Lecture 4 Outline: Infectious Diseases Flashcards
Overview of Infectious Diseases
- from 1950 until 1980 the management of communicable infectious diseases was well under control
- in 1970s and 80s new infectious agents appeared: via combo of environmental disruption and human mobility (increased gene mobility)
- emergence of antibiotic-resistant organisms
- resurgence of long-standing diseases (i.e. tuberculosis)
- new infectious agents appeared
Signs and Symptoms of Infectious Disesases
- blood composition: increased number or change in type of leukocytes
- change in mentation in older adults: confusion, memory loss, difficulty concentrating
- fever
- abscess
- rash with fever
- red streaks radiating from an infection site
- inflamed lymph nodes
- joint effusion
Fever
- can be associated with non-infectious event
- normal temp regulated by hypothalamus-can cause hypothalamus to reserve heat and increase heat production
- pyrogens: above 104 degrees (delirium, convulsions, irreversible cell damage)
Abscess
- localized infection and inflammation with purulent exudate (what contain pus)
- combo of leukocytes, dead organisms, and necrotic tissue (pus)
- rupture: drainage into other tissues spreading infection
Rash With Fever
- maculopapular eruptions-microbes penetratelayer of skin (i.e. measles)
- nodular lesions (i.e. pseudomonas)
- diffuse erythema (i.e. scarlet fever)
- vesiculobullous eruptions (i.e. herpes zoster)
- petechial purpuric eruptions (i.e. CMV)
Red Streaks
- radiate from infection site (aka blood poisoning)
- moe in direction of regional lymph nodes
- may be associated with lymphangitis
Inflamed Lymph Nodes
- palpable in cervical axillary or inguinal areas
- overlying skin may be erythematous and warm due to infections
- metastatic sites for cancer:common in supraclavicular and inguinal nodes
- usually hard and fixed to underlying tissue, no tenderness usually but swollen
Joint Effusion
-fluid gets into interstitial fluids and causes swelling
Definition and Overview of Infection
- process in which organisms establishes a parasitic relationship with its host involving reproduction of microorganism
- tissue-destroying microorganisms enter and multiply in body
- may take form of minor illnesses or result in life-threatening condition called sepsis
Steps of Infection
- transmission can have more than one outcome: pathogen contamination of body surface only, subclinical infection: no evident symptoms, clinically apparent infection: host-parasite interaction causes obvious injury, one or more clinical symptoms present, called infectious disease
- incubation period: period between pathogen entering host and appearance of clinical symptoms
- latent infection: occurs after microorganism has replicated, but remains dormant or inactive in host
- period of communicability: time period when organism can be spread
Viruses
- smallest organisms
- completely dependent on host cell (no metabolic capability)
- made up of DNA or RNA nucleus
- not susceptible to antibiotics
- viral infections develop when normal inflammatory and immune response fail: inner capsule releases genetic material
Bacteria
- well defined cell wall
- one-celled organisms with no true nucleus and reproduce by cell division
- pathogenic bacteria contain cell-damaging proteins
- exotoxins: released during cell growth
- endotoxins: released when bacterial cell wall decomposes
- both of the above cause fever and aren’t affected by antibiotics
- shape classification: cocci (spherical) bacilli (rods) spirilla or spirochetes (spiral)
- gram positive or negative or acid-fast
- motile or nonmotile
- tendency for capsulation but can be encapsulated or not
- sporulating or nonseparating
- aerobic or anaerobic (most human flora is anaerobic)
Fungi
- part of human body’s normal flora
- fungal diseases in humans called mycoses
- infection usually mild unless systemic or compromised immune system
- reproduce asexually and contain nucleus
- classification: yeast and mold
Parasites
- common in rural or developing areas
- organisms that live on or inside another organism
- enter through mouth or skin, depend on host for food and protection or harm the host
- ex: helminths (tapeworms)
Prions
- proteins without nucleic acids
- transmitted from animals to humans and cause rapidly progressive deteriorating state
- ex: mad cow disease-rare form of dementia, from beef infected with bovine spongiform encephalopathy, infects CNS leading to myelin destruction and neuronal loss
- symptoms: myoclonic jerking, ataxia, aphasia, vision disturbances, paralysis
Chain of Transmission
- pathogen
- reservoir
