Bacterial Pathogens Part I Flashcards
Gram-positive and Gram-negative
cell walls
Gram-positive: thick peptidoglycan and has tichoic acid, no outer membrane
Gram-negative: outer membrane, thin peptidoglycan, periplasmic space
Gram-positive cocci
- Gram-positive cocci (spheres)
- Staphylococcus
- Streptococcus
- Enterococcus
• Gram-positive bacilli (rods)
- Gram-positive bacilli (rods)
- Listeria monocytogenes
- Corynebacterium diphtheriae
- Bacillus anthracis
how to diff gram positive cocci’s
Catalase, benchtop test to detect presence of enzyme
Breaks down hydrogen peroxide to oxygen and water
Protective mecahnism for cells
catalase (+): staphylococcus - coagulase (+): S. aureus - coag (-): S. epidermidis S. saprophyticus S. lugdunensis S. hominis catalase (-): streptococoos, enterococcus (chains)
Staphylococcus
Staphylococci (clusters): Staphyloccocus aureus (S. aureus)
natural habitat
• Cocci in clusters
Grampositive cocci in clusters
Catalase and coagulase positive
Lives in the nares of the nose
Usually asymptomatic
Around 20% of people are not colonized
60% intermittent carriers
natural habitat:
- Skin
- Mucous membranes
- Respiratory tract
- Air, environment
Usually carried in the anterior nares of patients
and medical staff
In healthy subjects, 20% are not colonized, 20% are
persistently colonized, and 60% are intermittent carriers
Staphylococci (clusters): Staphyloccocus aureus (S. aureus)
associated infections
- Skin and soft tissue infections (boils, abscesses, impetigo, wound infections) - Osteomyelitis - Joint infections - Sepsis - Endocarditis - Prosthetic material infection - Necrotizing pneumonia - Toxin-mediated diseases (food poisoning, scalded skin syndrome, toxic shock syndrome)
Folliculitis Impetigo Erysipelas Cellulitis Scalded skin syndrome - Disruptions between skin cells - Blistering off of skim - Fever for babies - Sloughing off of skin with gentrle pressure
caused by?
Staphylococcus aureus
• Impetigo: superficial infection of the epidermis, outer layer
Usually face or extremities (gold crusting)
• Erysipelas: infection of upper dermis (raised, clear demarcation)
• Cellulitis: infection of deeper dermis and
subcutaneous fat
scalded skin syndrome • Occurs mostly in infants • Blistering, loss of superficial layer of skin • Fever, skin pain, irritability • Due to exfoliative toxin
Staphylococci (clusters): Coagulase-negative staphylococci (CNS)
Natural habitat and associated infections
Staphylococcus epidermidis
- Skin
- Mucous membranes
- Respiratory tract
- Air, environment (same areas as S. aureus)
Staphylococcus saprophyticus
- Genitourinary mucous membranes in women of child-bearing age
- Urinary tract infections
Usually cause prosthetic material infections
- Stitch abscesses
- IV catheter infections
- Catheter-associated urinary tract infections
- Prosthetic joint infections
- Sepsis
- Endocarditis (mainly with prosthetic valves)
Staphylococcus epidermidis
tests
Catalase positive and coagulase negative
Streptococci (chains): Streptococcus pyogenes (S.pyogenes)
• Gram-positive cocci in chains
On blood agar plates, some bacteria cause
the hemolysis of the red blood cells
Natural habitat
- Ubiquitous
- Skin
- Throats of asymptomatic carriers
Associated infections
- Skin and soft tissue infections (abscesses, erysipelas, cellulitis)
- Pharyngitis, tonsillitis
- Immune-mediated diseases (rheumatic fever, acute glomerular nephritis)
- Toxin-mediated diseases (scarlet fever, necrotizing fasciitis, toxic shock syndrome)
pharyngitis
Scarlet fever
Necrotizing fasciitis
caused by?
