Microbiology: Contamination and Colonization
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Microbiology: Contamination and Colonization

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Questions and Answers

What is the definition of contamination?

Invasion of pathogenic microorganisms into the tissue or onto the surface of a host or inanimate articles or solutions.

What can be a serious outcome of contamination?

Major outbreaks of infection.

What is colonization?

The presence of microorganisms that are not causing adverse clinical signs or symptoms.

What can colonization lead to?

<p>It may lead to infection if the conditions allow.</p> Signup and view all the answers

What are the types of infections discussed?

<p>Endogenous, exogenous, opportunistic, and superinfection.</p> Signup and view all the answers

What is the incubation period?

<p>The time from invasion of a pathogen until the first signs of infection.</p> Signup and view all the answers

What is pseudo-infection?

<p>A mismatch between laboratory results and clinical symptoms.</p> Signup and view all the answers

What are some types of pseudo-infection?

<p>Pseudo-bacteria, pseudomeningitis, pseudopneumonia, pseudobacteriuria.</p> Signup and view all the answers

What is necessary for establishing infections?

<p>A virulent organism must encounter a susceptible host.</p> Signup and view all the answers

What is contamination?

<p>Invasion of pathogenic microorganisms into the tissue or onto the surface of a host or inanimate articles or solutions.</p> Signup and view all the answers

What outcome can result from contamination?

<p>Both A and C</p> Signup and view all the answers

What is colonization?

<p>The presence of microorganisms on skin or mucous membranes that do not cause adverse clinical signs or symptoms.</p> Signup and view all the answers

Colonization results in significant tissue damage.

<p>False</p> Signup and view all the answers

What type of infection is caused by dormant pathogenic microorganisms reactivating?

<p>Endogenous infection</p> Signup and view all the answers

What is the incubation period of an infection?

<p>The time from the invasion of a pathogenic microorganism until the first signs of infection.</p> Signup and view all the answers

A mismatch between laboratory results and clinical symptoms is known as a ______.

<p>pseudo-infection</p> Signup and view all the answers

Which of the following is an example of pseudo-infection?

<p>Pseudopneumonia</p> Signup and view all the answers

What must occur for infections to be established?

<p>A susceptible host must encounter a virulent organism, gain access to the host, move to a favorable site, and multiply despite the host defenses.</p> Signup and view all the answers

Study Notes

Contamination

  • Definition: Invasion of pathogenic microorganisms into tissue or surfaces of a host or inanimate objects/solutions.
  • Microorganism count is insufficient to cause infection.
  • Contamination can be dangerous and cause infection outbreaks.
  • Outcomes:
    • Healing without problems.
    • Pathogenic microorganism replication and tissue invasion, interfering with healing.
    • Infection control efforts needed to reduce environmental contamination and prevent transmission.

Colonization

  • Definition: Presence of microorganisms on skin, mucous membranes, open wounds, or excretions/secretions without causing clinical symptoms.
  • Origin: From the external environment, associated with normal skin flora.
  • Site: Commonly in respiratory tract, genitourinary tract, anterior nares, axillae, groin, or open wounds.
  • Outcomes:
    • No reaction or mild reaction.
    • Colonization is the first step of the infectious process.
    • Microorganism replication is not enough to cause infection.
    • Can be temporary or long-term.
    • Host can become a carrier, shedding the organism to infect others (e.g., nasal MRSA carriers, carbapenem-resistant gram-negative bacteria carriers).

Infection

  • Definition: Invasion of the host by different microorganisms, with multiplication in tissues or on body surfaces causing tissue damage or disease.
  • Endogenous infection: Dormant pathogenic microorganisms reactivate in the host (e.g., Tuberculosis).
  • Exogenous infection: Pathogenic microorganism acquired from the external environment.
  • Opportunistic infection: Overgrowth and invasion by microorganisms in response to suppressed immune systems (e.g., oral candidiasis in diabetic or AIDS patients).
  • Superinfection: Results from long-term antibiotic use, depleting microbial flora.

Incubation Period

  • Definition: Time from a pathogenic microorganism invading a host until the first signs of infection or the time from invasion until transmission to another host.
  • Duration: Variable (hours to days), depending on the type of pathogenic microorganism, host, and environment.

Pseudo-infection

  • Definition: Mismatch between lab results (growth) and clinical symptoms/signs (absent).
  • Occurs when there's colonization of a pathogen without evident clinical signs of infection.
  • Results from contamination of specimens (superficial colonization or lab error).
  • Differentiation from true infection is crucial for proper patient treatment.
  • Types:
    • Pseudo-bacteria: Contamination with normal flora (e.g., Bacillus or Streptococcus spp.)
    • Pseudomeningitis: CSF contamination, bacteria or fungi without clinical symptoms
    • Pseudopneumonia: Contamination from bronchoscopes, respiratory equipment, or solutions
    • Pseudobacteriuria: Contamination of external urinary drainage system

Establishing Infections

  • Requires a susceptible host & a virulent organism.
  • Organism must gain access, move to a favourable site, and multiply despite host defenses.
  • Steps are numbered 1, 2, and 3.

