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Infectious Disease > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

characteristics of infectious diseases that set them apart from other human diseases

A

-unpredictable and explosive global impact
-frequent acquisition by host of durable immunity against reinfection after recovery
-reliance of disease on a single agent without requirement for multiple cofactors
-transmissibility
-potential for becoming preventable
-potential for eradication
-evolutionary advantage over human host bc of replicative and mutational capacities of pathogens -> highly adaptable
-close dependence on nature and complexity of human behavior
-frequent derivation from or coevolution in other animal species
-possibility of treatment for having multiplying effects on preventing infection in contacts and the community and on microbial and animal ecosystems

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2
Q

established infectious diseases

A

-endemic diseases that have been around to allow for stable and predictable level of morbidity and mortality
-viral and bacterial respiratory and diarrheal diseases
-drug susceptible malaria
-tuberculosis
-tropical disease- helminthic, parasitic disease
-nosocomial infections

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3
Q

newly emerging infectious diseases

A

-diseases that are recognized in the human host for first time
-HIV/AIDs, nipah virus, severe acute respiratory syndrome

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4
Q

reemerging infectious diseases

A

-diseases that historically infected humans but continue to reappear either in new locations or resistant forms

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5
Q

normal mechanisms which prevent infection

A

-normal flora
-hereditary factors
-cellular factors
-natural antibodies
-natural barriers to the entry of microorganisms
-non specific immune factors: cytokines, acute phase response, stress, hormones, age, complement, inflammation
-specific immune factors

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6
Q

normal flora prevents “invasion” of other organisms

A

-compete for the same nutrients
-competes for same receptors on host cells
-produces substances which are toxic
-low level stimulation of immune system

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7
Q

common “colonizers”

A

-skin- staph, strep, corynebacterium, candida
-mouth- strep (aerobes and anaerobes), candida
-colon- bacteroides, enterobacter, enterococcus, candida
-vagina- lactobacillus, costridium, enterobacter

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8
Q

natural barriers to infection

A

-intact skin (oily vs dry, inflammation)
-mucous membranes- cervical mucus, prostatic fluid, tears toxic to organisms)
-respiratory tract- filtration, cough, macrophages
-intestinal tract- pH, peristalsis, normal flora
-genitourinary tract- pH, hormones, urethra
-the eye- tears, anti microbial substances

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9
Q

examples of subtle or not-so-subtle immune impairments

A

-elderly
-diabetic
-pt who is s/p splenectomy

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10
Q

tuberculosis background

A

-discovered by robert koch
-mycobacterium tuberculosis
-afflicted human population since antiquity
-extreme weight loss
-aka- consumption, TB
-bacterial disease of lung
-caused by aerobic, nonmotile, acid-fast bacillus M. tuberculosis
-incubation- 2-12 weeks from exposure to positive purified protein derivative (PPD) test
-geographic regions- worldwide, more common in developing nations
-failure to thrive

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11
Q

tuberculosis today

A

-continues to plague us
-WHO estimates suggest 1/3 of global population currently suffers
-3 mil new cases appear annually
-multidrug resistance associated
-M. tuberculosis complex -> Refers to not only M. tuberculosis infections but also M. bovis*
-consumption of raw milk and unpasteurized dairy -> cause of human M. bovis infections

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12
Q

transmission of tuberculosis

A

-if 100 are exposed to M. tuberculosis -> 3/4th will suffer no infection -> 1/4 will develop primary TB
-of the cases -> 1/10 will progress to primary active TB and nearly 90% to latent infection
-latent cases -> another 90% will not develop clinical disease
-suppression of TB occurs 90% of primary infections and result in latent TB
-airborne droplets
-primary TB is either suppressed by immune system or cause active disease

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13
Q

tuberculosis: environmental factors

A

-occurs person to person via aerosolized droplets
-coughing/sneezing mostly but also talking or singing
-droplets of sputum -> evaporate -> only solidified parts remain -> some of which are M. tuberculosis laden
-evaporation time reflect their size
-larger one vaporize slower than smaller
-sometimes a function of conditions such as humidity

