Midterm #2 Review Flashcards
gram positive, spore forming rods
- Bacillus anthracis
- Bacillus cereus
- Clostridium tetani
- Clostridium botulinum
- Clostridium perfringens
- Clostridium difficile
gram positive, spore forming, aerobic
- Bacillus anthracis
- Bacillus cereus
gram positive, spore forming, anaerobic
- Clostridium tetani
- Clostridium botulinum
- Clostridium perfringens
- Clostridium difficile
gram positive, non-spore forming
- Listeria monocytogenes
- Corynebacterium diptheriae
gram negative bacilli
- Salmonellae
- Shigellae
- Escherichia coli
- Cronobacter spp.
- Vibrio and Campylobacter
- Pseudomonas
- Legionella
- Helicobacteraceae
- Alcaligenaceae
- gram positive
- spore forming
- aerobic
- causative agent of anthrax
- unique protein capsule; antiphagocytic
- exotoxin composed of 3 proteins
Bacillus anthracis
- gram positive
- spore forming
- aerobic
- motile
- non-encapsulated
- resistant to penicillin
- causes food poisoning
Bacillus cereus
- gram positive
- spore forming
- anaerobic
- produces lethal neurotoxin that causes rapidly fatal food poisoning
- neurotoxin blocks release of Ach in ANS
- causes botulism
Clostridium botulinum
- gram positive
- spore forming
- anaerobic
- exotoxin is called tetanospasmin
- causes tetanus
- spores found in soil and animal feces
Clostridium tetani
- gram positive
- spore forming
- anaerobic
- causative agent of gas gangrene
- 2 classes of infection: cellulitis/wound infection and clostridial myonecrosis
Clostridium perfingens
- gram positive
- spore forming
- anaerobic
- responsible for antibiotic-associated pseudomembranous enterocolitis
- infects the colon
- releases exotoxins
- exotoxin A: causes diarrhea
- exotoxin B: is cytotoxic to colonic cells
Clostridium difficile
- gram positive
- non-spore forming
- can cross 3 protective barriers
- psychrophile
- causes disease known as listeriosis in high risk individuals
Listeria monocytogenes
- gram positive
- non-spore forming
- pathogen responsible for diptheria
- colonizes the pharynx, forming grayish pseudomembrane composed of fibrin, leukocytes, necrotic epithelial cells, and its own cells
Corynebacterium diptheriae
- gram negative
- lactose non-fermenters
- motile
- causes enterocolitis and enteric fever
Salmonellae
- min dose of 10^5 required for symptoms to occur
- short incubation period (6-48hrs, usually 8-12hrs)
- caused by many serotypes of S. enterica
Enterocolitis (Gastroenteritis): key features
clinical:
- nausea, vomiting, profuse diarrhea
- fever, chills, headache, myalgia
- recovery within 2-3 days
- septicemia; rare complication in susceptible hosts
diagnosis:
- stool culture
Enterocolitis (Gastroenteritis): clinical and diagnosis
epidemiology:
- infection by ingestion of contaminated food or drink
- animal products and animals are major sources
- person-to-person spread may occur
treatment:
- antimicrobials not recommended
Enterocolitis (Gastroenteritis): epidemiology and treatment
- S. enterica serovar Typhi causes typhoid fever
- S. enterica serovar Paratyphi causes paratyphoid fever
- generalized infection
- multiplication in lymphoid tissue
- mortality is about 10% if left untreated
- survivors usually become convalescent carriers or chronic carriers
Enteric fever (typhoid and paratyphoid): key features
convalescent carrier
excreting bacteria for up to 3 months
chronic carrier
excreting bacteria for 6 months or occasionally life long
Enteric fever (typhoid and paratyphoid): diagnosis and epidemiology
diagnosis:
- isolation of organism from blood (1st week)
- isolation of organism from stool and urine (2nd-3rd week)
epidemiology:
- human carriers are only known reservoir
- infective dose is about 10^6
- major vehicles are sewage contaminated drinking water, shellfish, contaminated milk/milk products
- chronic carriers maintain endemic typhoid
Enteric fever (typhoid and paratyphoid): prevention
- sanitary disposal of human faeces
- scrupulous cleanliness while handling food
- purification and chlorination of water supplies
- vaccines are available but are of low efficacy
Escherichia coli (E. coli)
- gram negative bacilli
- lactose fermenters
- most numerous aerobic species of the normal human intestinal flora