- portal of exit
- mode of transmission
- portal of entry
- host susceptibility
Chain of Transmission: Pathogen
- any microorganism that has capacity to cause disease
- virulence: potency of pathogen in producing severe disease
Chain of Transmission: Reservoir
- environment in which organism can live and multiply such as animal, plant, soil, food, or other organic substance or combo of substances
- carrier: maintained environment that promotes growth, multiplication, and shedding of parasite without exhibiting sides of disease (hepatitis)
Chain of Transmission: Portal of Exti
- place from which parasite leaves reservoir
- site of growth of organism
- secretions, fluids, feces, open lesions
Chain of Transmission: Mode of Transmission
- contact: direct (physical contact of microorganism with host) or indirect (passive transfer from intimate intermediate object-fomite)
- airborne: disease-causing organism usually less than 5 microns capable of floating on air current for hours; then inhaled by host
- droplet: larger particles greater than 5 microns that fall out within 3 feet of source
- vehicle: infectious organism transmitted through common source (food/water) to many potential susceptible hosts
- vectorborne: involves insects and/or animals that act as intermediaries between two or more hosts (ticks)
- nosocomial infections: infections acquired during hospitalization (~5%)
Chain of Transmission: Portal of Entry
-site where pathogen may enter a new host
Chain of Transmission: Host Susceptibiltiy
-variable depending on many factors
Clostridium difficile (C Diff): Overview, Etiology, Transmission, and Risk Factors
- bacterial infection
- cause of nosocomial and community based diarrhea
- occurring exclusively in presence of exposure to antibiotics (wipes out intestinal flora)
- primarily in health care facilities and transferred via fecal-oral route
- non human reservoirs include water, raw veggies, and animals
- most common mode of transmission is patient to patient via contaminated hands of healthcare workers
- can also spread through bedpans, tubes, urinals, bed rails, call bells, etc
- happens a lot in old people because they have decreased stomach acid
- classically associated with use of antibiotic clindamycin (cleocin)
Clostridium difficile (C Diff): Pathogenesis, Clinical Manifestations, Medical Management, Prevention
- change in protective flora of enteric system induced by antibiotics allow growth and toxin production (toxins A and B)
- clinical manifestations: persistent diarrhea following antibiotic consumption, elevated WBC count, abdominal pain, cramping, or tenderness, nausea and vomiting, fever
- diagnosis and Rx: stool culture, assay to detect toxins in stool, prompt discontinuation of antibiotic agent, oral vancomycin if not responding
- prevention: hand hygiene, barrier precautions, environmental disinfection, and antimicrobial stewardship
Lyme Disease: Definition, Overview, Incidence, Pathogenesis
- infectious multi-systemic disorder caused by bacterium (spirochete) carried by deer ticks
- incidence: most prevalent vector-borne infectious disease in US, >90% of cases come from mid-atlantic, northeastern, and northcentral regions
- pathogenesis: infected tick injects spirochete-laden saliva into bloodstream or deposits fecal matter on skin; after incubating 3-32 days spirochetes migrate outward causing an inflammatory response (rash); disseminates to other skin sites or organs through the blood or lymph (may survive for years in joints)
Lyme Disease: Clinical Manifestations
- varied symptoms mimicking those of many other diseases
- stage 1: early localized state within days: EM (erythema migrans) is a red, slowly expanding bull’s eye rash (not everyone develops this) resolves spontaneously in ~4 weeks; flu-like symptoms
- stage 2: disseminated infection (weeks to months), if not treated may spread to NS, heart, and joints; neurologic symptoms: 15% of cases first to arise, manifested as aseptic meningitis, cranial nerve palsies, peripheral neuropathy, may improve or resolve if untreated; lyme arthritis (in ~50% of diagnosed cases): unilateral inflammation and swelling in large joints
- stage 3: late persistent (weeks to months)-60% get here if didn’t get early treatment, intermittent arthritis with marked pain and swelling occurs 6 weeks to several years after tick bite, usually only 1 or a few joints are affected-50% of people not treated progress to this stage
Lyme Disease: Medical Management
- diagnosis: CDC criteria, blood tests, Ab titers
- treatment: oral antibiotics (amoxicillin), NSAIDS and other drugs for arthritis pain as appropriate
