Lecture 7 Flashcards

Question

Bacillus anthracis

Answer 1

Gram positive Long chain rods Strict anaerobe Spore-forming

Answer 2

Thick protein coat develops around nucleoid Chromosomal DNA condenses Water is removed from cytoplasm

Answer 3

Horizontal transmission Most common route of infection in herbivores is ingestion of contaminated soil while grazing Gastrointestinal anthrax Can affect all species Cattle and sheep most commonly reported Zoonotic

Answer 4

Endemic in Saskatchewan since 2006 Environmental reservoir Soil, water, dried organic matter Can be aerosolized and spread in air/wind If flooding or excessive groundwater, can cause spores to reach surface faster and spread

Answer 5

Ingested spore enters the small intestine Germination triggered; bacteria replicates Incubation period a few hours to 3 weeks depending on infectious dose Vegetative B. anthracis produces exotoxin that are absorbed into circulation Toxin #1 –causes severe edema and tissue necrosis necrotic tissue has decreased oxygen so bacteria can spread Toxin #2– exotoxin kills WBCs so host cannot fight off the infection

Answer 6

Clinical signs are related to tissue necrosis and edema Most common clinical sign noted is death Edema toxin causes such severe damage to vessel walls that there is fatal hemorrhage Death usually occurs in 24-48 hours of start of clinical signs

Answer 7

Vegetative form easy to treat with antibiotics Vaccine available for at-risk animals Once spores form, very hard to destroy in environment Control spread of spores Prevent air exposure Plug all openings of carcass Secure head in a plastic bag tied tight around neck Protect from scavengers Burn carcass Anthrax is a REPORTABLE DISEASE Suspect and confirmed cases of anthrax must be reported to the CFIA

Answer 8

Diseases of public health importance that are tracked by the government Impact human health, animal health and the economy Must be reported to CFIA by diagnosing vet or lab

Answer 9

to identify source of infection to prevent spread to track rate of spread

Answer 10

High mortality or morbidity (often no treatment) High risk of transmission between animals Economic importance Zoonosis Emerging (newly evolving) diseases

Answer 11

Immediately notifiable diseases Diseases exotic to Canada or no have no control or eradication programs Only labs are required to notify Annually notifiable diseases Diseases present in Canada but not reportable or immediately notifiable Laboratories send information to CFIA

Answer 12

Widespread in nature Can be found in most species as part of normal GI flora Different from other Clostridia because is NOT a strict anaerobe Common cause of bacterial diarrhea: Most common cause of small animal diarrhea Scours (calves, lambs, piglets, foals) Some strains cause a fatal diarrhea in adult livestock (cattle, sheep, poultry) Associated with antibiotic triggered diarrhea in pocket pets Zoonotic

Answer 13

Commonly diagnosed by in-clinic fecal smear Swab of rectum or fecal sample Diagnosis is by over-representation of typical large gram positive rods, with or without spores

Answer 14

Range from non-pathogenic to primary pathogens Includes most of the intestinal pathogens Some saprophytic bacteria Many are coliforms Facultative anaerobes to strict anaerobes Flagella → motile Catalase negative Can be divided based on ability to ferment lactose

Answer 15

Escherichia* Salmonella* Enterobacter Klebsiella Proteus Yersinia

Answer 16

Selective – bile salts select for enteric bacteria Selective – crystal violet inhibits Gram positive growth Differential – lactose and phenol red identify bacteria that produce lactic acid

Answer 17

Gram negative bacilli Facultative anaerobe Motile Catalase negative Lactose fermenter (pink on MAC) Large grey colonies on BA (some are hemolytic) Normal intestinal flora Ubiquitous Coliform Can survive up to 6 months in manure Common in organic biofilms Some strains are non-pathogenic, some are opportunistic, others are pathogenic Depends on the strain and infectious dose A strain may be normal flora in one species, but will cause disease if introduced into another species Eg. EHEC O157:H7 E. coli can cause severe disease if allowed to invade internal organs Opportunistic, depends on health status of the host

Answer 18

Endotoxin – triggers inflammation Capsule – resists drying and phagocytosis Some strains are hemolytic Different strains produce different exotoxins Enterotoxins are toxins that act on the GI tract Acquired antibiotic resistance Hospital and community strains of multi-drug resistant E. coli

Answer 19

Hygiene Control of feces in the environment Control fecal contamination of food and water supplies, safe food preparation Host health Vaccination Fecal exposure Most disinfectants Pasturization

Answer 20

One of three most common causes of food-borne illness in people E. coli, Salmonella, Campylobacter Causes bacterial enteritis, resulting in diarrhea Fecal-oral transmission Animal-to-animal Zoonosis Contaminated meat, dairy and produce

