Microbiology Exam 2- Gram Positive Bacteria

Gram Positive Cocci

• Staphylococcus

• Micrococcus

• Peptococcus

• Peptostreptococcus

• Streptococcus

Staphylococcus

• Gram + cocci

• Clusters, pairs

• Facultative (can grow with oxygen, but can grow more slowly without oxygen)

• Catalase (an organism produces an enzyme catalase to break down hydrogen peroxide)

• Halotolerant

  • Mannitol salt agar (selective for organisms that are halotolerant)

Staphylococcus aureus

• Normal on skin (normal flora)

  • 25-35% of us carry it in nasal passage

• Can be pathogenic

• Yellow pigment

• 𝛾 hemolysis

Hemolysis of Blood Agar

• 5% sheep’s blood

• 𝛼 greening (partial break down of Red blood cells)

• β clearing (complete hemolysis)

• 𝛾 NO hemolysis

• Can be an indicator of pathogenicity

3 potential results of blood agar

• 𝛼 : Red blood cells not lysed. Causes darkening of the media. Can’t see through the media 

• β : completely lyses red blood cells

• 𝛾 : gama - organism doesn’t secrete anything that affects red blood cells

Staphylococcal skin infections

• pimples, boils/carbuncles, stye 

• different strains carry different toxins

S. aureus diseases

• TSS

• Pneumonia

• Impetigo

• Meningitis

• Food poisoning 

MRSA

• Methicillin resistant. S. aereus

• Hospital 

• Community

• Can lead to more serious infections and death

Staphylococcus epidermis

• Normal on skin, rarely causes infections

• Non-pigmented

• Rarely pathogenic 

• 𝛾 hemolysis

Micrococcus

• Gram + cocci

• Clusters, tetrads

• Catalase positive

• * Strict aerobe

  • CAN NOT GROW BY FERMENTATION

• Non-pathogenic

• Usually on inanimate objects

Peptococcus and Peptostreptococcus

• Gram + cocci

• Ferments peptone (ferments amino acids) not sugar

  • OBLIGATE ANAEROBE

• Normal flora of intestine, vagina 

• Postpartum septicemia, puerperal fever (worry about this postpartum in women)

Streptococcus

• Strepto = chain

• Catalase negative

  • AEROTOLERANT anaerobes 

    • don’t know how to use oxygen

  • FERMENTATION PRODUCT = LACTIC ACID

• 2 major groups based on hemolysis

  • β true lysis (beta hemolytic)

  • α greening

• Also separated by immunological groups (A-O)

  • Group A is associated with human diseases

    • β hemolytic 

Streptococcus pyogenes

• pyo = puss

• causes strep-throat

• scarlet fever

• flesh-eating strep disease. Can’t stop toxin with antibiotics. Need to amputate

Streptococcus pneumoniae

• AKA pneumococcus

• Encapsulated (makes a capsule that hides disease from your immune system)

  • Important to the discovery of DNA (F. Griffith 1920s)

• Bacterial pneumonia

• Otitis media > ear infection (ear canal)

• Meningitis

• Sinusitis 

Streptococcus mutans

• 𝛼 hemolysis

• Mouth (causes cavities)

• Needs sugar

• Lactic acid production leads to cavities 

Gram positive rods

• Bacillus

• Clostridium 

• Lactobacillus

• Listeria

• Mycobacterium 

• Mycoplasma

• Cornebacterium

• Propionibaterium

• Eubacterium 

• Actinomyces

• Streptomyces

Bacillus

• Means “rod”

• Gram +

• Endospore forming

  • position of endospore

• Aerobic or facultative

  • Catalase positive

• Forms a capsule

• Mostly found in soil

• Source of bacitracin and other antibiotics (bacitracin like triple antibiotic ointment)

Bacillus anthracis

• Causative agent of Anthrax (Koch)

• Endospores form only in aerobic conditions

• Anthrax affects mostly plant eating animals 

  • still occasional outbreaks

• Humans infected during occupational exposure

  • ranchers, tanners, slaughterhouse workers

• Bioterrorism 

• Cutaneous, respiratory or intestinal

• Forms smooth, shiny colonies (bc of capsule)

Anthrax

• Not normal in humans but can infect humans

• Common in cattle and sheep. Spores stick to blades of grass and animals eat grass

• Cutaneous easiest way to treat

  • Black necrosis

  • ________- from Greek “coal”

• Respiratory or pulmonary almost 100% fatal 

• Must remain on antibiotics for weeks

• Vaccine

Anthrax scare of 2001

• in mail

• Aug 2008

• Bruce Ivins

• Anthrax vaccine researcher

Clostridium

• Gram + rod

• Endospore forming 

• Strict anaerobes (obligate anaerobe. Killed by oxygen)

• Found in anoxic pockets in soil and in intestinal tract

• Anoxic pockets = areas depleted of oxygen)

C. botulinum

• causes severe/sometimes deadly food-poisoning

• Spores are especially heat resistant

• Botulism 

  • Food-borne - not infection

    • Ingestion of toxin easily inactivated with heat

    • Treat with anti-toxin

  • Infant under 1 yr

    • Associated with honey

    • Both toxin and infection 

  • Wound 

    • rare

• Botulism toxin is most potent toxin known

  • 1 ounce could kill US population 

  • Causes neuro-paralysis (prevents muscle contraction)

  • Fear it could be used in bioterrorism 

  • Vaccine?