- prognosis: good if treated early with antibiotic therapy
- no natural immunity that develops here
Staphylococcal Infections: Overview, Incidence, Risk Factors, Pathogenesis
- most common bacterial pathogens on skin
- leading cause of nosocomial and community acquired infections
- survives on fomites (surfaces)
- most common cause of infections
- S. aureus very virulent: about 90% of strains penicillin resistant and 50% to methicillin
- risk factors: spreads by direct contact, most common route of transmission is thought to be open wounds or from contact with a carrier: poor hand washing, poor personal hygiene, sharing personal items etc; most frequent site for colonization are nares; surgical, burn, and diabetic patients very susceptible
Staphylococcal Infections Pathogenesis
- s. aureus cannot invade through intact skin or mucous membranes
- virulent pathogen secreting membrane-damaging enzymes and toxins
- bones, joints, kidney, lung, and heart valves are most common sites of s. aureus infections
- MRSA: common in health care and athletic settings, overuse of antibiotics has fed increase in MRSA infection not resistant to vancomycin
Staphylococcal Infections: Clinical Manifestations, Medical Management
-starts out as small red bumps that resemble pimples, boils or spider bites consistent with folliculitis
-infection usually produces suppuration and abscess formation: can remain confined to skin or burrow deep in body to cause life-threatening infections
-consumption of toxins in contaminated food cause food poisoning
-diagnosis: culture from pus drainage is diagnostic, antibiotic sensitivity testing is important
-treatment: drainage of abscesses, administration of antibiotics
=prevention: good hand hygiene is most effective, follow contact precautions when working with patients
-prognosis: good with treatment unless antibiotic resistance is present; sepsis, infective endocarditis, visceral abscesses, and osteomyelitis are potentially lethal
-SIFTT: anyone with active infection should not be discharged fro IP setting, same germicidal cleaning measures required as in hospital setting cause spread by direct contact
Streptococcal Infections: Group A
-GAS
-s.pyogenes is prototypical GAS: two categories of diseases supportive and non-supportive
-typically transmitted via contact with respiratory droplets or after contact with clients who have infected secretions
types of GAS infections: streptococcal pharyngitis strep throat, scarlet fever, impetigo, erysipelas, necrotizing fasciitis, streptococcus pneumoniae
Streptococcal Pharyngitis (Strep Throat)
- incubation 1-5 days
- symptoms include pain with swallowing and fever
- diagnosis: throat culture or rapid diagnostic kits
- treatment: antibiotics with supportive measures
Scarlet Fever
- usually follows untreated streptococcal pharyngitis in children aged 2-10
- caused by a release of a pyogenic toxin
- presentation: sore throat, fever, strawberry tongue (white coated tongue with red papilla)
- rash first appears on upper chest, then spreads to extremitites
Impetigo
- usually caused by GAS but other streptococci or staphylococci species may be involved
- usually in children 2-5
- produces small molecules that develop into vesicles that become pustular and encrusted
- does not typically cause pain or fever
- scratching spreads infection and may progress into lymphangitis or cellulitis
- treatment should cover both streptococci or staphylococci species
Erysipelas
- type of cellulitis usually affecting face and legs
- red, shiny, and swollen in appearance with well demarcated margins between normal and infected skin
Necrotizing Fasciitis
- invasive infection of fascia: destroys tissue by releasing toxins; usually in legs
- infection spreads rapidly causing edema and tenderness
- characterized by thrombosis of blood vessels passing between skin and deep circulation, producing skin necrosis
- skin breaks down and bullae form that contain thick dark fluid cutaneous gangrene occurs
- can affect any part of body, but is most common on extremities, especially legs
- immediate surgery with aggressive debridement is mandatory and usually requires multiple procedures along with intensive antibiotics to save muscles and limbs
Streptoccoccus Pneumoniae
- group B
- transmission by direct contact or inhalation of droplets of respiratory secretions
- most common cause of community acquired pneumonia and death by a vaccine-preventable bacterial disease
- most common cause of meningitis in adults, infants, and toddlers
- clinical manifestations: fever, chills, pleuritis with pleuritic chest pain, dyspnea with productive cough or purulent sputum; diseases spreads rapidly over 24-48 hours
