Bacterial Involved in Respiratory Infections Flashcards by Jonathan Paul Ladera

2 functions of Normal Flora in maintaining the healthy state of the host

Competes with pathogenic mechanism

2. Produces substances which are bactericidal

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Most common cause of URTI

Rhinoviruses

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Common causes of Pharyngitis

S. pyogenes, C. diptheriae

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Causative agent of whooping cough

Bordetella pertussis

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Viral infections usually resolves around how many days?

1-2 days

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Causes of “strep throat”, scarlet fever, rheumatic fever and RHD

Group A streptococcus (S. pyogenes)

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Most common cause of newborn sepsis

Group B streptococcus

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General features of S. pneumoniae

gram (+), NM, encapsulated diplococci
Lancet shape
Fastidious
found in nasopharynx

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Two ways a person becomes infected with s. pneumoniae

Endogenous - carriers

Exogenous - droplet transmission

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Most important virulence factor of s. pneumoniae

CAPSULE (85 capsular serotypes)

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Functions of the capsule

antiphagocytic and antigenic

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Virulence factor responsible for release of intracellular virulence factor

Autolysin (peptodoglycan hydrolase)

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VF that attacks mamalian cells, causing lysis

Pneumolysin

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Contiguous spread of s. pneumoniae from the nasopharynx through the eustachian tube leads to?

otitis media

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Otitis Media is most common in children because?

Eustachian tube is more horizontal compared to adults

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Laboratory diagnosis of s. pneumoniae

Alpha hemolytic on BAP
G(+) diplococci on direct gram stain
Sensitive to optochin (>14mm) and (+) bile solubility
(+) quellung test

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Sensitivity of sputum gram stain and cultures

80% and 93%

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First line drug of S. pneumoniae

Amoxicillin

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Characteristics of PPV

23 different serotypes
90% of invasive strains
more expansive serovar protection in addition to the conjugated vaccine
indicated for 2 years old and above

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Characteristics of Prevnar(13 strains) and Synflovix (10 strains)

conjugated vaccine
<2 years of age
for adults also: PREVNAR -> 23 strains

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General features of S. pyogenes

G(+), NM cocci occuring in long chains

GROUP A, beta hemolytic streptococcus

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Most virulent GABHS

S. pyogenes

invade INTACT skin or mucous membrane
Low inoculum can cause infection
Nasopharyngeal carriage is common
Common cause of infection in neonates

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Composition of capsule of s. pyogenes

hyaluronic acid

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What is the role of fimbriae of s.pyogenes

Contains M protein (highly antigenic and give variability)

N Terminal has anti phagocytic activity

Lipotechoic acid for adherence

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Mediates attachment of S. pyogenes

protein F

What are the extracellular products of s. pyogenes

Streptococcal pyrogenic exotoxins (SPE) | Cytolytic toxins and other exoenzymes

Examples of Streptococcal pyrogenic exotoxins

``` SPE A and C (carried by bacteriophage) SPE B (cystein protease) ```

What cytolytic toxins damages cells resulting in release of lysosomal enzymes and degranulation?

Streptolysin O

What cytolytic toxin lyses RBC, leukocytes and platelets?

Streptolysin S

What enzyme catalyzes converion ofplasminogen to plasmin?

Streptokinase

Most common type of s. pyogenes infection

Acute pharyngitis or phayngotonsilitis

Give 2 non-infectious sequelae of s.pyogenes infection

Acute rheumatic fever | AGN

Laboratory diagnosis of S. pyogenes

``` Small opalacent colonies B-hemolytic sensistive to bacitracin Precipitin reaction: C-carbohydrate ASO and antiDNAse B CAMP negative ```

Test to identify group A beta hemolytic streptocci

CAMP

Treatment of s.pyogenes infection

Penicillin and macrolides

general features of H. influ

Gram (-) coccobacillus | Encapsulated

Other name for H. influenza

pfeifer's bacillus

6 distinct antigenic type of H. influ

``` Type A GLUCOSE Type B RIBOSE TYPE C GALACTOSE TYPE D HEXOSE TYPE E HEXOSAMINE TYPE F GALACTOSAMINE ```

Most important antigenic type of H. influ

``` TYPE B (ribose, ribitol, phosphate) antiphagocytic ```

Growth factors of H. influ

X factor - haemin | V factor: NAD/NADP - oxidation reduction process

Only natural host for H inlu

Human

Virulence factor of H influ that induces hypotension, shock and other systemic infection

Lipopolysaccharides

Thumb sign

Epiglottitis

Laboratory diagnosis of H. influenza

small g(-) coccobacilli (presumptive dx) Grows in the presence of X and V actors Grows in aerobic atmosphere enriched with 5-10% CO2

What do you call the phenomenon where H. influenza grows mercury droplet like colonies near S. aureus

