Bacteriology Flashcards

Question

What factors could predispose to mastitis ?

Answer 1

Factors which predispose to mastitis Any activity that leads to teat damage and loss of its ability to act as a barrier will allow the entry colonisation and invasion of pathogens - udder anatomy and physiology - stage of lactation (udder oedema early lactation in heifers) - milkers - milking equipment - environment (faecal contamination muddy) - teat damage by injury or viruses

Answer 2

The common causes of mastitis Infection of the mammary gland can be either via the haematogenous route or more commonly ascending from the teat canal. Haematogenous or lymphatic spread - Mycobacterium bovis - Brucella abortus - the above bacteria often become trapped in the mammary lymph nodes and are decimated from there (both are notifiable) - Leptospirosis flabby udder Bacteria that enter the teat canal and are spread within the herd are described as contagious - Staphylococcus aureus - Escherichia coli and Streptococcus uberis (faecal contamination) usually affect single animals. - Streptococcus dysgalactiae - Pseudomonas aeruginosa only results in disease after the cow has been repeatedly treated with antibiotics - Trueperella pyogenes + Cornybacterium pseudotuberculosis (abscess and severe mastitis)

Answer 3

Blue bag is mastitis in sheep Cause. Staphylococcus. aureus and Mannhemia haemolytica Transmission = The infection usually occurs shortly after birth or at weaning. Lambs/kids will spread the infection between mothers as they carry the bacteria in their oral cavities. Once a ewe is infected she may boot her lamb due to pain who will then attempt to suckle another ewe.

Answer 4

Postpartum dysgalactia syndrome (PPDS) Cause = Escherichia coli / Klebsiella species Transmission = sows being maintained in faecal rich environment Pathogenesis Endotoxin from these bacteria stimulate macrophages to release inflammatory cytokines which reduce the production of prolactin. This causes a loss in milk production even within unaffected teats. Clinical signs - suckling pigs decrease in size, restless and cry alot - sow may lay on cool grand to reduce the heat in her mammary - sow will avoid suckling due to pain - sow will pant a lot and become restless

Answer 5

Diagnoses of mastitis and interpretation Once mastitis is suspected Screening test 1. Collect a milk sample into a strip cup and observe for clotting, unusual colour, consistency and odour 2. Milking machines / robotic milkers have in line conductivity test - increased conductivity is due to increased sodium and chloride ions with decreased potassium ions and lactose indicating mastitis. 3. Rapid test Detect the enzyme lactate dehydrogenase (LDH). This enzyme acts as a marker of mammary cell changes as they are released by lysosomes when the mammary cells are damaged. Somatic cell counts These can either be collected on individual cows or on the bulk tank. - detect sloughed epithelial cells, secretory udder cells or leucocytes - high numbers indicate a case of mastitis Direct somatic cell counts - microscopy - automated cell counter (Fossomatic gold standard) If the somatic cell count is greater than >400,000/ml the milk will be discarded. Bacterial cultures and identification of individual milk samples is carried out if SCC > 2*105/ml milk.

Answer 6

The principals of mastitis control Acute mastitis = fever reddened and swollen mammary Peracute mastitis = high fever, purple udder, inability to rise - pathogen based treatment - generally acute infections with gram negative bacteria will self cure so need to treat with antibiotics Peracute mastitis = high fever, purple udder, unable to rise Chronic mastitis = more than 100 days in duration Poor prognosis cows with >3 episodes or a SCC >250,000 cells/ml in consecutive lactations should be culled Cases of subclinical mastitis are usually treated via dry cow therapy. By using a long acting intramammary antibiotic injected into each quarter at the end of lactation to eliminated persistent infections. Dry cow therapy is where the majority of antibiotic are used on farm as there is no long a withholding issue. To reduce this do not treat cows with less than <1 Mastitis episode over milking and low SCC prior to dry off

Answer 7

Coxiella burnetti

Answer 8

Genera Acinomycetota This genera contains pathogens including Actinobaculum, Actinomyces and Corynebacterium and trueperella. * These are gram positive pleomorphic rods or filaments * Tend to be intracellular pathogens (intracytoplasmic niche in phagocytic cells) * Non-motile * Facultative anaerobes Are known to cause a pyogranulomatous infection in soft tissues Mycolic acids * All contain an outer cell membrane rich in mycolic acids (this makes them more resistant to intravesical destruction.

