Introduction of infectious disease

Viruses

- Viruses are smallest pathogens. • All viruses are obligate parasites, that is they can survive only in a living cell. • The virus utilizes the cell's reproductive mechanisms, to multiply. The result is host cell damage or death.

Pathways Through Which Infectious Diseases Spread

-Being stuck by a sharp with infected body fluids. • Contact with infected individuals or surfaces, objects, clothing, and linens that carry body fluids. • Breathing spray from coughs, sneezes, talking. • Eating, drinking, or handling infected food, water, or dirt. • Being bitten by animals and insects, or by coming into contact with animals' body fluids.

Immunological methods

Detection of specific antigen or antibody. • Types of immunological methods: Detection of antigen- directly from the specimen • Precipitation • Immunodiffusion techniques • Agglutination: Clumping of antigen with its antibody • Complement fixation: antigen-antibody complex • Hemagglutination inhibition • Neutralization

Laboratory diagnosis of infectious diseases

Direct detection : • Microscopy = • Staining • Gram's staining • Acid fast staining • Immunofluorescent • Macroscopic = • Latex agglutination • EIA Detect of the pathogen by culture : • Isolation of bacterial pathogens • Isolation of viral pathogens Biochemical tests • Serology and immunological methods(specific antibody). • Molecular (genotypic) methods

Reservoir:

Habitat (man, animal, etc.) in which the infectious agent normally lives, grows, and multiplies. Reservoirs include humans, animals, and the environment.

Nosocomial infections

Hospital acquired infections

Disease:

Impairment of normal functioning, manifested by signs and symptoms

Vehicle:

Inanimate object (food, water, etc) that can carry an agent from one organism to another

Host:

Living animal or plant

Causes of Infectious Diseases

Microorganisms: • Bacteria • Viruses • Fungi • Protozoans

Salivary Biomarkers for Diagnosing of Periodontal Diseases

MyPerioPath® (OralDNA® Labs, Eden Prairie, MN) helps to identify the type and concentration of specific bacteria that are known to cause periodontal diseases.

Relationship between host and microorganisms:

Normal flora: Normal inhabitants of the host ex. S. Salivarius in saliva Commensalism - One organism benefits; the other unaffected; can be opportunistic infector Mutualism: Both organisms benefit E. coli assists in the synthesis of vitamin K and humans provide a conducive environment and food for the bacteria

Parasitism

One partner benefits at the other's expense; Example: tapeworm or leach

Symptoms Suggestive of an Infectious Disease

People may have a variety of symptoms: • Fever or chills. • Loss of appetite. • Fatigue. • Aches and pains. • Diarrhea or other bowel problems. • Difficulty breathing. • Rashes, jaundice. Or, they may have no observable symptoms at all!

Vector:

World Health Organization define vectors as "living organisms that can transmit infectious pathogens between humans, or from animals to humans." Example: blood-sucking insects, like mosquitos or ticks, which become infected and pass pathogens on to other animals or people.

Hand Hygiene

"Hand Hygiene (HH) has been cited frequently as the single most important practice to reduce the transmission of infectious agents in healthcare settings and is an essential element of Standard Precautions.

Salivary Biomarkers for Diagnosing Dental Caries

- Bacterial and host-derived proteins, enzymes, inflammatory mediators, ions and minerals in saliva may be used as salivary biomarkers for the diagnosis of dental caries. - Statherin, proline-rich proteins and histatin-1 levels are elevated in dental caries. Salivary calcium and phosphate concentrations are decreased. - The concentration of salivary Streptococcus mutans and lactobacilli are higher in patients with and in those at risk of dental caries. - Point-of-care salivary diagnostics based on microbial biomarkers such as Dentocult Strip Mutans (Orion Diagnostica, Espoo, Finland), Ivoclar CRT (Ivoclar Vivadent, Amherst, NY), CariScreen caries susceptibility test (Oral BioTech, Albany, OR) are available for the detection of increased caries risk or caries activity.

Molecular methods

- Detection of DNA, RNA or protein of the pathogen. - In many cases the infectious agent can be detected and identified by molecular analysis, even if it cannot be isolated or detected by immunologic means.

Primary Factors

- Infection ≠ Infectious Disease - Cooperation is the rule; disease is rare: - Enlightened self-interest: If host dies, parasite dies • Normal colonization with "smaller life" • Beneficial = Bacteria growing in intestine ("gut flora") make vitamin K • Unnoticed = Mites in hair follicles Characteristics related to the ability to cause disease: Virulence factors: - Suppress or bypass host control and allow microbial growth • Release products that damage host cells • Promote self- induced damage in host as a result of responding to infection. (cytokine storm)

What is an infectious disease?

