36-41 Flashcards
pathogenic yeasts characteritics
-BCL 2
-candida: grows as budding yeast
- Cryptococcus: produces a large mucopolysaccharide capsule
* This capsule is anti-phagocytic and immunosuppressive
* Malassezia: are bottle shaped cells and bright red under UV light
yeasts natural habitat
- Candida spp.
- Common in environment and associated with host
- Infections often caused by resident organisms
- Malassezia pachydermatis
- Found on the skin of mammals and birds
- Localized to anatomical sites with lots of sebaceous glands
- Cryptococcus spp.
- C. gattii associated with
trees and soil - C. neoformans found in
the droppings of pigeons.
-C. neoformans utilizes ionizing radiation for energy.
candida albicans birds
-crop thrush
-oral and crop candidiasis
-young birds, outbreaks in the flock, could be from coccidiostat treatment
-clinical signs; non specific, poor growth of chicks
-raised, focal thickenings of mucosa in GIT
-treatment: feed nystatin, topical, might be with vit A deficiency
-control: management, dip eggs in disinfectant, no cannibalism
candida albicans horse
-thrush
* Superficial infections are
the most common
presentation
* Thrush – on the mucous
membranes
* Systemic candidiasis
also occurs,
opportunistic
* Blood, respiratory tract,
joints,
Candida albicans people
Three syndromes recognized
1. Oropharyngeal
* White plaques on tongue
* Rare in healthy adults (in aids/cancer)
2. Genital/vulvovaginal: burning, discahrge, penile rash
3. Invasive: bloodstream infection in hospitalized patients. 19-24% mortality.
Malassezia pachydermatis dogs
- Causes superficial infections in warm, moist anatomic sites
- Interdigital skin
- Lips
- Ear canal,
-groin, skin folds - See erythema, greasy exudate, malodorous exudate
- With extensive lesions can see:
- Lichenification (thick skin)
- Hyperpigmentation
-treat: topical therapy, miconazole or chorhexadine. burrows solution for otitis.
-identify and control underlying disease which leads to this.
Cryptococcus spp.
* C. gattii cats
- Most common systemic mycosis of cats 8X more than in dogs
- Emerging (emerged?) pathogen in Canada
-upper resp signs: sneezing, nasal discharge, polyps
-neurological signs possible: depression, seizers, circling
-its an environmental organism worldwide
-treat: azole antifungals: itraconazole
-surgically excision of infected tissues
-follow up important: long term therapy or to-life (FIV)
Cryptococcus spp.
people
- Most often infects the lungs or central nervous system
- Pulmonary disease: Cough, chest pain, fever
- Cryptococcal meningits: Headache, fever, neck pain
C neoformans with people with pre existing conditions: aids, organ transplant
-potential zoonosis spread between sick people, or lab infection
pathogenic yeasts treatment options
- Candida - Often topical
- Combination of topicals and systemic therapy
- Nystatin orally
- Azoles +/- amphotericin B
- Malassezia - Often topical
- Shampoos/topical medications
- Azoles
- Cryptococcus spp. - Always systemic
- Fluconazole - if fails then itraconazole
- Amphotericin B
methicillin resistance
-actually means B-lactam resistance we dont use methicillin anymore.
-could be MRSP, MSRA, coNS.
-if we use drug and organism if b-lactam resistant we can use b-lactam B-lactamase inhibitors so the antimicrobial will work.
-methicillin R staph: have altered binding sites so the b-lactams cannot bind so they are still resistant and clavulanic acid wont work.
-have resistance due to the mec family of genes which decrease binding affinity.
The mec family growing resistance
mecA - classical gene - likely
originated from coagulase negatives
* mecB - originated in Macrococcus
caseolyticus
* mecC - first identified in S. aureus
* mecD - originated in Macrococcus
species
detecting methicillin resistance
-test with phenotypic resistance. gold standard is using mecA test.
-for staph peudointermedius can only use OXACILLIN
-pb2a latex agglutination
-selective and differential media
Methicillin Resistance Defined dates
- MRSA first identified in people in 1961
- In 1990s spread into the community
- In people associated with
- Higher mortality
- Higher health care costs
- In dogs, the same negative healthcare outcomes have not been
demonstrated - In Saskatoon, MR in animals first recognized in mid- to late 2000s
staph habitat characteristics
- Coagulase positive staphylococci ubiquitous
- 30% of people nasally colonized with S. aureus
- 90% of dogs colonized with S. pseudintermedius
-very normal in our environment.