Answer 21

Type and severity of diarrhea/damage depends on the strain and the exotoxin it produces 3 major groups (least to most severe): ETEC = Enterotoxigenic E.coli EPEC = Enteropathogenic E.coli EHEC = Enterohemorrhagic E.coli

Answer 22

Enterotoxigenic E. coli There are species specific strains Part of normal flora in healthy animals Infection of a susceptible host causes small intestinal,secretory diarrhea Enterotoxin acts on small intestine cells and causes them to secrete excess ions into lumen water follows No physical damage to intestinal cells Animal becomes dehydrated and loses electrolytes

Answer 23

Enteropathogenic E.coli Attach to the surface of intestinal cells and destroy the microvilli on them Without microvilli, there is decreased absorption of nutrients causing a malabsorptive diarrhea Malabsorption of nutrients (and water) Some microscopic damage to the intestines Diarrhea is mucoid and can be chronic Rabbits, humans, dogs most affected

Answer 24

Enterohemorrhagic E.coli Bacteria produce Shiga toxin Enters intestinal cells and blocks protein synthesis Loss of intestinal epithelial cells results in ulcers and bleeding Result is hemorrhagic diarrhea Many strains of EHEC are part of normal GI flora in veterinary species, but cause enteritis if transmitted to other species Certain strains of EHEC can cause significant disease in calves and piglets

Answer 25

AKA “hamburger disease” Part of normal flora in 30% of cattle Causes a zoonotic hemorrhagic enteritis in people Transmission: food-borne Beef (especially ground beef) Plants fertilized with contaminated manure Feces contaminated milk, unpasteurized milk O157:H7 contamination of meat and produce is responsible for millions of $ of recalls annually Illegal to sell meat with this strain of E. coli

Answer 26

General prevention: Hygiene during food processing and food handling Meat and produce inspection Avoid undercooked ground beef Avoid unpasteurized milk Wash raw fruits and vegetables Bacterial counts in fertilizer Targeted prevention: Cannot treat cattle due to normal flora, but can decrease the normal flora load that is made up of O157:H7 Cattle-specific vaccines Vaccine is specific to the O157:H7 strain Boosts immune system to recognize and decrease numbers of specific strain Decreases shedding of E. coli O157:H7 Reduction of human cases 50-85% in tests

Answer 27

Diet trend in dogs Part of the holistic and naturopathic movement Large portion of dogs fed RMBD will shed pathogenic/zoonotic E. coli in their feces and saliva Concern if anyone is immunocompromised

Answer 28

Most common Gram negative cause of septicemia Most susceptible are foals, calves, piglets lacking colostrum Can also occur in healthy neonates that ingest large quantities of fecal matter Infection enters through the umbilicus or ingestion of fecal matter →blood→ lungs, liver, spinal cord, heart, kidneys Diagnosis is usually by culturing internal organs, such as liver

Answer 29

Acute, severe clinical mastitis Any member of Enterobacteriaceae, E.coli most common Environmental mastitis Associated with fecal contamination of bedding Fecal E. coli→ infects mammary glands → colonization in milk → can reach peak numbers in hours Most cases, infection is cleared by immune system with only mild clinical signs In few cases, severe acute inflammation occurs High numbers of bacteria release large amount of endotoxin Can be local (mammary gland) → severe damage Or can spread systemically –> endotoxic shock Form of mastitis most likely to cause cow death Endotoxic shock Eurhanasia (loss of gland, pain, inability to treat)

Answer 30

Treatment: Fluids, stripping infected gland Often clinical course is too rapid to start effective antibiotic treatment many antibiotics are not allowed in food animals Prevention: Hygiene Vaccine given in dry period

Answer 31

E. coli can penetrate the eggshell and infect the yolk sac → spreads to embryo Will cause death of embryo Cellulitis in broilers Bacteria from feces enters via scratches and wounds in skin Most commonly affects breast and around the anus Infection of skin, subcutaneous and muscle → cellulitis Tissue becomes pale, yellow, white, firm Birds are condemned and cannot be eaten

Answer 32

Common cause of UTIs Issues with multi-drug resistant E. coli strains Both community-acquired and hospital-acquired multi-drug resistance E. coli can produce urease enzyme which is secreted into urine and increases pH to 7.5 Can lead to secondary struvite formation Risk factors: Female anatomy; estrus; fecal contamination Urinary catheterization; poor cystocentesis technique

Answer 33

Treatment depends on strain Most are easily treated Community-acquired multidrug resistant strains are harder to treat Nosocomial hospital-acquired multi drug-resistant strains are very hard to treat Identification of Gram negative rods on urine microscopy is an indication to send for culture and sensitivity