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14
Q

suspended droplets: tuberculosis

A

-suspended M. tuberculosis laden droplets cause infection
-once inhaled -> sequester in alveoli -> establish primary infection site
-some droplets never make it that far
-larger ones tend to attach to inside of nose or trachea
-smaller ones may be exhaled before they ever plumb respiratory tract
-flourish in crowded, poverty stricken settings

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15
Q

infectivity factors: tuberculosis

A

-virulence of its strain*
-population density
-rate and force at which an infected individual coughs or sneezes
-extent to which the pathogen has infiltrated the pulmonary spaces
-greater the number of pulmonary lesions -> greater bacterial load of M. tuberculosis

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16
Q

clinical diagnosis: tuberculosis

A

-historically relied on chest radiographs
-appearance of calcified pulmonary lesions were considered indicative of infection
-radiography lacks diagnostic sensitivity and specificity
-tuberculin skin test (TST)- most used tool
-uses purified protein derivative (PPD) that contains tuberculin- protein produced by M. tuberculosis- come back 2 days to check for indurations

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17
Q

primary TB infection that results in active disease

A

-primary progressive TB

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18
Q

latent TB

A

-can remain dormant for many years and if not treated will become active ->
-reactivation TB or progressive secondary TB
-in 10% of those infected

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19
Q

signs and symptoms of tuberculosis

A

-active pulmonary TB -> fever, malaise, fatigue, night sweats, weight loss, cough, dyspnea, pleuritic chest pain, hemoptysis
-symptom onset is gradual in reactivation TB
-extrapulmonary TB- disease that spreads outside lungs -> common in children and immunocompromised
-common extrapulmonary sites- pleura, meninges, lymphatic system, genitourinary (GU), bones

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20
Q

tuberculosis testing

A

-PPD screening tests for previous exposure
-chest x ray may show signs of active disease and may reveal miliary lesions, consolidation, cavity lesions, pleural effusions, nodular infiltrates, granulomas, mediastinal lymphadenopathy
-preference for lung apices predominantly on right side
-when testing for active disease -> Sputum for acid-fast bacilli (AFB) staining using Ziehl-Neelsen (ZN) stain- plated for culture and sensitivity -> testing using polymerase chain reaction- PCR
-culture is gold standard for dx- takes 4-8 weeks

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21
Q

treatment tuberculosis

A

-latent TB often treated with daily isoniazid with or without supplemental pyridoxine for 9 months
-daily rifampin for 4 months- alternative
-treatment of active and/or extrapulmonary TB requires multiple drugs including isoniazid, rifampin, ethambutol, streptomycin, pyrazinamide
-hard to treat due to bacterias slow reproductive rate

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22
Q

x-ray: tuberculosis

A

-chest x-ray (CXR) and chest CT
-typically show apical or posterior lung infiltrate
-cavities and air fluid levels may be present in 20% Of cases
-may show nonspecific “tree in bud pattern”
-modules, effusions, or miliary pattern may be present
-5% of cases have normal chest imaging
-would be done if induration is seen
-infiltrates

23
Q

prevention of TB

A

-case finding is the first step
-done with PPD test that can ascertain exposure
-proper identification of cases, diagnosis, start of appropriate drug regimen, aggressive follow up
-identification of close contacts such as household members -> may require treatment
-anti-TB vaccination routine childhood (not in US)
-Bacille-Calmette-Guerin (BCG) vaccine- 60-80% efficacy

24
Q

lyme disease

A

-causative agent- borrelia burgdoferi in north america -> B. afzelii and B. garinii in Europe
-vector:
-deer tick (Ixodes scapularis) in eastern US
-black legged tick (Ixodes pacificus) western US
-sheep tick (Ixodes ricinus) in europe
-taiga tick (Ixodes persulcatus) Asia
-reservoir- white footed mouse (peromyscus leucopus0
-incubation- 3-30 days
-geographic regions- northern latitudes of north america, europe, asia
-peak incidence- spring-fall, peaks in summer, in accordance with activity of nymph stage of Ixodes spp. ticks
-nymphs are more likely than adult ticks to transmit lyme disease