- most frequent cause of UTIs
- type of E. coli
- major cause of infant diarrhea in developing countries
- frequent cause of traveller’s diarrhea
- enterotoxins
Enterotoxigenic E. coli
- type of E. coli
- bloody diarrhea and dysentery similar to Shigella species
Enteroinvasive E. coli
- type of E. coli
- can cause severe diarrhea in infants, especially in developing countries
Enteropathogenic E. coli
- type of E. coli
- haemorrhagic collitis
- hamburger disease
- proper handling of food, safe preparation, and proper cooking practices are essential to prevent illness
E. coli O157:H7
- may colonize and infect hospitalized patients
- causes wound infections, bacteremia, and hospital acquired pneumonia
- may be naturally resistant to antibiotics
- Cronobacter Sakazakii linked to outbreaks of contaminated powdered infant formula
Cronobacter spp.
- gram negative bacterium
- produces an enterotoxin (cholera toxin)
- causes cholera: acute gastrointestinal illness
- profuse watery diarrhea (10-15 litres per day), cramps and vomiting
- enterotoxin binds cells in small intestine, cells secrete chlorides, Na+ absorption decreases, water accumulates in gut –> watery diarrhea
- can lead to severe dehydration and death if left untreated
- mainly water-borne
Vibrio cholerae
Campylobacter
- C. jejuni and C. coli
- major cause of human enteritis
- symptoms: fever, abdominal pain, bloody diarrhea
- maybe one cause of traveller’s diarrhea
- normal flora in birds and domestic animals
- some strains invasive, others toxigenic
- opportunistic pathogen
- found in many moist habitats and water
- source of infection can be humidifiers, etc.
- treatment is difficult because all pseudomonas are resistant to many antibiotics
Pseudomonas
- type of pseudomonas
- respiratory pathogen in cystic fibrosis patients
- infections in lesions of burn patients
Pseudomonas aeruginosa
- type of pseudomonas
- common contaminant of saline solutions and water
- able to multiply in low nutrient environment
- respiratory pathogen in cystic fibrosis patients
Pseudomonas cepacia
Haemophilus influenzae: key features and treatment
- part of normal nasopharyngeal flora in many adults and children
- causes invasive infection of young children
- meningitis, pneumonia, joint infections
- treatment: development of vaccine has decreased the number of cases in Canada
- can cause increased bronchial inflammation in patients already having chronic bronchitis
- microaerophillic, spiral bacilli
- most common cause of stomach ulcers
- urease: protection from low pH
- triple therapy treatment: antibiotics and H+ pump inhibitors
Helicobacter pylori
Bordetella pertussis and its 4 virulence factors
- whooping cough (violent cough)
- 4 virulence factors:
1. pertussis toxin (A-B)
2. extra cytoplasmic adenylate cyclase (weakens host defense)
3. filamentous heamgglutinin (bronchial attachment and exotoxin release)
4. tracheal cytotoxin (destroys ciliated cells –> poor clearance of mucous and bacteria) - prevention: vaccination with heat-killed organism
- causes legionnaires disease
- opportunistic pathogen
- may cause severe pneumonia
- grows in water and is found in shower heads, water tanks, air cooling/heating tanks
- exposure is by aerosol and there is no person-to-person transmission
Legionella pneumophila
- no cell invasion - bacteria bind to intestinal epithelial cells but do not enter the cell
- diarrhea caused by release of exotoxins (enterotoxins in the GI tract)
- enterotoxins cause electrolyte and fluid loss
- watery diarrhea with systemic symptoms (fever) - example includes Vibrio cholera
diarrhea - with or without systemic invasion
- factors allow binding and invasion of cell
- toxins released destroy the cells
- systemic immune response (fever)
- cell death results in blood stools
- examples include E. coli O157:H7
diarrhea with invasion of intestinal epithelial cells
- abdominal pain and diarrhea containing red and white cells
- fever, headache, and increased white cell counts
- examples include Salmonella enterica serovar Typhi, Yersinia entercolitica, Campylobacter jejuni
diarrhea with invasion of lymph nodes and bloodstream
biochemical classification of gram negative bacteria
- ability to ferment lactose to gas and acid
