T2-Systems_Infectious Diseases Flashcards
The invasion of the human body by pathogenic microorganisms can produce harmful and have potentially lethal consequences. What is the name for the illnesses caused by these means?
Infectious diseases
Microscopic organisms (can be pathogens or non-pathogens)
Microorganisms (aka Microbe)
The presence and multiplication within a host of another living organism, with subsequent injury to the host.
Infection
Ability of an organism to enter, multiply and survive in a host
Infectivity
Any organism capable of supporting the nutritional, physical growth requirements of another organism.
Host
The act of establishing a presence within a host
Colonization
Disease-producing potential of an invading organism
Virulence
An organism so virulent that it is rarely found in the absence of disease
Pathogen
A multitude of non-harmful bacteria inhabiting the internal and external exposed surfaces of the human body.
Microflora
Free-living organisms that obtain nutrition from dead or decaying organic materials in the environment.
Saprophytes
An organism that produces an infectious disease only when the healthy and immunity of the host has been severely compromised
Opportunistic pathogen
Microflora acquires survival needs from the host, but the host is not adversely affected by this relationship.
Commensalism
microflora referred to as commensal flora, normal flora, resident microbiotica
Where is normal flora located in the human body?
Skin, nose/pharynx, mouth, colon/rectum, vagina/distal urethra/perineum
An interaction in which colonizing organisms and host both derive benefits
Mutualism
eg. bacteria that live in intestines and feed off undigested food, producing vitamins beneficial to humans
An interaction in which a colonizing organism benefits and the host sustains an injury
Parasitic
What is the name for protein particles that lack any kind of demonstrable genetic material and are mutated forms of the host protein?
Prions
How do prions work?
- protein particles that lack any demonstrable genetic material
- may affect other normal proteins and alter them
- aggregate in the brain and form plaque
- identified in a number of incurable and transmissible degenerative neurological diseases
- defective protein may be inherited
- cannibalism has been implicated as a transmission mechanism, as well as eating animals that are infected by a prion disease
- lack reproductive and metabolic functions so antimicrobial agents are useless
Tx is palliative
What are two examples of prion diseases?
Creutzfeldt-Jakob
Kuru
What do Rickettsia, Chlamydia, Coxiella, Mycoplasmas have in common?
- combine the characteristics of bacteria AND viruses
- obligate intracellular pathogens (i.e. they require a host)
- most produce a rigid petidoglycan cell wall, reproduce asexually and contain RNA and DNA-like bacteria
What is Rickettsia?
- transmitted by insect vectors
- cause diseases like Rocky Mountain Spotted Fever
- rash and small hemorrhages
What is Chlamydia?
- common sexually transmitted infection that can lead to pelvic inflammatory disease and sterility in women
- infants born to infected mothers can get eye infections and pneumonia
What is Coxiella?
- Q (query) fever + flu-like illness
- can progress to become systemic affecting heart, lungs and GI
- obtained through animal contact (animal infected spray and contaminated milk)
- initial exposure, remission and then severe organ issues a few years later
What are Mycoplasmas?
- commonly cause pneumonia
What is a prokaryotic cell?
No cell membrane
What is a eukaryotic cell?
Cell contains cell membrane, nucleus, organelles, etc
What are fungi?
- free living eukaryotic saprophytes
- few are capable of causing disease in humans (and most of these are limited to skin + subcutaneous infections)
eg. Candida (harmless fungus on skin, but can cause oral cavity infection and vaginal infection in immunosuppressed people)
What are the two types of fungi?
Yeast: single-celled organism, reproduce asexually
Mold: grow in long filaments called hyphae
Both yeasts and mold produce a rigid cell wall layer that is chemically unrelated to the peptidioglycan of bacteria and therefore is not susceptible to the effects of antibodies (require anti-fungal)
What are parasites?
- a member of the animal kingdom that infects and causes disease in other animals
- include Protozoa, Helminths, Arthropods, Bacteria and Viruses
Define Protozoa
- unicellular eukaryotes that may reproduce sexually or asexually
- most are saprophytes
- some are pathogenic to humans (eg. malaria, amoebic dysentry, giadiases)
Define Helminths
(aka worms)
- include roundworms, tapeworms, flukes
- reproduce sexually (usually through fertilized eggs)
Define Arthopods
- include tics, mosquitos, biting flies, lice, fleas and mites
What is the study of factors, events, circumstances that influence the transmission of infectious disease in human populations?
Epidemiology
What does epidemiology focus on?
- incidence of disease
- prevalence of disease
- source of infection
- portal of entry (where on the body)
- site of infection
- virulence factors
- signs / symptoms
- clinical course of disease
What is the ultimate goal of epidemiologic studies?
the interruption of the spread of infectious disease and its eradication
What refers to the host, object, location or substance from which an infectious agent is acquired, including modes of transmission?