Answer 9

Corynebacterium. pseudotuberculosis Caseous lymphadenitis sheep and goats ulcerative lymphangitis in cattle and horses Also known as cheesy gland The source = the mucosa Transmission = * shearing, food, or trauma or coughing of sheep with abscesses * enters through wounds Target cells = neutrophils and macrophages Virulence factor = Phospholipase D Results in hydrolysis of sphingomyelin causing cell destruction and bacterial spread. Kills macrophages haemolysin and bacterial icterus

Answer 10

Cheesy gland = Corynebacterium Pathology C.pseudotuberculosis enters via wounds causing an expanding non painful lesions at the regional lymph node. From here it may spread via blood or the lymphatic system and causes abscessation of internal lymph nodes or organs (visceral or internal form). The slow developing abscesses contain concentric rings of inspissated pus and fibrous tissue giving an onion like appearance. Phospholipase D Results in hydrolysis of sphingomyelin causing cell destruction and bacterial spread. Kills macrophages haemolysin and bacterial icterus Clinical signs Abscessation of regional lymph nodes and internal organs Slow developing – laminated abscesses “onion skin” * This disease results in carcass trimming and downgrading. * In wool sheep it decreases clean fleece yield * Internal abscesses in the lungs can cause chronic weight loss (thin ewe syndrome) even death * One of the most important causes of weight loss in sheep * The incidence of abscesses steadily increases with age * High fever, anorexia, anaemia and cellulitis at the infection site Pus is usually cream to slightly green or red tinged and does not have a bad smell.

Answer 11

Truepearella. pyogenes Skin abscessation and internal organs The most common cause of abscesses in cattle and pigs. Transmission = wounds ticks, food, wires and feet Target cells = neutrophils Pyolysin A haemolysin cholesterol dependant porin, often found together with obligate anaerobes

Answer 12

Trueperealla pyogenes The most common cause of abscesses in cattle and pigs Pathology Skin abscessation and internal organs - brain, lungs and join - Watery to creamy consistency, colour grey-green, foul odour Pyolysin A haemolysin cholesterol dependant porin, often found together with obligate anaerobes Clinical signs * Sitting lamb disease where the tail has been docked too short. * Cattle with micro-damage to the lumbar vertebrae through excessive riding

Answer 13

Trueperealla. pygenes An unusual condition is pituitary abscess syndrome where the purulent exudate and necrosis will develop in the pituitary fossa and adjacent organs in sheep – potentially secondary to ear infections or head butting. Clinical signs - Head pressing bulging eyes, abnormal stance and recumbency - Lesions are often unilateral and result in cranial nerve malfunction - Diagnose through the presence of bacteria and neutrophils in the spinal fluid

Answer 14

Actinomyces. bovis Actinomyces is an obligate anaerobe that is a commensal of the oral cavity of cattle Source = oral mucosa Transmission = Periodontitis due to coarse feed or entrapment of grass awns, wounds in the mouth. Associated with a change in teeth. Cholesterol dependent pyolysin Elicits the splendore Hoepli phenomenon a protective inflammatory derived layer.

Answer 15

Lumpy jaw = Actinomyces. bovis Pathogenesis It causes a slowly progressive granulomatous disease of the jaws of 2-5 year old cattle known as lump jaw. * Lumpy jaw – usually soft tissues and bones of the face. Can gravitate into the lungs. * Initially cause soft tissue inflammation and then penetrate into the bony tissue * Slowly developing, grey, watery, large splendore-Hoepli bodies Clinical signs * Infection of the bone causes a chronic inflammatory response characterised by the presence of yellow granules known as Splendore hoepli bodies “sulphur granules” and pus * Distruction and remodelling of the bone results in an enlargement of the affected bone and facial distortion * The bone takes on a honey comb appearance and is easily fractured Cholesterol dependent pyolysin Elicits the splendore Hoepli phenomenon a protective inflammatory derived layer.

Answer 16

Actinobacillus ligniersii Wooden tongue Gram negative bacillus rod Source = oral mucosa commensal Transmission = lesions follow damage to the mucous membranes Cholesterol dependent pyolysin Elicits the splendore Hoepli phenomenon a protective inflammatory derived layer. Pathogenesis Wooden tongue – soft tissues of the head.