- production of H2S
- ability to hydrolyze urea
- ability to liquify gelatin
- ability to decarboxylate specific amino acids
- growth media (EMB and MacConkey)
- classified based of surface structure
classification of gram negative bacteria: ability to ferment lactose to gas and acid
E. coli and most enterobacteriaceae ferment lactose while Salmonella, Shigella, and Pseudomonas do not
Eosine-methylene-blue (EMB)
- methylene blue inhibits gram positive
- lactose fermenters are deep purple to black
MacConkey
- bile salts inhibit gram positive
- lactose fermenters develop pink-purple colouration
3 major surface antigens of the enterics
O antigen
- most external component of LPS
- differs from enteric to enteric
K antigen
- this is a capsule that covers the O antigen
H antigen
- is part of the subunits of the bacterial flagella (only motile bacteria with have H antigen)
mycobacteria
- group of bacteria including the causative agents of tuberculosis and leprosy
- high content of lipids (waxes)
- waxy coat renders bacteria resistant to disinfectants and interferes with gram stain
- mycobacteria are acid fast and resist decolourization
- use Ziehl-Neelsen staining technique (acid-fast technique)
Ziehl-Neelsen staining technique
- Ziehl-Neelsen carbol fuchsin to the slide for 5 minutes while applying heat
- follow with a gently wash with water to cool the slide
- acid alcohol is now added to decolourize the slide
- wash the slide in water again and counterstain with methylene blue for 1-2 minutes
- chronic slow-progressing pulmonary infection
- transmission by aerosol droplets
- obligate aerobe, facultative intracellular parasite
- 4-6 weeks to see colonies on a plate
- Lowenstein-Jensen medium
- use microscopy of sputum smears as first line of diagnosis
- infection develops in stages
Mycobacterium tuberculosis
primary tuberculosis
- aerosol inhalation
- bacteria multiplication in alveoli
- macrophage ingestion of bacilli and formation of 1* complex
- foci of infection in lungs (may be spread to kidneys, bones, meninges)
~ 6 weeks ~ - CMI is fully active, infection is stopped (majority of cases)
- some bacilli survive, reactivation several years later
post-primary tuberculosis
- late reactivation of lesions in lungs, kidneys, bones, etc
- 5% of cases, higher in patients with AIDS
- chronic infection
immunity in tuberculosis
- cell-mediated immunity is most important (T-cells)
- mantoux test is done to test immunity
mantoux test
- tuberculin solution is injected intradermally
- wait 48-72 hours
- check for induration
- record diameter of induration
>10mm: positive
5-9mm: doubtful, maybe cross reaction with other mycobacteria
<4mm: negative - a positive test does not necessarily mean there is currently an active infection
atypical mycobacteria
- occasionally isolated from patients with chronic pulmonary disease
- M. kansassi, M. avium, M. intracellulare
- indisguishable from TB
- higher resistance to anti-TB drugs
- give ‘doubtful’ mantoux test (5-9mm)
- M. marinum
- M. fortuitum
- all these infection are most typically seen in the immunocompromised
M. marinum
skin infections
M. fortuitum
soft tissue abscesses
mycobacterium leprae
- causes leprosy
- 2 kinds: tuberculoid leprosy and lepromatous leprocy
- rarely found in developed countries
- visible nerve enlargment
- few erythmatous plaques
- few bacilli in infected tissues
- many lymphocytes and granulomas in infection tissues
- low infectivity
tuberculoid leprosy
- no visible nerve enlargment
- many erythromatous nodules
- many bacilli in infected tissue
- high infectivity
lepromatous leprosy
spirochetes
- spiral shape pathogens
treponema pallidum
- causes syphilis
- non-gram stainable, helical bacteria
- unculturable in vivo
- use dark field microscopy
primary syphilis
- appearance of chancre 3-4 weeks after infection
- fluid from lesion contains bacteria -> seen under dark field microscopy
secondary syphilis
- 6 weeks after appearance of chancre
- generalized or local rash
- mucosal lesions with many treponemes
- spontaneous remission may occur after 1 or 2 phase
- no symptoms of infection
- non-transmittable after 4 years
- congenital infection may occur
which phase of syphilis?
