Exam 3 - Module 10

Emerging Infections

• The growing number of previously unknown infections is a rising problem, nearly 40 new infections arise in a generation
• Some infections originate in animals and then spread to humans
• ZIKV (Zika virus) rapidly became a global health concern
• ZIKV was discovered in rhesus monkeys in Uganda (1947), mosquitoes (1948)
• The first human cases occurred in Uganda and Tanzania in 1952 and Nigeria in 1953
• A major ZIVK outbreak occurred on Yap Island in Micronesia in 2007
• The number of sexually transmitted ZIKV cases has increased
• ZIKV can be transmitted through body fluids in nearly all sexual activity
• Semen may contain infectious virus for up to 6 months after symptom onset
• ZIKV can be transmitted via mother to child during pregnancy or delivery
• ZIKV may cause miscarriage, fetal death, microcephaly, and ocular disorders
• The CDC reported 231 symptomatic ZIKV cases and 554 cases in U.S. territories, as of Sept 6, 2017
• Mosquito breeding site destruction is the most effective way to limit Zika spread
• Insect repellent, protective clothing, limiting travel are prevention strategies
• Public health agencies are concerned about the potential reversion of some slowly spreading or initially isolated infections
• WHO developed a list of emerging viral diseases requiring urgent attention because of their epidemic potential
• Diminished insecticide use and increased global warming facilitates the spread of insect vectors

Microorganisms and Humans: A Dynamic Relationship

• The human body provides beneficial nutrients for microorganisms
• Humans have a complex relationship with microorganisms, including commensal, mutualistic, and pathogenic interactions
• Many microorganisms live within the normal microbiome without causing disease
• Physical barriers and other mechanisms maintain beneficial homeostasis with normal flora
• For example, the gut microbiota helps digest food, inhibit pathogenic microorganisms, and produce usable metabolites
• Opportunistic microorganisms can cause infection if defenses are weakened
• True pathogens have developed methods to circumvent body defenses
• Clinical infectious disease results from pathogenic microorganisms
• Microorganisms are classified by morphology and life cycles, disease-causing groups also share clinical properties
• Infection occurs when microorganisms colonize/multiply in a host, causing damage

Process of Infection

• Infection includes colonization, invasion, multiplication, and dissemination of pathogenic microorganisms
• Colonization involves adherence to tissue through surface receptors
• Invasion allows the microorganism to penetrate surrounding tissue
• Multiplication occurs rapidly in the warm, nutrient-rich host environment
• Viruses replicate inside infected cells, and some bacteria are intracellular pathogens
• Virulence factors (toxins, adhesion molecules) and ability to evade immunity are needed for successful spreading
• Biofilms can anchor to surfaces and resist immune defenses
• Growth in biofilms protects against host defenses/antibiotics and allows exchange of genetic information for resistance
• Biofilms can form on implanted medical devices and are associated with chronic infections
• Stable bacterial colonization requires adhesion, often mediated by pili (fimbriae), surface glycoproteins, or complement-related receptors
• Invasion leads to confrontation with defense mechanisms
• Evasion can result in multiplication in the blood, or sepsis
• Bacteria protect from phagocytosis by producing toxins that destroy phagocytic cells
• Extracellular enzymes break down complement components, clotting factors, immunoglobulins, cytokines, and antimicrobial peptides
• Some intracellular microorganisms can enter a latency phase until reactivation occurs
• Initial infection symptoms are fatigue, malaise, weakness, and loss of concentration
• Generalized aching and loss of appetite are other symptoms
• Fever is a hallmark infectious disease symptom – a regulated increase in body temperature in response to pyrogens

Factors Influencing Capacity of Microorganism to Cause Disease

• Ability to spread and cause disease, like measles vs HIV is Communicability
• Ability to trigger an immune response Immunogenicity
• Infectivity is the ability to invade and multiply in the host
• Mechanism of action is how the microorganism damages tissue
• Pathogenicity is the ability to produce disease, depending on other factors
• Portal of entry is how the infection enters the body
• Toxigenicity is the ability to produce toxins, influencing virulence
• Virulence is the capacity to cause severe disease

