Micro Bio

Topics: Immune system, Bacteria, Infectious disease Pages: 8 (1133 words) Published: June 21, 2013
REVISION

COMMON TYPES OF MICROBES

1

BACTERIA
Difference between Gram Positive and Gram Negative Shapes of bacteria and examples What shapes have you learnt? GRAM STAIN: The process! You should work on your lab notes. LECTURE 2

GRAM STAIN
Developed by a Danish called Christian Gram in 1884 Stain a heat-fixed smear with a dye like crystal violet and fix with Iodine Then wash with ethanol or acetone Finally counterstain with a dye of different colour such as safranin (what is its colour? You have used it before!)

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5

Gram positive

Gram negative

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3

GRAM POSITIVE CELL WALL
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Consists of
a thick, homogenous sheath of peptidoglycan 20-80 nm thick tightly bound acidic polysaccharides, including teichoic acid and lipoteichoic acid cell membrane

Retain crystal violet and stain purple

GRAM POSITIVE WALL

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4

GRAM NEGATIVE CELL WALL
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Consists of
an outer membrane containing lipopolysaccharide (LPS) thin shell of peptidoglycan periplasmic space inner membrane

Lose crystal violet and stain red from safranin counterstain

GRAM NEGATIVE CELL WALL

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5

ENDOSPORES
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Resting, dormant cells produced by some G+ genera: Clostridium, Bacillus & Sporosarcina Have a 2-phase life cycle – vegetative cell & an endospore

sporulation -formation of endospores germination- return to vegetative growth hardiest of all life forms withstand extremes in heat, drying, freezing, radiation & chemicals not a means of reproduction

ENDOSPORES
12

resistance linked to high levels of calcium & dipicolinic acid dehydrated, metabolically inactive thick coat longevity verges on immortality 25, 250 million years. pressurized steam at 120oC for 20-30 minutes will destroy.

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ENDOSPORES

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LABORATORY SESSIONS
Making of culture medium 2. Recall your investigations on Culturing Effectiveness of Soaps and Alcohols What kind of culture medium did you use? Milks What did you do to investigate the effect on “temperature” treatment to milk? 1.

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PHYSICAL AND CHEMICAL
MICROBIAL CONTROLS

PHYSICAL AND CHEMICAL
MICROBIAL CONTROLS

DEFINITIONS:
Sterilization Disinfection Sanitization Antiseptic Pasteurization

8

NOSOCOMIAL INFECTIONS
Definition Universal/ Standard Precautions Use of disinfectants Vincent’s Lecture

PRIONS
Prof Maxwell’s notes and this lecture! Definitions What are the common infectious diseases by prions? Any treatments? Epidemiology, aetiology,…….

9

TAPEWORMS
Prof Maxwell’s notes What is the disease that is caused by “tapeworm”? Aetiology, epidemiology, sign and symptoms, pathogenesis, prevention and control

MRSA
Methicillin-resistant Staphylococcus aureus (MRSA) infections Control of infection in health care settings: 1. Control the reservoir 2. Interrupt the transmission 3. Prevent access of agent to new host 4. Increase resistance of new host

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MRSA
Major reservoir: humans • S. aureus can be normal flora - Nares - Pharynx - Skin - Axilla - Perineum

MRSA-TRANSMISSION
Patient-to-patient via transient carriage on hands of Health Care Workers (HCW) HCW-to-patient through chronic HCW carrier Via devices or environmental surface

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MRSA- CONTROL
Infection control measures: Contact precautions -Hand hygiene -Protective barriers - Patient placement - Environmental cleaning - Patient education - Patient transport - Dedicated patient care equipment Appropriate use of antibiotics

CHAIN OF INFECTION

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CHAIN OF INFECTION
I. Infection cycle is well defined A. Infective agent: pathogen such as a bacteria or virus B. Reservoir 1. Place where causative agent can live 2. Common reservoirs include human body, animals, environment, and fomites or objects contaminated with infectious material that contains the pathogens

CHAIN OF INFECTION
C. Portal of exit 1. Way for causative agent to escape from the reservoir 2. Pathogens can leave the body through urine, feces, saliva, blood, tears, mucous discharge,...
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