special bacteria & fungi Flashcards
what are some characteristics of spirochaetes?
- long, thin spiral-shaped bacteria
- gram negative
- anaerobic
- classical ultrastructure
- ancient lineage
- ubiquitous
- most are living, few are pathogenic
how can spirochaetes cause chronic infections?
- evade immune system
- hypersensitivity reactions develop
what are the 3 basic elements of the Spirochaete ultrastructure?
- outer sheath
- endoflagella (between cell wall & outer sheath & enables motility)
- protoplasmic cylinder (composed of cell wall & cell membrane)
what makes spirochaetes different to conventional bacteria?
- distinguished by the location of their flagella which runs lengthwise between cell wall & outer sheath
- endoflagella are an important virulence factor for Spirochaetes
what are the characteristics of Rickettsiales bacteria?
- small obligate intracellular parasites
- minute coccobacili
- gram negative bacteria but stain poorly
- energy parasites - have an ATP transport system that allows them to steal host’s ATP
describe the maintenance of Rickettsiales?
- maintained in reservoirs (animals, insects & humans)
what is the mode of infection for Rickettsiales?
- use arthropod vectors
- parasites of vascular epithelium
- enter endothelial cells & cause necrosis of vascular lining
how can Rickettsiales be cultured?
- Rickettsiales will grow in cell cultures & embryonated eggs but not on artificial media due to being intracellular parasites
describe the lifecycle of Rickettsia rickettsi
- R.rickettsi infects a tick feeding on blood of an infected animal
- it invades a host cell & reproduces & infects more host cells
- female tick transmits it to her eggs by transovarial transmission
- infected larval tick gets onto a new host
which bacteria causes spotted fever?
Rickettsia
- R.rickettsia causes Rocky Mountain Spotted Fever
- R.australis causes Queensland Tick Typhus
which bacteria causes Epidemic typhus?
- Rickettsia prowazekii
- louse-borne disease
- domestic animals are incidental hosts
name the disease Orientia tsutsugamuchi bacteria cause?
- scrub typhus
- mite-borne disease
- dogs are incidental hosts & only have subclinical infection
- primarily a human pathogen
Features of Coxiella brunetti? What disease it causes, mode of transmission, vectors?
- causes sporadic abortion in ruminants & Q fever in humans
- obligate intracellular pathogen
- produces an endospore-like form
- aerosol transmission occurs in domestic animals & humans
- arthropod vectors
what makes Rickettsiae & Coxiella different from conventional bacteria & Chlamydiales?
- host-cell dependence AND poor affinity for basic dyes AND requirement for an invertebrate vector distinguishes Rickettsiae & Coxiella from conventional bacteria & Chlamydiales
list 6 features of chalmydia
- small obligate intracellular parasites
- true energy parasites (cannot make ATP so must steal ATP from host)
- contain DNA, RNA & ribosomes
- contain an inner & outer membrane
- no peptidoglycan
- no vectors
what type of infections does Chlamydia cause?
- causes chronic infections of the epithelial of the mucous membranes
brief describe the lifecycle of chlamydia
- complicated lifecycle
- alternates between non-infectious proliferation & infectious non-proliferation stages
what are elementary bodies?
- infectious form of chlamydia
- non-replicating, non-metabolically active form
- extracellular form
what are reticulate bodies?
- non-infectious form of chlamydia
- metabolically active & replicating form
- intracellular form, more fragile
What are Mollicutes?
- a class of bacteria characterised by the absence of a cell wall
- genus Mycoplasma (contain most the animal pathogens)
- genus Ureaplasma (associated with reproductive disorders)
key characteristics about Mycoplasmas
- pleomorphic & LACKS A CELL WALL
- resistant to penicillin bc it does not have a peptidoglycan cell
- smallest self-replicating organism
- fried egg appearance
describe the pathogenicity of mycoplasma
- infect a wide host range
- mycoplasmas are extracellular pathogens that adhere to epithelial surfaces using adherence proteins
- produce toxic metabolic products
- causes immunopathogenesis
- cause chronic low-grade infections
- close contact required for transmission
- clinical manifestations = respiratory & urogenital tract infections, arthritis, mastitis & septicemia
what is enzootic pig pneumonia?
- chronic respiratory disease
- affects respiratory tract
- chronic non-productive cough, polyarthritis, poor growth & high morbidity
what us mycoplasma haemofelis?
- a parasite of red blood cells
- transmission through arthropods/bite wounds
what are fungi?
- eukaryotic organisms
- do not contain chlorophyll
- have cell walls of chitin, filamentous structures & produce spores
- mostly cause opportunistic infections
- can tolerate acids, osmotic pressure & dehydration
- aerobic or facultative anaerobes
what are the 3 categories fungi?
- yeasts (appear more bacteria-like in colony morphology & consistency)
- mould or hyphae (fuzzy appearance)
- dimorphic fungi (can appear as yeast or mycelium depending on environmental conditions)
how can fungi be identified?
- can be identified based on microscopic appearance in tissue or on routine culture media
features of yeasts
- unicellular fungi
- non-filamentous
- typically oval or spherical cells
- reproduce by mitosis
- yeasts are facultative anaerobes - allows them to grow in a variety of environments
features of moulds
- multicellular
- filamentous fungi
- identified by physical appearance, colony characteristics & reproductive status
define thallus
- body of a mould or fleshy fungus, consisting of many hyphae
define hyphae
- long filaments of cells joined together
- grow by elongating at the tips (each part of a hyphae is capable growth)
- vegetative hyphae = portion that obtains nutrients
- reproductive or aerial hyphae = portion connected with reproduction
define mycelium
large, visible, filamentous mass made up of many hyphae
define septate hyphae
cells divided by septa
define coenocytic hyphae
long continuous cells that are not divided by septa
describe dimorphic fungi
- can exist as both multicellular fungi (moulds) or yeasts
- many species are pathogenic
describe the lifecycle of fungi
- filamentous form can reproduce asexually by fragmentation of their hyphae
- fungal spores are formed from aerial hyphae & are used for both sexual & asexual reproduction
compare sexual spores and asexual spores?
- asexual spores - are formed by the aerial hyphae of one organism & new organisms are identical to parent
- sexual spores - formed by fusion of nuclei from 2 opposite mating strains of the same species
what are dermatophytes
- cause fungal infections of the skin, hair & nails
- secrete keratinise (an enzyme that degraded keratin)
how do subcutaneous mycoses cause fungal infections
- fungal infections beneath the skin
- caused by saprophytic fungi that live in soil or on vegetation
- infections occur by implantation of spores or mycelial fragments into a skin wound
- can spread into lymph vessels
how do systemic mycoses cause fungal infection?
- fungal infections deep within the body
- can affect a number of tissues & organs
- usually caused by fungi that live in the soil & are inhaled
- not contagious
what are conidospores, clamydospores, sporangiospore?
- condiospores - unicellular or multicellular spore that is not enclosed in a sac
- clamydospores - thick-walled spore formed within a hyphae segment
- sporangiospore - asexual spore formed within a sac
