Path 3100 Exam 1

Cocci

Sphere shaped bacteria.

Diplococci

Streptococci (chains)

Staphylococci (groups)

Bacilli

Rod shaped bacteria

Pleomorphic

The ability of some micro-organisms to alter their shape or size in response to environmental conditions

Spirochete

Spiral shaped bacteria

Flagella

Protein filaments on the outside of bacteria that provide locomotion.

Pili

Small protein fivers that allow bacteria to attach to a host.

Endospores

Bacterial DNA and cytoplasm produced during adverse conditions.

Are resistant to extreme temperature, chemicals, toxins, detergents, as well as radiation.

Produced by some gram positive bacteria.

Importantly, the Bacillus and Clostridium species produce spores.

Capsules

Covers the cell wall and shields the bacteria from immune and phagocytic responses.

Usually made of polysaccharides.

One of the most important virulence factors.

Think of it as the invisibility cloak.

Factors Affecting Microbial Growth

Temperature (30-35 C)

pH (6.0-8.0)

Osmotic pressure

Chemical requirements (i.e. carbon, H2O, nitrogen, sulfur, phosphorus, trace elements)

Atmosphere (O2 or CO2 concentrations)

Obligate Aerobes

Require O2

Obligate Anaerobes

Will not grow in presence of O2

Facultative Anaerobe

Grows with or without O2

Capnophilic

Grows best when atmosphere is enriched with extra CO2

Pattern of Microbial Growth

Lag Phase: growth is undetected

Log Phase: constant, maximal growth rate

Stationary Phase: cells dying= cells dividing

Death phase: most cells are dying

Cell structure of prokaryotes versus eukaryotes

Prokaryotes:

No nucleus

Haploid genome

Single, circular, double stranded DNA called a nucleoid

Energy is generated by the cell membrane

Cell wall

Ribosomes are 70s

Have plasmids (small circular DNA that can be passed on)

Eukaryotes:

Nucleus with double stranded DNA

Diploid genome

Nucleolus is site of ribosomal RNA synthesis

ER is where protein is synthesized

Mitochondria is site of energy production

Not common to have cell walls

Double lipid bilayer plasma membrane

Taxonomic Hierarchy and Example

Domain: Bacteria

Phylum: Proteobacteria

Class: Gammaproteobacteria

Order: Enterobacteriales

Family: Enterobacteriaceae

Genus: Escherichia

Species: coli

Notice that genus is capitalized and species is not.

Strain

Used to describe genetically identical or clonal representatives of species.

Isolate

A representative bacterial colony recovered from a particular source.

Gram Positive Cell Wall

Thick peptidoglycan layer

Teichoic acid and lipotechoic acid are unique to these cell walls.

Appears purple when stained.

Gram Negative Cell Wall

Thin peptidoglycan layer

Outer membrane is outside the peptidoglycan layer.

Appears pink when stained.

Acid-Fast Cell Wall

Gram positive cell wall structure but also has a waxy layer bound to the exterior of cell wall.

Examples: Mycobacterium and Nocardia

Do not stain well with gram stain.

Bacteria with no cell walls

Mycoplasma

Gram Stain Procedure

Crystal Violet: Net (+) charge is attracted to bacterial (-) charged cells

Iodine: mordant (dye fixative)

Alcohol: decolorizer; removes dye from gram negative cells but not gram positive cells

Safranin: counterstain (responsible for the pink coloring in gram negative cells)

Beta hemolytic species

Strep pyogenes (Group A)

Strep agalactiae (Group B)

Alpha hemolytic species

Streptococcus pneumoniae

Streptococcus bovis (Group D)

Enterococcus (Group D)

Non-hemolytic / gamma

S. bovis (Group D)

Enterococcus

Infections caused by Streptococcus pyogenes

Pharyngitis, tonsilitis, swollen lymph nodes

(Strep throat)

Otitis media

Scarlet fever

Impetigo

Cellulitis

Post-strep problems:

Rheumatic fever

Acute glomerulonephritis

Infections caused by Streptococcus agalactiae

(Produces capsules)

Infections:

Colonizes genital tract

Leading cause of meningitis, septicemia, and pneumonia in neonates

UTI

Post-surgical gynecologic infections

Streptococcus pneumoniae

Gram-pos. cocci

Abundant capsule producer: resists phagocytosis

Infections:

normal flora of upper resp. tract

otitis in children

bacterial pneumonia

meningitis

sinusitis

Viridans Streptococcus

AKA: Alpha-hemolytic Strep.

