Gram Positive Bacteria - Lecture 5 Flashcards
What are streptococcus sp. characteristics? (Morphology)
These bacteria are gram positive COCCI bacteria that are organized in chains (~2-6/chain)
How are streptococcus bacteria clasified?
These are classified based on their hemolytic activity. Classified as alpha, beta or gamma.
Beta-hemolytic bacteria are further classified based on Lancefield groupings (A-U), which is their cell wall carbohydrate antigen.
What are the four streptococcus human pathogens?
1) Streptococcus pneumoniae
2) Streptococcus pyogenes
3) Streptococcus agalactiae
4) Streptococcus mutans
Describe alpha-hemolytic bacteria.
What colour does it appear on a blood agar where the colonies grow?
Give an example.
Partial hemolysis
Appears green in colour
S. pneumoniae
Describe beta-hemolytic bacteria.
What colour does it appear on a blood agar where the colonies grow?
Which further classes are the most pathogenic?
Give an example.
Complete hemolysis
Appears as a full clearing on and around where the colonies grow
Lancefield groups A and B are the most pathogenic
S. pyogenes (group A) and S. agalactiae (group B)
Describe gamma-hemolytic bacteria.
What colour does it appear on a blood agar where the colonies grow?
Give an example.
No hemolysis
No clearing
Enterococcus faecalis
What is another name for streptococcus pneumoniae?
Pneumococcus
Describe pneumococcus: morphology, encapsulated or acapsular, bile sensitivity or not?
Diplococci
Encapsulated
Bile sensitivity
What are two features of a pneumococcus infection?
Bacterial pneumonia
Bacterial meningitis
What bacterial infection is described as:
Fever, malaise, cough, pleuritic chest pain
Purulent or bloody sputum
Otitis media (inflammation of the inner ear)
Bacterial pneumonia
What bacterial infection is described as:
Stiff neck, headache, fever (characteristic triad)
Bacterial meningitis
streptococcus pneumoniae is the most common cause of meningitis in children
How is streptococcus pneumoniae transmitted and how long is the typical incubation period?
Transmitted via respiratory droplets
Incubation period is 1-3 days
What are treatment strategies for streptococcus pneumoniae?
Vaccine preventable
Broad-spectrum antibiotic resistance tests
What else is Streptococcus pyogenes known as?
Group A Streptococcus (GAS)
GAS is CAMP-tes negative, meaning what?
CAMP-factor does NOT increases hemolytic activity (unlike beta-hemolytic S. aureus)
What are clinical features of GAS?
Pharyngitis/Tonsilitis - aka “strep throat”
Scarlet fever
Infections of the skin
Describe pharyngitis/tonsilitis (strep thoat)
Inflammation of the pharynx/tonsils
Fever, malaise, sore throat
Describe scarlet fever
Occurs in patients with strep throat (usually children)
Erysypelas (rash), typically on the face, “strawberry tongue”
What are four infections of the skin caused by GAS? (give brief descriptors)
1) Impetigo - superficial, common in children, contact sport
2) Cellulitis - subcutaneous, inflammation of the skin and dermal layers
3) Folliculitis - inflammation of the hair follicles
4) Necrotizing fasciitis - aka flesh-eating disease
What are some potential complications of GAS infections? (3)
Acute rheumatic fever
Acute glomerulonephritis
Infective cardiopathies
What complication of GAS infection is described as:
Polyarthritis, carditis, rheumatic heart disease
May occur weeks following GAS infectoin
Acute rheumatic fever
Which complication of GAS infection could lead to an autoimmune disease - antibody cross-reactivity against joints and myocardium (type II hypersensitivity)
Acute rheumatic fever
What complication of GAS infection involves inflammation of the glomeruli (kidney) and may occur weeks following the GAS infection of the URT or skin
Acute glomerulonephritis
What is the most common infective cardiopathies (a complication of a GAS infection)
Endocarditis most common
How are GAS infections transmitted and how long is the typical incubation period?
Transmitted via respiratory droplets
Incubation period - 1-5 days
What are treatment strategies of GAS infections?
Penicillin and related antibiotics, cephalosporins
What else is streptococcus agalactiae known as?
Group B streptococcus (GBS)
Are GBS CAMP-test positive or negative? meaning what?
Encapsulated or acapsular?
CAMP-test positive - meaning CAMP-factor increases hemolytic activity
Encapsulated
What are clinical features of GBS? Briefly describe. (5)
1) Symptomatic in newborns, elderly, immunocompromised, risk of maternal transmission
2) Newborn pneumonia - fever, myalgia, fatigue, consolidation of the lung, chest pain
3) Meningitis (neonatal) - fever, headache, neck stiffness
4) Sepsis - leading cause of neonatal sepsis
5) UTI - less common
How are GBS infections transmitted?