  • used for botox lol

C. tetani

• Tetanus (lockjaw) muscles contract but can’t relax

  • Toxin mediated

• Found especially in soil enriched manure

  • Normal flora in horses, cattle

• Deep cuts or puncture wounds

• Vaccine since 1933

• Rust nail > not the rust. Rusty means it’s been there for a long time and may have spores.

C. perfringes

• Causes tissue death

• Common type of food poisoning

• Gas gangrene

  • Deep wounds

    • spores germinate where O2 low (poor circulation)

    • Toxins and enzymes released to kill cells

  • Foul odor

  • High fever, shock, massive tissue destruction 

C. difficile

• Normal flora of intestine (in all our intestines and kept in check)

• Resistant to many antibiotics

  • flourishes when antibiotics taken

• Nosocomial infection (happens a lot in hospitals)

• Resistant to alcohol based sanitizers

Lactobacillus

• Lacto - it ferments

• Produce lactic acid during fermentation

• Non spore forming

• Common in dairy products, cheese, sourdough, sauerkraut

• L. delbrueckii used for yogurt

• L. acidophilus used for acidophilus milk- for lactore intolerate people 

• Acidophile (tomato juice peptone agar is selective)

Lactobacillus acidophilus

• normal flora for women > helps prevent infection of pathogenic bacteria 

• Very resistant to acid 

  • pH 4

• Normal flora in vagina (which is acid naturally) of women of child bearing age

Listeria

• Very short rods of 0.5 micrometers

  • non-spore forming

• L. monocytogenes - foodborne illness listerosis

  • Gastrointestinal - may lead to meningitis

  • Increases risk of spontaneous abortion 

• Psychrotolerant - refrigeration doesn’t slow growth (can grow in colder temps)

• Outbreaks with non-pasteurized cheese products, cold cuts

• Immunocompromised most susceptible to listerosis

• There is a bacteriophage spray available to treat food 

Mycobacterium

• Considered Gram + but also acid fast due to unique cell wall (Acid fast stain - carbolfuchsin stains bright pink/red) 

  • Mycolic acid

• has a thin layer of peptidoglycan 

• has a different fatty acid called mycolic acid

M. tuberculosis

• Grow in white blood cells and induce host response - similar symptoms as pneumonia

• Cause of tuberculosis (a.k.a. consumption)

• ¼ of world has it, ~ 1 million die each year, 10 million new cases every year. U.S. about 20k cases.

• Treat with antibiotics but some are resistant

• PPD screening (the disease is very contagious so healthcare workers have to be tested before entering into the field) 

M. leprae

• Very difficult to culture in laboratory

  • Armadillo footpads

• Hansen’s disease or leprosy 

  • ~200k new cases/year worldwide

  • Can have 30 yr incubation 

  • Peripheral tissue distruction 

• Lepromin skin test

• Antibiotics

Mycoplasma

• In general, too small to be seen with light microscope

• Very small genome

• NO CELL WALL (bc always inside another cell)

• Phylogenetically related to gram positive bacteria

  • Lost cell wall? 

• M. pneumoniae can be cause of bronchitis and pneumonia (walking pneumonia)

• Antibiotics but not? (can’t use penicillin bc doesn’t have peptidoglycan)

Cornebacterium

• Aerobic non-motile, club shaped or V-shaped

Corynebacterium diptheriae

• Diptheria

• <5 cases/yr in US

• Toxin carried by prophage within C. dip.

  • produces a poison. The toxin is the protein

• Pseudomembrane can cause suffocation (lesion in back of throat blocks airway and you die. sorta looks like strep throat)

• Treat with antitoxin and antibiotics

• Vaccine very successful

  • the vaccine is for the toxin

Propionibacterium

• Aerotolerant, ferment (catalase neg.) lactic acid to produce propionic acid and CO2

• used to make swiss cheese

  • Lactobacillus and propionibacterium

Propionibacterium acnes

• Acne > different than single pimples

• Hormones stimulate excess sebum - microorganisms feed on 

  • Aerotolerant

• Ducts become plugged and may repture - more secretions

• P. acnes infects, more inflammation, tissue damage

• Some antibiotics help

• Accutane - prevent sebum production

  • Dangerous for pregnant women

Eubacterium 

• true- bacterium

• Obligate anaerobe (anaerobic)

• Major normal flora of large intestine

• Opportunistic pathogen

Actinomyces

• Primarily in soil

• Form branching filaments (almost fungus-like hyphae)

• Do not form spores

• Can contribute to Madura foot

Streptomyces

• Primarily in soil (earthy smell)

• Over 500 species

• Also form branching filaments

• Form true spores (different than endospores)

  • release spores like a fungus

• Also Madura foot

• Source of many antibiotics

  • in order to survive in the soil, constantly poisoning other bacteria