latent syphilis
- obliterative endarteritis
- can involve skin, mucosae, nervous system, cardiovascular system and tissues
- very rare
- can cause lethal symptoms
which type of syphilis?
late syphilis
serology testing for syphilis
2 step serology test:
non-treponemal tests (VDRL, RPR, Wassermann)
- non-specific: use cardiolipin as antigen
- screening
- positive in early stages
treponemal tests
- specific: use treponemal extracts
- FTA-ABS: fluorescent treponemal antibody absorption
- MHA-TP: microhemagglutination of T. pallidum
- used to confirm positive VDRL
- lyme disease
- tick bites
- affects skin, joints, nervous system, and heart
- common in US, rare in Canada
- use serology for diagnosis (ELISA)
- organism is very difficult to see under microscope
- difficult to culture
- serology does not give positive result in first 2-4 weeks of infection
borrelia burgdorferi
lyme disease: treatment
- doxycycline, amoxicillin, cefuroxime for early disease
- for neurological and musculoskeletal manifestations, undergo prolonged treatment
lyme disease: prevention
- avoid ticks and wear protective clothing in woods (long sleeves and pants)
- vaccine available: ospA antigen of organism
- obligate intracellular energy parasites; cocci
- can not make their own ATP or other energy intermediates
- can not be grown on artificial media
- life cycle has 2 forms: elementary body and reticulate body
chlamydiae
elementary body (chlamydiae)
- 300-400 nm
- infectious form
- no growth or replication
reticulate body (chlamydiae)
- 800-1000 nm
- replication and growth
- STD chlamydia
- most commmon STD in Canada and US
- males: urethritis
- females: cervicitis
- many patients are asymptomatic and untreated due to limited diagnostic tools
- untreated male: prostatitis, epididymitis
- untreated female: PID, tubal infertility, ectopic pregnancy, chronic pelvic pain
- 2 biovars: trachoma and LGV
- Trachoma: 15 serovars
- LGV: 4 serovars
chlamydia trachomatis
other infections caused by C. trachomatis
- trachoma: chronic ocular infection; leading cause of blindness in middle east, north africa, and south east asia
- conjunctivitis in newborns –> perinatal transmission
- lymphogranuloma venereum: STD from some serotypes of C. trachomatis; endemic in tropical and subtropical countries
Chlamydia pneumoniae
- respiratory tract infections, mild pneumonia
- usually sub-clinical infections
Chlamydia psittaci
- bird pathogen
- can transmit to humans
- pneumonia or endocarditis
mycoplasma
- smallest free-living bacterium (100-300nm)
- saprophytes, part of normal flora of oropharynx and genital tract of humans and animals
- lack true cell wall
- some species are pathogenic
mycoplasma pneumoniae
- primary cause of atypical pneumonia
- more common in younger individuals (15-35 years)
- rarely complications lead to meningoencephalitis, myocarditis
- diagnosis is usually clinical, no lab confirmation
- treatment: erythromycin or tetracycline
genital mycoplasma
- Mycoplasma hominis
- Ureaplasma urealyticum
- part of normal genital flora
- rate of colonization increases with number of sexual partners
- may cause urethritis, epididymitis, pelvic inflammatory disease and postpartum fever
fungi
- eukaryotic
- lack chlorophyll
- cannot generate energy through photosynthesis
- aerobic
dimorphic fungi
fungi that grow as either yeast or mold (depends on temperature, environmental conditions, etc)
hyphae
threadlike, branching tubules composed of fungal cells attached end to end
molds (mycelia)
multicellular colonies composed of clumps of intertwined and branching hyphae
saprophytes
fungi that live and use organic matter such as soil, rotten vegetation as the energy source
spores
reproducing bodies of molds
yeast
- unicellular growth form of fungi
- can appear spherical to ellipsoidal
- reproduce by budding (if they do not separate, they form long chains of yeast cells known as pseudohyphae)
levels (depth) of infection by fungal pathogens
[skin]-superficial-cutaneous-subcutaneous-systemic-[bloodstream]
- pityriasis versicolour (multicoloured) caused by Malassezia furfur - hypo or hyperpigmented patches that remain white if you suntan