How long is the typical incubation period of GBS?
Transmitted via respiratory droplets
Incubation period 5-7 days
What are treatment strategies of GBS infections?
Penicillin and other bata-lactams
What does viridans streptococcui include?
Includes streptococci mutans and other commensals of the mouth
Are viridans streptococci optichin-sensitive or nonsensitive, encapsulated or acapsular?
Optihin-sensitive
Acapsular
These clinical features are characteristic of which bacterial infection?
1) Symptomatic in newborns, elderly, immunocompromised, risk of maternal transmission
2) Newborn pneumonia - fever, myalgia, fatigue, consolidation of the lung, chest pain
3) Meningitis (neonatal) - fever, headache, neck stiffness
4) Sepsis - leading cause of neonatal sepsis
5) UTI - less common
GBS clinical features
These clinical features are characteristic of which bacterial infection?
1) Impetigo - superficial, common in children, contact sport
2) Cellulitis - subcutaneous, inflammation of the skin and dermal layers
3) Folliculitis - inflammation of the hair follicles
4) Necrotizing fasciitis - aka flesh-eating disease
GAS clinical features
These clinical features are characteristic of which bacterial infection?
1) Plaque, tooth decay, cavities
2) infective cardiopathies - subacute infective carditis
Viridans streptococci
Wha are the assoiciated risk factors of cardiopathies? and describe presentation.
Risk factors: congenital heart defects/valvular defect, artificial heart valves, diabetes, dental surgery.
Presentation: slowly progressing, low grade to no fever, chest pain and sepsis
What are clinical features of viridans streptococci? (2)
1) Plaque, tooth decay, cavities
2) infective cardiopathies - subacute infective carditis
What is the incubation period of viridans streptococci?
variable incubation period
What are the treatment strategies for viridans streptococci?
Brushing and antiseptic mouthwash, antibiotics for sepsis and cardiopathy
What are the characteristics of Staphylococcus?
Gram positive cocci
Organized in grape-like clusters
Catalase-positive, facultative anaerobes
What are human pathogens of Staphylococcus? (3)
1) Staphylococcus aureus - skin infection, bacterial pneumonia, bacterial meningitis
2) Staphylococcus epidermidis - sepsis (IV catheters and medical prostheses
3) Staphylococcus saprophyticus - UTIs, cystitis
Give three characteristics of Staphylococcus aureus
1) Opportunistic pathogen - resident on skin
2) Characteristic golden colonies (“aura” = golden)
3) Identification - morphology, coagulase (+)
What are some diseases caused by Staphylococcus aureus? (7)
1) Skin infections - impetigo, abscess, cellulitis, scalded skin syndrome
2) Sepsis/Septic shock
3) Bacterial pneumonia
4) Bacterial meningitis
5) Mastitis
6) Infective cardiopathy
7) Food poisoning
These diseases can all be caused by which bacterial infection?
1) Skin infections - impetigo, abscess, cellulitis, scalded skin syndrome
2) Sepsis/Septic shock
3) Bacterial pneumonia
4) Bacterial meningitis
5) Mastitis
6) Infective cardiopathy
7) Food poisoning
Staphylococcus aureus infection can cause these diseases
What is described as a collection of pus in a tissue associated with inflammation?
An abscess
What is described as blisters and sores (pustulous or not), found commonly on the face/neck?
Impetigo
What is described as an inflammation of connective tissue in the dermal, subcutaneous layers of the skin?
Cellulitis
What is described as pain and redness of the skin, blisters and desquamation?
Scalded skin syndrome
Describe staphylococcal bacterial pneumonia (caused by staphylococcus aureus)
How would it be treated?
Commonly nosocomial, secondary pneumonia
Fever, chest pain, coughing, difficulty breathing
Patchy areas of consolidation in the lung
Rapidly progressive
Treat with antibiotics, steroids
Describe Sepsis
Septic inflammatory response, spread to various organs
Multiple presentations, organ effects, may lead to secondary infection even following clearance from the blood
What percentage of bacterial meningitis is due to staphylococcal aureus?
1-10% of meningitis
What is meningitis?
What does it cause/symptoms?
Inflammation of the meninges in the brain causing cognitive impairment and fever
Describe acute infective endocarditis:
What is it, and what are the symptoms?