- mortality rate is high without treatment
- diagnosis: lab exam of sputum, CSF, or blood and culture of organisms
- treatment: antibiotics, vaccine for adults and young children and infants
- prevention: rate has decreased in young children with vaccines as well as adults
Gas Gangrene: Definition and Overview
- Group B
- rare but severe and painful
- usually follows trauma or surgery
- gangrene is death of body tissue associated with loss of vascular supply followed by bacterial invasion and putrefaction
- occurs in wounds infected by anaerobic bacteria, leading to gas production and tissue breakdown
- spreads rapidly to adjacent tissues and can be fatal within houts of onset
Gas Gangrene: Pathogenesis, Clinical Manifestations
- anaerobic conditions necessary, but rare in humans; produced only in presence of extensive devitalized tissue
- skin darkness
- thick discharge with foul odor and sometimes gas bubbles
- produces myositis and anaerobic cellulitis affecting only soft tissue
Gas Gangrene: Medical Management and SIFTT
- diagnosis: anaerobic cultures of wound drainage and radiographs showing gas in tissues
- treatment: surgery to debride surface necrotic tissues, amputation may be necessary
- prognosis: 20% of cases in extremities will be fatal, poorer prognosis with abdominal wall, uterus or bowel
- watch for: cool skin, pallor or cyanosis, sudden severe pain, sudden edema and loss of pulses; be prepared for foul odor; use sterile technique, double bag drainage and dressings, no special cleaning required after discharge
Pseudomonas: Overview and Pathogenesis
- group B
- one of most common hospital or nursing home-acquired pathogens
- associated with pneumonia, wound infections, urinary tract disease, and sepsis in debilitated people
- thrives on moist environmental surfaces
- among most antibiotic-resistant bacteria
- pathogenesis: produces array of proteins, which allow it to attach to, invade, and destroy host tissue, while avoiding host inflammatory and immune defenses; many strains produce proteoglycan that surrounds bacteria, protecting them from mucociliary action, complement, and phagocytes
Pseudomonas: Clinical Manifestations and Medical Management
- vascular thrombosis and hemorrhagic necrosis particularly in lungs and skin
- causes infections of respiratory tract, bloodstream, CNS, skin and soft tissues, bones and joints of body
- diagnosis: isolate organism
- treatment: antibiotics; debridement/drainage of infected wound
- prognosis: good for local infections, septicemic pseudomonas associated with high mortality rate
Viral Infections
- bloodborne viral pathogens
- herpes
Bloodborne Viral Pathogens
- hepatitis B and C and HIV are greatest concern for HCW
- prevented by following standard precautions
Herpesviruses: Incidence, Etiolgy, Risk Factors, and Pathogenesis
- subclinical primary infection is more common than clinically symptomatic illness
- each type persists in latent state for rest of one’s life
- incidence, etiology, and risk factors: 70% of americans over 12 have HSV-1 which causes cold sores; 1/5 have HSV-2, the principal cause of genital herpes; more common in women
- pathogenesis…
- both types can infect eyes and other organs
- initial infections often asymptomatic, although minor localized vesicular lesions may be evident: makes patient a carrier susceptible to recurrent attacks
- primary infection occurs when virus enters peripheral sensory nerves and migrates along axons to sensory nerve ganglia in CNS (usually via break in mucous membrane)
- may be latent for years
- stress, heat, cold, menses, fever, lack of sleep, or even sun exposure can cause virus to travel back down sensory nerves to surface of body (outbreak)
Herpesviruses: Clinical Manifestations and Medical Management
- HSV-1 (first episode) primarily affects skin and mucous membranes: cold sores, mouth sores, symptoms usually resolve 3-14 days
- HSV-2 most often acquired through sexual contact, sores usually crust over and heal in 1-3 weeks; ulcers on genital area, buttocks, urethra, or bladder; c/o tingling in involved area, malaise, dysuria, and dyspareunia
- severe illness in immunocompromised patients
- diagnosis: clinical diagnosis usually insensitive, so cultures of vesicular fluid is standard lab test (Ab test)
- treatment: no immunization available, anti-viral drugs can minimize recurrences
- prognosis: good
Herpes Zoster-Varicella Zoster Virus: Incidence and Pathogenesis
- 10-20% of population develops secondary form resulting in herpes zoster or shingles