MRSP in western canada
- Historically, resistance in S. pseudintermedius was rare in Western Canada
-first report 2009
-* Signs of UTI, multi-resistant S. pseudintermedius recovered - No identifiable risk factors, had resistance to most drugs in vet med. used tetra.
another case
* 6-year-old, neutered male Great Dane
* History of soft tissue sarcoma, MRSP grown on wound and lead to necrotizing facitisits
S. psudo infection types
- Opportunistic pathogens
- Types of S. pseud infections
- Pyoderma (skin) ***
- Otitis (ears) *** these are most common
- Urinary tract infections
- Wound infections
- Surgical site infections
- Nosocomial infections
- MRSP is frequently community acquired
MRSP zoonosis/ interspecies
- We share organisms with our pets (MR or not)
-don’t panic if your pet is positive. not usually considered a major zoonosis. - In cases of canine MRSA:
- Don’t attempt decolonization
- Remember hygiene!
- Hand washing
- Avoid saliva and nasal secretions
- Keep animals away from wounds/indwelling devices
-people do get some infections aquired from dogs. mostly skin infections.
treatment options for MRSP
- MR = resistance to ALL β-lactam drugs
- Because MR is NOT due to the production of β-lactamases,
drugs like amoxicillin + clavulanic acid are NOT helpful - Susceptibility profiles of Staphylococci are changing, and
laboratory guidance is VERY important for aiding therapeutic
selection - MR doesn’t just affect companion animals, watch out for these
bugs in livestock:
* Mastitis in cattle
* Bumble foot in chickens
* S. hyicus greasy pig disease or MRSA skin infection in pigs
MRSA different species
- Dogs and cats
- Frequently human associated strains
- Horses
- Equine specific strains
- Wildlife (many species!)
- Many species
- Livestock associated
- Particular strain - ST398
- Pigs
- Cattle
MRSA ST398
- First identified in 2005 in The Netherlands
- Highly prevalent among pigs – approximately 40%
- Spill over into people
- 760X as likely to be colonized
- Inefficient human-human spread
- Highly associated with livestock
- Particularly pigs
- Reported from other species too
- Veal calves, dairy cattle,
MRSA veterinarians
- General population ~1.5%
-vets are more likely to get MRSA than other people. 45% in swine.
-occupational hazard
ESBLs AND CARBAPENEMASES mechanism if action
- Attack physiological processes
or structures unique to bacteria - Cell wall
- Cell membrane
- Nucleic acid synthesis,
metabolism and organization - Protein synthesis
Importance of β-lactams
- Most commonly used antimicrobial class in companion animals
- Very important in production medicine
- Critically important for human health
- Safe, effective, bio-available, spectrum of activity
B lactamase inhibitors
-binds the betalactamase so it cannot act on the B-lactam
-Clavulanic Acid
-Sulbactam
-Tazobactam
-avibactam: newest one wider spectrum of enzymes including class A, C, D. HUMANS ONLY
-Able to inhibit narrow-spectrum Class A
β-lactamases
Extended Spectrum β-lactamases
- Class A enzymes
- Can be inhibited (in vitro) by the β-lactamase inhibitors
- Resistance to the oxy-iminocephalosporins
- 3 rd generation cephalosporins
betalactamases
-enzymes which hydrolize the B ring and inactivates B-lactamase drugs
-class A: gram pos, ESBL
-class b: gram neg, carbopentinasese
-class c: gram neg
-class d: oxacillnases, OXA type
ESBLs and Carbapenemases
-gram negative problem
* These broad spectrum β-lactamases are
going to be the “Next Big Thing” in the
veterinary AMR world.
Carbapenemases
- Carbapenems are one of our last lines of defense!
