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
