Micro - Respiratory Flashcards
Virus persistence on dry inanimate surfaces
Adenovirus - 7 days – 3 months
Rhinovirus - 2 hours – 7 days
Coronavirus - 3 hours
RSV - Up to 6 hours
Upper RT sx’s
- Sinusitis
- Rhinitis
- Otolaryngitis
- Laryngitis
- Pharyngitis
Lower RT sx’s
- Bronchitis
- Bronchiolitis
- Pneuomnias - CAPs (acute or subacute/chronic), nosocomial
Viruses w/main pathology elsewhere besides RT
Measles, chickenpox, smallpox, coxsackievirus, norwalk virus
Adenovirus
Family: Adenoviridae Genus: Mastadenovirus
Replication = Class I (nucleus)
Clinical syndromes: pharyngitis, conjunctivitis
• Fiber protein: attachment to host cell rec
• Rec varies w/ viral serotype:
– Serotypes 2 & 5: rec = CAR (Coxsackie Adenovirus Receptor)
• Cell surface glycoprotein belonging to IgG superfamily.
• Penton base has toxic activity
– Inhibition of cellular mRNA synthesis
– Cell rounding
– Tissue damage
Rhinoviruses
Virus family: Picornaviridiae
Icosahedral, non-enveloped
Clinical syndrome: Common cold. Humans are sole reservoir. Young children: more severe. Single community: often contains simultaneously circulating serotypes
– Single individual may be co-infected.
Relatively stable in environment, optimum temperature for growth is 33-35C (URT ideal for infxn), Ag drift.
Cell receptor = ICAM-1, Viral shedding
via surface cleft/canyon
Coronaviruses
Family: Coronaviridiae
• HCoV-229E, HCoV-OC43, SARS-CoV
Clinical syndromes: Common cold, SARS
Enveloped, helical nucleocapsid, characteristic fringe = surface/spike glycoproteins. S protein. Peplomers - define tropism, attach to prots or carbs, site of main Ag epitopes: Abs are neutralizing.
Re-infection by the same serotype possible: neutralizing Abs are short-lived. Transmission via droplets: fecal-oral route also possible.
Replication optimal at 33-34C in ciliated nasal epithelium. Difficult to isolate & grow
Human parainfluenza viruses (HPIV)
Virus Family: Paramyxoviridae
Subfamily: Paramyxovirinae
Genera: Respirovirus: HPIV 1 & 3
Rubulavirus: HPIV 2 & 4. Also includes mumps
Clinical syndrome: laryngotracheobronchitis; bronchitis
Enveloped. Glycoprotein with HN activity
• Fusion Factor (F) – viral entry. Abs against F protein = neutralizing
• V proteins (fusion proteins): evasion of immune response.
• Functions: – Prevent apoptosis, alter cell cycle, inhib dsRNA signalling – Prevent IF biosynthesis
Pneumovirus
Family: Paramyxoviridae, Subfamily: Pneumovirinae, Genus: Pneumovirus
• Enveloped, helical nucleocapsid
• Virally-encoded surface proteins:
– Fusion factor (peplomer): main viral Ag
– G glycoprotein : involved in attachment – Two subgroups: A & B
• Lacks glycoprotein with HN activity
Croup aka laryngotracheobronchitis
- HPIV, Pneumovirus, RSV
- Mostly young children and infants
- Swelling and narrowing of the airway
- Cough sounds like barking of a seal
RSV
• Entry is via epithelia of nose and eye.
– Large droplets on contaminated hands or surfaces (self-
inoculation).
• F & G proteins mediate attachment; F mediates membrane fusion.
• Primary site of replication = nasopharyngeal epithelium.
– Direct cytopathic effect loss of function.
• Can spread into lower RT after 2-5 days via various suggested mechanisms
• CD8+ T cells: subsequent dz enhanced when children vaccinated using heat-killed vaccine
Influenza
Virus survives drying for ± 24 hours, depending on ambient humidity
• Epidemics rarely continue in a community for more than 4 to 6 weeks
– Most people recover spont and gain long- lasting (but weak) immunity to that strain.
– Patient is contagious from before sxs
appear (end of day 1) for next 7 days
– Risk of secondary infxnn highest in time
from 6 to 12 days after infxnn
Children: same as those in adults, plus
– Higher fever
– G.I symptoms: (Vomiting, Abdominal pain)
– Earache (Otitis Media)
– Muscle pain and sometimes swelling
– Croup often but not always
– Febrile Convulsions (Children under 3: Rare)
Complications:
• Rare Neurological syndromes: Guillain Barre, Encephalitis, Reye’s Syndrome in Children – aspirin and aspirin containing drugs.
Influenza A
Only influenza A further classified by subtype on the basis of HA and NA. Influenza A subtypes and B viruses are further classified by strains.
Influenza A: All 15 “H” and 9 “N” found in Birds, domestic Ducks most commonly. Chickens -> sweeping epidemics. Pig is mixing bowl. Man can get from pig or duck
Hemagglutinin: • Major Ag against which neutralizing antibodies are directed.
– Highly variable -> evolution of new strains.
• 4 HA subtypes described in humans: HA1-3, HA5
Requires cleavage to be active:
– Carried out by cellular proteases found only in RT.
– Proteases probably define tissue tropism
Neuraminidase = Sialidase enzyme:
• removes term sialic acid residues from glycoproteins and
glycolipids.
Two subtypes described in humans: N1 and N2.
NO stimulation of neutralizing antibodies
Influenza B
Influenza B viruses are usually found only in humans.
•Two lineages of influenza B: •Victoria-like •Yamagata-like
•Only 1 is covered by the trivalent seasonal flu vaccine.
SHORTER TIME TO DEATH THAN INFLUENZA A
Amantadine & Rimantadine
– Inhibit uncoating of Influenza A only Target is M2 Protein
– No effect on Influenza B or C
• Excessive use of antimicrobials virtually guarantees the development of drug- resistant infectious agents
– Amantidine Resistant Influenza A
Zanamivir & Oseltamvir (Tamiflu®)
– Inhibit Neuraminidase: Without this, virus binds to its own sialic acid and forms useless clumps – blocking release.
– Work on Influenza A and B, not on C
• Excessive use of antimicrobials virtually guarantees the development of drug- resistant infectious agents
– Tamiflu Resistance
STREPTOCOCCI General Characteristics
Metabolism - fermentative with lactic acid production
Oxygen requirements - facultative anaerobes, • growth enhanced by CO2
• Nutritionally fastidious
– Normal culture medium = Blood agar (BA) • Yeastextract+peptone+5%blood
Lancefield classification NOT useful for some streptococci, e.g., S. pneumoniae. Used with serology & hemolysis patterns for preliminary ID (before 16S rRNA sequencing avail).
