Lecture 1

Question 1

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

Answer 1

-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

Question 2

established infectious diseases

Answer 2

-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

Question 3

newly emerging infectious diseases

Answer 3

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

Question 4

reemerging infectious diseases

Answer 4

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

Question 5

normal mechanisms which prevent infection

Answer 5

-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

Question 6

normal flora prevents “invasion” of other organisms

Answer 6

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

Question 7

common “colonizers”

Answer 7

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

Question 8

natural barriers to infection

Answer 8

-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

Question 9

examples of subtle or not-so-subtle immune impairments

Answer 9

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

Question 10

tuberculosis background

Answer 10

-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

Question 11

tuberculosis today

Answer 11

-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

Question 12

transmission of tuberculosis

Answer 12

-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

Question 13

tuberculosis: environmental factors

Answer 13

-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

Question 14

suspended droplets: tuberculosis

Answer 14

-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

Question 15

infectivity factors: tuberculosis

Answer 15

-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

Question 16

clinical diagnosis: tuberculosis

Answer 16

-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

Question 17

primary TB infection that results in active disease

Answer 17

-primary progressive TB

Question 18

latent TB

Answer 18

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

Question 19

signs and symptoms of tuberculosis

Answer 19

-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

Question 20

tuberculosis testing

Answer 20

-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

Question 21

treatment tuberculosis

Answer 21

-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

Question 22

x-ray: tuberculosis

Answer 22

-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

Question 23

prevention of TB

Answer 23

-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

Question 24

lyme disease

Answer 24

-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

Question 25

systemic effects of lyme disease

Answer 25

-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

Question 26

signs and symptoms of lyme disease

Answer 26

-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

Question 27

syphilis

Answer 27

-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

Question 28

signs and symptoms of syphilis

Answer 28

-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

Question 29

syphilis diagnosis

Answer 29

-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)

Question 30

syphilis treatment

Answer 30

-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

Question 31

rocky mountain spotted fever (RMSF)

Answer 31

-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)

Question 32

signs and symptoms of RSMF

Answer 32

-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

Question 33

RSMF diagnosis

Answer 33

-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

Question 34

RSMF treatment and prevention

Answer 34

-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

Question 35

chlamydia

Answer 35

-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

Question 36

signs and symptoms of chlamydia

Answer 36

-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

Question 37

chlamydia testing and treatment

Answer 37

-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

Question 38

gonorrhea

Answer 38

-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

Question 39

gonorrhea signs and symptoms

Answer 39

-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

Question 40

disseminated gonococcal infection (DGI)

Answer 40

-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

Question 41

gonorrhea treatment

Answer 41

-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

Question 42

leprosy

Answer 42

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

Question 43

leprosy presentation

Answer 43

-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

Question 44

leprosy signs and symptoms

Answer 44

-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

Question 45

leprosy diagnosis and treatment

Answer 45

-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

Question 46

cholera

Answer 46

-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

Question 47

transmission of cholera

Answer 47

-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

Question 48

diarrhea and vomiting: cholera

Answer 48

-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

Question 49

aggressive rehydration: cholera

Answer 49

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

Question 50

dressings

Answer 50

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

Question 51

acetaminophen

Answer 51

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

Question 52

sensitivity

Answer 52

-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

Question 53

specificity

Answer 53

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