Classification of Infectious Diseases by Prevalence and Spread

• Endemic is the constant rate of infection in a population
• Epidemic occurs when the number of new infections exceeds the usual number
• Pandemic is an epidemic spreading over a large area
• The CDC's National Notifiable Diseases Surveillance System monitors, controls, and prevents disease spread
• STIs were among the most common reportable diseases in 2015

Transmission of Infection

• Microorganisms transmit through various forms of direct contact
• Indirect transmission occurs via contaminated materials or vectors
• Iatrogenic transmission results inadvertently from medical procedures
• Fecal-oral transmission occurs through ingesting feces contaminated substances
• Zoonotic infections can transmit directly from animals or indirectly through vectors

Classes of Infectious Microorganisms

• These include Fungi, viruses, bacterial, protozoal, parasitic
• Bacteria are unicellular microorganisms with a prokaryotic make up
• Divided into groups like "true bacteria," filamentous, spirochetes, mycoplasma, rickettsia, and chlamydia
• Bacteria can be gram-positive or gram-negative
• Gram staining differentiates bacteria based on cell wall structure
• Pili and flagella are surface structures that promote adhesion and tissue invasion
• Pili expressing adhesins bind to host cell components
• Some Bacteria produce toxic molecules to harm host cells, disrupt tissue, and affect inflammation
• Exotoxins are proteins released during growth, classified by mode of action (Type I, II, III)
• Certain exotoxins are botulinum, tetanus, diphtheria, and cholera toxin
• Endotoxins (lipopolysaccharide [LPS]) are part of the gram-negative bacterial cell wall, released during lysis
• Lipid A is responsible for inflammation, fever (pyrogenic bacteria), vasodilation, decreased oxygen delivery, cardiovascular shock, etc.
• Responses to bacterial infection can cause tissue damage
• Bacteria employ immune evasion mechanisms
• Rapid progression can overwhelm the initial immune response
• Protection against phagocytosis is achieved with capsules, toxins that kill phagocytes, enzymes that damage phagolysosomes
• Some bacteria neutralize the toxic environment of the phagolysosome or escape from it
• Bacteria block Ag (antigen) recognition by coating with host proteins or capsules resembling host components
• Antigenic variation allows pathogens to alter surface antigens
• Resistance to complement is achieved through capsules, degradation of complement factors, or use of regulatory proteins
• Some bacteria suppress immune responses by blocking T cells or impairing signals
• Staphylococcus aureus (S. aureus) is a commensal and opportunistic pathogen with numerous virulence factors contributing to invasive infection and antibiotic resistance

Infectious Fungi

• Fungi are eukaryotic microorganisms with rigid cell walls
• They can be molds (mycelium), yeasts, or be dimorphic
• Fungal infection is called mycosis
• Pathogenic fungi can be from the environment, transmitted by inhalation or wound contamination
• They can also exist as human commensals causing superficial mycoses
• Human-to-human transmission is common for dermatophytes that causes skin, nail, and hair infections
• Systemic mycoses often start as pulmonary infections after spore inhalation
• Opportunistic fungal infections are common in immunocompromised individuals
• Diagnosis involves microscopic observation and culture
• Fungi have polysaccharide surface molecules that promote adhesion to receptors
• Toxins are produced that promote infection, evade immune responses, or cause cancer
• Enzymes are secreted that damage tissue and initiate inflammatory responses
• The immune response to fungal infections involves cell-mediated immunity
• Hyperinflammatory responses can enhance fungal virulence
• Persistent infections can lead to granuloma formation while pulmonary exposure can also elicit IgE responses and allergic pneumonitis
• Fungi employ evasion mechanisms that include being dimorphic and encapsulated
• Some produce toxic metabolites and can survive in phagocytes to elude lysosomal destruction
• Altered antigen expression can provide protection
• Certain yeasts stimulate production of immunosuppressive cytokines
• Candida albicans is a common cause of fungal infections on the skin, GI tract, mouth, and vagina.
• C. albicans can form biofilms on medical devices and undergoes morphologic changes

