Title: Medical Microbiology SBM 2044
1Medical MicrobiologySBM 2044
- Assoc Prof Dr Othman Abd Samah
- Tel 09-5716744
- Email oas_at_iiu.edu.my
- Sr. Intan Azura Shahdan
- Tel 09-5716400 ext 2816
- Email intan_azura_at_iiu.edu.my
2SBM 2044 LECTURE 1 INTRODUCTION TO MODULE
Value 4 credit hours
- Methods of assessment
- Module Aims Objectives
- Course structure, Reading, etc.
- Introduction Recall some foundations from
Principles of Microbiology SBM 2053
3SBM 2044 Aims
To foster knowledge and understanding of
certain microbial pathogens, selected to
illustrate
- various kinds of host-pathogen interactions
- experimental approaches used to study
bacterial/viral pathogens - molecular mechanisms in bacterial pathogenicity
- clinical diagnosis and treatment
4Course Content
- Microbes Man interactions Week 1-3
- Medical Bacteriology Week 4-6
- Medical Virology Biological Agents of Warfare
Week 7-10 - Medical Mycology Week 11-12
- Emerging infectious diseases Week 13
- Introduction to the diagnosis and treatment of
infection Week 14
5 Microbes Man interactions
Lecture 1
- Why is this subject important?
- Factors influencing bacterial-host interactions
Lecture 2
- Introduction to bacterial pathogenesis
Lecture 3
- Weapons delivery and deployment
6Today
- How do we recognise pathogens?
- Only a tiny proportion of all known microbes
cause disease - How do we identify a particular microbe as the
cause of a particular disease? - Which microbes cause disease?
- How do they do it?
- How do we stop them?
- How do we identify a particular microbe as the
cause of a patients illness?
7Deaths in children (0 4 years) in 1998
Data from WHO 1999
8Vineeth, 7 months old and identified as
HIV-positive, cries at the Community Health
Education Society orphanage in Madras, India.
The WHO estimates 800,000 children were infected
with HIV in 2001 alone, almost all through
mother-to-child transmission.
9(No Transcript)
10Premature deaths (0 44 years) in 1998
Nutritional
Maternal
Perinatal
2
3
10
INFECTIOUS DISEASE
18
48
19
Various non- communicable
Injuries
Data from WHO 1999
11Human priorities ?
Spending 1995 (in billions )
Deaths 1945 1993 (in millions)
AIDS Malaria TB
War
15
23
150
864
AIDS Malaria TB
Military
12Malaysian Facts
- Population 24,821,286 (July 2007 est.)
- Death rate 5.05 deaths/1,000 population (2007
est.) - HIV/AIDS (2003 est.)
- adult prevalence rate 0.4
- people living with HIV/AIDS 52,000
- HIV/AIDS - deaths 2,000
- REFERENCE www.cia.gov/library
13How do we identify a particular microbe as the
cause of a particular disease?
- The Koch Henle postulates
- Isolate the organism from every case
- Propagate in pure culture in vitro
- Reproduce disease by injecting the organism into
a suitable recipient - Re-isolate the organism
- OK for major acute diseases like plaque,
smallpox, typhoid..
14- Pathogens vs. non-pathogens the Normal Flora
- Only a minute fraction of the organisms in the
environment cause disease. - Isolation of an organism from a patient does not
imply disease. - many different forms of association between
microbes and humans - many yet unknown, non-culturable eg. In soil,
water, extreme environments - Others colonise other living organisms, virtually
all multicellular organisms have their own normal
flora, organisms with which they coexist.
15Factors controlling growth
1. Nutrient availability
- Major C, O, H, N, S, P, K, Mg, Ca, Fe, Na, Cl
- All present in vivo, but all not readily
available - to infecting bacteria e.g. Fe
- Concentration in plasma ca. 20µM
- All heterotrophic (need organic C source)
16Factors controlling growth
2. Physical environment
- Water activity (aw) - not limiting in vivo
- Osmotic pressure (p) - moderate/high
- Too high for some bacteria
- Oxygen availability depends on location in
vivo
17Factors controlling growth
2. Physical environment contd.
- Temperature 37ºC little variation
- pH Mostly ca. pH 7.0 in vivo, but can vary
18Factors controlling growth
3. Competition from normal flora
- Cells occupying your space
Approx. number
Total
10
1013
Human
90
1014
Bacteria
19NORMAL HUMAN FLORA
- Internal organs/tissues normally sterile
- External surfaces accessible internal
niches - colonised by certain bacterial species
include
- Conjunctiva (eye surface)
- Nares (nostrils) nasopharynx
20NORMAL HUMAN FLORA
- Numbers composition varies depending on
location
Mouth 1010
Skin 1012
Intestines 1014
- May also vary at different sites on same tissue
e.g. skin - approx 2 square meters -
moist areas more densely populated
- Complex flora gt 200 species
21NORMAL HUMAN FLORA
- Staphylococcus epidermidis
- Coryneforms (e.g. Propionibacterium acnes)
- 20 30 individuals Staphylococcus aureus
- Mostly S. epidermidis certain coryneforms
- Occasionally S. aureus, some streptococci,
- Neisseria sp.,
Haemophilus sp
22NORMAL HUMAN FLORA
- Oral cavity multiple sp., including
- Oral streptococci (a haemolytic)
- S. salivarius, S. mutans, S. sanguis
- Lactobacillus sp, Staphylococcus sp.
- Corynebacterium sp.
- Many anaerobes esp. Bacteroides sp.
- Nares S. epidermidis, Corynebacteria,
- S. aureus (20 30 individuals)
- Nasopharynx Mostly a-haemolytic streptococci
- other Streps., Neisseria sp.,
23NORMAL HUMAN FLORA
- GI Tract multiple sp., including for example
- Escherichia coli other Enterobactericeae
- Antherior urethra S. epidermidis, enteric
bacteria
- Vagina various sp., including
- Lactobacillus acidophilus
24Different types of symbiotic associations
Mutualism
Commensalism
reciprocal benefit
Harmless
Parasitism
unilateral benefit
25Factors controlling growth
4. Host defences Innate and specific
- Dynamic, interactions with bacteria outcome
- depends on the balance
Host defences
Bacterial virulence
Multiple factors
Multiple factors
- Pathogenicity usually a multifactorial process
- Normal flora - balance in a particular host
niche, - but not necessarily at other sites
26Virulence
- Quantitative extent of ability to cause
disease
Completely avirulent
Extremely virulent
Overwhelm defenses rapidly kills host
No capacity to survive in/on host
27Opportunistic pathogens
Completely avirulent
Extremely virulent
B
H
H
B
Normal defences No disease
Compromised defences Disease
28- Other sites are normally sterile, and the
presence of bacteria suggests an infection - Blood (septicaemia)s
- Cerebrospinal fluid (meningitis)
- Deep tissues (abscesses)
- The digestive tract contains large numbers of
organisms up to 1/3 of faeces can be bacteria
some anaerobes are actually oxygen-sensitive
29- The vast majority of normal flora organism do not
cause disease, but coexist with the host - - commensals
- Much of the normal flora is actually beneficial
to the host they can exclude pathogen, by
producing antibiotics, or other bactericidal
substances (bacteriocins) - Removal of the normal flora by e.g. antibiotics
can make the host much more susceptible to
pathogenic organisms which would otherwise not
cause disease because the normal flora will
prevent them from colonising the host.
30Homework
- Read about the Roles of Normal Flora
- Brooks chapter 11
- OR
- Schaechter chapter 2