Treponema pallidum (syphilis) Leptospira spp. (hemorrhagic fever) Borrelia recurrentis (relapsing fever) Borrelia burgdorferi (Lyme disease)

3.10 Flashcards by sophie rosen

Typical Bacteria

• Gram stain differentiation

§ Reflects a fundamental differentiation based on
permeability, presence or absence of outer membrane
and cell wall thickness

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• Cellular morphology

§ 4 typical cell types

v Gram (+) rods
v Gram (+) cocci
v Gram (-) rods
v Gram (-) cocci

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• Gram positive rods have more in common with

(1) than with gram negative rods

gram positive cocci

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Ø Gram positive cocci (2)

Staphylococci

* Streptococci

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• Staphylococci (3)
types (3)
found in?

§ S. aureus; S. saprophyticus; S. epidermidis
§ Found in many body sites; primarily skin infections &
wounds; carbuncles; abscesses; leading to life
threatening deep tissue infections: osteomyelitis,
endocarditis
§ Severe intoxications; Food poisoning

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Streptococci (4)

§ Alpha or beta hemolysis
   v Alpha: S. pneumoniae
   v Beta: Groups A-T; Group A most prevalent in human
disease
§ Oxygen-tolerant anaerobes

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Gram negative cocci (2)

Neisseria meningitidis

* Neisseria gonorrhea

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Gram positive rods (2)

Non-Spore-forming aerobic rods

* Spore-forming rods

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Non-Spore-forming aerobic rods

§ Corynebacterium diphtheriae and related diphtheroids

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Spore-forming rods (3)

§ Aerobic: Bacillus anthracis (anthrax)
§ Anaerobic: Clostridium species
v C. botulinum; C. tetani; C. perfringens; C. difficile

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Ø Gram negative rods

• Enteric bacteria (3)

§ Enterobacteriaceae (facultative anaerobes)
v Escherichia coli; Salmonella spp.; Shigella spp.;
Yersinia spp. (pestis; pseudotuberculosis)
§ Vibrio cholerae; Campylobacter jejuni; Helicobacter pylori

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Significant non-enteric Gm- rods: (5)

§ Pseudomonas aeruginosa
§ Haemophilus influenzae
§ Bordetella pertussis
§ Brucella abortus
§ Legionella pneumophila

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Gram negative rods (contin.)
• Strictly anaerobic Gm- rods
§ Bacteroides fragilis (4)

ü Most common organism in the human intestine.
ü Can cause serious disease when deposited into deep tissues.
(abscesses)
ü Can be also be found in gingival pockets
ü Very stinky

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Acid-fast bacteria

• Mycobacterium tuberculosis; M. leprae

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Spirochetes (4)

Treponema pallidum (syphilis)
Leptospira spp. (hemorrhagic fever)
Borrelia recurrentis (relapsing fever)
Borrelia burgdorferi (Lyme disease)

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Strictly intracellular bacteria (5)

Chlamydia trachomatis (most common STD)
Chlamydia pneumoniae
Rickettsiae (Rocky mountain spotted fever)
Ehrlichia (arthropod borne)
Coxiella burnetti (Q fever)

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staphyle =

cluster of grapes

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coccus =

sphere

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aureus =

golden colonies

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Staphylococcus

Characteristics: (3)

Gram+ cocci, catalase+

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o2?

staphylococcus aureus

O2 can
be used (faculative anaerobe)

Ø catalase

Reduces the potential of phagocytes to kill

Ø coagulase (2)

The tissue-invasive potential of staphylococcal infections is directly
proportional to coagulase production (S.aureus; not in other Staph. species).
• coagulase binds prothrombin: fibrinogen is cleaved anti-phagocytic fibrin coating

clumping factor

fibrinogen-binding protein: cell surface proteins that bind to foreign
materials (like sutures) and to extracellular matrix.