- Infectious diseases are illnesses caused by microorganisms - Factors involved: - Organism referred as pathogen • Host is the human • Method of spread is referred as transmission - Infectious diseases can be passed from person to person. • Pathogens can be passed from nonliving objects and from other living things

What is a noninfectious disease?

- Noninfectious diseases do not spread from person to person - Etiologically these diseases are not due to an infectious agent - • Environmental factors can cause noninfectious disease. • Example: Fluorosis. - Mutagens are substances that cause mutations, or changes, in DNA. Mutations may result in disease. • Example: Sporadic Alzheimer's disease - Cancer is a group of noninfectious diseases caused by both hereditary and environmental factors.

Skin-

- Outside layer of skin is tough and made up of dead cells. This makes it difficult to get germs through

Advantages of molecular testing for viral infection

- Rapid antigen tests are not sensitive. • Viral culture methods are too slow and limited in viral menu • Molecular tests exhibit good sensitivity, specificity and are safe. • Clinical presentation for respiratory infection is not specific • Many viruses present simultaneously through out the year...flu season is not just flu • Molecular tests identify approximately 50% more viral pathogens than culture • Lower Respiratory infections: 250,000 death/year from Flu and 100,000 non Flu

How are infectious diseases transmitted?

- Reservoirs represents a source where pathogen is maintained. It can be an animal, the environment (stagnant water - Legionella), or even soil (Clostridia) - Vector: Agent that spreads pathogens from host to host 1. Arthropod: flea; mosquito, tick 2. Inanimate: things, toys, dirty hands, needles.

Saliva-based Detection of Infectious Diseases

- There are more than 1000 nonpathogenic and pathogenic organisms in the oral cavity. • For several of the pathogenic organisms such as H. pylori, M. tuberculosis, B. burgdoferi, Shigella, T. solium, and the human immunodeficiency virus (HIV) salivary biomarkers have been identified. • Only OraQuick Advance® Rapid HIV-1/2 Antibody Test (Orasure Diagnostics. Bethlehem, PA), which tests for HIV-specific antibodies, is available for point-of-care use

Detection by growing microbial culture: Five basic techniques to grow, examine and characterize microorganisms.• They are called the 5 'I's

1. Inoculation: Inoculum-tiny sample introduced into culture medium 2. Incubation: Growing in controlled environment 3. Isolation. Separating species grown in culture medium 4. Inspection: Morphologic characteristics 5. Identification: Biochemical tests. (Enzymatic tests-catalase, oxidase, decarboxylase; fermentation of sugars, capacity to digest or metabolize complex polymers and sensitivity to drugs can be used in identification)

Carrier:

A carrier (healthy carrier or asymptomatic carrier) is a person or other organism that has become infected with a pathogen, but that displays no signs or symptoms. Although unaffected by the pathogen, carriers can transmit it to others or develop symptoms in later stages of the disease

Fungi

A fungus (fungi ) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds. These organisms are classified as a kingdom, which is separate from the other eukaryotic life kingdoms of plants and animals. Mycosis, in humans and domestic animals, is a disease caused by any fungus that invades the tissues, causing superficial, subcutaneous, or systemic disease.

Bacteria

Bacteria are simple, single-celled microorganisms that live in air, soil, food, and in and on the bodies of plants and animals, including humans - Some bacteria injure cells by releasing toxins

Host Factors

Barrier to infection • Intact skin and mucous membranes • Secretions Response to infection • Innate immunity: Non-specific and immediate, includes phagocytes and neutrophils • Adaptive immunity: Specific to organism, includes antibodies and activated lymphocytes

Where infectious agents are often detected?

Blood or Body Fluids: Urine • Feces • Tears • Phlegm • Saliva Vomit • Sweat • Semen • Vaginal fluid Food • Water • Organic matter • Pets • Pests

Fungal staining.

Budding yeast and pseudohyphae of Candida albicans, stained with periodic acid-Schiff (PAS) and Gram's staining stain.

Individuals at most risk of developing infectious disease: Common factors:

Common factors: • Babies, children, and elders. • People with pre-existing conditions and weak immune systems. • People on an unhealthy diet. • People with poor personal hygiene habits. • People living compromised environments. • Stress and anxiety prone individuals.

How are infectious diseases be transmitted? Contagious diseases

Contagious diseases can be spread easily from person to person or from other organisms to people. Water and food supplies can be contaminated and cause sickness. • Diseases can be spread through air and through contact with an infected person. • Insects, ticks, and other animals can spread disease. • Objects that are handled by sick people or that come in contact with infected animals or contaminated food can pick up pathogens. • Contaminated needles can transmit diseases.

