Bacteria Flashcards
Define microbiology:
Study of microorganisms and their relationships to humans
Microorganisms are any organism or replicating entitiy that is microscopic or small in size
How can micro-organisms be classified?
Cellular (made of living or once living cells) vs Acellular (made of organic molecules))
Prokaryotes (without membrane bound nucleus) vs Eukaryotes
General structure of Bacteria
Genetic info: circular DNA, no nuclear membrane, plasmids
Ribsomes: only organelle present, 70S ribosomes
Complex cell wall
External features: capsule, flagella and pilli
Gram staining: method, theory and results
Method: fix bacteria to slide, flood with iodine and crystol violet, decolorise with acetone or alcohol, counterstain such as safarnin
Theory: Gram positive bacteria have large amounts of peptidoglycan, gram-negative have small amounts so doesn’t retain retain crystal violet during decolorisation
Results: Gram-positive = blue/purple, gram-negative = pink (due to safarnin counterstain), can also have gram-variable and gram-unreliable
Gram Positive Cocci
Staphylococcus aureus, streptococcus pneumoniae
Gram Positive Rods
Listeria monocytogenes, corynebacterium diphtheriae
Gram Negative Cocci
Neisseria meningiditis
Gram Negative Rods
Escherichia coli, Salmonella species
Areas of the body that are sterile:
Blood, tissue and organ systems; CNS; lower respiratory tract; sinueses; inner and middle ear; renal system to posterior urethra; female reproductive system to cervix, eye
Area of the body that are colonised with bacteria:
Nose, throat, mouth, skin, vagina, urethra, large intestines
What is the difference between colonisation and infection?
Colonisation is non harmful and has a mutualistic/ symbiotic relationship with host
Infection occurs when pathogens or organisations multiply to form a colony which causes harm to the host or are present in areas which should be sterile
Host, pathogen and environmental factors leading to infection:
Microbial factors: virulence factors which help spread of infection
Infectious dose: number of bacteria needed to cause infection
Presence of endotoxins: from GN bacteria which elicit strong immune response making patient appear spetic
Release of exotoxins: from GP bacteria, massive immune stimulation, toxic shock syndrome
Host factors: age, gender, ethnicity, medical condition/ drugs, immunocomprimised, foreign objects, vaccination
Environmental factors: crowding, seasonal variation, sanitation, socioeconomic
Why is pre-antibiotic sampling important?
Antibiotics might have suppressive effect on condition which isn’t caused by bacteria so this may worsen without knowing. Make sure treating correct thing with correct medication
Define Sepsis
Physiological response to severe infection involving cytokine cascades, free radical production and vasoactive mediators
SOFA score to tell how sever
What are the broad principles of management of infection?
Investigative (imaging, cultures), conservative (rehydration, nutrition, oxygen, support affected organs), Antibiotics (‘golden hour’), Surgical, Infection control, public health