- tinea nigra (black coloured) caused by Exophiala werneckii - painless patches on soles of hands and feet
- pigment change of skin
- treatment: spreading dandruff shampoo containing selenium sulfide over skin
superficial fungal infections
common ones include microsporum, trichophyton, and epidermophyton
- Tinea corporis (body)
- Tinea curis (groin)
- Tinea pedis (feet)
- Tinea capatis (scalp)
- Tinea unguium (onychomyosis)
treatment usually topical imidazoles (keep skin dry)
- Candida albicans (mouth, groin, and vagina)
cutaneous fungal infections (skin, hair, nails)
dermatophytic fungi
- live in dead, horny layers of skin, hair, and nails
- secrete enzyme keratinase (digests keratin), thereby resulting in scaling of skin, loss of hair, and crumbling of nails
dermatophytosis
infections of the hair, skin, and nail
Tinea corporis
- body
- ringworm
- looks like ring-shaped worm under skin
Tinea cruris
- groin
- jock itch
- itchy red patches on groin and scrotum
Tinea pedis
- feet
- athlete’s foot
- commonly begins between toes
Tinea capitis
- scalp
- primarily in children, seen as scaly, red lesions with loss of hair
Tinea unguium
- onychomyosis
- nails are thickened, discoloured and brittle
Candida albicans
- can infect the mouth (oral thrush), groin (diaper rash), and vagina (vaginitis)
subcutaneous infections
- Sporothrix schenkii
- Phialaphora and Cladosporium
Sporothrix schenkii
- causes sporotrichosis, an occupational hazard for gardeners
- subcutaneous nodule appears and becomes necrotic and ulcerative
- ulcer may heal but new nodules will arise nearby and along the lymphatic tracts of the arm
- treatment with potassium iodide or amphotericin B
Phialaphora and Cladosporium
- cause chromoblastomycosis
- found on rotting wood, infection follows puncture wound
- violet-coloured wart like lesions (cluster of lesions resemble cauliflower)
- treatment with intraconazole and local excision
systemic fungal infection
- 3 fungi that cause systemic disease in humans are: Histoplasma capsulatum, Blastomyces dermatitis, and Coccidioides immitis
- Cryptococcus
Histoplasma capsulatum, Blastomyces dermatitis, and Coccidioides immitis
- similar mechanisms of disease
- acquired by inhalation (inhaled as spores) but are not transmitted person to person like TB
- local infection in lung, then bloodstream dissemination
- 3 clinical presentations:
- asymptomatic
- pneumonia
- disseminated
Cryptococcus neoformans
- polysaccharide encapsulated yeast
- inhaled in lungs
- usually asymptomatic
- major manifestation in meningoencaphalitis
- most cases occur in immunocompromised persons (~10% of AIDs patients develop Cryptococcus)
- treatment with amphotericin B and flucytosine
- treatment may last for 6 months (AIDs patients may need for life)
Aspergillus flavus
- spores of this mold are everywhere
- some develop type 1 hypersensitivity reaction (IgE-mediated)
- persons with lung cavitations from TB or malignancies can get aspergillus fungal ball (aspergilloma) in cavity
- immunocompromised person can develop invasive pneumonias and disseminated diseases
- A. flavus and other fungi produce toxins called mycotoxins
- A. flavus produces aflatoxin (contamination of grains, peanuts, rice)
parasitism
- intimate and obligatory symbiotic relationship between 2 organisms of different species
- short term (mosquito) or permanent (tapeworm)
- very common
parasite
- metabolically and physiologically dependent on host
- ‘true parasites’ include protozoans (single celled), helminths (worms), and arthropods (ectoparasites)
‘success’ of parasites is defined in terms of:
- prevalence in hosts
- number of host species available
- geographic range
- number of offspring
- available routs of transmission
Giardia lamblia
- most frequently identified intestinal parasite worldwide
- protozoan
- can cause acute giardiasis
G. lamblia: symptoms
- most infections are asymptomatic (carreirs)
- retardation of growth and development in young children (failure to thrive)
acute giardiasis: - diarrhea
- weight loss
- abdominal discomfort
- nausea
- vomiting
G. lamblia: prevalence
- most common infection of intestinal tract worldwide
- 2-5% in industrialized world