Answer 17

Bacterial infections of the urinary tract are most common in multiparous, post parturient cows (about 83 days post partum). The disease is sporadic and its prevalence low Cause = Corynebacterium. Renal, C. cystitidis and C.pilosum These bacteria are commensals of the vagina and prepuce and can be spread from cow to cow via urine droplets. Predisposing factors = Anatomical defects (IE trauma due to partus), high protein diet increasing urine PH is conducive to tcolonisation and proliferation of bacteria. Pathogenesis The bacteria once infecting the bladder move up the urinary tract and usually produce the enzyme urease. - Urease allows the bacteria to utilise urea as an energy source - Majority of damage is associated with the cellular response. - Initially Haematuria (presence of blood in urine) - Fever, anorexic and urinate frequently - Colic - Polydipsia and polyuria Diagnosis Based upon the clinical picture and confirmed by blood chemistry (high urea and creatinine levels) Carry out urine examination and culture. Treatment = penicillin or potentiated sulphonamides for Corynebacterium infections

Answer 18

Actinobaculum. suis - Frequent urination with blood-stained urine - Confirm diagnosis through culture

Answer 19

Corynebacteriales = Rattles, Dermatophilosis and Nocardiosis All bacteria within the order Corynebacteriales have an outer membrane rich in fatty acids and tend to be environmentally resistant. Nocardia and Dermatophilus – produce bacterial spores further enhancing their environmental survival. Prescotella equi the agent of rattles Characteristic of genera Corynebacterialles - Soil inhabitants (few exceptions) - Gram positive rods

Answer 20

Prescottella equi Epidemiology Prescottella equi is the cause of chronic bronchopneumonia and typhlocolitis in 1-6 month old foals. (peak 6-12 weeks of age in foals). This is a non-spore forming bacterium which forms rods in culture and a coccus in the host. Prescotella equi is an opportunistic pathogen in other animals/humans and can infect any tissue (especially the skin and RS) Epidemiology - Soil saprophyte prefers to grow in warm soils, that are high in manure (containing volatile fatty acids). - Can be found in the manure of all herbivores - Equine virulent strains (carry in a plasmid genes that encode for VAPA protein) have a preference for horse manure - Grows in the large intestine of foals (<12weeks of age) - More common in horse breeding facilities where Prescottella equi has time to build up over many years. Infection = inhalation of dust particles by foals Usually infected when antibodies obtained from colostrum is declining VapA Reduces lysosome maturation and prevents acidification of the phagolysome.

Answer 21

Prescottella equi Pathology Once inhaled the bacterium will enter the alveolar macrophages and stimulate an inflammatory reaction. - This leads to a multifocal pyogranulomatous inflammation - Bacteria coughed up from the lung are swallowed and result in typhlocolitis Macrophages are not effective, the bacterium can survive and multiply in the phagocytic vesicle by preventing its maturation with virulence factor VAPA Virulence factors VAP - Are produced by equine strains of P.equi in the phagocytic vesicle when the temperature is greater than 34 degrees. - VapA reduces lysosome maturation and prevents acidification of the phagolysome. Clinical signs The early stages of disease are difficult to detect. Affected foals develop a low grade cough and wheeze, fever. - Often appear bright and suckle well until critically ill - Days later respiratory rate increases - Diarrhoea in 50% of foals

Answer 22

Prescottella equi Diagnosis - Thoracic ultrasound examination every two weeks until two months of age - Age of animal and clinical signs - Presence of opaque densities in a radiograph of the lungs - Conformation by the presence of intracellular bacteria and alveolar macrophages on TTWW cytology - Transtracheal wash and culture of P.equi - PCR to detect ChoE and vapA genes Control - Foals with lung abscesses <10cm2 in total may recover even without antibiotics - Target foals with large lung abscesses - Very few antibiotics able to penetrate cells as well as abscesses - Control is based on rotation of foaling and foal camps, sunlight exposure and regular removal of faeces - Potential use of firing where foals are fed a live virulent strain at 2,7 and 14 days of age to stimulate immunity (natural epidemiological cycle of P.equi) The most effective treatment is prolonged oral with a combination of macrolide (erythromycin, clarithromycin) and rifampin. These combinations need to be used for at lesat one week post cure. It is possible to utilise immune stimulants to increase the production of cytokines such as IL-6 and interferon gamma. (hyperimmune plasma) No vaccine is commercially available as of yet

Answer 23

Nocardiosis - granulomas which rupture This is a rare disease in animals; Gram positive, filamentous, branching bacteria produce spores in their aerial filaments or hyphae. Common soil microbe that will infect animals usually via skin wounds. Pathogenesis - Able to survive within phagocytes as the mycolic acids in their cell walls inhibit phagosome-lysosome fusion. - Induce localised granulomas that rupture draining a viscous pus which is often red tinged, containing microcolonies of Nocardia - Splendore hoepli bodies (sulphur granules) - Common infection of the udder in cattle - In cats and dogs lesions of the skin, mouth and thorax - Nocardial abortions may occur in horses and pigs - Zoonotic cutaneous, eye and pulmonary infections in people. Cytology - can acid stain - will grow on Sabourad's agar - Dermatophilosis will not acids stain or grow on Sabourad's agar.

