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