- Broad spectrum drugs
- Capable of degrading the vast majority of β-lactams
- Variety of enzymes with carbapenem degrading activity
- KPC type
- Metallo-β-lactamases (VIM, IMP and NDM)
- Oxacillinases
-our worst nightmare. - Distinct epidemiological characteristics
New Delhi Metallo-β-lactamase
- Decubital ulcers, UTI with ESBL
producing K. pneumoniae - Rectal swab screening revealed
carbapenem resistant E. coli
-associated with travel to india in water and livestock in china. - Present on broad host range plasmids
- Found across the Enterobacterales (also non-fermenters!
identification of β-lactamases
ESBL: use phenotypic tests to show resistance to b-lactamases.
Carbapenemases :Modified Hodge Test
mycobacterium characteristics-
-slow growing, non motile rods
-they have gram pos peptidoglycan although they don’t
stain using Gram’s procedure.
-* Mycobacterium are described as acid-fast, they retain the stain following decolorization with acid alcohol.
-* Non-MTb complex described based on pigment production:
* Photochromogens - pigments with light exposure
* Scotochromogens - pigments without light exposure
mycobacterium BCL
-* Organism is important historically
* M. tuberculosis discovered by Robert Koch
(of Koch’s postulates fame) in 1882.
-hard to work with
-BCL 2 M. avium, lapreamurium, leprae, ulcerans
* Biocontainment level 3 - M. tuberculosis
mycobacterium host habitat
Host associated - although can survive for periods in
environment
-* Mycobacterium tuberculosis complex organisms
* Respiratory tract (M. bovis, M. tuberculosis)
* Feces (M. bovis)
* Milk (M. bovis)
* Urine (M. bovis)
* Mycobacterium avium subsp paratuberculosis
* Feces
Mycobacterium tuberculosis complex
- Group of organisms associated with granulomatous disease zoonotic!!!!!
- Mycobacterium tuberculosis - primarily human disease
- Estimated that ~1/3 of global population latently infected, synergism with HIV
- Zoonotic infections with other MTb complex
- M. bovis used to be very common cause of TB in Canada
Mycobacterium bovis
-causes BOVINE TB in cattle, wild unglulates and humans
* Mycobacterium bovis associated with disease in humans and ruminants
- In cattle disease takes several forms
-no outward clinical signs: detected through survellience
-generalized: ematiaction, lethargy, weakness
-respiratory: chronic intermittent, cough
-have destructive granulatomatous, caeseating lesions
-transmission: between contagious and suseptible animal nose to nose, ingestion of contaminated feed or water.
-long incubation period with period of latency
what happens if a case of mycobacterium bovis?
bovine TB **CFIA reportable
- Quarantine
* Movement restrictions
* Investigation
* Farm history and vet records
* Tuberculin skin tests + IFNɣ blood test
* Necropsies on positive animals
* Humane depopulation
* Cleaning and disinfection
* Compensation: The CFIA pays compensation
tests for mycobacterium bovis
-bovine TB tests
1. Intradermal tuberculin skin test
* Very sensitive, less specific (can’t have false negatives!)
* Delayed type hypersensitivity (type IV)
* Cell mediated immunity
* inject M. bovis antigen, In positive animals see swelling develop over 24-72 hours
- Comparative Cervical Tuberculin Test
- Injection of M. bovis and M. avium antigen
- Measure difference in swelling between antigens
- IFNɣ blood test
* Less sensitive, very specific (identify false positives)
* Blood collected from those which react to tuberculin test
* Expose white blood cells in blood to antigen, measure production of cytokine as a response
-test lymph nodes, lung tissues PPE NEEDED**
-control in canada relies on survenillance and stamping out.
mycobacterium bovis in wildlife 2 pops in canada
-bovine TB in wildlife, elk, ect
* Wood bison in Northern Alberta and NWT
* Elk in Riding Mountain National Park Manitoba
Mycobacterium tuberculosis people
-granulatamous disease
-zoonosis
-1/3 of global pop latnetly infected
-synergism with HIV
Mycobacterium avium subsp. paratuberculosis cattle
-causes JOhnes disease cattle/ sheep
-* Chronic, contagious granulomatous enteritis
* Persistent diarrhea
* Weight loss
Animals NOT generally febrile or depressed
* 50% of animals can be sub-clinical
* Thickening of distal small intestine characteristic lesion
-slow progressing disease, no clincal signs if under 2 years
-worldwide distributtion
-no treatment or vaccine
-test feces, blood, ilieal lymph nodse
Mycobacterium lepraemurium
- causes feline leprosy
-chronic diseasae with singular or multiple nodules
-cutanous lesions on head, neck, forelimbs
-in coatsal areas
-treatment: surgical excision, anjunctive antimicrobials
Mycobacterium leprae
-causes leprosy in people
* Slowly progressing disease of the skin, peripheral nerves, eyes and upper respiratory tract
* Historically affected people ostracized
* Thought to be genetic predisposition, ~5% of people
susceptible.