Source of infection:
- Endogenous: Acquired from host’s own microbial flora
- Exogenous: Acquired from sources in external environment
- Contact transmission: Transfer of microbes by physical contact
- Droplet transmission: Microbes spread across a short distance (less than 1 meter) by droplets
- Airborne transmission: Microbes spread by air currents (longer than 1 meter)
- Vector-borne transmission: Microbes spread by animals or biting arthropods
- Vehicle-borne transmission: Infection transmitted by a contaminated source
- Nosocomial infections: Infection acquired during hospitalization
- Community acquired: Infection acquired outside of healthy care settings
The process by which a pathogen enters a body and gains access to susceptible tissue:
Portal of entry:
- Penetration: any disruption in integrity of body’s surface barrier from abrasions, burns, penetrating wounds, medical procedures, etc.
- Direct contact: transmitted directly from infected tissue or secretions to exposed, intact mucous membranes, including sexual contact, congenital infections
- Ingestion: entry of infectious agent through oral cavity and GI tract
- Inhalation: entry through respiratory tract
What refers to the part of the body that is infected?
Site of infection: local or systemic
What is the capacity of a microorganism to cause disease
Pathogenicity
(Virulence is the degree of pathogenicity based on invasive and toxic qualities, adherence to skin and ability to avoid host defences)
What are universal precautions?
- hand washing, wearing gloves and protective clothing
- adequate cleaning
- use of disinfectants
- sterilization of fomites
What is the disease presentation? (aka clinical picture)
Symptomatology
What are the 5 phases of the disease course?
- Incubation: pathogen begins active replication w/out symptoms
- Prodromal: initial appearance of symptoms
- Acute: host experiences maximum impact and the most symptoms of the infectious process
- Convalescent: containment of infection, progressive elimination of the pathogen, repair and resolution
- Resolution: total elimination of the pathogen from the body
What are some exceptions to classical presentation?
- Chronic infections: continuous s/s for months or years without a convalescent stage
- Subclinical illness: progresses from infection to resolution without clinically apparent symptoms
- Insidious: prodromal phase is gradual
- Fulminant: abrupt onset of illness with little or no prodromal phase
What are diagnosis and treatment based on?
Diagnosis: history, physical exam, culture, serology
Tx: Antimicrobial agent, immunotherapy, surgical intervention
What are bacteria (and classification)?
- prokaryotes
- can cause disease by producing toxins, invading tissue or both
- Classifications:
by Scientific Name: species and strains
by Staining: color they turn after treated with specific chemicals (Gram +ve = purple; Gram -ve = pink)
by Shape: Spheres (cocci), Rods (bacilli), Spirals (spirillum)
by Oxygen need: Aerobes (need oxygen), Anaerobes (do not need oxygen), Facultative (can live with or without oxygen)
Describe bacterial structure
- prokaryotes
- cell membrane
- external capsule
- flagella
- pili (aka fimbriae)
- spores (a latent form with a coating that is highly resistant to heat and other adverse conditions) = long survival time
What is secreted by bacteria?
Toxins:
- Exotoxins: secreted by Gram +ve, diffuse through body. eg. neurotoxin (tetanus bacillus) and enterotoxins
- Endotoxins: Gram -ve and released when bacteria dies. Cause fever, weakness and shock
Enzymes: cause damage to host tissue
What are bacterial defences?
- Biofilm: secretion that helps bacteria attach to other bacteria, cells/tissue (eg. dental plaque)
- Capsule: protection from macrophage ingestion
- Outer membrane/cell wall: protection from antibotics, membrane releases endotoxins
- Spores
- Flagella
- Antiobiotic resistance
What are some bacterial diseases caused by staphylococcal?
- Staphylococcal (Staph): more than 30 strains
What are some disease caused by Streptococcal?
- Streptococcal (Strep): strains from A-G, most common are A (found in throat and skin) and B
Strep A: Strep throat, scarlet fever, impetigo, flesh eating disease (necrotizing fasciitis)
Strep B: carried w/out illness until immune system is weak + can develop into UTIs, pneumonia; transmitted to newborns causing blood infections and meningitis
infections of intestines like e.coli, cholera, salmonella
What are other diseases?