25
Q

systemic effects of lyme disease

A

-tick borne spirochetal zoonosis
-affect skin, joints, nervous system, heart
-disease is broken down into 3 stages of infection- early localized, early disseminated, late disseminated
-culture of B. burgdorferi in Barbour Stoenner Kelly medium of biopsies of EM skin lesions -> IgM and IgG serologica antibody testing can be obtained but is limited of use early in disease course

26
Q

signs and symptoms of lyme disease

A

-early localized infection is characterized by circular outwardly expanding bulls eye rash -> erythema migrans (EM) -> 70-80%
-flulike symptoms - fatigue, malaise, headache, myalgia, fever -> present or delayed
-early disseminated infection occurs within several days to weeks of initial EM lesion and can present as multiple areas of EM
-within months pts may develop neurologic symptoms -> facial palsy (can be bilateral), photosensitivity, polyneuropathy, vertigo, ataxia, insomnia, memory loss, psychosis, meningitis, encephalitis

27
Q

syphilis

A

-the great imitator- presents differently
-causative agent- Treponema pallidum subsp. pallidum
-incubation- 10-90 days, average 3 weeks
-geographic regions- worldwide
-sexually transmitted
-gram negative spirochete Treponema pallidum subsp. pallidum
-chronic
-4 stages: primary, secondary, latent, and tertiary
-US men who have sex with men (MSM) - highest risk
-can be acquired congenitally

28
Q

signs and symptoms of syphilis

A

-primary infection- presence of 1 or more firm, painless, nonpruritic chancres
-secondary- 4-10 weeks later untreated, symmetric, nonpruritic, reddish-pink rash on trunk, pals, and soles
-condyloma latum- lesions that appear on mucous membranes -> resolve over 3-6 weeks without treatment -> enters latent (dormant) phase
-1/3 pts will develop tertiary syphilis over 3-15 years without treatment

29
Q

syphilis diagnosis

A

-darkfield microscopy or direct fluorescent antibody testing performed on fluid or smears from lesions
-serological tests are either nontreponemal (screening) or treponemal specific (confirmatory) -> RPR, VDRL, TRUST
-positive results followed up with confirmatory treponemal-specific testing -> T. pallidum enzyme immunoassay (TP-EIA) or fluorescent treponemal antibody absorption (FTA-ABS)

30
Q

syphilis treatment

A

-benzathine penicillin G 2.4 mil units IM x 1 for primary, secondary, or latent infections less than 1 years duration
-latent for more than 1 year or indeterminate age and tertiary infections other than neurosyphilis -> benzathine penicillin G 2.4 mil units IM weekly x 3
-neurosyphilis is difficult to treat -> requires 18-24 mil units continuous IV for 10-14 days

31
Q

rocky mountain spotted fever (RMSF)

A

-causative agent- rickettsia rickettsii in america
-vector- US: American dog tick (Dermacentor variabilis), rocky mountain wood tick (D. andersani), brown dog tick (Rhipicephalus sanguineus); Central and south america: cayenne tick (amblyomma cagennense)
-transovarial transmission- female ticks pass infection to their eggs in process
-reservoir- small woodland animals, domestic dogs, cats, deer
-incubation- 2-14 days
-geographic regions affected- north atlantic and south central regions of US, north america, central america, and south america
-peak incidence- late spring early summer
-tick borne rickettsial zoonotic disease caused by rickettsia rickettsii
-gram negative obligate intracellular bacteria
-transmission of the infectious agent occurs within 6-10 hours of tick attachment (faster than lyme)

