Post on 11-Aug-2020
Prof. Beata Sobieszczańska
Wrocław Medical University
Dept. of Microbiology
S. epidermidis
S. saprophiticus
Coagulase - negative
Coagulase enzyme
production
Staphylococcus
Coagulase - positive
Staphylococcus
aureus
Staphylococcus aureus
Virulence factors
associated with the cell
wall:
Peptidoglycan+LTA
Coagulase two types (CF)
Glycocalix
A protein
Surface adhesion
proteins e.g. fibronectin,
collagen, fibrinogen binding
components
Staphylococcus aureus
TOXINS:
Cytolytic exotoxins =hemolysins=pore-forming toxins (toxins: alpha, beta, delta, gamma)
Leukocidin Panton-Valentine
Superantigens:
Exfoliatins (ETA, ETB)
Enterotoxins
Toxic shock syndrometoxin -1 (TSST-1)
Superantigen
Superantigens (Type I toxins)
Unusual bacterial toxins that
interact with exceedingly large
numbers of T4 lymphocytes
This results in the secretion of
excessive amounts of cytokine IL-2
and the activation of self-reactive
T-lymphocytes
Superantigens (Type I toxins)
• Toxic shock syndrome toxin-1
(TSST-1) some strains of Staphylococcus aureus
• Staphylococcal enterotoxins (SE)
• Staphylococcal exfoliative toxin (ETA, ETB)
• Pyrogenic exotoxin (Spe) – toxic shock-like syndrome (TSLS) – rare invasive strains and scarlet fever strains of Streptococcus pyogenes (group A)
Staphylococcus aureus
ENZYMES:
Coagulase
Fibrinolysin
Catalase
Hyaluronidase
Staphylococcus aureus
Source of infection = reservoir (the origin from
which a host acquires the infection):
Human carriers, diseased persons
Transmission:
directly (contact with carriers or infected individual)
indirectly (contaminated surfaces or medical
equipment, food)
Staphylococci – resistant to drying (prolonged
survival), disinfectants, antimicrobials
Routes of transmission of microorganisms to humans:
• person-to-person direct contact = direct contact with diseased person or carrier (touching, kissing, sexual intercourse etc.)
• air-borne route = inhalation of microorganisms spread to the air by infected individuals coughing or sneezing
• exposure to contaminated fomites (objects or materials that are likely to carry microorganisms) such as clothes, utensils, and furniture e.g. keyboard, cell-phones, pens, sharp objects – inhalation or puncture wounds
• by food or water = food-borne (undercooked or fresh food of animal origin, food contaminated by carriers, unwashed vegetables, unpasteurized milk etc.)
• vectors (insects) transmitting microorganisms from animals to humans or from human-to-human e.g. fleas, fly, mosquitoes, bugs
Toxin-mediated (toxin-related) disease –
clinical symptoms are caused by toxin
(damage to cells and tissues)
Pyogenic/purulent = pus producing
Pyrogenic = inducing fever
Staphylococcus aureus – types of infections
Skin &
wound
infections
Endocarditis
Pneumonia
Bacteremia
Food
poisoning
SSSS
TSS
Purulent Toxin-mediated
Skin infections:
impetigo
folliculitis
furuncles
carbuncles
Wound infections
postoperative or
posttraumatic
Osteomyelitis
Pneumonia
Bacteremia
Endocarditis
Septic arthritis
Pyogenic/suppurative
infections
Other staphylococci
Staphylococcus epidermidis
Part of normal flora of the skin and anterior nares
Important cause of infections from prosthetic implants (catheters, heart valves)
Virulence factors: slime layer, lipase
Staphylococcus saprophiticus
Part of the normal vaginal flora
A frequent cause of cystitis in women
Virulence factors: urease
Streptococci
Streptococcus
Lancefield classification
(β-hemolytic) A, B, C, D, E, F, G …….
Group A – Str. pyogenes (GAS)
Group B – Str. agalactiae (GBS)
α-hemolytic:
Oral (viridans) streptococci
Str. pneumoniae
non-hemolytic:
Enterococci (α, β, Ɣ)
Streptococcus
Streptococcus pyogenes
Virulence factors:
Cell wall associated:
Hyaluronic acid capsule
M protein (molecular mimicry – auto-antibodies)
Extracellular:
Streptolysin O (hemolysin)
Pyrogenic streptococcal exotoxins PSE: A, B, C
(former name: erythrogenic toxin)
Streptokinase
Hyaluronidase
Fibronectin-binding proteins
No spread
to blood
PSE+ strain
Post-streptococcal rheumatic fever (ARF) = autoimmune disease
Acute rheumatic fever
Post-streptococcal acute glomerulonephritis
= immune complexes
Streptococcus pyogenes
The most common cause of bacterial
pharyngitis or pharyngotonsilitis
Streptococcus pyogenes
Scarlet fever/scarlatina (pyrogenic exotoxin (PSE) in
non-immunized individuals)
Streptococcus pyogenes
• Erysipelas
• Streptococcal toxic shock syndrome (PSE)
• Bacteremia, sepsis, septic shock
• Pneumonia
Other streptococci
Streptococcus agalactiae (GBS)
Meningitis and septicemia in neonates
Infections in adults: endometritis in postpartum women, septicemia, pneumonia in immunosupressed individuals, UTI, soft tissue infections, endocarditis, bone & joints infections
Virulence factors:
Glycocalix & pili - attachment
Glycosyltransferase – invasion of blood-brain barrier
Polysaccharide capsule – anti-phagocytic
Other streptococci
Streptococcus pneumoniae - diplococci
Capsule – anti-phagocytic (>90 serotypes)
Hyaluronidase
IgA protease
Diseases:
Pneumonia
Sinusitis
Otitis media
Meningitis
Other
STREPTOCOCCUS PNEUMONIAE
Purulent:
Otitis media
sinusitis
pneumonia
INVASIVE:
meningitis
bacteremia, sepsis
endocarditis
peritonitis
Serotypes:
2, 3, 5, 8, 14
Mortality:
15-25%
Anti-pneumococcal vaccines
Prevents any type of pneumococcal disease
Two types:
1. Polysaccharide (PPSV23, Pneumovax) – for
people 2 through 64 years old with certain medical
conditions and 19 through 64 years old who
smoke cigarettes – ineffective in children <2 years
old (against 23 different serotypes)
2. Conjugate (PCV13 capsular polysaccharide +
diphtheria toxoid) against 13 different serotypes –
for all children younger than 2 years old and adults
ENTEROCOCCI
Enterococcus faecalis &
E. faecium cause >90% infections in human
normal intestinal flora of humans and animals
resistant to environmental factors and many antimicrobial agents
Source of infections: endogenous
Indirect: contaminated surfaces & medical equipment
ENTEROCOCCI:
virulence factors
proteins binding ECM = colonization
lipoteichoic acid = fibronectin binding,
induction of cytokines
hyaluronidase = invasion into tissue
Most common infections: UTI,
endocarditis, catheter-related blood
infections
Other: intraabdominal and pelvic infections,
bacteremia, postoperative wounds
infections, meningitis – uncommon
(neurosurgical procedures)
Streptococci in oral cavity
Streptococcus: mitis, mutans, salivarius, sanguis, milleri
normal flora: oral cavity, intestines, urethra
endogenous infections: dental carries, endocarditis, mixed infections within oral cavity (e.g. abscesses)
Thank you for your
attentionNext lecture and class:
Clostridium, Bacillus
Murray chapter 30