Answer 24

Describe Dermatophilosis in animals – Dermatophilus congolensis infections Dermatophilus congolensis, is an exudative to proliferative pustular dermatitis which is chracterised by scab formation. - Usually affects cattle, sheep and horses + zoonotic occasionally affecting humans - More prevalent in tropical areas with high rainfall (rain scald) - This disease results in damage to hides, decreased productivity IE drop in milk production, and rarely death. Epidemiology Infection occurs via the skin either by direct contact with an infected animal or indirectly from plants/insects, ectoparasites. - Wet skin and lesions are attractive to flys - Trauma (constant wetting, bites portal of entry) - Prolonged wetting of the skin such as that which occurs during the rainy season results in emulsification of the protective sebum layer and maceration of the stratum corneum of the skin facilitating the spread of disease.

Answer 25

Dermatophilus congolensis Infection The resistant endospore form, when in contact with water will lose its outer layer and become a zoospore (flagella) that can attach to the skin. Once attached it germinates to produce branching filaments. These produce parallel rows (typical morphology of endospores). - Zoospores are chemotactic to CO2 that diffuses through the skin Pathology Alternating layers of exudate and thick laminated crust After germinating the branching filaments of D.congolensis invade the living cell layers of the epidermis and sheaths of hair and wool follicles. - Extensive proliferation of the organism occurs - They stimulate kertinisation of the epidermis and induce an acute inflammation reaction, that is characterised by the accumulation of an exudate rich in neutrophils beneath the invaded part of the epidermis - The organisms do not penetrate the layer of exudate - The new epidermis is forming under the exudate is invaded from the side - Once enough skin is infected it forms a thick laminated crust composed of alternating layers of para and orthokeratotoc hyperkeratosis and exudate Alternating layers of hyperkeratosis and exudate Immunity is primarily cellular

Answer 26

Dermatophilus congolensis Clinical signs - Vary in severity - Mild cases may only be detected on palpation of the hair coat and fleece - Acute – chronic cases localised to widespread lesions - Exudative to proliferative epidermitis - Subsequent formation of scabs and crusts - Under the scabs hair tends to matt or break leaving detached raw areas - Strawberry fotrot, lumpy wool in sheep, localised and generalised lesions

Answer 27

Dermatophilus congolensis Diagnosis The diseases is suspected when there is an outbreak of proliferative dermatitis (exudative lesions and skin crusts) in more than one species of animal during the wet season. - Confirm diagnosis examination of biopsy material from lesions - Smears prepared from affected skin (gram stain, Giemsa, CAMs quick). Examine for the presence of branched filaments that are transversely and longitudinally septate - DOSE not stain acid fast - Small B haemolytic colonies - Concave base of freshly removed scabs Control of Dermatophilosis Cattle are rarely treated as in most cases symptoms are limited and will heal when conditions become dryer Sheep - Isolate from infected sheep - Cull chronically affected sheep - Avoidance of excessively wet pastures - Tick and fly control - Good dip tank management (drain regularly) - Carry out shearing and dipping during dry times of the year - No vaccine - High value animals may be treated with oxytetracycline Horses Since the condition in horses is unsightly and possible zoonotic treatment is carried out - Emollients or gentle bathing of crusts with warm water and soap wil add in the removal of thick crust. (daily chlorhexidine , benzoyl peroxide)ghg - Severe lesions treated with antibiotics penicillin / streptomycin - Keep animal equipment clean and dry

Answer 28

Cord factor is produced by mycobacterium species trehalose dimycolate (TDM) Assist in protecting the bacteria from phagocytic killing, especially the action of interferon gamma.

Answer 29

Pathogenic members of mycobacterium and related genera are known to cause chronic garnulomatous lesions in people and animals. - Thick mycolic acid layer covering the peptidoglycan layer in the outer membrane - Resistant to desiccation and improves their survivability in the host (especially the monocyte macrophage) - Slow to replicate (slowest being Mycobacterium avium every 12 hours) - Facultative intracellular parasites (survive cytoplasm and phago-lysosome) - Chronic insidious (presence only revealed late in the disease process) - Poor antigenicity of the cell wall Effective immunity is predominantly cell mediated. A special acid fast stain known as the Ziehl Neelsen stain will stain them a deep red. (other bacteria stain blue, green of the counter stain)

Answer 30

Mycobacterium - Thick walls rich in mycolic acids are impermeable to the usual method of gram staining (gram positive beaded rods if visible) - Able to resist acid degradation in the phago-lysosome within macrophages - Gram positive - Rarely take up the gram or Romanoski type stains. The stain must be heated to render the wall permeable to stains like other bacteria. - Resist a strong acid decolouristaion. A special acid fast stain known as the Ziehl Neelsen stain will stain them a deep red. (other bacteria stain blue, green of the counter stain)