32
Q

signs and symptoms of RSMF

A

-mild disease- fever, malaise, myalgia, nausea, vomiting, headache, arthralgia, rash
-rash- centripetal inward spreading macular rash, beginning on wrist, forearm, and ankles and spreading inward toward the trunk
-palms and soles are involved in up to 80%
-severe disease- skin necrosis, digit gangrene, acute respiratory distress syndrome, pulmonary edema, nausea, vomiting, abdominal pain, diarrhea, confusion, acute renal failure, meningoencephalitis, ataxia, blindness

33
Q

RSMF diagnosis

A

-consider for pts presenting with fever, rash, and history of tick exposure/bite
-labs will reveal hyponatremia, thrombocytopenia, elevated liver enzymes, increased bilirubin, and increased BUN
-western blot with cross absorption
-detection of rickettsial nucleic acids by PCR in blood, skin biopsy

34
Q

RSMF treatment and prevention

A

-prevent by avoiding tick exposures and early removal of attached ticks
-early therapy improves outcomes and prevents severe complications or sequelae
-more severe infection are seen in males, alcoholics, elderly, african american, immunocompromised, pts with G6PD deficiency
-fever without rash can occur in elderly and african americans

35
Q

chlamydia

A

-causative agent- Chlamydia trachomatis
-incubation- variable- average: 1-3 weeks
-urethritis in men
-cervicitis in women
-frequently asymptomatic
-most common STI
-all SA women < 25 and > or equal to 25 at higher risk of infection should be screened annually

36
Q

signs and symptoms of chlamydia

A

-men- urethritis, dysuria, and clear, scant urethral discharge
-epididymitis and/or epididymo-orchiditis can also occur -> unilateral testicular pain and swelling
-prostatitis
-women- affects cervix and can progress into upper genital tract -> salpingitis and PID
-cervicitis- discharge, intermenstrual bleeding, dyspareunia, pelvic pain
-cervical discharge and friability may be present on exam
-PID can be asymptomatic and insidious or acute

37
Q

chlamydia testing and treatment

A

-nucleic acid amplification testing (NAAT) - gold standard for diagnosis
-rapid version is available -> 90 mins
-uncomplicated chlamydial urethriits or cervicitis- single 1 oral dose of azithromycin or doxycyclin 100 mg orally twice a day for 7 days
-PID is treated with ceftriaxone and doxycycline +/- metronidazole, IV and hospital admission may be required

38
Q

gonorrhea

A

-the clap
-causative agent- Neisseria gonorrhoeae
-incubation- 1-14 days, average 2-5 days
-geographic regions- worldwide
-men- urethritis
-women- cervicitis
-2nd most common STI

39
Q

gonorrhea signs and symptoms

A

-men- urethritis, purulent urethral discharge and dysuria
-unilateral testicular pain and swelling -> epididymitis and/or epididymo-orchiditis
-women- affects cervix and can progress into upper genital tract causing salpingitis and PID
-cervicitis- discharge, intermenstrual bleeding, dyspareunia, urethritis, dysuria, pelvic pain
-cervical discharge and friability may be present on exam
-PID- frank abdominal pain with systemic symptoms - fever, chills, nausea, vomiting
-PE for PID will show cervicitis, cervical motion tenderness, adnexal tenderness, peritonitis
-tubo-ovarian abscess, infertility, increased risk for ectopic, perihepatic adhesions (Fitz-Hugh-Curtis syndrome*) as a late symptoms of PID
-extragenital infection in rectum, pharynx, conjuctiva
-disseminated gonococcal infection (DGI) can occur

40
Q

disseminated gonococcal infection (DGI)

A

-sign/symptom of gonorrhea
-1. triad of polyarthritis, tenosynovitis, dermatitis
-2. septic arthritis (commonly affects knees)
-disseminated gonococcal meningitis and endocarditis can also occur but is rare