Predominant organisms of the upper resp. flora

Most common cause of subacute bacterial endocarditis

Enterococcus

Gram-pos cocci

Over 30 species

Two species responsible for human infection:

E. faecalis

E. faecium

Relatively low virulence

Infections:

Normal GI flora

UTI

Endocarditis

Wound infections

Gram Positive Cocci

Staph: aureus, epidermidis, saprophyticus

Strep: agalactiae, pneumoniae, pyogenes

Enterecoccus species: E. faecalis, E. faecium

Gram Positive Bacilli

Clostridium: perfringens, difficile, tetani, botulinum

Bacillus: anthracis, cereus

Listeria monocytogenes

Corynebacterium: diptheriae, jeikeium

Gardnerella vaginalis (gram-variable)

Nocardia spp.

Classification of Staphylococcus

Staphyle: Greek for "bundle of grapes"

Normal flora of the skin, mucous, feces

Facultative anaerobe

Tolerates high salt environments (skin)

Non-motile

Catalase (+)

Gram-Positive cocci in clusters

Staph. aureus

Most virulent Staph.

Found of skin, in nose, axillae and groin

Coagulase (+)

Leukocidin- exotoxin that kills neutrophils

6 types of enterotoxins

Lipases

Hyaluronidase- dissolves interceullular matrix of tissues

Protein A- binds to Fc portion of IgG and prevents phagocytosis

Hemolysins: alpha and delta

Diseases: skin infections, osteomyelitis, pneumonia, food poisoning, gastroenteritis, toxic shock syndrome

Staph. epidermidis

Low virulence

Inhabits skin of most people

Diseases: endocarditis (heart valves infected), prosthetic infections, IV site infections (sepsis)

Loves to form biofilms on plastic

Staph. saprophyticus

Strong association with UTI

Has a unique binding property to transitional epithelium

Areas of the human body that Staph. resides

Skin, mucous membrane, nose

Significance of MRSA

Most strains of S. aureus are resistant to penicillin, so methicillin/nafcillin/oxacillin is used.

A rise of MRSA has occurred.

Scary.

The only two gram-positive bacilli species that produce spores:

Clostridium

Bacillus

Listeria monocytogenes

Gram-pos. bacilli

Frequently found in the environment

Causes stillbirths and meningitis in animals. Human diseases appear in neonates, pregnancy, and immunocompromised.

CAN GROW IN REFRIGERATION and consequently has a higher mortality rate that other organisms.

Associated with food borne illness, especially from dairy.

Corynebacterium Species

Gram positive bacilli

All Corynebacterium are diptheroids

Environmental and normal flora of humans and animals.

Skin, oral cavity, and urogenital tract.

Opportunistic organism.

Considered contaminants when isolated

Pleomorphic, resembles "Ls" and "Vs" and may palisade

Corynebacterium diphtheriae

Corynebacterium jeikeium

Corynebacterium diptheriae

Produces an exotoxin when infected with a phage

The toxin affects myocardium and PNS, which causes death by asphyxiation or myocarditis

Diptheria the disease: pharyngitis with thick leathery-grey membrane, fever and malaise.

Treated with diptheria antitoxin and antibiotics.

Immunizations available.