Preparing an Initial Line List and Epidemic Curve

  • Line list: Single most important tool for outbreak investigation, facilitating early discussion and effort.
  • Line list includes patient signs and symptoms.
  • Line listing (chart of specific cases): Table with abstracted information.

Data Included in Line Listing

  • Demographic information: Age, sex, occupation, hospital number, admission date, surgery date.
  • Clinical data: Signs/symptoms, onset/times, outcomes, lab results, antimicrobials, other medications.
  • Exposure information: Procedures/surgery, medical devices/equipment.
  • Any other potentially relevant data.

Characterize Outbreak by Time: Epidemic Curve

  • Definition: Graph of the number of cases by their date of onset.
  • Shows frequency of new cases over time based on disease onset.
  • Helpful for graphing cases of an outbreak.

1-Point/Common Source Outbreaks (Epidemics)

  • Shape: Sudden steep upslope, peak, and sudden downslope.
  • Interpretation: People exposed to the same source over a relatively brief period.

1-cont. Point/Common Source Outbreaks (Epidemics)

  • Shape: Plateau instead of a peak.
  • Interpretation: Exposure to the same source over an extended period.

2-Propagated (Continuing) Epidemic

  • Definition: Infections transmitted between people over a longer period, rather than a single source.
  • Explosive: Rapid person-to-person transmission (examples like chickenpox).
  • Characteristics: Intervals between peaks similar to average incubation period, progressively larger peaks at regular incubation intervals.
    • The pool of susceptible people is depleted through control or exhaustion.

Propagated (Continuing) Epidemic

  • Shape: Series of progressively taller peaks.
  • Interpretation: Person-to-person spread.

Infection prevention and control of communicable diseases

  • Prevention and control measures are needed.

What is communicable diseases?

  • Communicable diseases are characterized by the presence of a living infectious agent that is transmissible.
  • Factors influencing communicable disease: agent, mode of transmission, host, and environment

Some Factors that Render Patients More Susceptible to Infection

  • Extremes of age
  • Underlying diseases
  • Treatment with antimicrobials, corticosteroids, or immune suppressive agents
  • Irradiation
  • Broken first line of defense (surgery, anesthesia, indwelling catheter)
  • Long hospital stay

Sources of Infective Agents

  • Human sources: Patient (endogenous flora), healthcare workers, visitors, individuals with infectious diseases, patients in incubation period, chronic carriers
  • Environmental sources: Equipment (e.g., CBG, stethoscope), medication, working surfaces, keyboards, and telephones.

Components of Infection Disease Process

  • Causative agent
  • Reservoir of the infection
  • Portal of exit from the reservoir
  • Mode of transmission
  • Portal of entry into host
  • Susceptible host
  • Chain/spread of infection

Susceptible Host and Pathogen

  • Susceptible Host: Elderly, infants, immunocompromised (anyone!), based on the need for control measures.
  • Pathogen: Bacteria, virus, fungi, parasite.

Reservoir

  • Definition: Source that enables the growth and multiplication of disease causing microorganism. (Patient, animal, plant, soil, air, water, or environment)
  • Sources of infection: Origin of an infection that's able to be transferred. (Endogenous or exogenous).
  • Fomites: Inanimate objects that can contaminate and spread disease (e.g., towels, sinks, bed rails).
  • Reservoir examples and associated microorganisms: Water (e.g., Pseudomonas), Bowel (E. coli), Nose (Staph. Aureus)

Portal of Exit

  • Pathway microorganisms leave the reservoir.
  • Routes: Bloodstream (devices), skin openings (wounds, rashes, surgery sites), mucous membranes (eyes, nose, mouth), respiratory system (lungs), urinary/reproductive system (vagina, urethra), digestive system (mouth, anus).

Modes of Transmission

  • Contact: Direct (touch) or indirect (surfaces)
  • Droplet: Transmission through droplets (e.g., coughs or sneezes)
  • Airborne: Spread through airborne particles
  • Fomites: Transmission via inanimate objects
  • Vectors: Transmission by insects or other animals.

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Description

Explore the concepts of contamination and colonization in microbiology. Learn how microorganisms invade tissues and the implications of their presence without causing infection. Understanding these processes is crucial for effective infection control and public health.

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