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