- Rheumatic Fever: inflammatory disease affects heart, joints, skin, brain - causes a ring/snakelike rash
- Bacterial meningitis: People will be positive for Brudzinski’s sign (extreme pain with hip flexion) or Kernig’s sign (extreme pain with neck flexion)
- Respiratory tract infections: upper tract – strep; lower tract – bacterial pneumonia, bronchitis; tuberculosis (mycobacterium tuberculae, waxy)
- Enteric infections:
e.coli
cholera
salmonella (some varieties can even lead to Typhoid fever)
shigella (spread via fecal oral route) - Urinary tract infections
- Lyme’s disease: bulls’ eye rash (aka erythema migrans), tick-borne infection
What are viruses and how do they work?
- smallest obligate intracellular pathogen (require a host)
- incapable of replication outside host/living cell
- penetrate a living cell and use that material to create viral progeny
- attach to a host, enter it and release its genetic material
which forces the host cell to replicate the virus - host cell usually dies, at which point, virus is released
What are the routes of viral invasion?
- nasal, respiratory
- oral, gastrointestinal
- blood and bodily fluids
Body’s response to viral infection?
- Inflammatory response: vascular congestion and leakage of exudate
- Immune response: collection of lymphocytes in infected tissue
What are types of childhood viral infections?
- Poliomyelitis (Polio): affects NS, can lead to paralysis
- Rubeola (Measles): respiratory infection, causes toal body skin rash
- Rubella (German Measles): skin and lymph nodes, blueberry muffin rash
- Mumps: affects Parotid glands (spread through saliva)
- Chicken Pox: itchy rash with fluid-filled blisters
- Shingles (aka Zona, aka Herpes-Zoster): acute CNS infection, neuralgic pain, vesicle eruption on skin (rash) in a dermotomal pattern consistent with the Dorsal Root Ganglion where the virus was dormant
What are some common viral infections?
- Common cold: mild upper respiratory tract infection
- The flu (influenza): lower respiratory tract infection; three types (A, B and C); high mortality rate in seniors
- SARS and MERS: Severe acute respiratory syndrome; initial presentation are cold like symptoms
- Intestinal flu (aka Viral Enteritis, Gastroenteritis): spread through oral fecal route
- Herpes Simplex Type 1: oral, skin lesions near lips - Cold Sores/Fever blisters
- Herpes Simplex Type 2: genital infection
- Human Papilloma Virus (HPV): genital warts
- Mononucleosis (Mono): swollen glands, enlarged spleen, hepatitis
- Human Immunodeficiency Virus (HIV): leads to AIDS (Acquired Immunodeficiency Syndrome), spread through bodily fluids
- Viral Hepatitis - Hep A: acute infection, not permanent
- Viral Hepatitis - Hep B: serious, chronic/carrier stage, spread by bodily fluids/feces
- Viral Hepatitis - Hep C: serious, leads to cirrhosis of liver and liver cancer
- Viral Hepatitis - Hep D: only present with Hep B
- Viral Hepatitis - Hep E: clinically resembles Hep A
What are STIs?
Sexually Transmitted Infections:
- any infectious condition spread through sexual contact
- agents of infection include bacteria, viruses, chlamydia, fungi, protozoa and parasites
- portals of entry: mouth, genitals, urinary meatus, skin, rectum
What is Condylomata Acuminata?
Genital warts:
- caused by HPV
- most are asymptomatic; some infections result in warts
- link to cervical cancer
What is Candidiasis?
Yeast infection, thrush:
- caused by Candida albicans (most commonly) yeast
- common vaginal infection; autoinoculation (infection in eye) possible
- may cause dyspareunia (pain with sex)
What is Trichomoniasis?
- caused by anaerobic protozoa
- symptoms: green/frothy/stinky discharge
- strawberry spots (small hemorrhagic areas on cervix) may appear
What is Chlamydia?
- cervix hypertrophies, becomes red and raw (erythematous), swells (edematous) and extremely friable
- left untreated, may lead to Reiter syndrome: reactive arthritis that leads to conjunctivitis, urethritis and mucocutaneous lesions (“can’t see, can’t pee, can’t dance with me”)
Which virus causes blueberry muffin rash?
Rubella (German Measles)
Which STI causes strawberry spots?
Trichomoniasis
Which STI leads to the “can’t see, can’t pee, can’t dance with me” phenomenon?
Chlamydia
What is Gonorrhea?
- more likely to infect woman (90%)
- may cause inflammation of fallopian tubes (salpingitis)
What is Syphillis?
- has three stages:
Primary: lesion on site (chancre), apparent usually within 3 weeks
Secondary: maculopapular rash (reddish eruptions on skin especially on hands and feet), also elevated, red-brown lesions called condylomata lata
Tertiary: latency period - may last for life, can develop as long as 20 years after initial infection, lesions may include cardiovascular or CNS lesions or gumma: rubbery, non-inflammatory, necrotic lesions on liver, testes or bone