Answer 31

Mcobacterium Transmission = Enter into the body either through inhalation, ingestion or percutaneously. The local phagocytic cells (receptor dependant) phagocytose the mycobacterium. Being receptor dependant (antibody dependant killing is not induced). This allows mycobacteria to survive and divide in phagocytic cells. To kill mycobacteria requires activated macrophages ie those primed by interferon Y produced by differentiated TH1 cells by the respiratory burst or phagosome acidification, phagosome – lysosome fusion. This is augmented by cytotoxic T cells that lyse infected macrophage releasing the bacteria and thus making them accessible to the immune system. Amycolic acid In the cell wall known as trehalose dimycolate (TDM) or “cord factor” is thought to assist in protecting the bacteria from phagocytic killing, especially the action of gamma interferon. The infected macrophages recruit other macrophages to the site of infection ensuring a predominantly granulomatous inflammation. As more cells are recruited they re-organise into discrete granulomas or tubercules. These granulomas typically consist of a central area of necrosis, sometimes with minerlisation surrounded by giant, epitheloid cells, lymphocyts and fibroblasts encased in a collagen layer.

Answer 32

Mycobacterium bovis Epidemiology In many countries including Australia bovine tuberculosis is a notifiable disease. This is not just because it is a chronic debilitating desease but also because the agent is zoonotic - Affects the lymphohematogenous system - Primary lesions common in the lower respiratory tract - People = dead end host - absent in Australia Bovids such as cattle and buffaloes are the primary maintenance hosts, the bacterium is able to infect a wide range of animals including humans, dogs, badgers and possums. Transmission = inhalation and ingestion h

Answer 33

Mycobacterium bovis Pathology Transmission = inhalation or ingestion The bacteria are then ingested by macrophages and transported to the nearest lymph node. Inflammation at the site of entry and the regional lymph node is know as primary complex. If the animal has incomplete immunity the lesion/s will enlarge slowly eventually resulting in significant tissue damage and clinical disease. Bacteria may remain viable in thses lesions and reactivate years later where they may disseminate through out the body and cause numerous small areas of necrosis and ultimately the clinical presentation of disease. Clinical signs - Gradual weight loss - Persistent cough (lung infection) - Especially noticeable on exercise or when the animal gets up after a period of rest - Enlarged lymph nodes - M.bovis usually results in lesions of the lung and associated lymph nodes however any organ may be affected.

Answer 34

Mycobacteria tuberculosis bovis Diagnosis Confirming the diagnosis of Bovine tuberculosis is critical as a positive result often ends in the animal being killed. - Based on the presence of a specific immune response Intradermal tuberculin Test where an infected animal will show a localised area of inflammation 2-3 days after a purified protein derivative (PPD) suspension of the bacteria has been injected into the skin. -48-72hours -Neck caudal fold of the skin -Type 4 hypersensitivity response (can utilise calipers) -Animals in the late stage of tuberculosis may become insensitive to the intradermal test -Late stage = ELISA measurable antibodies and clinically thin, enlarged superficial lymph nodes, cough) Positive animals are slaughtered and examined for any granulomatous lesions. Particular attention is paid to the lymph nodes of the head, thorax and udder. Lesions are collected and submitted for organism detection by culture and qPCR. -Radioisotope broths are used to speed up the process (extremely slow growing may take upto 2 months) -typical granulomatous response numerous giant, epitheloid and a central area of necrosis that may contain areas of minerlisation. Control Australia has been declared free of the disease by WOAH. - Routine surveillance completed at the abattoir by meat inspectors - “stamping out” - Strict importation regulations, permits

Answer 35

Johne's disease Epidemiology Mycobacterium avium ssp. Paratuberculosis (Mptb) is the agent of paratuberculosis or Johne’s disease. A slowly progressive granulomatous disease of the intestine that affects predominantly ruminants (zoonotic). Since it is a very slow developing disease it may not be recognised within a herd for many years. The disease caused by sheep strains of Mptb are endemic in many states of Australia, less common are the cattle strains of MpTB. Transmission = usually to calves in utero (26%), and other young animals within the first few weeks of life. (faecal oral route, maternal milk) Repeated exposure to the agent is required for infection.