- 20-30% in developing world
- prevalence rises through infancy and childhood and declines in adolescence (related to faecal-oral route of transmission)
- other high-risk groups include travellers and immunocompromised
protozoan life cycle
- multiply using a form of life cycle that is consisting of 2 important components
1. cyst
2. trophozoites
cyst form: protozoan life cycle
- similar to bacterial spores
- protect cell
- do not multiply
- form that is found in the environment and is infectious
- will try to get into a host
trophozoite form: protozoan life cycle
- once cyst makes enters a host, turns to trophozoite form
- trophozoite form multiplies inside host
G. lamblia: diagnosis
microscopy (stool exam)
- look for cysts
- cysts concentrated by flotation and identified using bright-field microscopy
- immunofluorescence microscopy using fluorochrome-conjugated mAb’s that bind to cyst wall
immunological testing
- detection of Giardia-specific antigens in faeces
is G. lamblia treatable?
yes
parasites and drug resistance
just like bacteria, parasites can develop drug resistance as well
G. lamblia: prevention
- water filtration
- cysts resistant to chlorination
- ozone/UV light promising
- EPA method 1623
- public health education
Trichomonas vaginalis
- possibly the most common STD worldwide (200 million cases)
- transmitted through mucous membrane contact (no resistant cyst stage)
Trichomonas vaginalis: symptoms
- 40-50% asymptomatic carriage
- vaginitis (trichomoniasis) with itching, foul-smelling, sometimes frothy discharge
- may increase susceptibility to cervical cancer and HIV infection
- infection during pregnancy may result in premature delivery and low birth weight
- males usually asymptomatic; occasionally urethritis, prostatitis
Trichonomas vaginalis: diagnosis
- microscopy (wet mounds) to identify trichonomads in vaginal or urethral discharge
Trichonomas vaginalis: treatment
- treated with drugs
- to avoid re-infection, testing and treatment of partners is important
Toxoplasma gondii
- recognized as a human pathogen in early 1900’s
- very common worldwide
- large number of mammals and birds act as intermediate hosts
- cats are the only definitive hosts
intermediates hosts
- although parasites can infect these animals, they do not shed cysts
- cannot pass on cysts through faecal material to contaminate food or any other environmental material
Toxoplasma gondii: transmission
- ingestion of sporulated oocysts
- contaminated soil/sand
- contaminated fruits and veggies’- waterborne outbreaks - ingestion of tissue cysts
- consumption of raw or poorly cooked meat - congenital infection of fetus- infection acquired during pregnancy (most severe if acquired in first trimester
symptoms of toxoplasmosis
- immunocompetent host
- 90% asymptomatic
- lymphadenopathy
- headaches
- muscle aches
- fever
- malaise - immunocompromised host
- encephalitis
- myocarditis
- pneumonia - congenital infection
- hepatosplenomegaly
- mental retardation
- retinochoroiditis
- hydrocephalus
treatment of toxoplasmosis
- diagnosis based on serological assays
- immunocompetent patients normally don’t require treatment unless symptoms become severe or chronic
- immunocompromised patients require prompt treatment with a combination of pyrimethamine and sulfadiazine
- congenital infections:
- mother/fetus can be treated to reduce incidence and severity of fetal infection
- infected newborns can also be treated to minimize sequelae
malaria: transmission
- anopheline mosquitoes (vectors)
- blood transfusion/shared needles
- congenital infection
- ‘airport’ malaria
malaria: symptoms
- spiking fever and chills
- flu-like symptoms (myalgias, headaches, abdominal pain, malaise)
- severe symptoms (seizures, coma, renal failure, respiratory failure)
Malaria prophylaxis: treatment
- anti-parasitic drugs used for treatment and prevention
- drug resistance is a serious problem
malaria: control/prevention
- eradication or control of mosquitoes (resistant to insecticides)
- protection against mosquito bites:
- avoid rural areas at night
- long-sleeved shirts/long pants
- insect repellant
- bed netting
Cryptosporidium spp.