Inflammation of the endocardium
Sudden onset of fever, new/changing heart murmer, chest pain, Osler’s nodes and Janeway lesions on the hands and feet
What bacterial infection can cause mastitis?
Describe mastitis
Common treatments
Caused by Staphylococcus aureus
Infection of the breast tissue
Abrasions and skin breaks during breastfeeding common, risk of sepsis and ineffective cardiopathy
Very common in cattle
Common treatments: antibiotics, surgery
Describe food poisoning as caused by Staphylococcus aureus
Source
Mishandled meat, poultry, eggs, dairy
Salt-stable (cured foods)
Mostly due to toxin production (heat-stable)
produce enterotoxins A-E
Do not reheat food that has been at room temperature for more than 2hrs
Causes severe vomiting 2-4hrs after infection
What are drug-resistant staphylococcus aureus?
Caused by what?
Methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA & VRSA)
Caused by antibiotic overuse, misuse, and patient non-compliance
Nosocomial
What are treatment strategies for MRSA and VRSA?
Incision, drainage or surgery of affected area
1st and 2nd generation glycopeptide antibiotics - inhibit bacterial cell wall and RNA synthesis
Streptogramins - inhibit bacterial ribosome
staphylococcus aureus caused epidermidis is commensal of the skin. is it
Coagulase positive or negative?
Hemolytic or non-hemolytic
Encapsulated or acapsular?
Coagulase negative
Non-hemolytic
Encapsulated
Septicemia is caused by an opportunistic infection transmitted from what (typically)?
Medical devices - catheters, shunts, prostheses etc.
Biofilm formations on devices is a major virulence factor due to adhesion molecules and ability to bind to plastic device
What are some clinical features of staphylococcus aureus epidermidis?
Depends on site of infection
UTI - pain or difficulty urinating
Subacute infective endocarditis
What are treatment strategies for staphylococcus aureus epidermidis?
vancomycin and related, although antibiotic resistance is common
Staphylococcus saprophyticus
Coagulase positive or negative?
Drug resistant? to what?
Encapsulated or acapsular?
Coagulase negative
Novobiocin resistant
Some capsulated, some acapsular strains
Treatment for Staphylococcus saprophyticus
Treat with Quinolones - inhibit DNA replication and trimethoprim - folic acid and metabolism inhibitor
Give characteristics of Bacillus sp.
Gram - or +
Catalase - or +
Size
Oxygen tolerance
Spore-forming or not
Gram (+) rods, catalase (+)
Relatively large bacteria (35um long)
Aerobic or facultatively anaerobic
Sporeforming
Give four important species of Bacillus
1) Bacillus subtilus
2) Bacillus cereus
3) Bacillus anthracis
4) Bacillus thurigiensis
Describe the characteristics of endospores including structure, conditions of formation, content
Dormant, hearty, nonreproductive structure
Formed ‘from within’, during conditions of stress
Genetic material, some cytoplasm, tough exterior
‘Cryptobiotic’
What makes endospores particularly hearty
Resist heat, freezing,
dessication
Resist acidity, chemical disinfectants, irradiation
Commonly found in soil and water
Survive long periods of time (millions of years)
Endospores can survive unfavourable conditions for extremely long periods of time
Conditions that favour vegetation lead to germination of spores (sufficient nutrients, oxygen, moisture, etc.)
Other than Bacillus, what are some other spore forming bacteria?
Clostridium sp. cyanobacteria
Saporophytes a classification of bacillus
How do they obtain nutrients?
Where do they live?
Obtain nutrients from dead organic matter
Saprophytic bacteria live mostly in soil/water
Give three Saprophyte human pathogens
1) Bacillus subtilus - food poisoning
2) Bacillus cereus – food poisoning, mastitis, skin infections
3) Bacillus anthracis – anthrax
diseases
What are some saprophyte probiotics? (3)
1) Lactobacillus sp.
2) B. subtilis
3) B. cereus
What is a saprophyte insect pathogen?
Bacillus thuringiensis
This bacteria is a saprophyte and member of the resident gut flora. It is motile (flagellate) and may appear in groups or chains. What is it?
B. subtilus
Pathogenic B. subtilus can cause ___1___
It is ___2___ in early phase and ___3___ in late phase
4) How long does it take to resolve and 5) how long is the incubation period?
1) food poisoning - rare
2) Emetic
3) Diarrheal
4) 24-48hrs
5) Short incubation - hours
What are virulence factors of B. subtilus?
Sibtilisin - serine endopeptidase
Catalase - metabolize H2O2
This bacteria is a saprophyte and a member of the resident gut flora. It is motile (flagellate), appears in groups or chains and is β-haemolytic. What is it?