Answer 36

Johne's disease (Mycobacterium avium sp. Paratuberculosis) Pathology Oral infection with this slow-growing mycobacteria results in phagocytosis by macrpphages in the lymphoid tissue of the small intestine. The intestinal wall becomes thickened due to the proliferation of large numbers of epitheloid cells and will resemble the gyri of the brain. - Spreads haematogenously - Diffuse granulomatous inflammatory response occurs in the distal intestine (ileum) - Intestinal lymphatics and associated lymph nodes - Incubation 15-18 months - Intestinal wall thickening and poor nutrient absorption Clinical signs The progressive granulation of the intestinal mucosa gradually leads to - Malabsorption - Diarrhoea - Hypoproteinaemia - Emaciation and death - Bottle jaw - Extremely hungry - Lymphagiectasia (epitheloid cells block the lymphatics becoming twisted and having a glassy appearance.) Only one in 20 infected animals will show clinical evidence of disease.

Answer 37

Johne's disease (Mycobacterium avium sp, Paratuberculosis) Diagnosis Due to its long incubation period and non-specific clinical signs, the disease in live animals can be difficult to diagnose. Since animals shed bacteria prior to the development of clinical signs and maintain appetite diagnosis must be made early - Farm history - Presence of emaciation and diarrhoea in older animals (>2 tooth) - Abattoir surveillance - Acid fast staining of rectal swabs and serology to screen animals (pink cocci) - Preclinical stage = ELISA tend to be positive just prior to clinical signs (herd test) - Clinical stage = Pooled culture of faeces qPCR by a certified laboratory (ion chelating agent known as mycobactin J) can take 2-3 months to culture Describe the control of Johne’s disease This is a notifiable disease in Australia states and territories and control is based upon the disease status of the state and whether the individual farm is accredited free. Johne’s disease is a category 1 restricted matter and under the biosecurity act. - Quality assurance program SheepMAP, goatMAP, alpacaMAP - Vaccination is possible Gudiars bacterin vaccine for endemic farms - All positive animals should be culled

Answer 38

Morphology of the Enterobacterioles or coliforms Coliforms especially E.coli are amongst the most common group of bacteria identified in Veterinary diagnostic laboratories. - Gram negative - Non spore forming - Mostly motile - Oxidase negative - Facultative anaerobic - Rod or coccobacilli - collectively known as coliforms The most pathogenic members of this enormous order are Escherichia coli and Salmonella enterica. Escherichia coli, Salmonella species, Yersinia and Klebsiella spp and Proteus sp. All members of this family have an endotoxin as part of their cell wall and therefore the potential to cause endotoxaemia. The natural habitats of the enterobacteriales Most pathogenic members are found in the gastrointestinal tracts of animals where they reside as intestinal commensals.

Answer 39

E.coli vrs Salmonella E.coli MacConkey agar = which contains bile salts and crystal violet is one agar designed to selectively allow the growth of the class E.coli a lactose fermenter on agar. - Produces indole - XLD yellow colonies Salmonella enterica - Non lactose fermenter on MacConkey agar - XLD reduces iron salts to hydrogen sulphide (black colonies) - Dose not produce indole - Citrate positive Isolation on xylose-lysine-deoxycholate (XLD) Salmonella In addition various typing schemes are used and include 1. Serotyping antigens; flagella H antigen, Capsule K antigen, O antigen outermembrane polysaccharide chain. (only smooth colony types of Escherichia coli on MacMonkey agar – thick outer membrane can be serotyped) 2. Biotyping – arrays of biochemical and phenotypic test 3. Phage typing 4. Genotyping – shigatoxin specific genes for virulence factors 5. Genetic fingerprinting

Answer 40

Describe the general pathogenesis of the enterobacterioles Diseases caused by the enterobacteriales fall into three categories 1. Enteric disease with diarrhoea 2. Septicaemia 3. Localised pyogenic infections Since these bacteria are ubiquitous disease only occurs when the predisposing factors associated with the animal host, environment or agent occur. Host factors - Age neonate, genetic F4 piglets, immunity - Stress, nutrition or concurrent infections Environmental factors - Chilling eg temperature - Overcrowding and faecal rich soils, increases the exposure to pathogens Agent factors - Only those members that are able to adhere to the intestinal tract and produce toxins or invade the host will cause disease. There is a balancing act Transmission = faecal oral route Occasionally the respiratory, urogenital or wounds may act as ports of entry. Umbilicus in a neonatal animal where entry via this route leads to a localised infection which spreads to the rest of the body via blood vessels (haematogenous).

Answer 41

Describe the pathogenesis of septicaemia? Members of the gammaproteobacteriaceae all have liposaccharide (LPS) as a component of their outer cell membrane. The pathogens have factors that allow them to attach, invade, overcome the host’s immune defences and multiple within the host. Animals who have not received sufficient maternal antibodies or have not developed a strong adaptive immunity are prone to these infections. Septicaemia when it develops is usually a endotoxemia as once the bacteria have proliferated they die, and release their LPS which set of the systemic inflammation cascade.

