Bacterial Involved in Respiratory Infections Flashcards
2 functions of Normal Flora in maintaining the healthy state of the host
- Competes with pathogenic mechanism
2. Produces substances which are bactericidal
Most common cause of URTI
Rhinoviruses
Common causes of Pharyngitis
S. pyogenes, C. diptheriae
Causative agent of whooping cough
Bordetella pertussis
Viral infections usually resolves around how many days?
1-2 days
Causes of “strep throat”, scarlet fever, rheumatic fever and RHD
Group A streptococcus (S. pyogenes)
Most common cause of newborn sepsis
Group B streptococcus
General features of S. pneumoniae
gram (+), NM, encapsulated diplococci
Lancet shape
Fastidious
found in nasopharynx
Two ways a person becomes infected with s. pneumoniae
Endogenous - carriers
Exogenous - droplet transmission
Most important virulence factor of s. pneumoniae
CAPSULE (85 capsular serotypes)
Functions of the capsule
antiphagocytic and antigenic
Virulence factor responsible for release of intracellular virulence factor
Autolysin (peptodoglycan hydrolase)
VF that attacks mamalian cells, causing lysis
Pneumolysin
Contiguous spread of s. pneumoniae from the nasopharynx through the eustachian tube leads to?
otitis media
Otitis Media is most common in children because?
Eustachian tube is more horizontal compared to adults
Laboratory diagnosis of s. pneumoniae
Alpha hemolytic on BAP
G(+) diplococci on direct gram stain
Sensitive to optochin (>14mm) and (+) bile solubility
(+) quellung test
Sensitivity of sputum gram stain and cultures
80% and 93%
First line drug of S. pneumoniae
Amoxicillin
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
Characteristics of Prevnar(13 strains) and Synflovix (10 strains)
conjugated vaccine
<2 years of age
for adults also: PREVNAR -> 23 strains
General features of S. pyogenes
G(+), NM cocci occuring in long chains
GROUP A, beta hemolytic streptococcus
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
Composition of capsule of s. pyogenes
hyaluronic acid
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
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
