Infections

What stain does gram positive bacteria have and why

purple due to the peptidoglycan layer being exposed

examples of ram positive

Streptococcus, Staphylococcus, clostridium.

what type of infections does gram positive cause.

skin and respiratory infections

Gram negative examples and what infections do they cause

Cholera, gonnorrhoea, E.coli. Cause uti and abdominal infections.

which bacteria causes most bacterial infections

bacteria part of natural body flora

A change in what can cause bacteria to cause infection

environment or habitat.

What causes Community acquired pneumonia

flora in the nasal cavity and the nasopharynx. mix of gram positive and negative anaerobes

which bacteria cause CD (clostridium difficile)

Gram positive anaerobe. Minor part of gut flora.

risk factors of cd

exposure to broad spectrum antibiotics, PPI use, Multiple antibiotic exposures.

Which bacteria causes Pseudomonas Aeruginosa

Gram negative bacillus, not part of natural flora, can live in various environments. Opportunistic pathogen.

What does opportunistic pathogen mean?

Is waiting silently until the right time to attack

Which patients are most susceptible

Immunocompromised - weakened immune system

example of medicine that synthesise cell wall

Penicillins, vancomycin, Cycloserine, Carbapenems.

DNA gyrase

Quinolones - ciprofloxacin, nalidixic acid

RNA elongation

Actinomycin

Protein synthesis 50s

Erythromycin, clindamycin

30s proteins

Tetracyclines, streptomycin, spectinomycin

cytoplasmic membrane

daptomycin

Antimicrobial resistence

The loss of effectiveness of any anti-infective medicine

Antimicorbial stweardship

An organisational or healthcare system wide approach to promoting and monitoring judicious use of antimicrobials to preserve their future effectiveness.

systemic signs of infection (systemic=whole body)

Fever, Headache, chills.

Local signs

Pain, heat, swelling, puss

vital signs

Change in body temp, Hypotension, tachycardia(faster heart rate)

haematology signs (blood)

increased white blood cells count, increased platelets

Bio chemistry signs

increased serum creatinine, increased liver function test

what is the aim of an antibiotic

Kill pathogenic bacteria, whilst causing no harm to human tissue

How does the antibiotic do that

Target the physiology and biochemsitry that are unique to bacteria and then: Bind to target site, bind to as many sites as possible and bind as long a time as neccessary to kill bacteria.

what need to ensure when prescribing antiobiotic

The right concentration and the right duration of course.

name the 4 mechanisms of antibiotic resistence

Penetration resistence (impermeability), efflux pump, hydrolysis, mutation of the binding site.

how does penetration resistance work

Antibiotic cannot enter the bacterium because cell wall or membrane blocks it.

example of bacteria doing this

Gram negative bacteria restricting entry through porins.

antimicroial for eye infection

chloramphenicol

dental infection

amoxocillin or metronidazole.

Blood infections

penicillins, vancomycin, metronidazole

cardiovascular infections

Amoxicillin, vancomycin, flucloxacillin

bacterial vaginosis

oral or topical metronidazole or topical clindamycin

chlamydial infection

doxycycline

skin infection

hydrogen peroxide 1% cream, flucloxacillin or if allergic to penicillin - clarithromycin

COPD

amoxocillin, clarithromycin

acute cough

doxycycline, amoxocillin, clarithromycin.

which patients should not receive cephalosporins

with history of immediate hypersensitivity to penicillin and other beta-lactams.

what class of antibiotics are cephalosporins

broad spectrum

examples of type of infections that cephalosporins treat

pneumonia, meningitis, UTIs

how does efflux pump antiobiotic res mech work

The bacterium actively pumps out the antibiotic before it can reach its target.

which antibiotics is common for efflux pump resistance

Tetracycline and fluoroquinolone

How does hydrolysis antibiotic res mech work

Bacterium podruce enzymes that destroy or inactivate the antibiotic.

Example of hydrolysis resistance mechanism

B-lactamases breaking down penicillins and cephalosporins

how does the mutation of the binding sight mech work

The antibiotics target changes shape due to mutation so drug can no longer bind effectively.

example of mutation of the binding site mechanism

MRSA altering penicillin binding proteins - macrolide resistance from ribosomal mutations.

What are Aminoglycosides

Class of potent, bactericidal antibiotics

what are aminoglycosides used for

Primarily to treat serious bacterial infections esepcially caused by grame negative bacteria such as pseudomonas aeruginosa and e coli.