-easily treated with antimicrobials
* In Americas association with armadillo contact
* Southern United States/ brazil
Mycobacterium spp
-Mycobacterium spp. isolated from domestic animals and
humans
* Suspect with chronic, granulomatous infections
* Failed multiple rounds of antibiotics?
* animal is immunosuppressed?
* Identification can be a challenge - PCR and sequencing of
phylogenetically informative genes, need consultation
lab identification of mycobacterium
- Intradermal testing
- False positives:
- Cross reactivity with other Mycobacterium species
- VACCINATION - this is a huge challenge and why we don’t vaccinate in Canada
- False negatives:
- Improper handling of reagents or improper testing procedure
- MUST be licensed by CFIA to perform this test!
-PRC, Acid fast stained smears, serology
mycobacterium zoonosis
- Mycobacterium spp. generally have a broad host range and
should be considered zoonotic - Organisms of particular concern are in the Mycobacterium
tuberculosis complex (M. bovis most relevant in N. America) - In United States, M. bovis responsible for ~2% of cases of TB
- Transmission through contaminated or unpasteurized dairy
- Pasteurization is key!
- Contact with infected tissues when hunting also possible
mycobacterium related diseases
- MAP associated with hiv
- Mycobacterium avium associated with chrones disease
- Mycobacterum lepraemurium not considered to be zoonotic
Treatment Options mycobacterium
- Classically susceptibility testing done by agar dilution
-ag animals: not treated
-companion animals: polypharmacy necessary to prevent
development of resistance, need specialist, lots of intrinsic resistance
Molecular Epidemiology Defined
“Molecular epidemiology is a branch of epidemiology and
medical science that focuses on the contribution of potential genetic and environmental risk factors, identified at the molecular level, to the etiology, distribution and prevention of
disease within families and across populations.”
-Where and how are people/animals getting sick and in the case of infectious diseases, how are the pathogens transmitting. What’s the source, and how can it be stopped?
Susceptibility Data in molecular epidemiology
- Advantages:
- Information you have already
- Information that you are comfortable/familiar with
- Quick, cheap
- Disadvantage:
- Resistance phenotype VERY POORLY predicts relatedness!!
Phenotypic Prediction Problems
- Homogenizing effect of local antimicrobial use
- Horizontal gene transfer
- Common things are common!: Regionally, unrelated organisms often have similar susceptibility profiles
Molecular Epidemiological Techniques
- Allow us to compare the relatedness of isolates
- Methods based on detecting polymorphisms (differences) in the genome
- How do we do this?
- Based on DNA sequence directly
* Specific gene(s)
* Whole genomes - Based on DNA sequence indirectly
* Restriction digestion patterns
* PCR
* Combination of techniques
Pulsed Field Gel Electrophoresis
-pure culture on agar, put some on broth and let put in agar plug, lysis of bacteria in plus, restriction on digestion of DNA resolution of DNA frangments in banding patterns.
-interpreting you compare banding patterns of isolates to eachother.
-same banding pattern= related
Multi-Locus Sequence Typing
-pure culter on agar, DNA extraction then PCR for 7 genes. then sequence and use web data base to compare sequence and identify.
-databases online so take DNA sequence from 7 genes and then search, and overall profile defines sequence type.
Whole Genome Sequencing
Whole Genome Sequencing
* Rapid developments
-replacing pulse feild and multi locus sequence tests
-Allows 10 4-10 9 DNA fragments to be sequenced simultaneously
Where are Molecular Epidemiological
Techniques Used?
- The goal is source attribution
- Outbreak investigation
- At a national/international level
- Within a health care facility
- To track the movement of strains within the community/animals/people
- Studies of bacterial evolution
- To monitor the dissemination of mobile genetic elements
- Many countries have national level organizations which utilize these techniques in ongoing disease surveillance