B. cereus
What are four clinical presentations of pathogenic B. cereus?
1) Food poisoning (2-5%) - diarrheal (long incubation), Emetic (short incubation)
2) Mastitis
3) Skin infection
4) Diseases associated with the sepsis in immunocompromised patients
This bacteria is a saprophyte, nonmotile (aflagellate) and chainforming. It is an etiological agent of anthrax diseases and was discovered by Robert Koch in 1877. What is it?
B. anthracis
What are Koch’s four postulates?
- The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
- The microorganism must be isolated from a diseased organism and grown in pure culture.
- The cultured microorganism should cause disease when introduced into a
healthy organism. - The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific
causative agent.
What are the three classifications of B. anthracis?
Which is most fatal, very rare?
Causes?
1) Pulmonary anthrax - most fatal
- Caused by inhalation of spores (not contagious)
2) Cutaneous anthrax
- Introduction of spores through breaches in the skin
3) Intestinal anthrax - very rare
- Ingestion, symptoms of food poisoning
Describe the Early stages of pulmonary anthrax
Fever, coughing, sore throat, fatigue, sweating, vomiting, diarrhea, headache, nausea, chest pain, and shortness of breath
Describe the late stages of pulmonary anthrax
High fever, chest pain, hemorrhagic pathology, death within 48 hours
Describe the appearance of cutaneous anthrax
Lesions with black necrotic center
What could Septicemia following an infection of anthrax lead to?
Meningitis
What are virulence factors of B. anthracis?
Anthrax lethal toxin – degrades host signalling
pathway components, leading to cell death
Anthrax edema toxin – causes accumulation of fluid in tissue
What are the incubation periods of B. anthracis infections?
1) pulmonary
2) Cutaneous
3) GI
1) 1-7 days
2) 1-2 days
3) 1-7 days
What are treatments for B. anthracis?
Vaccine limited availability (military personnel)
Early tx very key – 60 day regimen of ciproflaxin (quinolone) or doxycycline (tetracycline)
Give characteristics of Clostridium sp.
Gram - or +
Morphology
Oxygen tolerance
Spore-forming or not
Gram positive
Rods
Anaerobic (mostly obligate anaerobic)
Endospore forming
What are four Clostridium human pathogens?
1) Clostridium tetani
2) Clostridium botulinum
3) Clostridium perfringens
4) Clostridium difficile
What do free radicals/reactive oxygen species (ROS) do? (4)
1) Modify proteins
2) Regulate the function of proteins
3) Damage nucleic acid
4) Cause cell death
What antioxidant defenses to some bacteria posses? (3)
1) Superoxide dismutase
2) Peroxidase
3) Catalase
What are four diseases caused by Clostridium sp.?
1) C. tetani - Tetanus
2) C. botulinum - Botulism, Floppy baby syndrome, Wound infection
3) C. perfringens - Gastroenteritis, Gas gangrene
4) C. difficile - Antibiotic-associated diarrhea
Describe C. tetani
Oxygen tolerance
Motility
Appear as ‘tennis rackets’ under microscope examination
Obligate anaerobe
Motile
Describe generalized tetanus and what it may lead to
Prolonged contraction of skeletal muscle fibers
Characteristic opisthotonus
–Severe hyperextension and spasticity of head, neck, and spine
–Spasm of axial muscles of the spinal column leads to characteristic arching
May lead to respiratory failure
Hypertension, tachycardia
How is C. tetani transmitted?
What is its incubation period?
Transmitted via infected wounds
Incubation period usually 1 wk, but could be several months
How is neonatal tetanus infection transmitted?
Infection through umbilical stump
Describe localized tetanus
Spasms are isolated to the site of injury
Self-resolving
What classifies cephalic tetanus?
CNS involvement - rare
What is the treatment for C. tetani?
Vaccine (tetanus shot) = toxoid vaccine
Childhood vaccine with booster recommended every 10 years
Administered following severe trauma to the skin (postexposure prophylaxis)
What is C. botulinum oxygen tolerance?
Obligate anaerobe - expresses superoxide dismutase
How is food-borne botulism transmitted? (What are risk factors)
Ingestion of spores from improperly canned foods
Sporulation may occur at higher pH
What are symptoms of botulism?
Flaccid muscle paralysis - slurred speech, droopy eyelids, difficulty swallowing, generalized muscle weakness
Botulinum toxin is a neurotoxin with multiple serotypes. Which serotypes cause human disease and how does the toxin act?
Serotypes A-G exist, with A, B, E & F causing human disease.