How do aminoglycosides work

They inhibit the bacterial protein synthesis by binding to the 30s ribosomal sub unit

examples of aminoglycosides

streptomycin, gentamycin, amikacin, neomycin, tobramycin

What is bactericidal antibiotic and how it works

kills bacteria by destroying cell wall and damging bacterial DNA

examples of bactericidal

aminoglycosides, penicillins, fluoroquinolones, cephalosporins

what about bacteriostatic

stops bacteria growing and multiplying by inhibiting protein synthesis, block metabolic pathways and preventing cell replication

examples of bacteriostatic

tetracyclines, macrolides, sulfonamides

how do penicillins and cephalosporins mech work

destroy cell walls

aminoglycosides mech

cause faulty protein synthesis which leads to cell death

fluoroquinolones mech

damage DNA replication

which antibiotic is preffered for more serious infections

bactericidal

tetracyclines mech

stop protein synthesis

macrolides mech

stop protein synthesis

sulfonamide mech

block folate synthesis

what is folate

vitamin B9 which is essential for making DNA and RNA so is needed for cell growth and division.

aminoglycosides increase risk of deafness for patients with what?

mitochondrial mutation

what do urine dipstick tests show?

leukocyte esterase (suggests infection) and nitrates (produced by some bacteria). nitrates are only significant if the patient has urinary symptoms

what are glycopeptides used to treat?

Severe infections from gram positive bacteria like MRSA.

how do glycopeptides work

inhibit cell wall synthesis by binding to the precursors of peptidoglycan which prevents the cell wall from being built and leads to the death of the bacteria.

what do antibiotics commonly target

protein synthesis

where does protein synthesis occur in bacteria

bacterial ribosomes

which drugs act on the 50s ribosomal subunit

macrolides(erythromycin), chloramphenicol, clindamycin, lincomycin

drugs that act on 30s ribosomal subunit

tetracyclines, streptomycin, spectinomycin, gentamycin, kanamycin, amikacin, nitrofurans.

which drugs inhibit tRNA function and how

mupirocin, puromycin - prevent peptide chain formation

what do macrolides do and how

reversibly bind to the 50s ribosomal subunit which prevents bacteria from producing the proteins bacteria need to grow and multiply - inhibiting protein synthesis.

how can macrolides also be bactericidal aswell as bacteriostatic

it is generally bacteriostatic however can be bactericidal at higher concentrations or depending on the specific organism.

How are macrolides characterised

By a large macrocyclic lactone ring structure and are a common alternative for patients with penicillin allergies.

what class of antibiotics are quinolones

broad spectrum antibiotics used to treat variety of infections

why are quinolones not always first choice treatment

they can be very effective but can cause serious long lasting or irreversible side effects that effect tendons, muscles, joints, nerves and mental health.

examples of quinolones

ciprofloxacin, levofloxacin, moxifloxacin

How do quinolones work

kill bacteria by inhibiting DNA gyrase and topoisomerase IV which are essential for DNA replication and maintenance. They trap these enzymes in a complex with DNA which prevents them from ligating double stranded DNA breaks they create - leads to fragmentation of bacterial chromosome and then cell death.

What are narrow spectrum antibiotics

Target specific, limited groups of bacteria (only gram+ve or only gram -ve) Useful when cause of infection is known and minimises disruption of normal flora.

Broad spectrum antibiotics?

Act against a wide range of bacteria, inluding both gram positive and gram negative species. Useful when cause is unknown but carry a higher risk of resistence and C. difficile infection.

what class are tetracyclines

broad spectrum can treat wide variety of infections even non infectious, inflammatory conditions

how do tetryacyclines work

inhibit bacterial protein synthesis by binding to 30s ribosomal subunit - prevents aminoacyl-tRNA from binding to the acceptor (A) site on the mRNA ribosome complex.

What type of effect is tetracyclines

They block elongation of protein chain which is a bacteriostatic effect.

which drug blocks RNA polymerase which stops transcription

rifampicin

how does actinomycin work

interferes with RNA elongation

what class is trimethoprim and what does it treat

Synthetic antibiotic used to treat malaria, respiratory and urinary infections(usually in conjunction with a sulphonamide).

trimethoprim mechanism

inhibits bacterial enzyme dihydrofolate reductase which stops production of tetrahydrofolate (THF) from dihydrofolate. THF is essential for synthesising DNA,RNA and proteins - blocking its production prevents bacteria from repilcating and kills them.

what is nitrofurantoin used for

used to treat UTI.

how does nitrofurantoin work

it becomes reduced by bacterial enzymes into highly reactive intermediates - which then damage multiple essential bacterial components and processes.

why is it hard for bacteria to become resistant to nitrofurantoin

its multi target system makes it difficult for bacteria

what is clindamycin used for

To treat a variety of serious bacterial infections - those for the lungs, skin, blood and internal organs.

When is it mainly used for

when penicillin is not suitable due to allergies or resistance

how does clindamycin work

Inhibiting bacterial protein synthesis.

What type of antibiotic is it

Lincosamide antibiotic and actsa primarily as a bacteriostatic antibiotic but can be bactericidal at higher concentrations or against more susceptible organisms

what do systemic signs indicate

whole body involvement and commonly include fever, chills, headache. anorexia. These symptoms reflect activation of the immune system and inflammatory cytokines

what is mitronidazole used for

antibiotic and antiprotozoal medicine used to treat a variety of bacterial and parasitic infections.

what type of drug is metronidazole and how does it work

Prodrug that primarily works by damaging DNA of susceptible anaerobic bacteria and protozoans. It selectively targets these microorganisms because they possess specific intracellular enzymes that activate the drug - which doesnt occur in human cells or aerobic bacteria.