Pathology: Infectious Disease

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Infectious Disease (definition)

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Disorders in which cell injury is caused by a pathogen

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Definition of Pathogen, Resident (Normal) Flora

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Pathogen = any disease producing microorganism
Resident (normal) Flora = Mocroorganisms that live in or on the host without causing disease. Establish a mutually beneficial relationship with the host, protecting the type of disease produced

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Chain of Transmission - Steps (6)

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Pathogen -> Reservoir -> Portal of Exit -> Mode of Transmission -> Portal/Mode of Entry -> Susceptible Host

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Chain of Transmission - Examples of each step

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Pathogen - Bacteria, Viruses, Fungi, Protozoans, Prions, Chlamydia, Rickettsia, Mycoplasmas, Helminths
Reservior - Humans, animals, plants, soil, food, organic substances
Portal of Exit - GI Tract, Genitourinary Tract, Respiratory Tract, Open Lesions
Mode of Transmission - Contact (direct/indirect), airborne, droplet, vehicle (water/food - direct/indirect), vectorborne (insects or animals)
Portal/Mode of Entry - mucous membranes, inhalation, ingestion, percutaneously, transplacentally
Susceptible Host - host characteristics, general health and nuturitional status, living conditions, personal behaviors

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Infection (definition)

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Infection = Invasion and multiplication of microorganism in body tissues

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Subclinical Infection
-Latent Period
-Communicable Period
-Carrier

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Subclinical Infection = Signs and symptoms not detectable by clinical exam, but lab tests reveal an immune response and/or the pathogen
Latent Period = Period during which the pathogen is inactive and manifestations of the disease are no longer detectable
Communicable Period - period during which a pathogen is capable of being transmitted
Carrier - individual who harbors the microorganisms of a disease without manifesting symptoms and is capable of transmitting the infection

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Clinical Infection
-Incubation period

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Clinical Infection = Signs/Symptoms are detectable by clinical examination
Incubation Period = Period between the pathogen entering the host and the appearance of the first signs and symptoms

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Inflammation (definition)

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Inflammation = A localized nonspecific protective response elicited by injury which serves to eliminate the injurious agent, remove the necrotic tissue, and initiate healing

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Immune System Response

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A specific response to individual pathogens, as long as the pathogens, as long as the pathogen has antigenic characteristics
Immunodeficiency may be caused by an infection

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Bacteria
-Definition
-Growth
-Classified By
-Examples

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Bacteria = single-celled prokaryotic microorganisms with cell walls
Grow - independently on artificial media without the need for other cells
Classified By - shape, response to staining, motility, tendency towards capsulation, capacity to form spores, oxygen utilization
Examples - C-diff, pseudomonas, salmonella, staphy, strep

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Virues
-Definition
-Requirements
-Classified By
-Examples

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Viruses - Subcellular organisms made up only of RNA or DNA contained in protein shell
Require - living cells in which to survive and replicate
Classified By - type of nucleic acid they contain and by shape of thier protein coat
Examples - hepatitis, herpes, HIV, influenza

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Fungi (yeasts or molds)
-Definition
-Examples

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Fungi = single-celled (oval-shaped) or multi-cellular (filamentous) eukaryotic microorganisms with cell walls
Examples - Candida Albicans, Histoplasmosis

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Protozoans
-Definition
-Examples

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Protozoans = single-celled eukaryotic microorganisms with cell membranes
Examples - cryptosporidiosis, pneumocystis carinii, toxoplasma gondii

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Factors that Influence Host Susceptibility

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Demographics
Personal Behaviors
Living Conditions

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Host Risk Factors

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Malnutrition, Chronic Illness (diabetes mellitus, cancer, heart disease, renal failure), Age (infants, elderly), Immunosuppression (immunodeficiency diseases, drug-induced, stress, splenectomy), Breaches of Bodies Integrity (catheters, tubes)

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Pathogenesis depends on?

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Capability of hte pathogen to bypass or inactivate the anatomic and physiologic defenses (lines of defense) of the body

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Mechanisms of Spread (4)

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-Contact and spread rapidly on wet epithelial surfaces (mucous membranes) and slowly on dry epithelial surfaces (skin)
-Microorganisms may not be able to travel beyond the epithelium, only proliferate in the epithelium, or penetrate the epithelium (independently or through an open cut or sore)
-Follow tissue planes of least resistance and the regional lymphatic and vascular anatomy
-Travel in the blood (free or carried by cells) to distant sites

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Mechanisms of Injury (3)

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-Contact or enter host cells and directly cause cell death
-Release endotoxins or exotoxins that kill cells at a distance and/or release enzymes that degrade tissue components
-Induce host cell responses that may cause additional tissue damage, usually by immune-mediated mechanisms

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Clinical Manifestations:
Systemic

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Symptoms: Fever, chills, malaise, enlarged lymph nodes
Result from: chemicals (endotoxins, exotoxins, cytokines) released from pathogen and immune system cells

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Clinical Manifestations:
Regional - Musculoskeletal
(tendons & bursae, bone, joints, muscle)

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Tendons & Bursae - pain, swelling
Bone - pain, swelling
Joints - pain, swelling, decreased ROM
Muscle - pain, swelling, decreased strength

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Clinical Manifestations:
Regional - Nervous
(Brain & Meninges, Peripheral Nerves)

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Brain & Meninges - Altered mental status and/or consciousness, headache, stiff neck
Peripheral Nerves - sensory, motor, and/or autonomic deficits

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Clinical Manifestations: Regional - Skin

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Skin Lesions
Purulent drainage from abscess, open wound, or skin lesion
Rash or red streaks
Itching