Answer 42

Describe the Escherichia coli infections “colibacillosis” Escherichia coli is the cause of colibacillosis (diarrhoea or septicaemia) in neonatal calves, lambs piglets, pups and chicks. In some instances also cause opportunistic infections such as environmental mastitis cows, urinary tract infections and ear infections dogs. Colisepticaemia Watery mouth in lambs (Colisepticaemia) Colisepticaemia is caused by virulent strains of E.coli and is more common in neonatal animals who have not received sufficient maternal or passive immunity. Pathology Prominent clinical signs noted in neonatal lambs between 12-72 hours of age that are suffering from colisepticaemia. Transmission = E.coli ingestion - These lambs are usually born in dirty camps, come from multiple births and have failed to obtain sufficient colostrum. - The ingested E.coli proliferate in the intestine releasing endotoxins which result in intestinal hypomotility - The endotoxins can then be taken up systemically Clinical signs - Dull - Wet mouth excessive salivation - Eyes appear puffy - The abdomen is often distened Watery mouth is diagnosed by culturing E.coli from a whole blood sample. Treatment = fluids, glucose, anti-inflammatory drugs and a bacteriostatic antibiotics early in disease may be successful.

Answer 43

Enteritits caused by Escherichia coli strains Enteritis in the neonatal animal occurs in animals that have failed to receive maternal immunity and is caused by different pathogenic strains of E.coli 1. Enterotoxigenic E.coli (ETEC) – most common - fimbrial antigens F4, F5,F^ and F41 and heat labile toxins LT - exotoxin educes upregulation of membrane pumps leading to hypersecretion of ions followed by water - white scours 2. Enteopathogenic E.coli (EPEC) - more severe / lesser known / some animals develop dysentery - intimin type three secretion system - stimulate actin reorganisation = pedestrals 3. Enterohaemorrhagic or shigatoxin producing E.coli (STEC) - STEC = enterohemorrhagic shigatoxin - A portion attaches to ribosome 28 removing an adenine residue preventing it from interacting with elongation factor halting protein synthesis = cell death

Answer 44

1. Enterotoxigenic E.coli (ETEC) Enterotoxigenic ST and LT - Guanylate cyclase and ADenylate cyclase Pathology ST and LT - Guanylate cyclase and Adenylate cyclase E.coli strains with the fimbrial antigens: F4,F5,F6 and F41 adhere to the brush border of the intestinal cells and produce a heat stable (ST) or heat labile (LT) toxins. These toxins are internalised in the cells and adhere to guanylate cyclase and adenyl cyclase receptors respectively increasing the production of cyclic guanosine. Monophosphate (cGMP) and cyclic adenosine phosphate (cAMP). Both affect the ion channels within the cell membrane by increasing ion loss and reducing ion intake. - Intestinal lumen high osmolality than the cells causing water loss into the intestinal lumen by osmosis - Acts as a water pump drawing water from the interstitium through the intestinal epithelium and into the intestinal lumen across a water gradient This results in dehydration and metabolic acidosis in untreated animals can lead to death. There is no structural damage of the intestinal cells. Clinical signs - Whitish watery diarrhoea (white scours) - Severe dehydration

Answer 45

E.col (EPEC) Enteropathogenic EPEC is a lesser known cause of diarrhoea in calves, piglets and pups. Since the colon is usually more severely affected, some animals will develop dysentery. It can even be a common infection in children. It affects neonatal and animals up-to 2 months of age. This group of pathogens produce an adhesion protein known as intimin (Type three secretion system) that adhere tightly with the enterocytes and stimulate and stimulate actin reorganistaion of the enterocyte cytoskeleton to form pedestrals. These pedestrals improve the contact of the bacterium with the cell. - Decreases absorptive surface - Interferes with ionic exchange - Bacterium presence stimulates an inflammatory response - While most of the intestinal tract is affected the colon has the most severe lesions Most strain of EPEC will produce shigatoxin – however its affect is more important in people.

Answer 46

E.coli and shigatoxin pathology Zoonotic – once common in children who visited petting zoos EHEC strains produce intimin leading to the typical attaching and effacing lesions as well as shigatoxin. STx1 and STx2 both shigatoxins have the same mode of action. After attachment E.coli produces shigatoxin, an A-B toxin (B toxin = porin) that is taken up by the cell via endocytosis. The vesicle moves to the endoplasmic reticulum, where the A portion moves out of the vesicle and attaches to ribosome 28s. Shigatoxin removes an adenine residue from the ribosome, preventing it from interacting with ELONGATION factor. This halts protein manufacture and the cell dies.