Streptococcus pyogenes
pharyngitis
- Scarlet fever
- Associated with pharyngeal infection
- Due to pyrogenic exotoxins
- Red rash with sandpaper texture
- Small red spots on the soft and hard palates
- “Strawberry tongue, no treatment
Necrotizing fasciitis
• Infection of deep tissues that results in destruction of muscle fascia and subcutaneous fat
sig pain in soft tissue
Streptococci (chains): Streptococcus agalactiae (S. agalactiae)
natural habitat and associated inf
AKA group B strep
Vagina
- Cervix
- Gastrointestinal tract
- Postpartum sepsis
- Neonatal pneumonia
- Neonatal sepsis
- Neonatal meningitis
Streptococci (chains): Streptococcus pneumonia (S. pneumoniae)
natural habitat and associated inf
- Upper respiratory tract
- Asymptomatic carriage
common (30-70% in young children but <5% in adults) - Pneumonia
- Otitis media
- Sinusitis
- Sepsis
- Meningitis
Streptococcus pneumoniae
appearance
• Gram-positive diplococci
Streptococci (chains): Viridans group streptococci (VGS) Made up of five groups S. mitis group S. anginosus group S. mutans group S. salivarius group S. bovis group
natural habitat and associated inf
- Mouth
- Gastrointestinal tract
- Respiratory tract
- Urogenital tract
- Environment
- Dental caries
- Brain, oropharynx, GI tract abscesses
- Sepsis
- Endocarditis (usually in those with already abnormal heart valves)
Enterococci (chains): Enterococcus faecalis and faecium
Two main species E. faecalis E. faecium Formerly called Group D Streptococci Vancomycin resistant enterococci = VRE
natural habitat and associated inf
Skin - Mouth - Gastrointestinal tract - Urogenital tract - Environment Can grow in hiigh pH, high salt Can grow bile which is pretty harsh (dont need to know)
- Post-surgical wound infections (especially GI or
GU surgeries) - Intra-abdominal infections and abscesses
- Sepsis
- Endocarditis
Cause cavities, abcesses
Blood stream infections
Listeria (bacillus): Listeria monocytogenes
Only human pathogen is L.
monocytogenes
natural habitat and associated inf
- Gastrointestinal tract, foudn in stool
- Environment
- Usually causes disease in pregnant women, infants, the elderly, and those with certain underlying diseases (immunocompromise, cancer, alcoholism) -Diarrhea, gastroenteritis - Sepsis - Endocarditis - Meningitis - Spontaneous abortion, stillbirth
what bacteria
• Typically infects humans by entering food production
• Able to grow at 4°C
Listeria monocytogenes
Corynebacterium (bacillus): Corynebacterium diphtheriae
> 100 species in the
Corynebacterium genus
Most important human
pathogen is C. diphtheriae
natural habitat and associated inf
- Nasopharynx
- Skin
- Environment
-Respiratory diphtheria
-Cutaneous diphtheria
Widespread availability of vaccine and inclusion in
routine childhood immunization schedules has
significantly reduced rates of respiratory diphtheria
• toxin causes disease with pseudomembrane formation and respiratory compromise, sometimes with myocardial, nervous system, and kidney toxicity
which bacteria causes this?
C. diphtheriae
Bacillius (bacillus): Bacillus anthracis (ie, anthrax)
natural habitat and associated inf
- Infected animals
- Spores in soil, water, vegetation (persists in soil for many years)
- Bioterrrorism
- Cutaneous anthrax
- Cutaneous diphtheria (95% of anthrax cases) with painless ulcer
- Inhalation anthrax
- Gastrointestinal anthrax
- Anthrax meningitis
- Injection anthrax
describe inhalational anthrax
caused by Bacillus anthracis
• Inhalational anthrax
• Inhaled spores germinate in lungs and cause fever, declining
respiratory status, pleural effusions, and mediastinal widening
• High mortality rate
describe bioterrorism
caused by Bacillus anthracis
• Anthrax is one of the most likely biological weapon agents to be used
because:
• Anthrax spores are easily found in nature, can be produced in a lab, and can
last for a long time in the environment
• Anthrax can be released quietly and without anyone knowing. The microscopic spores could be put into powders, sprays, food, and water
Amerithrax: “one of the largest and most complex [investigations] in the history of law enforcement”
Gram-negative cocci (3)
- Neisseria gonorroeae
- Neisseria meningitidis
- Moraxella catarrhalis