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Clinical Manifestations:
Regional - Cardiovascular

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Change in pulse rate, hypotension
Petechial hemorrhages

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Clinical Manifestations:
Regional - Pulmonary

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Tachypnea, dyspnea, cough, sputum production, chest pain, hoarseness, sore throat, nasal drainage

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Diagnosis: Lab Tests and what they detect (3)

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1) Cultures - microorganism
2) Microscopic exam of tissue fluids and/or excised tissue - microorganism, evidence of microorganism, immune response to microorganism
3) Immunologic Tests (body fluids, skin) - evidence of microorganism, immune response to microorganism

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Treatment: Types (3)

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1) Pharmacotherapy
2) Drainage or debridement (enzymatic, hydrotherapy, surgical)
3) Supportive Therapy - addressing the clinical manifestations of the infection

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Treatment: Pharmacotherapy
-Types
-Effectiveness

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-Antimicrobial or antibiotics
-Effectiveness: depends on etiologic agen and the system affected
-Antibiotic resistant bacteria

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Treatment: Antibiotic- Resistant Bacteria (classification, association)

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Classified according to the name of the drug and the associated resistant bacterial strain.
Associated with misuse and overuse of antibiotics in the treatment of infections or potential infections, resulting in a "survival of the fittest" bacterial strain

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Prognosis

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Varies depending on:
Host, etiologic agent, system affected

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Rehabilitation Issues

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-Receive appropriate immunizations
-Be observant of precautions
-Be aware of the clinical signs and symptoms of infectious pathologies and potential secondary complications

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Pulmonary Tuberculosis: Definition

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An infectious, inflammatory systemic disease that affects the lungs and may desseminate to involve lymph nodes and other organs

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Pulmonary Tuberculosis: Classification - Primary

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Initial infection wiht mycobacterium tuberculosis, usually asymptomatic and almost always remains quiet after the development of a hypersensitivity to the microorganism

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Pulmonary Tuberculosis: Classifications - Secondary

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Develops as a result of either endogenous or exogenous reinfection by mycobacterium tuberculosis. Can occur decades after initial infection, particularly when the immune system is weakened. Most common form of clinical TB

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Pulmonary Tuberculosis: Risk Factors

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HIV+, Age (>65)

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Pulmonary Tuberculosis: At Risk Populations (9)

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Economically disadvantaged or homeless, non-white populations, foreign-born individuals, substance abusers, children (< 5 years), current or past prison inmates, peoiple with diabetes mellitus, end-stage renal disease, and immunocompromised

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Pulmonary Tuberculosis: Transmission

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qInhalation of infected airborne particles

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Pulmonary Tuberculosis: Initial Infection

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Mycobacterium Tuberculosis establishes itself in alveoli of the lungs
Epithelial cells encapsulate the bacteria

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Pulmonary Tuberculosis: Progression in the Presence of an Intact Immune System

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Lymphocytes and macrophages form granulomas around the encapsulated bacteria, rendering the infection inactive (latent). +ppd, -CXR

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Pulmonary Tuberculosis: Progression if Infection Not Controlled By Immune System

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Granulomas become nectrotic and eventually produce fibrosis and calcification of the tissues
Spread to other regions of the body

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Pulmonary Tuberculosis: Clinical Manifestations (systemic, regional or pulmonary)

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Often occur over 1 year after initial exposure
Systemic - Fever, malaise, anorexia, weight loss
Regional or Pulmonary - Cough, bloody sputum, pleuritic pain

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Pulmonary Tuberculosis: Treatment

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Pharmacotherapy - Active TB and certain cases of inactive TB - intense 6 months of meds
Surgery - multi drug resistant complications of TB

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Pulmonary Tuberculosis: Prognosis

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Good if infection is localized to the lungs and is treated
Not as good if multi-drug resistant strain, occurs in the aged, debilitated, or immunocompromised
Untreated - 50-80% fatal

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Pulmonary Tuberculosis: Rehabilitation Issues

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Perform a thorough chest assessment and musculoskeletal evaluation
Be aware of secondary effects of TB on the musculoskeletal system, such as disuse atrophy and decreased endurance

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Viral Hepatitis: Definition & Classification

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An acute or chronic inflammation of the liver caused by a virus
Classification: according to etiology, viral (several types), chemical (toxic), alcohol abuse, or autoimmune

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Viral Hepatitis: Risk Factors of Hepatitis C (6)

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Injection Drug Use, Received Blood Transfusion or Organ Transplant Before July 1992, Evidence of Liver Disease, Liver Transplant Recipient, Infants Born to HCV-Infected Mothers, Long-Term Kidney Dialysis

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Hepatitis C: Transmission

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Parenteral (inoculations, blood transfusions), Unidentified Exposure

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Hepatitis C: Acute

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Incuabation Period of 6-12 weeks
Virus establishes itself inside of hepatocytes, replicates, and causes cell injury
Inflammatory response and varying levels of tissue repair
>70% develop chronic Hepatitis (over 6 months)

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Hepatitis C: Acute Clinical Manifestations

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Malaise, Fatigue, Fever, Nausea, Vomiting, Diarrhea, Anorexia, Right Upper Quadrant Discomfort, Jaundice, Dark-Colored Urine, Light-Colored Stools (75% are subclinical or asymptomatic)

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Hepatitis C: Chronic Clinical Manifestations

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Fatigue, Malaise, Loss of Appetite, Bouts of Jaundice, Mild Hepatomegaly, Mild Splenomegaly
(May experience sporadic remission, no progression for years, rapid progression)