Answer 47

Oedema disease in pigs (shigatoxin) Oedema disease is a sporadic, global disease in commercial piggeries caused by shigatoxin ST2e-producing strains of E.coli Pathology The ST2e associated damage of the arterioles results in widespread oedema. The piglets have swelling. Odema is present in the greater curvature of the stomach, between the mucosa and the muscle layers. Jelly like areas of oedema may be present in the mesocolon, larnx and the kidney capsule. Clinical signs - 30% of the best piglets - Outbreak by deaths in some and nervous signs in others - CS usually appear 10 days after weaning - Swellin eyelids, snout and ears - Brain odema results in apparent blindness - Head pressing and incoordination - Lay down with paddling movements Diagnosis - Clinical signs - Culture beta haemolytic E.coli that contains genes coding for F18 and ST2e - ST2e detection in the intestines and bloodstream - Use only fresh carcases for toxin identification Treatment = - Water medication with ampicillin, teracyclines , neomycin or potentiated sulphonamides - Limit disease by adding zinc oxide to the diet - Restrict feed intake and increase the roughage - Depopulate, sanitise and repopulate after three weeks

Answer 48

Uropathogenic E.coli (UPEC) in dogs. Female dogs are susceptible to infections with uropathogenic E.coli. Intestinal commensal E.coli colonises the vaginal and periurthral tissue and moves up the urethra to the bladder (ascending infection). Pathology P fimbriae and fusiform vessicles These bacteria have special adherence fimbriae, P fimbriae that attach to the bladder epithelium of dogs. - Forming biofilms - The biofilms protect the bacteria against flush out and antibiotic destruction. - Fusiform vesicles (assist the bladder in stretching and returning to its normal size), these same vesicles assist in the internalisation of E.coli into cells. - E.coli in these vesicles rapidly multiply and persist in the bladder epithelium. - Stimulate inflammatory response Clinical signs - Cystitis - Increase in bladder cell turnover Uropathogenic strains produce haemolysins and thus are beta- haemolytic on blood agar. E.col has a further adaptation to beta-lactam antibiotics- some strains are not killed but produce cross walls and daughter cells. These become elongated forming long filaments.

Answer 49

Salmonella - salmonellosis In mammals and birds, salmonella enterica and occasionally salmonellae of reptile origin are responsible for salmonellosis. Salmonellosis is characterised clinically by - septicaemia, acute enteritis, chronic enteritis - extraintestinal infections such as abortion or joint ill Although the disease affects all animals it is particularly prevalent in stressed animals kept in high densities. (intensive farming) In salmonella there are 3 types of carrier states 1 Active carriers; individuals infected and actively shedding in stool. Animals still shed salmonellae for a period following recovery. 2 Latent carriers; individuals are infected with salmonella but the bacteria is inactive. During periods of stress the bacteria may activate and start shedding. (intestinal lymphatic tissue) 3 Passive carriers; The uninfected individuals pass the bacteria intact through the intestines. They will not shed once removed from the source of bacteria. Humans, animals and their environment which includes food sources are linked The intricate web of salmonellae dissemination and faecal oral transmission The environment - Although the bacteria colonises and multiples in the intestinal tract, it can survive for several weeks in a dry environment, and even months in a moist environment. (ultra violet light and heating at 60 for 90mins will destroy the bacteria)

Answer 50

Pathogenesis of salmonella Macropinosome Transmission = faecal oral route Incubation period = 4 days Salmonella uses fimbriae to colonise the small and large intestine and ‘M cells’. Salmonella uses a molecular syringe to inject proteins into the cell. Type 3 secretory system These proteins effect a rearrangement of the cell actin proteins so that projections engulf the the bacterium in a macropinosome. Macropinosome (vacuole excess extracellular fluid). - These vacuoles are less subject to fusion with lysosomes (not phagocytic) - They survive in the vacuole by delaying maturation, and making their outer membrane more resistant to attack. - Bacteria can divide within these vacuoles The vacuolated bacteria eventually move to the basement membrane end of the cell where they are released into the interstitium where they are engulfed in the same way by macrophages, dendritics cells and neutrophils. Clinical signs Necrotising fibrinous enteritis - Serotypes causing an enteritis also initiate a secretory diarrhoea using shigatoxins and stimulate intestinal inflammation with the migration of neutrophils into the intestinal lumen. - More sever enteritis than E.coli - Lesions most severe in the lower ileum and the large intestine - Thrombi in blood vessels

Bacteriology Flashcards

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