- recognized as human pathogen (1976)
- reported in humans worldwide
- causes cryptosporidiosis
- most common symptoms of cryptosporidiosis is watery diarrhea; other symptoms include dehydration, weight loss, abdominal pain, fever, nausea, vomiting
- chronic, debilitating, and potentially life-threatening symptoms in immunocompromised
cryptosporidiosis: symptoms and treatment
- most common symptoms of cryptosporidiosis is watery diarrhea; other symptoms include dehydration, weight loss, abdominal pain, fever, nausea, vomiting
- chronic, debilitating, and potentially life-threatening symptoms in immunocompromised
- no drug treatment available
Cryptosporidium: transmission
water
- numerically the most important mode of transmission (contaminated drinking water)
- recently numerous outbreaks associated with water parks/pools
C. parvum: transmission
person-to-person
- ingestion of oocysts due to poor hygiene (e.g. day care)
autoinfection
- thin-walled oocysts are released into the lumen and cause autoinfection
- responsible for chronic and life-threatening disease in immunocompromised
zoonotic
- cattle serve as important reservoir hosts
- calves with diarrhea can excrete up to 10^10 oocysts/day
- environmental contamination; veterinary personnel and animal handlers at increased risk (petting zoo visitors)
C. parvum: diagnosis
microscopy
- oocysts shedding intermittent; multiple stools examined
- concentration methods can be used when low oocyst shedding
- wet mounts or permanent stains are used (acid-fast)
- fluorescein-labelled IgG mAb is used in immunofluorescense microscopy
C. parvum: control/prevention
- watershed management
- flocculation/sand filtration
- resistance to chlorination
- ozone, UV light
- water testing (EPA method 1623)
- public health education
Cyclospora cayetanensis
- identified as a coccidian protozoan parasite and named in 1993
- pretty widespread
- endemic countries include: Nepal, Haiti, Peru, and Guatemala
- cause cyclosporiasis
cyclosporiasis: symptoms and treatment
- low infectious dose
- incubation period approx. 1 week
symptoms: - profuse and prolonged diarrhea
- abdominal pain
- nausea
- vomiting
- fatigue
- fever
- loss of appetite
treatment - effectively treated with bactrim
cyclosporiasis: diagnosis
- microscopic examination of wet mount stool for oocysts
- staining methods
- many microscopic and staining methods used to diagnose
cyclosporiasis: transmission
- person-to-person transmission unlikely
- zoonotic transmission unlikely
- most earlier outbreaks were waterborne
numerous foodborne outbreaks in recent years - 90-99% of cases in US are foodborne
- contamination of food
- direct contamination
- indirect contamination
direct contamination
- infected pickers, sorters, inspectors, or other food handlers (poor hygiene, sporulation)
indirect contamination
- contaminated water used for irrigation, mixing pesticides, washing equipment, washing hands
eneterobius vermicularis (pinworm)
- very common worldwide
- highest incidence in school-age children
- up to 50% of children in north america
- more of a nuisance than a health problem
- eggs ingested (faecal-oral route)
- very mild symptoms
pinworm: symptoms
- mild infection of caecum/colon
- may cause itching (pruritus ani) leading to disturbed sleep, irritability
- scratching may cause secondary infections
pinworm: diagnosis/treatment
- scotch-tape test of perianal area
- microscopic identification of eggs; adult female worms may also be present on the tape
- drug of choice is pyrantel pamote
pinworm: control/prevention
- personal hygiene education for children (wash hands)
- discourage scratching, nail biting
- frequent bathing; regular change of underclothing, pajamas, and bedding
Trichinella spp.
