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Infectious and Parasitic disease II
Overview
Respiratory infections GI and liver infections Meningitis Sexually transmitted diseases
Respiratory infections
Viruses most common Range from self limited, common cold to life
threatening infection. Rhinoviruses
Viruses responsible for common cold Composed of single stranded RNA,
unencapsulated. Induce production of IgG and IgA antibodies by
the host to the particular subtype. 100’s of subtypes
Influenza viruses
Contain 8 single stranded RNAs bound to nucleoproteins that determine the subtype, A, B or C.
Have envelope containing a hemagglutinin and a neuraminidase which project out from the envelope and determine the further subtype of the virus eg. H1N5.
Affect nasal channels, sinuses, eustachian tubes, tonsils and bronchioles.
Hyperaemia, swelling, lymphomonocytic and plasmacytic infiltation of submucosa with oversecretion of mucus.
Influenza viruses
Clearance of the virus occurs when cytotoxic T cells kill virus infected cells.
Host develops antibodies to H and N components therefore preventing re-infection.
Mutations occur in H and N, allowing new strains to emerge.
Major complication is bacterial superinfection with pneumococcus, staphylococcus or haemophilus.
Haemophilus influenza
Gram negative bacteria. Major cause of epiglottitis, meningitis and
laryngotracheobronchitis – all life threatening conditions that affect children.
Bacteria has a capsule that helps it evade host immune system.
Children are vaccinatied against H. influenza type B.
Causes fibrin rich exudates of neutrophils.
TB
TB
Bacillus – Mycobacterium tuberculosis Important infectious disease worldwide,
particularly in the developing world – 2 – 3 million deaths from TB per year.
AIDS patients particularly vulnerable – multidrug resistant forms developing.
Primary infection: resolves in 95% as causes T cell mediated response.
Classification of pnemonias
Community acquired Strep pneumoniae Haemophilus influenza S. aureus Mycoplasma pneumonia Chlamydia pnemonia
Hospital acquired Strep pneumoniae Haemophilus influenza E coli Klebsiella Serratia Pseudomonas aerguinosa
Pneumonia in immunocompromised
Diarrhoeal diseases
Major causes: Campylobacter Salmonella Rotavirus Shigella E. coli
Epidemiology
Sporadic or outbreaks Eg Campylobacter – sporadic Shigella – outbreak Related to their transmissibility Big outbreak – Epidemic
Seasonal pattern Age Patient profile
Diarrhoea kills by dehydration. Spread:
Faecal/oral route Infection from animal (zoonosis)
Bacteria causing diarrhoea
Staph aureus Bacillus cereus Clostridium perfringens Clostridium botulinum E coli Vibrio cholera Aeromonas species Yersinia enterocolitica Campylobacter Shigella Salmonella
Viral causes
Rotavirus Adenovirus Norwalk/SRS viruses
Parasites
Cryptosporidium Giardia Entamoebae
Syndromes
Food poisoning Gastroenteritis
Tends to refer to greenish watery diarrhoea from small intestine
Dysentary Tends to mean from large bowel. Mucus, possibly blood in the stool.
E coli
Bacteria can be typed according to their cell antigen.
E coli are identified by an O antigen.
Various serotypes eg 044, 0157
Common serotype = 078
E. coli 0157
Haemorrhagic colitis. Very low infective dose
required. Infected food especially
ground beef Person to person
spread. <5 years and the
elderly. Barbeque season.
Clinically: Incubation 4-9 days Watery blood stained
diarrhoea. Occasional vomiting. Low grade fever. 10 days.
Hepatitis
Complication of Hepatitis C
HCV infection
Acute hepatitis
Recovery (50%)
Chronic persistant hepatitis (50%)
Chronic hepatitis (50%)
Chronic active hepatits
Cirrhosis
Hepatocellular ca
Other viral causes of hepatitis Cytomegalovirus Epstein Barr virus Herpes simplex Yellow fever
Other causes of hepatitis:- Drugs- Autoimmune- Chemical
Meningitis
Meningitis
Organisms: E. coli Listeria Haemophilus influenza Strep pnemonia Neisseria meningitidis Fungi:
Cyptococcal meningitis Viral meningitis TB meningitis Protozoal meningitis (acanthamoeba)
Neisseria meningitidis (meningococcus)
1-3 day incubation Carried in throat by
10%. Droplet spread. Carriage increased
when cough and cold going around.
Clinical symptoms and signs: Neck stiffness Aversion to light Irritable Headache Pyrexial illness Purpura (spots that do
not blanch)
3 main types: A, B, C Lab diagnosis:
Lumbar puncture should show: Raised WCC Low glucose Raised protein Bacteria
Neisseria meningitidis (meningococcus)
Vaccines available for types A and C. A most common internationally B problematic in Europe C less of a problem
Neisseria meningitidis (meningococcus)
Sexually transmitted diseases Syphilis Gonorrhoea Chlamydia Genital mycoplasms Vaginitis
Gardnerella vaginalis Trichomonas vaginalis
Warts – papilloma viruses Genital herpes
Syphilis
Syphilis
Initial contact causes primary syphilis chancre, 2-10 weeks after contact
Secondary syphilis 1 to 3 months after with flu like illness, measle like rash,
myalgia and headache. Tertiary syphilis – 3-30 years later
Neurosyphilis Cardiovascular syphilis Progressive destructive disease
Treatment = Penicillin
Gonorrhoea
Neisseria gonorrhoea, gram –ve diplococcus Infects mucosa
Urethritis Cervicitis
Complications: Pelvic inflammatory disease Septic arthritis Opthalmia neonatorum
Chlamydia
Chlamydia trachomatis
Chlamydia
Lives and reproduces intracellularly. Must use other cells’ DNA to reproduce. When enters cell, maturation arrest occurs
and get multiplication inside cell and then released.
Causes: Chlamydial urethritis and cervicitis Opthalmia neonatorum