How are infectious diseases be transmitted? Transmission

Direct spread: by contact or airborne particles from infected to uninfected (Contagious disease) Food or environment-borne: water, food, or soil contaminated by infected person and serve as reservoir for spread Zoonotic: infection transmitted to humans from an animal host or reservoir Mother-to-infant: shared blood circulation before birth or exposure during delivery (Vertical )

Examples of viral diseases detected by serology

Epstein-Barr virus • Rubella virus, Measles,Mumps • Hepatitis A, B, C, D, and E viruses • Human immunodeficiency virus

Exposure and the Risk of Infection

Factors include: •Type of organism • Dose of organism • Virulence of organism • Mode of entry • Host resistance : • Incubation period • Communicable period • Reservoir • Host defense mechanisms

Virulence factors:

Factors that cause disease or aid in spread of disease quickly in host or to other hosts.

• Stomach acid-

Germs that enter the mouth and stomach are killed by saliva and stomach acid.

Detection of antibody ***

Seroconversion occurs when antibody is produced in response to a primary infection.: IgM: early in infection (2-3 weeks) transient (3-6 months) Occasionally persists longer IgG: late response (highest in 4-6 months) usually permanent for life IgG avidity: High: past infection Low: new infection

Protozoans

Single-celled organisms that are much larger and more complex than bacteria are known as protozoans. Protozoans have the ability to move through fluids in search of food.

Other agents

Some infectious diseases are caused by animals such as mites, lice, and certain worms.

Agent:

Something that produces or is capable of producing an effect. Example: microorganism

Standard Precautions

Standard Precautions combine the major features of Universal Precautions and Body Substance Isolation and are based on the principle that all blood, body fluids, secretions, excretions (except sweat), nonintact skin, and mucous membranes may contain transmissible infectious agents. "Standard Precautions include a group of infection prevention practices that apply to all patients, regardless of suspected or confirmed infection status."

Salivary Biomarkers for Diagnosing Premalignant and Malignant Oral Lesions

The only currently available point-of-care technology to identify patients at risk of oral cancer is OralRisk® HPV (OralDNA® Labs, Eden Prairie, MN). It identifies biomarkers for oral human papilloma viruses, several strains of which are known to be associated with oral cancer.

Infection:

The state produced by the establishment of an infective agent in or on a suitable host , host may or may not have signs or symptoms.

Reasons for "Outbreaks"

Three major factors critical for infectious disease outbreaks: Pathogen • New or new to population • Increased virulence due to genetic change or recombination • Drug resistance Host • Breakdown in defense (nutrition, infection, cancer, injury) • Genetic variation in immune response Transmission • Altered environment resulting in new exposures • New patterns of behavior (needle sharing, sex partners, travel)

Safety measures and Prevention: Rationale

Transmission of infectious agents within a healthcare setting requires three elements: 1. A source (or reservoir) of infectious agents 2. A susceptible host with a portal of entry receptive to the agent 3. A mode of transmission for the agent

What are Transmission Based Precautions ?

Transmission-Based Precautions are designed to supplement standard precautions in patients/residents with documented or suspected infection/colonization of highly transmissible or epidemiologically important pathogens.

• Mucus-

Traps germs and contains chemicals to attack and destroy the germs.

Hairs-

Traps germs around eyes and nose and keeps them from getting in the body. Cilia keeps germs out of the lungs.

Direct Microscopy

Two basic purposes: 1-Initial detection of microbes 2-Preliminary or definitive identification of microbes. The microscopic examination of clinical specimens is used to detect: • Bacterial cells, • fungal elements, • parasites (eggs, larvae, or adult forms), and • viral inclusions present in infected cells. Characteristic morphologic properties can be used for the preliminary identification of: • most bacteria and • are used for the definitive identification of many fungi and parasites.

Tears

Wash out germs from your eyes.

Determine disease pathology

What organ systems are involved? • Pathogens have characteristic patterns of infection and damage. •What damage has occurred? • Histologic examination of affected tissues to identify cell and tissue response (type and extent of inflammation, fibrosis, cell death) •Routine stains, immunochemistry or nucleic acid hybridization in tissues to look for organisms

Saliva-

anti-microbial peptides, enzymes and removal by lubrication

Contact percautions

hand hygiene gown gloves

Droplet precautions

hand hygiene mask

Airborne precautions

hand hygiene negative pressure room N95 mask

• All diseases could be classified as

noninfectious or infectious diseases

Virulence:

potency; how quickly the microbe infects, spreads, causes tissue damage or disease symptoms. Influenza A H5N1, very virulent form of flu, or encapsulated pneumococci

Individuals at most risk of developing infectious disease: Specific factors:

• Genetics • Race • Geographic area. • Occupation. • Gender

Detection of Outbreaks

• Unusual pattern of disease detected by public health monitors (sentinel surveillance) or health care professionals. • Higher than usual number of cases • Unusually poor response to therapy • New kind of disease

Determine disease epidemiology

•Characteristics of sick individuals and healthy individuals • Age, race, sex, income, residence •Travel, occupation, diet, medications • Determine factors more common in disease group than healthy group (risk factors)