- very commonly found worldwide
- small roundworm found worldwide in many carnivorous and omnivorous animals, including humans
- transmitted through ingestion of larvae in raw or poorly cooked meat
- survives as an adult in small intestine; as larvae encysted in striated muscle
Trichinella spiralis
- domestic form
- humans, swine, rats (responsible for endemicity)
- horses (probably fed animal products as supplement)
Trichinella nativa
- sylvatic or wild form
- humans, bears, wild boar, wolf, fox, walrus, etc
Trichinellosis: symptoms
- symptoms dependent on phase of life cycle
- when larvae excyst (grow into worms) in small intestine: diarrhea, abdominal pain, comting
- when next generation of larvae migrate into muscle tissues: facial edema, conjunctivitis, fever, myalgias
- occasional life-threatening manifestation include myocarditis, CNS involvement, and pneumonitis
Trichinellosis: treatment
- different options of drugs based on phase of life cycle
- steroids may be used to reduce inflammation
trichinellosis: control/prevention
- rodent control
- avoid garbage feeding to livestock
- inspection programs
- cooking/freezing (making sure meat is cooked well)
Diphyllobothrium spp.
- broad fish tapeworm
- large tapeworm
- adult tapeworm inhabits the small intestine of humans and other fish-eating mammals
- larval stages in freshwater fishes which act as intermediate hosts
Diphyllobothrium spp.: transmission
- transmitted through the consumption of raw or poorly cooked freshwater fish containing infective larvae
Diphyllobothrium spp.: symptoms
- most cases are asymptomatic
- abdominal pain, dizziness, fatigue, vomting, diarrhea/constipation
- vitamin B12 deficiency with pernicious anemia
Diphyllobothrium spp.: diagnosis and treatment
- stool examination for eggs (microscopy) or proglottids (segments)
- proglottids can sometimes be fund in stool sample
- anthelmintic drugs effective
Taenia spp.
- large tapeworms (up to 20 m in length)
- adult stage inly found in humans
Taenia spp.: transmission
transmitted through ingestion of larvae in raw or poorly cooked meat
Taenia saginata
beef tapeworm
Taenia solium
pork tapeworm
Taenia spp.: symptoms, diagnosis, and treatment
symptoms
- mild abdominal complaints
diagnosis
- eggs or proglottids in stool
- serological techniques
treatment
- anthelmintic drugs
- surgery
T. solium neurocysticerosis
- infection with larval stage following ingestion of T. solium eggs (humans act as the intermediate host)
- larvae migrate and develop in brain
- intracranial hypertension, hydrocephalus, convulsive seizures
Taenia spp.: control/prevention
- both species are rare in Canada
- routine inspections
- cooking meat readily kills larvae
- in endemic countries: sanitation, prevent access of pigs to human faeces
Schistosoma spp.
- blood flukes
- worldwide (200-300 million cases)
- free-swimming larvae in fresh water penetrate skin and develop in blood vessels surrounding intestine or bladder
- 3 main species: S. haematobium, S. japonicum, and S. mansoni
- transmission by skin penetration
schitosomiasis: symptoms
- usually not very severe
- symptoms are rare except in heavily infected individuals
- rash, itchiness from penetrating larvae
- fever, lymphadenopathy, hepatosplenomgaly
schitosomiasis: diagnosis and treatment
- microscopic examination for eggs in faeces or urine
- treated with drug
schitosomiasis: control/prevention
- eliminate habitat for snails which act as intermediate hosts
- spraying with molluscicides
- improves sanitation
- avoid contact with fresh water in endemic areas
