Microbiology/Clin pathology Flashcards
Which cells stain gram positive and which stain gram negative?
the purple gram stain is retained by gram positive cell walls which appear purple and is lost by gram negative cell walls that stain up pink with a counter stain.
What is the outer membrane that gram negative bacteria possess?
The main difference is that gram negative possess an outer lipid membrane containing lipopolysaccharide (LPS), making the gram negative cell wall generally more impermeable to factors include antibiotics.
What is the gram positive cell wall made up of?
The gram positive cell wall doesn’t have an outer membrane, often has a thicker peptidoglycan layer which contains a negatively charged polymer such as teichoic or teichuronic acid.
What are acid fast bacteria?
Not all bacteria can be differentiated simply into gram positive and gram negative on the basis of wal lstructure and staining. the other group have a cell wall similar to gram positives but with some additional lipid containing components that alter the staining properties of the organism meaning that acid cannot remove the initial stain used. (ziehl neelsen stain). Acid fast bacteria stain pink and non acid fast bacteria stian blue.
what are s layers and what bacteria possess them?
include roles such as avoidance of host defences and adherence to host cell surfaces, eg campylobacter, bacillus anthracis.
which bacteria survive within phagocytic cells?
some bacteria survive and proliferate within phagocytic cells e.g salmonella, listeria, mycobacterium survive intracellular killing by prevention of phagosome.
which bacteria evade immune response by having an intracellular location?
brucella, listeria, mycobacterium. Certain body sites are poorly accessible to the immune response, eg mammary gland, salivary gland, bile duct and kidney tubules.
Describe the enterobacteriaceae family of bacteria
gram negative, non sporing rods, facultative anaerobes with many being motile via peritrichious flagella. examples include E coli, s typhimurium, shigella, dysenteriae, yersinia pestis, k pneumoniae, P mirabilis (proteus)
Which bacteria are a common cause of UTI in dogs and cats?
E coli (uPEC) - common cause. most infections will clear but some animals may be more prone to infections due to anatomical differences or genetic susceptibility. infection often originates from strains present in the GI tract. Many infections may be asymptomatic but others indue considerable inflamation in the urinary tractand therefore pain and discomfort for the patient.
how does Enteropathogenic E coli cause pathology?
it causes diarrhoeal disease in many mammals including calves, pigs, cats dogs and humans. Characteristic pathology as it induces the formation of attaching and effacing lesions in the gastrointestinal tract.
Describe the streptococcus species bacteria?
Gram positive cocci, typically in chains. classification is based on a combination of factors that include haemolysis, cell wall antigens and fermentation. B haemolytic streptococi on horse blood agar produce complete haemolysis producing a clear zone around the bacterial colony. a- haemolytic produce incomplete haemolysis or a green discolouration and non haemolytic produce no haemolysis.
describe the genus clostridium?
gram positive rods - anaerobes of varying sensitivity to oxygen, produce spores, commensals and saprophytes present in intestinal tracts, in the soil and in decaying organic matter. pathogenic species usually produce highly active exotoxins.
What does C novyi type B infection causE?
Blacks disease of sheep.
What does C chaveoi cause?
Blackleg
What is the causative organism of pulpy kidney?
C perfringens type D
what is the pathogenesis of pulpy kidney?
C perfringens type D.excess digestible carbohydrate entering the small intestine initiates disease, stimulates growth of saccharolytic bacteria. E toxin - a protoxin that is activated by intestinal trypsin or chymotrypsin. local epithelial damage precedes and facilitates absorption of the toxin and damage to the endothelium, particularly of kidney and brain. Hyperglycaemia due to enhanced glycogenolysis leads to glucosuria and large numbers of non sporing clostridia are found in the intestinal tract.
What is the most common causative agent in canine pyoderma?
Staphylococcus pseudintermediate also coagulase negative staph, streptococci, microccus, acinetobacter.
What would be an appropriate antibiotic choice for a canine pyoderma?
Erythromycin, lincomycin, clindamycin. These antibiotics have a narrow spectrum of action and are bacteriostatic. TMPS may also be considered but should be avoided for long term use. They are bactericidal. Cephalosporins (cephalexin) often used as first line but these should be reserved for cases which are resistant to other bacteria.
What are the possible causes of hypercalcaemia in a dog?
Hyperparathyroidism
Addisons
Renal
Dietary, Vit D (granulomatous disease can cause hyper vit D)
Idiopathic
Osteolysis or bone growth
Neoplasia (PTHrp, lymphoma, anal sac adenocarcinoma)
What are the four changes needed to diagnose multiple myeloma?
bone lytic lesions
Hyperglobulinaemia
Plasma cells in bone marrow aspirate
Bence jones proteinuria
What is bence jones proteinuria?
when light chains of the globulins break off and passed in the urine. Can do protein electrophoresis on urine to detect which type of proteins.
Why may there be an increase in Y globulins?
most commonly increase in a condition where there is an acute immune response to antigenic sitmulation usually resulting in a polyclonal gamopathy.
What type of globulins increase in nephrotic syndrome?
a2 globulins and B globulins
What does normocytic normochromic anaemia suggest?
non regenerative
What does macrocytic hypochromic anaemia suggest?
Regenerative anaemia
What does microcytic hypochromic anaemia suggest?
iron deficiency anaemia
What is rouleaux formation?
Stacks of aggregates of red blood cells. Normal in cats and horses but not in dogs. Rouleaux formation indicates hyperglobulinaemia. Fibrinogen or immunoglobulins eg reactive inflammation or antigenic stimulation.
How can you differentiate between autoagglutination and Rouleaux formation?
slide agglutination test - add saline & if clumping disperses then it is rouleaux formation.
What changes are usually seen in a stress leukogram?
segmented neutrophils & monocytes are increased, Lymphocytes and eosinophils are decreased.
What changes are seen in toxic neutrophils compared to normal neutrophils?
bone marrow producing cells faster than usually and can get some changes including vacuolation, cytoplasmic basophilia, dohle bodies (small blue/grey indistinct dots in neutrophils), toxic granulation (rare)
What liver indicators can be used to detect cholestasis?
GGT, ALP - bone, cholestasis, steroid induced in dogs Bilirubin Bile acids Cholesterol
What liver enzymes can be used to measure liver damage?
GLDH
ALT
SDH (large animal)
AST (liver, muscle, RBCs)
What tests can be used to measure liver function?
Protein - albumin, globulin, clotting factors, glucose, urea, ammonia, cholesterol, bile acids.