Ø protein A

Anti-phagocytic, competes with neutrophils for Fc portion of opsonizing IgGs (on cell surface of S.aureus but not on other staphylococcal strains)

Ø leukocidin

secretion: inhibits phagocytosis by granulocytes by forming pores in phagosomal membranes, and kills phagocytes. Major factor in pus formation.

digestive enzymes

digestive enzymes proteases, DNase, nuclease, lipases | hyaluronidase (spreading factor: digests extracellular matrix)

staphylokinase

converts plasminogen to plasmin, increasing invasion by digesting fibrin clots and cleaves C3b and IgG to inhibit phagocytosis

β-lactamase

Enzymatic digestion of penicillins (90% strains have plasmid-based antibiotic resistance)

α-, β-, γ-, and δ-toxins are all

hemolysins: lyse erythrocytes (lab phenomenon)

§ α-hemolysins (pores) are (4)

hemolytic, leukocytic, destroy skin, cause smooth muscle paralysis

§ β-hemolysins are cytolytic sphingomyelinases that destroy ---

nerves

§ γ-hemolysins lyse like related --- on neutrophil lysosomal membranes

leukocidin

Empyema:

Empyema: Collection of pus in a naturallyexisting anatomical cavity (e.g. lungs)

pyogenic infections:

pus-forming (massive amounts of neutrophils and other leukocytes are lysed by bacterial factors (e.g. leukocidin) and release their lysosomal contents in attempting phagocytic killing of the staphylococci).

Invasive pus-forming infections (4)

FOLLICULITIES FURNUNCLES CARBUNCLES (SYSTEMIC) BACTEMIA FEVER

superangtigens- overrides the

specificity of the t cell response

Ø enterotoxins Heat-stable (cooking doesnt help!) toxins A, B, C1, C3, D, E are super-Aglike: cause of

gastrointestinal upset typical of food poisoning (Vomiting may be induced by inflammatory reaction of subepithelial macrophages to toxins with a resulting change in vascular permeability)

Toxic Shock Syndrome Toxin TSST:

mass activation of T cells leads to large | production of inflammatory cytokines (heat and protease-resistant TSST-1; chromosomal gene)

exfoliative toxin

{heat-stable, chromosomal), B (heat-labile, plasmid) : SSSS | staphylococcal scalded-skin syndrome

TSS: Toxic Shock Syndrome

Increased oxygenation of vagina by tampons, and | foreign surface adhesion, caused massive growth

SSSS: Staphylococcal Scalded Skin Syndrome

Ø exfoliative toxins A, B cause loss of layers of the skin in SSSS Nester 04 Fig. Murray05 Fig.22-5 Neutralizing A

Nosocomial Staphylococci a

surgery, implant & instrument risk

Nosocomial (hospital instruments and implants) infections (often coagulase-negative S.epidermidis)

Endocarditis: • acute: ---% S.aureus • if artificial heart valves: ---% S.epidermidi

60 | 80

S.epidermidis:

dental extraction risk

``` most frequent causes of bacterial arthritis by age oeganism: staphylococcus aureus neonates 2 mo-2 ye 30-10 yr adult ```

10-125% 25-50% 25-50% 25-75%

Gram+ cocci, aerobic / facultatively anaerobic coagulase+ catalase+ Epidemiology (4)

``` skin + mucosa +aerosols surface survival (hospital instruments, implants) nosocomial (hospitalacquired) high temperature (40ºC) and salt resistant ```

β-lactamase (plasmid): >---% penicillin resistant

penicillin-binding protein 2a (chromosomal): causes --- Resistance

Methicillin

--% of hospital strains are MRSA; --% of community strains are MRSA What can you do in case of (Enterococcus-derived) VRSA ? nothing

50 | 20

Coagulase─ : Other Staphylococci like S.epidermidis or S.saprophyticus (2)

* Thick cell wall, slime capsule, (S.saprophyticus: urease secretion → acute cystitis * Opportunistic hospital pathogens (instruments, catheters, heart valves)