Infection /certified fixed orthodontic courses by Indian dental academy

Infection

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Overview
• Types of Microorganisms
• Principles of Infection
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–
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Transmission
Host resistance
Virulence and pathogenicity
Control of transmission and infection

• Development of Infection
– Onset and course
– Clinical signs and symptoms
– Diagnostic tests

• Antimicrobial Drugs

Microbiology
• Study of microorganisms
– Bacteria, viruses, protozoa, fungi

• Many are prokaryotes
– Simple in structure
– Complex cell wall

• Many are pathogenic
• Vary widely in growth needs
– Specific req are basis for lab tests
• Grown in petri dish in specific culture medium
– Culture contains nutrients for specific microbial group
» Need for oxygen, carbon dioxide, pH, temp varies

Classification of Bacteria
• Bacilli
– Clostridium tetani

• Spirals
– Treponema pallidum

• Cocci
– Diplocci
– Streptococci
– Staphylococci
• Staphylococcus
aureus

Bacterial Structure
• Rigid cell wall
– 2 types
• Gram negative
• Gram positive

• Cell membrane
– Semipermeable
– Metabolic processes occur here

• External capsule/slime layer
– On some; extra protection, interferes w/
phagocytosis

• Flagellae

Bacterial Structure
• Pili or fiimbriae
– Usually gram neg; attach bacterium to tissue
– Transfer DNA to another bacterium =
mutation

• Cytoplasm
– Chromosome (long strand of DNA)
– Ribosome (RNA)
– Plasmids (DNA fragments)
• Imp for drug resistance

Bacterial Structure
• Some secrete toxic substances, toxins, enzymes
– Toxins
• Exotoxins: gram pos; diffuse thru body fluids
– Often interfere w/ nerve conduction
– Stimulate antibody/antitoxin production

• Endotoxins: gram neg; released after organism dies
– Causes fever, weakness, circ problems
» Increase cap perm, loss vasc fluid, endotoxic shock

– Enzymes
• Damage host cells/tissues
• Ex: Hemolysin destroys RBC

Hemolysin and RBC


Bacterial Structure
• Some form spores
– Latent form resistant to heat
– Survive long time as spore; cannot reproduce
in this state
– Resume normal state when conditions
favorable
– Ex: tetanus, botulism


Tetanus, Botulism Spores


Bacteria: Reproduction
• Duplicate thru
binary fission
• Generation time:
minutes – hours
• Limiting factors to
growth:
– Nutrients, oxygen,
effects of increased
metabolic wastes,
changes in pH and
temp

Viruses
• Very small
intracellular parasite
• Obligate
• Called virion when
outside of cell
• Consists of:
– Protein coat (capsid)
– Core
• RNA or DNA

Viruses: Replication
• Attach to host cell and inserts genetic
material
• Viral DNA or RNA takes over cell
– Uses host cell to replicate new viral
components

• New viruses assembled, leave host cell
• Host cell damaged to killed in process
• Viruses then attack more healthy cells

Viruses
• Tend to mutate
– Difficult to acquire immunity, develop antibodies
and vaccines

• Some alter host chromosomes
– Leads to malignant cells and cancer

• Viruses difficult to control
– Unique structure
– Hide in host cells
– Drugs cannot attack b/c lack own metabolic
processes and structures

Chlamydiae, Rickettsiae,
Mycoplasmas
• Similar to bacteria and viruses
• Divide by binary fission
– Require living cells for reprod

• Chlamydiae
– Very primitive; lack many metabolic
processes
– Common STD


Chlamydiae Reproduction


Rickettsiae
•
•
•
•
•

Gram neg
Live inside host cell
Transmitted by insects (ticks, lice)
Attack bv walls (rash, sm hemorrhages)
Typhus fever, Rocky Mountain spotted fever


Mycoplasma
• Smallest cellular microbe
• Lack walls
– Not affected by antimicrobial drugs

• Common cause of pneumonia


Fungi
• Found everywhere
• Infection results from 1-celled yeasts or
multicellular molds
• Eukaryotes
• Growth promoted by warmth and
moisture
• Some beneficial
– Produce yogurt, beer
– Source of antibiotic drugs

Pathogenic Fungi
•
•
•
•

Tinea pedis
Candida
Histoplasma
Ringworm


Protozoa
• Eukaryotes
• Unicellular, mobile,
lack cell wall, irreg
shapes
• Some can live indep
(dead or organic
matter); others are
parasites


Protozoa
• Trichomonas vaginalis
– Flagella, sexually transmitted, attach to mucous
membrane and cause inflammation

• Plasmodium vivax
– Malaria; nonmotile; found in RBC and undergo
stages of life cycle

• Amoebas
– Entamoeba histolytica
• Parasite in lg intestines; cause amebic dysentery; resist
phagocytosis
• Infection spread thru oral-fecal route