- local disease brought about by reactivation of same virus, varicella-zoster virus (VZV) that causes systemic disease called varicella (chicken pox)
- causes significant pain, adults over 50 yo and individuals that are immunocompromised are at risk
- pathogenesis: VZV has capacity to persist in body (in sensory nerve ganglia) as latent infection; acute inflammation of dorsal root ganglia; enters through respiratory tract and conjunctiva; mechanism for reactivation of VZV unknown
Herpes Zoster-Varicella Zoster Virus: Clinical Manifestations
- after 2-4 days, severe, intermittent, or continuous, deep pain may occur as well as chill and low-grade fever
- after pain starts, small, red, nodular lesions begin to erupt on painful areas-they change rapidly into pus or fluid filled vesicles
- shingles can occur on face, trunk, and limbs-most often involves trunk or area of 5th cranial nerve (face)
- vesicular lesions occur unilaterally in the distribution of a specific dermatome supplied by a dorsal root: can lead to postherpetic neuralgia (PHN) (pain in area of recurrence that persist after the lesions have resolved)
Herpes Zoster-Varicella Zoster Virus: Medical Management and SIFTT
- diagnosis: clinical symptoms, lab test from vesicular fluid
- treatment: bedrest until fever has gone down, keep skin clear, antihistamines or creams for itching, antiviral meds
- prognosis: recovery from varicella infection usually results in lifetime immunity
- prevention: varicella vaccine recommended for children at 12-18 months before age 13 if they have not had chickenpox; zostavax for adults 60 and older
- SIFTT: adults with shingles are infectious to persons who have not had chickenpox; susceptible healthcare workers with significant exposure to varicella should be relieved from direct client contact from day 10-21 after exposure…if workers develop chickenpox, varicella lesions must be crusted before they return to direct client contact; neither heat nor ultrasound should be used on person with shingles because these modalities can increase severity of person’s symptoms
Infectious Mononucleosis: Overview, Incidence, Pathogenesis, Medical Mangement
- primarily affects young adults and children
- both genders affected equally
- spreads by oral-pharyngeal route most likely in saliva
- “kissing disease”
- caused by Epstein-Barr virus
- pathogenesis and clinical manifestations: HA, profound fatigue, myalgia, abdominal discomfort, hepatomegaly, increased lymphocytes and monocytes, enlarged spleen (may cause referral of pain to upper left quadrant), splenic rupture (person with infectious mononucleosis should avoid trauma)
- diagnosis: physical assessment, lab tests, positive heterophil (monospot) test
- treatment: rest and supportive care, no specific intervention alters or shortens the disease process
- prognosis: excellent, virus can live indefinitely in B lymphocytes so reactivation can occur
Cytomegalovirus (Herpes Virus Type 5)
- commonly occurring DNA herpesvirus
- frequently increases with age: 4/5 adults older than 35 have it, few symptoms for majority of people
- etiologic and risk factors: transmitted by human contact
- pathogenesis and clinical manifestations: spreads via lymphocytes or mononuclear cells and causes inflammatory reactions
- in normal adults, infection is usually asymptomatic
- diagnosis: culture or serologic ID of virus antigens
- treatment: relief of symptoms, pharmacologic treatment in immunocompromised individuals
- prognosis: poor for those with transplanted organs or immunocompromised states
Viral Respiratory Infections
- influenza
- respiratory syncytial virus (RSV)
Influenza
- influenza viruses A and B cause human influenza epidemics usually appearing each winter
- mode of transmission: person to person by inhalation of aerosolized virus or direct contact
- incubation period is ~1-4 days
- vaccination: recommended before beginning of each flu season for: people over 50, diabetics, renal dysfunction, nursing home residents, people with chronic lung or heart disease, immunosuppression, HCW’s, pregnant women–associated with reduced hospital rates
- genetic mutations very common
- antiviral agents help decrease duration and severity of S&S: antibacterial antibiotics are used only for bacterial complications
- good prognosis unless you get bacterial or viral pneumonia
Respiratory Syncytial Virus (RSV)
- virus that infects lungs and breathing passages
- causes pneumonia, bronchiolitis, and tracheobronchitis in infants and very young children
- in adults it appears as a mild respiratory tract infection and tracheobronchitis