41
Q

gonorrhea treatment

A

-uncomplicated- ceftriazone 250mg IM and 1g of oral azithromycin
-azithromycin is thought to reduce likelihood of emerging gonococcal resistance to cephalosporins
-epididymo-orchitis, prostatitis, and proctitis are treated with IM ceftriaxone and 10 days of oral doxycycline
-conjunctivitis- 1g ceftriaxone IM and 1g oral axithromycin

42
Q

leprosy

A

-Hansen disease
-causative agent- Myobacterium leprae
-reservoir- armadillos
-incubation- 9 months- 20 years; average 5 years
-geographic regions- india, brazil, indonesia (highest)

43
Q

leprosy presentation

A

-infection of skin, nasal mucosa, cutaneous nerves
-caused by slow growing gram positive intracellular bacteria M. leprae
-WHO classifies:
-paucibacillary (tubercular)- 5 or less lesions
-multibacillary (lepromatous)- 6 or more lesions

44
Q

leprosy signs and symptoms

A

-cutaneous skin lesions, neuromas, sensory loss
-hypopigmented skin patches, decreased sensation, paresthesisas, muscle weakness, thickened earlobes, loss of eyebrow/eyelashes, nasal perforation, saddle nose, corneal scarring leading to blindness
-well defined, hypopigmented, anesthetic macule with anhidrosis and raised granular margin
-diminished sensation -> leads to burns, wounds on soles and palms
-severe- auto-amputation of digits, peroneal, tibial, ulnar neuropathy

45
Q

leprosy diagnosis and treatment

A

-skin biopsy and polymerase chain reaction (PCR) testing to confirm
-dapsone was used as a single agent to treat until resistance emerged
-multidrug therapy is required now for 6-12 months longer
-2 current treatment protocols
-paucibacillary leprosy is treated with dapsone and rifampicin for 6 months
-multibacillary leprosy is treated with dapsone, rifampicin, and clofazimine for 12 months

46
Q

cholera

A

-blue death
-causative agent-vibrio cholerae
-incubation- 1-5 days; average 2-3 days
-geographic region- resource poor countries, mostly in africa, asia, the caribbean, central and south america
-peaks before and after rainy seasons
-acute, afebrile, painless, bacterial diarrheal illness
-profound fluid loss
-rice water stools
-severe cases can cause severe electrolyte abnormalities, renal failure, acidosis, hypovolemic shock, circulatory collapse, death

47
Q

transmission of cholera

A

-spread efficiently in environment
-Vibrio-contaminated water, uncooked/undercooked food, inanimate objects such as soiled linen
-poor sanitation, inaccess to potable water, poor personal hygiene
-incubation 24-28 hrs
-onset is sudden
-painless, copius, watery, diarrheal episodes
-vomiting and abdominal cramping
-many cases remain asymptomatic
-5% will develop cholera gravis -> severe, fatal dehydration if untreated

48
Q

diarrhea and vomiting: cholera

A

-profuse watery diarrhea
-frequent and explosive
-stool volumes may exceed 250 mL per kg of body weight during a 24 hr period
-initial stools may contain solid fecal matter -> but classic appearance is opaque, whitish, nonmalodorous liquid -> rice water
-vomiting often occurs during initial stages - function of decreased gastric and intestinal motility

49
Q

aggressive rehydration: cholera

A

-cornerstone of treatment
-antibiotics like doxycyclin may reduce length/severity of infection -> does not cure
-fluid and electrolyte replacement - first line therapy

50
Q

dressings

A

-use dry dressings on wet wounds
-use wet dressing on dry wounds
prevents bacteria from thriving
-silver nitrate on burns

51
Q

acetaminophen

A

-can be hard on liver
-dont prescribe for liver issues

52
Q

sensitivity

A

-catches the people who have a condition
-higher sensitivity -> higher pick up of people with condition
-1000 people show signs of irregular breast tissue -> 900 people have abnormal biopsy -> 90% sensitivity

53
Q

specificity

A

-specific to people who dont have the condition
-if its not specific enough you are treating people for conditions they dont have -> false positive

Infectious Disease (10 decks)

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