Infectious Parasites and Protozoans

• Parasites are benefit at the expense of the host
• They range from unicellular protozoa to large worms (helminths)
• Parasite invasion may be extracellular or intracellular, involving adherence and matrix breakdown
• Some are obligatory intracellular parasites
• Toxins are less prevalent in parasitic diseases compared to bacterial ones
• Parasites produce toxins or release enzymes that disrupt cell membranes
• Damage from multicellular parasites is due to accumulation in tissue or can cause Malabsorption and anemia.
• Parasites employ different mechanisms to evade the immune system
• Certain organisms are obligate intracellular inhabiting macrophages with several various survival means inside.
• Some produce toxins that stop breakdown of phagosome/lysosome or release enzymes that disrupts phagocyte membranes
• Can also escape from the phagosome and grow in the cytoplasm
• Certain organisms can hide themselves by coating themselves with host proteins or through antigenic variation
• Caused by Plasmodium, Malaria evades complex immune stages for survival

Infectious Viruses

• Viruses are microorganisms of nucleic acid (RNA or DNA, single- or double-stranded) protected by a protein capsid, sometimes surrounded by an envelope.
• May or may not use reverse transcriptase
• Viral diseases are the most common human afflictions
• Destroy or damage cells upon replication and are intracellular
• binding to host cell receptors, followed by entry through fusion or endocytosis are components of Viral evasion
• replication is using the host cell’s machinery to produce viral components, which are then assembled and released, and can cause latency
• Rarely produce toxins some can cause cellular destruction.
• Virus symptoms are due to responses from the host inflammatory. Hepatitis virus can provoke damage from immune.
• As obligate intracellular pathogens they hide and proliferate
• Virus can interfere with immunity and block viral substances and TLR signaling
• Block through protein capsids.
• Antigenic Diversity can increase via translation.
• They induce Immunosuppresion T cells.
• Interfere with antigen processing or produce complement blocking.
• Influenza virus aerosol ssRNA via viral surface antigens (hemagglutinin and neuraminidase), affecting infection rate.
• Causes severe pathogenesis influenced by host/immune factors

HIV and AIDS

• HIV causes AIDS via the reduction of CD4 T cells, this in turn causes the body to is vulnerable to an opportunistic infection.
• Highly mutable is the virion. Copies of RNA and reverse transcriptase with Integrase found is less virulent strain in western Africa.
• Viral DNA is integrated into the cell (provirus,Transcription of Viral DNA (provirus)/translation new virions follow
• Death is due to a decrease in CD4 T cells during AIDS
• Manifestation during Stage is to base via 180 count, while 1-3 counts progress the disease to a development based.
• During early infection and after acute viral, Early Antibiotic Detection infection may acute anti bodies can identify
• HIV Can Reduce Prevent Viral
• Anti-reverse transcription does not clear HIV: the genome integrates into hosts (Primary reservoir
• Challenges such as High mutation and diversity are difficult.
• Can lead to progressive encephalopathy Infections with fluids to reduce Pediatric infections.

Countermeasures Against Pathogens

• Drug resistance leads the causes. Emerging resistance pose factors.
• Resistance from inherit to resist. Bypassing antibiotics
• Immunity is caused via inducing protection from diseases
• Vaccines are organisms that induce humoral prevention

The Physiology of Stress and its Effects

• Western culture emphasizes a strong work ethic which views idleness as taboo which causes a adaptive and survival-related psychological response
• Stress to individual coping, generally, cute immune-enhancing, while chronic stress is often immune-suppressive,
• In the brain activation initiates and activates neural sensory. Many hormones play a to role
• Release of hormones from adrenal and the body increases for heart flight.
• the system is from anterior and released hormones for immunity.
• Increase all but decrease, or are altered.
• Uncontrollable can develop to increase risks.
• Enkephalins have play
• distress

Pediatric Skin Conditions: A Concise Overview

• Diagnosis history conditions
• Acne from is cause of to years of life.
• With skin to or response.
• A can the