Wagner

1. the organism must be present in every case of a disease

2. The organisme must be propagated in culture

3. The organism must cause the same disease when inoculated into a naive host

4. The organism must be recovered from the newly diseased host

Enhance the disease-causing ability of pathogens

• contain genes encoding for virulence factors

• Have been acquired by horizontal gene transfer

• E.g. type IV sectretion system oh H. Pylori; type III secretion system of S. Typhiurium; iron uptake of Y. Enterocolitica; enterotoxins & lipoproteins of S. Aureus

1. the phenotype under study should be ascociated with pathogenic strains of a species

2. Specific inactivation of the suspected virulence gene(s) should lead to a measurable loss in virulence or pathogenicits. The gene(s) should be isolated by molecular methods

3. Reversion or replacment of the mutated gene should restore pathogenicity

The multicellular movement of bacteria across a surface driven by rotating helical flagella

The movement of individual bacteria in liquid driven by rotating flagella

The surface movement of bacteria powered by the extension and retraction of pili

Active surface movement involving focal-adhesion complexes

Passive surface translocation powered by grwoth & facilitated by a surfactant

1. low affinity interactions

2. High affinity interactions

• organized, high density communities of baceria

• Exopolymer matrix

• Localized differences in expression of proteins

• Cell-cell communication by secreted small molecules

• Protect inhabitants from antimicrobial compounds

• Support of dormant, persistent cells

• S. Aureus: alpha toxin, leukocidine, perfingolysin

• E. Coli: alpha toxin

• C. Perfringens: enterotoxin

• V. Parahaemolyticus: haemolysin

• C. Botulinum: C2 toxin

• C. Perfringens: toxiN

• V. Cholerae: RTX

• Diphtheria toxin

• P. Aeruginosa: exotoxin A

• Shiga toxin

• Cytolethal distending toxins

• Pasteurella multocida toxin

• E. Coli: ST/LT

• Clostridial cytotoxin

• Cholera toxin

• Pertussis toxin

• Bordetella DNT

• Anthrax toxin

• Super antigen

• Staphylococcal exofoliation

• B. Fragilis toxin

• H. Pylori: VacA

• Aerolysin

• C. Botulinum neurotoxins

• Tetanus toxin

• Substrates are targeted to the injectisome by cognate chaperones

• Substrate unfolding by the systems ATPase

• Translocation of unfolded substrates mediated by export apparatus: Mechanism unclear, PMF involved

• Strict secretion hierarchy:

  • early substrates build up needle

  • Intermediate substartes: Needle tip/translocon

  • Late substartes: effectors

Dont kill bacteria - elimination by microbiota & immune system

• lower probability of developing resistance

• Maintenance of commensak microbiota & colonization resistance

Extracellular immune avoidance

-> protects from complement binding & phagocyte recognition (e.g. S. Pneumoniae)

Extracellular immune avoidance

-> reverse opsonization by binding Fc part of antibodies

S. Aureus

Extracellular immune avoidance

-> helps to avoid recognition by specific antibodies (e.g. flagella & pili antigens of Salmonallea, P. Falciparum ertythrocyte membrane proteins)

• where did it originate/portal of entry: food-borne, airborne, blood borne or sexually transmitted

• Where is the disease manifested: organ system

• What is the patient history

• Contact to other animals: zoonotic disease

• Differential diagnosis

  • Microscopy: shape (rods, cocci, …) Gram +/-

  • Culture: liquid, plate (ptimal vs. slective

  • Molecular diagnosis (PCR)

  • Biochemical differentiation

  • Serology

Skin infection

Symptoms: Boils

Etiological agent: S. aureus

Virulence factors: coagulase, proteins A, TSST, leukicidin, exfoliative toxin

Source: skin

Treatment: Erythromycin, vancomycin,…

Skin infection

Symptoms: Skin lesions, usually facial

Etiological agent: S. Pyogenes

Virulence factors: M-protein pili, C5a peptidase, hemolysin, pyrogenic toxins

Source: Skin

Treatment: Penicillin G

Respiratory tract infection

Symptoms: Tracheal pseudomembrane

Etiological agent: Corynebacterium diptheriae

Virulence factors: diphtheris toxin

Source: Humans/airborne

Treatment: Penicillin

Respiratory tract infection

Symptoms: fever, chills, cough, boody sputum, fatigue, weight loss

Etiological agent: Mycobacterium tuberculosis

Virulence factors: cord factor, wax D, intracellular growth

Source: Humans/respiratory droplets

Treatment: rifampin, isoniazid, ethambutol

Respiratory tract infection

Symptoms: fever, chills, cough, chest pain

Etiological agent: S. pneumoniae

Virulence factors: capsule, pneumolysin

Souce: Humans/inhalation

Treatment: macrolides, quinolones, ceftriaxone

Gastrointestinal trat infection

Symptoms: delayed onset (18h) diarrhea, abdminal pain

Etiological agent: S. typhimurium

Virulence factors: T3SS, intracellular growth

Source: chicken, other animals, fecal-oral route

Treatment: oral rehydration, antibiotics only if severe

Gastrointestinal infection

Symptoms: quick onset (4h) nausea, vomitting, diarrhea

Etiological agent: S. Aureus / Hleicobacter pylori

Virulence factors: enterotoxin

Source: preformed toxins in food

Treatment: supportive

Gastrointestinal tract infection

Symptoms: watery diarrhea

Etiological agent: vibrio cholerae

Virulence factors: cholera toxin, toxin-coregulated pili, ToxR regulator

Source: human waste contamination

Treatment: oral rehydration, antibiotics

Cardiovascular system infection

Symptoms: fever, pain, weakness, heart murmur

Etiological agent: Strep mutans & other Gram+ cocci

Virulence factors: biofilm formation, glycocalyx

Source: oral flora, injury in oral cavity

Treatment: intravenous PenicillinG, surgery

Systemic infection

• causen by Borrelia burgdorferi - spirochete

• Transmitted by ticks

• Bacterium can traven anty part of the human body

• Three stages

  1. bulls eye rash (erythema migrans)

  2. Joint, muscle & nerve pain

  3. Arthritis with WBCs in the joint fluid

• Treatment with antibiotics is recommended for all stages