Corynebacterium jeikeium

Normal flora of skin

Opportunistic

Causes diseases with prosthetic heart valves

Septicemia

Skin infections

Nocardia Species

Environmental

Not normal flora

Gram positive bacilli

Shows branching and beading

Strict aerobe

Smells like dirt

Opportunistic

Causes bronchopulmonary and cutaneous infections

Gardnerella vaginalis

Only species

Facultative anaerobe

Gram stain- variable

Fastidious organism

Causes bacterial vaginosis: green frothy discharge with foul odor

Clue cells

Bacillus species

Low virulence

Found in soil, water, dust, and animal products

Common laboratory contaminants

PRODUCES SPORES

Gram Stain- box car shaped gram-variable

Aerobe or facultative anaerobe

Bacillus anthracis

Bacillus cereus

Bacillus anthracis

Major pathogen

Causes Anthrax

Used for biological warfare

Three types of anthrax disease: pulmonary, cutaneous, GI

Bacillus cereus

Opportunist

Food poisoning especially with rice

Can also cause eye and wound infections but is less common

Clostridium species

Gram-positive bacilli

Inhabits soil, water, vegetation, and bowels

Significant pathogens of livestock and wildlife.

ANAEROBES

PRODUCE SPORES

Clostridium perfringens

Produces many exotoxins

Gram-positive bacilli, box car shaped

Rapid growth

Produces high amounts of gas

Gas gangrene

Food poisoning

Wound infections

Clostridium difficile

Normal bowel flora

Antibiotic therapy can cause this to overgrow

Produces toxins that cause blood diarrhea

Development of a pseudomembrane

Smells like horse manure

Colonies of it have a "ground glass" appearance

Treatment: stool transplant

Clostridium tetani

Gram-pos. bacilli

Found in soil, dust, and human/animal excreta

SPORES enter the body through wounds

Produces toxins that block relaxation of muscles

Causes tetanus

Treated with an antitoxin and penicillin

Preventable with an immunization

Clostridium botulinum

Spores are found in soil, water, and surface of vegetables

Diseases caused by inadequate food processing

Causes paralysis in muscles

The reason we don't give babies honey and certain food supplements.

Treated with an antitoxin and penicillin

Compare and Contrast Neisseria gonorrhoeae and Neisseria meningitidis

gonorrhoeae is always a pathogen, meningitidis may be found as commensal

Menigitidis is lethal, while gonorrhoeae is rarely lethal

gonorrhoeae is killed rapidly in the blood stream

gonorrhoeae is not encapsulated

Menigitidis causes systemic infection

Both :

gram-negative dipplococci

Both have pili

aerobic

require CO2 for growth

fav. temp is 33-37 C and moist

fastidious

non motile

affinity for mucous membranes

How to recover, isolate, and identify Neisseria and Moraxella catarrhalis

Neisseria Species

Many are isolated from humans

Many are flora of mucous membranes and respiratory tract and urogenital tract

Gonorrhoeae and meningitidis are primary pathogens

Neisseria gonorrhoeae

Gram-neg cocci

Spread with sexual contact

Very sensitive to atmosphere and temperature.

Only inoculated to selective nutrient dense media. Then brought to a high CO2 rich environment.

Oxidase positive- an enzyme that oxidizes a colorless reagent to form a deep purple color in 10 seconds.

Gonorrhoeae is often paired with clamydia

Treated with ceftriaxone and azithromycin

Many strains resistant to penicillin

Very fastidious organism.

Preferred method of identification is Nucleic Acid Amplification Tests (NAAT)

Neisseria meningitidis

Found in the nasopharynx

Spread by respiratory droplets

5-15% of teens and young adults are carriers

Common transmission in close quarters

Disease seen in children and young adults

Meningitis: fever, headache, stiff neck, photophobia, irritability

Meningococcemia: petechial rash, shock and disseminated intravascular coagulation

Specimen found in CSF or blood

Detected with PCR

Treated with penicillin

Moraxella catarrhalis

Gram-negative diplococci

Normal flora of upper respiratory tract

Grows well on lab media

Diseases: otitis media, sinusitis

Causes pneumonia and bronchitis in the immunocompromised

When cultured, similar to Neisseria

Treated with antibiotics and decongestants

Classification of Streptococcus

From the greek: "streptos" meaning "twisted"

Gram positive cocci

Oval or round, usually in chains

Normal flora in oral cavity, nasopharynx, and GI tract

Facultative anaerobes

Catalase negative

Non-spore forming

Alpha and beta hemolysis

Toxins: streptolysin O and S

Streptolysin O and S

O- oxygen labile (subsurface hemolysis)

S- oxygen stable (surface hemolysis)