MIC342 - Miss Rashidah Hj Iberahim

Chapter 4 – NORMAL FLORA & HOST PARASITE

RELATIONSHIP

Miss Rashidah Hj Iberahim

Types of Pathogens

Primary Pathogens Cause disease upon infection, not normally associated

with host1. Plague (Yersinia pestis), 2. influenza virus

Opportunistic Pathogens Cause disease under some circumstances, sometime

members of normal flora1. Pseudomonas,2. Candida albicans

Progression of Disease

Transmission: infectious dose from 10-106 organisms

Incubation period: few days (common cold)-weeks (hepatitis A)-months (rabies)

Convalescence: Clearing (Strep throat, S. pyogenes) Latency (Chicken pox, tuberculosis, cold sores)

Koch’s Postulates Proposed by Robert Koch Conclude that a microbe causes a particular

disease

Must fulfill four postulates1. Microorganism must be present in every case of

the disease

2. Organism must be grown in pure culture from disease hosts

3. Produce the same disease from the pure culture

4. Organism recovered from experimentally infected hosts

Molecular Postulates

Describe virulence factors Four postulates 1. Virulence gene or its product must be present 2. Virulence gene must transform a non-pathogen

into a pathogen 3. Virulence gene must be expressed during

disease process 4. Antibodies against gene products are protective

Establishing an Infection

1. Encounter: fecal-oral (cholera) human-human (tuberculosis) animal-human (rabies) vector-borne (plague, lyme disease) environmental contact (anthrax)

Establishing an Infection

2. Adherence Prevents early clearance Often bind host tissues via pili Specificity can determine host range of

pathogen

Establishing an Infection 3. Colonization: multiplication and maintainance

Competition with normal flora Resist:

1. bile 2. stomach acid 3. peristalsis 4. skin secretions 5. IgA (mucosal antibodies)6. compete with host for iron

Establishing an Infection

4. Molecule Delivery Affects target cell

structure and host response

Invasion:Breaching Anatomical Barriers

Find new niche with few competitors Gain access to rich nutrient supply

1. Skin: tough barrier, rely on wounds or insect vectors2. Crossing mucous membrane (e.g.

intestinal epithelial cells)

Definition of normal flora

m/org that normally found in particular area that do not cause harm to host cell and body system

Also known as microflora

MIC341 - Miss Rashidah Hj Iberahim

*microorganism in perianal area enter the urinary tract

(UT) causing infection in internal UT

Can prevent infection by: Medical asepsis – personnel and hospital environment

should be clean from pathogens Surgical asepsis – instrument used should be sterile and

including the surgical room What did you implement in daily life?

Harmful

Normal Flora

More bacterial than human cells in the body provide some nutrients (vitamin K) stimulate immune system, immunity can be cross-

reactive against certain pathogens Prevent colonization by potential pathogens

(antibiotic-associated colitis, Clostridium difficile)

Normal flora of body system

Skin Gram positive org:1. Staphylococcus sp,2. Micrococcus,3. Coryneform bacteria/Demodex folliculorum (opening

glands – eyebrows)

Urogenital 4. M. smegmatis,5. Lactobacili,6. Streptococci,7. Staphylococcus,8. E.coli

Body system w/out normal flora

Lower respiratory tract Systemic and cardiovascular Nervous system

MIC342 - Miss Rashidah Hj Iberahim

Skin Flora

MIC341 - Miss Rashidah Hj Iberahim

Different area consist of different microflora.

Example armpits vs forehead. Moisture area will support larger populations;

nutrients from oils and sweat Those normal flora might have capability to

produce oils that known as fatty acid providing an acidic condition of particular area

Initiating host defense against infection in the 1st line stage

But, excess of oils production might resulting an odour of unpleasant smell to the body

Oils production

MIC341 - Miss Rashidah Hj Iberahim

Beside oils, the 2nd line of host defends is the

sweat that are salty However, in opposite situation, there are

bacteria that able to live in salty area such as Staphylococcus sp.

Majority of the skin flora – Gram +ve : Staphylococcus, Micrococcus and Corynebacterium

Hair follicles inhabitants – mite Demodex folliculorum

Sweating

MIC341 - Miss Rashidah Hj Iberahim

3rd line defends is regarding the keratin-

degrading fungi It helps in rapid and continuous shedding of

skin cells replacing layer by layer Removing of skin cell together with group of

m/org on the skin

Skin shedding

MIC341 - Miss Rashidah Hj Iberahim

Gram positive org.

1. Staphylococcus sp2. Micrococcus3. Coryneform bacteria

Demodex folliculorum (opening glands – eyebrows)

Normal flora

MIC342 - Miss Rashidah Hj Iberahim

Urogenital Flora

MIC341 - Miss Rashidah Hj Iberahim

Al parts are sterile except urogenital opening Urine collection should have ‘clean catch’ technique E.coli and Lactobacillus are common flora =

100,000 bact/ml of urine Collection during direct puncture (suprapubic) =

sterile sample Acid pH, high salt and urea concentration leads to

high m/org growth Urine sample should be refrigerated during

transportation if delay – high multiplication if stir in RT

Urogenital

MIC341 - Miss Rashidah Hj Iberahim

Mycobacterium smegmatis (acid fast staining

bacili) live in external genitalia of female and male

Esp under penis of uncircumsized male – smegma

If included in the sample, might leads to confusion wt the tuberculosis patient which actually having M. tuberculosis

In male, 1/3 of deep are for genital area don’t have normal flora

Cont.

MIC341 - Miss Rashidah Hj Iberahim

Due to hormonal changes.. Child-bearing – lactobacili numerous in vagina

(eating glycogen) Glycogen in vaginal cell will be fermented

become lactic acid and pH decrease to 4.7 Childhood and after menopause, lactobacili

absent coz no glycogen –replaced by streptococci and staphylococci due to alkaline pH in vagina

In female..