?

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Dye used to determine the amount of bacteria in milk by measuring the amount of oxygen present
Microbes will use up the available oxygen and change the color of the dye
If the milk is completely blue it means there are either no or almost no microbes present
If the milk is only slightly blue it means there are some microbes present but not a large amount
If the milk is white it means there is a large amount of bacteria present in the milk

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Biological Oxygen Demand (BOD)

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The amount of oxygen microorganisms use when they metabolize the organic material in milk

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Pasteurization?

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Heating up of food to a certain temperature for a certain amount of time to kill off microbes without changing the food

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Lactobacillus acidophilus

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Most commonly used fermenter to make yogurt currently

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How much E. coli is acceptable in drinking water?

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Absolutely none

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Molds

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Grow as filamentous colonies
Multicellular

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Yeasts

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Single celled
Produce creamy colonies

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Candida Albicans

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Pathogenic yeast
Often the cause of vaginal infections when the pH of the vagina is raised toward neutrality
Also the cause of thrush

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Thrush

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An infection of the mouth which can cause overgowth of the colon when antibiotics have killed off the normal bacterial residents

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Superinfection

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When one microbe colonizes all of an area of the body because the other normal flora have been killed off

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Aspergillus niger

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Common, harmless mold
Can be opportunistic and infect the lungs if given the chance
Starts out as white filamentous growth which rapidly turns black
Produces spores in chains on top of bulbous conidiophores

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Penicillium notatum

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Famous for its production of the antibiotic penicillin
Several species are used to produce speciality cheeses
Ubiquitous in many environments
Begin as white filamentous growth that mature and turn green, beige, or blue
Surface often appears wrinkled
Produces chains of spores in brush-like structures

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Eosin Methylene Blue Agar

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Also called EMB agar
Inhibits growth of gram-positive organisms
Differentiates between lactose and non-lactose fermenting organisms
Most common intestinal pathogens cannot ferment lactose

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Hektoen Enteric (HE) Agar

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Selects for gram negative bacteria
Salmonella: black colonies
Shigella: green colonies

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Blood Agar

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Differential media that is not selective
Distunguishes many pathogens based on their hemolytic properties
Normally used for Stahpylococcus and Streptococcus species
Groups microbes into three categories: alpha, beta, and gamma

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