- signs include low-grade fever, tachypnea, nasal congestion, coughing, sore throat, earache, fever, and wheezing
- transmitted by respiratory secretions (via large droplets) during close contact or on fomites or hands (incubation period 4-5 days)
- diagnosis: culture of nasopharyngeal secretions
- treatment: hydration, humidification of inspired air, ventilatory support as needed
- only viral disease that has its maximum impact very early in life
Anthrax
- infection of skin, lungs, or GI tract: bacillus anthracis spores (transmitted by contaminated animals, animal products, hides, and soil)
- inhaled spores enter lymph nodes
- S&S (incubation up to 14 days) red-brown bump on skin-turns into black scab, swollen lymph nodes, nausea, vomiting, fever, muscle ache, and HA, respiratory problems, shock and coma
Botulism
- paralytic illness: endotoxin-clostridium botulinum acts at NMJ prevention ACh release and blocking neural transmission; inadequately cooked, contaminated foods
- S&S (12-36 hours after digesting food): initially, dry mouth, sore throat, weakness, dizziness, vomiting, and diarrhea
- cranial nerve impairment, weakness and muscle paralysis follows
Legionnaires Disease
- infection caused by Legionella pneumophila
- inhalation of organism from A/C units, water faucets, showerheads, humidifiers, and contaminated respiratory equipment
- S&S (most people don’t get sick; occurs in middle aged or older): dry cough, fever, purulent sputum, myalgia, GI distress, pneumonia, and CV collapse (those with weakened immune systems)
- no indication it’s transmitted from person to person
- most likely transmitted via inhalation or aspiration
Leprosy
- infection caused by mycobacterium leprae
- respiratory transmission leads to systemic infection with progressive cutaneous lesions that attack PNS
- lesions on skin, pharynx, nose, larynx, eyes, muscle weakness, paralysis
Rabies
- acute CNS infection transmitted by animal bite
- virus replicates in striated muscle cells and spreads along nerve pathways to SC and brain where it replicates again and moves into other tissues
- prodromal (early warning signs) symptoms: local and radiating pain, burning, pruritus, and tingling at bite site as well as HA, nausea, sore throat, excessive salivation
- excitation phase: about 2-10 days after S&S being, intermittent hyperactivity, anxiety, apprehension, fever, shallow respirations, altered level of consciousness
- hydrophobia: about 50% of patients get this which causes forceful, painful pharyngeal muscle spasms that expels fluid from the mouth, swallowing problems cause frothy drooling, seizures, and cardiac arrhythmias
- treatment: no Rx after symptoms appear; post exposure-4 does immune globulin
Rocky Mountain Spotted Fever
- infection caused by Rickettsia rickettsii carried by dermacentor ticks
- multiply within endothelial cells: leads to thrombosis and leakage of RBCs
- S&S: fever, HA, myalgia, nausea, vomiting, rash develops (wrist, ankle, and spreads to trunk)
Rubella
- german measles
- produces distinctive 3 day rash and enlarged lymph nodes
- transmitted through contact with blood, urine, stool, or nasopharyngeal secretions from infected person: communicable from ~10 days before rash appears and ~5 days after
- mildly itchy rash that usually begins on face and spreads rapidly, covering trunk and extremity within hours
- rash usually disappears on 3rd day: rapid appearance and disappearance distinguishes it from rubeola
- treatment: antipyretics and analgesics for fever and joint pain
- primarily affects skin and lymph nodes
STDs: OVerview, Incidence, Etiologic and Risk Factors
- 19 million Americans contract STD each year
- 1/4 sexually active people carry STD other than HIV
- syphilis has steadily increased since 2000 particularly in black men and men who have sex with men
- gonorrhea has reached all time lows
- chlamydia and HPV are epidemic
- 45 million people have chronic genital herpes with 1 million new cases every year
- 1.1 million Americans have HIV/AIDS with 42,000 new cases per year
- etiology: 25% of all STD’s occur in people 25 years old and younger
- multiple sex partners, partner with know risk factor, sharing needles, blood transfusion between 77 and 84
STDs: Pathogenesis, Clinical Manifestations, Medical Management
- caused by bacteria, viruses, or occasionally parasites
- manifestations vary according to STD
- prevention: abstinence and or mutually monogamous sexual relationship; proper condom use can reduce transmission
- testing: recommended chlamydia testing for sexually active adolescents and women every 6 months
- older women at high risk with history of previous infection