Other Parasites: Helminths
• NOT microorganisms; but are parasitic
worms
• Multicellular, eukaryotic, vary in size
• 3 stage life cycle
– Ovum
– Larva
– Adult

• Found in intestines, blood
• Diagnosis by observation of ova in stool
specimen
• Common in NA:
– Pinworms, hookworms, whipworms, round worms

Ascaris (Round worm)


Principles of Infection:
Transmission
• Chain of events
• Reservoir: Source of infection
– Person with obvious infection
– Carrier
– Animal
– Contaminated food, water, soil, equipment


CHAIN OF INFECTION


Modes of Transmission
• Direct contact
• Indirect contact
• Droplet
transmission
• Hands
• Vector-borne
• Nosocomial


Host Resistance
• What factors would decrease host
resistance?
• Prophylactic antimicrobial medication
– Required for indiv w/ low resistance prior
to exposure to microbes

• Interferon
– Proteins produced by human host cells
• In response to viral invasion of cell
– “Save yourselves”!!!

Virulence and Pathogenicity
• Pathogenicity: capacity of microbes to
cause disease
• Virulence: degree of pathogenicity of
specific microbe
– Based on:
•
•
•
•

Invasive qualities
Toxic qualities
Presence of pili or fimbrae for adhesion
Ability to avoid host defenses (mutate)

Drug Resistant Microbes
• Staphylococcus
aureus
• Neisseria
gonorrhoeae
• Myobacterium
tuberculosis
• Streptococcus
pneumoniae
• Haemophilus
influenzae

Steps to Minimize Risk of Infection
1. Locate, remove reservoir host
2. Block portal exit of microbes from reservoir
3. Know mode(s) of transmission of specific
infections
4. Block portals of entry
5. Cleaning
6. Sterilization
7. Disinfectants
8. Antiseptics

The interaction between the 6
elements of the chain determine
whether an infection will result.


Development of Infection: Onset
and Course
• Incubation period
– Organism present; no clinical signs,
symptoms

• Prodomal period
– Symptoms; don’t feel like yourself

• Acute period
– Fully developed infection


Development of Infection: Clinical
Signs and Symptoms
• Local signs
– Inflammation
– Purulent exudate if bacterial infection;
serous exudate if viral
– Tissue necrosis
– Lymphadenopathy
– Respiratory effects

• Systemic signs
– Fever, fatigue, headache, nausea

Development of Infection:
Diagnostic Tests
• Cultures and stains
– bacteria

• Blood tests
– Bacteria
• Leukocytosis

– Virus
• Leukopenia

– Increase in neutrophils
w/ acute; increase in
lymphocytes and
monocytes w/ chronic

• Radiologic exams

Guidelines for Antimicrobial Drug
Usage
•
•
•
•
•
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Regular intervals
Until prescribed meds used
Follow directions
Choose best drug
Patient allergies
Antibiotics = BACTERIA, NOT
VIRUSES!

Classification of Antimicrobial
Drugs
•
•
•
•
•

Antibiotics
Antimicrobials
Bactericidal vs. Bacteriostatic
Broad vs. Narrow Spectrum
1st and 2nd Generation Drugs


Mode of Action
• Antibacterial drugs
• Antiviral drugs
• Antifungal drugs


Mode of Action: Antibacterial
Drugs
• Operate in 1 of 4 ways:
• Interferes with bacterial wall synthesis
– Ex: Penicillin

• Increase permeability of bacterial cell
membrane
– Ex: Polymyxin

• Interferes w/ protein synthesis and
reproduction
– Ex: Tetracyclin

• Interferes w/ synthesis of essential
metabolites
– Ex: Sulfonamides

Mode of Action: Antiviral Drugs
• Decrease reproduction of virus inside host
cell
– Does not destroy virus

• Meant to control not cure
• May interfere with:
–
–
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Viral attachment to host cell
Shedding of protein coat
Protein synthesis
Viral replication

• Significant adverse effects

BIBLIOGRAPHY
• Clinical Periodontology 9th Ed, by –Newman, Takei
and Carranza
• Oral microbiology 4th edition by Philip marsh and
Michael v.martin.
• Text book of microbiology for dental students by Pro
C.P Baveja
• essential microbiology for dentistry by L.P
Samaranayake.
• Jawetz,Melnick and adelberg’s medical microbiology
by Brooks,butel and morse
• lippincott’s illustrated reviews : microbiology by
William,harriet and bruce.
• Textbook of diagnostic microbiology by Coonie
R.Mabon and george manuselis
• Textbook of microbiology 6th edition by
ananthanarayan and CKJ Paniker.

Thank you
Leader in continuing dental education


Infection /certified fixed orthodontic courses by Indian dental academy

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