Toxin acts by blocking the release of acetylcholine from motor nerve endings
How is infant botulism transmitted?
“floppy baby syndrome”
Food-borne
Honey - spores found in honey can germinate in the less acidic gut of newborns
What is wound botulism?
Infection of wound with spores
What are treatments for C. botulinum?
Antitoxin - antibody against botulinum toxin
Ventilator for respiratory complications
No vaccine available
What are commercial uses for C. botulinum?
Muscle pain disorders
Hyperhydrosis
Botox - cosmetic
Compare direct vs indirect pathology
Direct pathology comes from the effect of the pathogen of a cell, tissue or organ
- Viral replication and lysis in a tissue causes damage to that tissue
- Bacterial toxins may cause local or distal effects - tetanospasmin and botulinum toxin exert their effect in the CNS even though the bacteria don’t replicate in the CNS
Indirect pathology comes from secondary effects and immune pathology
- Cell damage mediated by inflammatory mediators at a site of replication
- Symptoms associated with tissue remodeling following damage
Which bacteria is non-motile and double-zone heamolysis?
C. perfringens
Describe the effects of Clostridium perfringens enterotoxin (CPE)
Tissue necrosis
Destroys tight junctions between endothelial cells in the gut
What are symptoms of C. perfringens
Diarrhea, vomiting, abdominal cramping, fever
Clostridial necrotizing enteritis (rare, fatal)
How long is the incubation period for C. perfringens?
8-24 hours
Gas gangrene is a serotype of C. perfringens, which one? and what is it also known as?
How is it transmitted?
Serotype A
aka clostridial myonecrosis
Transmitted by infection at a site of trauma, usually lacking blood supply - contaminated surgical equipment, gloves et.
What are the symptoms of gas gangrene?
what is its incubation period?
Muscle wasting
Edematous, necrotic blisters
Putrefcation of tissue with smell
Incubation period 1-4 days
What are the virulence factors of C. perfringens?
α-toxin – destroys tissue and produces gas
β, ε, ι toxins – increase vascular permeability
δ, φ toxins – haemolysins
What are treatments for C. perfringens?
Amputation
Penicillin, clindamycin, rifampicin, metronidazole
Describe C. difficile:
Motility?
Oxygen tolerance?
Opportunistic?
Motile
Obligate anaerobe
Opportunistic pathogen
Describe antibiotic resistant diarrhea (c. difficile)
occurs as a consequence of antibiotic useage
Fever, diarrhea, vomiting, abdominal pain, crampin
Describe pseudomembranous colitis (c. difficile)
Inflammation of the colon
Pseudomembrane formation in the colon
Abdominal pain with rebound tenderness
What are treatments for c. difficile?
What is the recurrence rate
Halting current antibiotics
Vancomycin, metronidazole
Recurrence rate is extremely high
How is c. difficile transmitted and how can it be prevented?
Transmitted fecal-oral
Prevented via hygiene!!
This bacteria is gram positive and polymorphic.
It’s toxin inhibits translational machinery.
What is it?
Corynebacterium diptheria (diptheria)
What are clinical features of diptheria?
Sore throat, low fever, dark pseudomembrane on the tonsils, pharynx, and/or nasal cavity
Fever, chills, fatigue, sore throat, hoarseness, cough, headache, painful swallowing, difficulty breathing
Skin lesions also common
What are complications of diptheria?
Cardiac and nervous system complications
How is diptheria transmitted and what is its incubation period?
Transmitted through contact, respiratory droplets and contaminated food
Incubation period 2-5 days
What are treatments for diptheria?
Toxoid vaccine available (pentavalent or DPT)
Responsive to multiple antibiotics
Severe cases treated with diptheria
antitoxin
Describe characteristics of Listeria monocytogenes (lysteriosis) Gram positive/negative? Morphology Food- air- water-borne? Oxygen tolerance? Motility? Psychrotrophic? Reproduction? Hemolysis? Catalase positive/negative>
Gram positive Rod-shaped Food-born pathogen Facultative anaerobe Motile Psychrotrophic (survive cold temps) May reproduce extracellularly or intracellularly in macrophages Beta-hemolytic Catalase positive
What are clinical presentations of Listeriosis?
Diarrhea, fever, muscle aches
CNS involvement
20-30% fatality rate in infected patients
How is listeriosis transmitted and how long is its incubation period?
Transmitted through ingestion of contaminated food (processed or fresh)
incubation period is 1-70 days (typically 2-3 wks)
What are treatments for listeriosis?
Ampicillin or other antibiotics