Answer 34

Can be difficult since it is normal flora and ubiquitous Culture Testing for specific strains Testing for specific enterotoxins Testing for antibiotic sensitivity E. coli has lots of plasmid-based antibiotic resistance Post-mortem samples MUST be from freshly dead animals Intestinal bacteria (especially Clostridium and E. coli) spread rapidly post-mortem

Answer 35

Gram negative Rods Facultative anaerobe Motile due to flagella Non-lactose fermenting on MacConkey’s Fastidious – May require special transport media Enteric, coliform Primary pathogen Found in all animal species Present in very low numbers in intestines and feces of most NORMAL, HEALTHY domestic animals but is NEVER considered normal flora Animals are asymptomatic carriers Animal reservoirs are maintained by animal-to-animal spread and the use of Salmonella-contaminated animal feeds

Answer 36

Diseases caused by Salmonella enterica 3 types of clinical disease: Enteritis – Secretory diarrhea Septicemia Enteric fever Pathology and clinical disease are similar in people and animals

Answer 37

Reservoir is asymptomatic carriers Shed intermittently when stressed Feces, egg, milk, contaminated meat Most common transmission: Fecal-oral Food borne Direct from pet reptiles/turtles to peopl

Answer 38

Most common clinical presentation 6-48 hours after minimum infectious dose Nausea, fever, vomiting, cramps Secretory diarrhea Bacteria infect cells and alter electrolyte absorption minimal damage to the intestinal cells Last 2 days to 2 weeks, then will resolve if host is otherwise healthy Animal may continue to shed bacteria for a long time after clinical stage resolves

Answer 39

Salmonella is one of the major causes of food-borne illness in people Sources of food-borne infection include: Contaminated poultry, eggs and dairy Children acquire bacteria most commonly by fecal-oral transmission from contaminated animal feces especially from turtles, lizards Other sources include contaminated water, rodents, wild fowl

Answer 40

Genus contains a number of bacteria that cause serious disease Tuberculosis Leprosy Bacteria cell structure Very small rods Colonies can form hyphae Distinct cell wall Outermost layers of cell wall contain a lipid layer and a wax layer (mycolic acids) “ACID FAST” Stain with acid fast technique – penetrates wax layer Do not stain properly with Gram stain Resistance Wax layer is very protective Lots of antibiotic drug resistance Very resistant to pH change, detergents, drying IMMUNOGENIC Great at activating inflammation Purified cell wall is a component added to many vaccines to enhance immune activity

Answer 41

Aerobic Non-spore forming Nonmotile Catalase positive VERY LONG generation time Fast growing species produce visible colonies in 7 days Some species can take 2 years to produce colonies

Answer 42

M. bovis 10% of infected animals develop clinical disease 90% are latent infections Hard to identify Can spread infection Slow progressive lung disease - eventually fatal Hard to treat due to drug resistance Reservoirs in wildlife (deer, elk) Can spread to most other mammals, including people Most common route of transmission: respiratory

Answer 43

Post-mortem necropsy Presence of tubercules + culture Tuberculin testing CFIA-certified test Tuberculin (cell wall extract from the bacteria) is injected into skin Animals that have been infected for at least 1 month will respond to the tuberculin and create an inflammatory lesion at the injection site Identifies both silent carriers and clinically affected animals

Answer 44

Reportable Disease (Canada and USA) Suspicion of bovine TB must be reported Mandatory testing of herds in high risk areas Riding Mountain National Park, MB Large population of infected elk If suspect animals found at slaughter, herd will be tested by CFIA

Answer 45

Quarantine Investigation Positive animals and all exposed, susceptible animals are destroyed on premises Cleaning and disinfection No restocking for 45 days Producers are compensated per head

Answer 46

Smallest prokaryotes 0.3- 0 .8 micron diameter Structurally simple Lack cell wall Pleiomorphic Simple genome 470 - 700 genes Limited genes – limited enzymes = limited functions that cell is able to carry out Has complex nutritional requirements Lots of essential aa and cofactors Require external sources of sterols Can hijack host cell’s enzyme pathways

Answer 47

Different species of Mycoplasma infect different hosts, different tissues within the host and cause different diseases Difficult to treat because: No cell wall Few enzymes to target with drugs

Answer 48

Mycoplasma haemofelis Infect RBCs; surface attachment Small blue to purple “dots” on the surface of RBCs Can find with Diff-Quick stains Usually cocci, can be a ring-shaped, cocco-bacilli Less often in the cytoplasm Causes anemia Immune system attacks RBCs that have the Mycoplasma Initial diagnosis is usually on erythrocyte morphology Species-specific, but similar diseases in cattle, dogs, people, mice Can spread via arthropod vectors Ticks, lice, mosquitoes

Answer 49

Fecal-oral contamination

Answer 50

Doesn't gram stain Use acid fast instead

Answer 51

No cell wall Few enzymes to target with drugs

Answer 52

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