Satellite phenomenon

Treatment of H. influenzae

Inhibited by ampicillin, chloramphenicol, tetracycline, 3rd generation ephalosporins, co-amoxiclav, ciprofloxacin and azithromycin

treatment for meningitis caused by H. influenzae

3rd generation cephalosporins and chloramphenicol

Prevention against H. influenzae

Immunization with conjugate Hib vaccine | 2,4,6 months

Prophylaxis for H. influenzae

Rifampicin daily for 4 days

General features of S. aureus

G(+) grapelike clusters Produces catalase and coagulase Resistant to heat and drying

Location of S. aureus in the body

skin, anterior nares, and other mucous membranes

Host to lysogeic bacteriophages

S. aureus

Virulence factor of s.aureus that promotes colonization of host tissues

surface proteins (adhesins, fibronectin binding protein)

VF of s. aureus that promotes bacterial spread in tissues

Invasins (leukocidin, kinases, hyaluronidase)

VF of s. aureus that inhibit phagocytic engulfment

Protein A

VF of s. aureus that damages host tissues or otherwise provoke symptoms of disease

Exotoxins

Laboratory Identification of s. aureus

``` Gram + smooth,round, yellow colonies B-hemolytic Grows in MSA nd 15% NaCl catalase and coagulase (+) ```

Example of staphylococci that is resistant to Novobiocin

S. saprophyticus

Example of staphylococci that is susceptible to novobiocin

S. epidermidis

Treatment for S. aureus

Vancomycin (if penicillin resistant) and Linezolid if vancomycin resistant

General features of Bordetella pertussis

``` small g(-) bacilli catalase and oxidase (+) (+)capsule with agglutination property Strict aerobe ```

Two variations of B. pertussis

1) Phase variation | 2) Antigenic Variation

What is different phases of Phase variation

Phase 1: antigenically cometet virulent strain Phase 2 and 3 : intermediate phases Phase 4; Avirulent

What is Antigenic Variation

Low temperature or high magnesium may cause organism to change its antigen becoming avirulent

VF of B. pertussis that protects the bacteria from bactericidal processes

Polysaccharide capsule

Different toxins produced by B. Pertussis

Filamentous hemagglutinin - adhesion | Pertussis toxin - increases histamone release and enhance inflammation

VF of BP that inhibits phagocytosis and NK cell function

Adenylate cyclase

VF of BP that causes paralysis of cillia, tissue necrosis, airway obstruction and paroxysms of cough

Tracheal endotoxin

Very strong vasoconstrictor and causes ischemia and extravasation of leuocytes

Dermonecrotic (heat labile) toxin

Phases of whooping cough

Incubation (1 week) Catarrhal (1-3 weeks) : flu-like symptoms Paroxysmal Phase (3-6 weeks): episodic cough for 3 weeks duration with elevated WBC counts

Culture media of B. pertussis

Bordet-gengou

Laboratory dx of B. pertussis

Oxidase(+) Urease (-) | Dewdrop colonies

SPecimen for recoveryof B.pertussis

Nasopharyngeal washing/swab : Dacron or calcium alginate swab

Cough plates

borget gengou - potato glycerol | Regan lowe - charcoal blood agar

Treatment of B. pertussis

Erythromycin

Prevention of B. pertussis

Killed whole cell vaccine | Acellular vaccine

General characteristics of C. diphtheriae

pleomorphic , non spore forming G(+) with poyphosphate granules Catale and oxidase (+)

Media used to enhance metachromasia of C. diphtheriae

Loefller's agar

Color of colonies of C. diphtheriae on Tinsdale agar

brown to black

Lethal dose of Diphtheria toxin

0.1 ug/kg affects ADP ribosylation

Pseudomembrane formation and bull neck

C. Diphtheriae

API coryne System

Most useful 20 biochemical tests Results within 24 hours (enzymatic) Usease, sugar, and gelatin (5 days)

Treatment of C. diphtheriae

Supportive Antibiotic (penicillin, erythromycin, penicillin tetracycline, rifampicin, clindamycin, erythromycin) ANtitoxin (MUST)

General features of MTB

Obligate aerobe Intracellular Slow grower Beaded appearance - glycogen metaphosphate

Cell wall of MTB

High molecular weight mycolic acids and waxes

Induce caseation necrosis

Phospholipids

Responsible for granuloma formation

Peptidoglycan + mycolic acids

Primary dye of Zhiel neelsen

carbolfuchsin

Counter stain for AFS

methylene blue

Diagnosis of MTB

3 sputum samples | 1/3 (+) is enough

Special stain for MTB

Auramine Rhodamine Stain

Solid Media for MTB

Lowenstein-Jensen Medium

Liquid Media for MTB

BACTEC system

Major surface protein for s. pyogenes

M protein