Preventing and managing infection Flashcards
Learning outcomes
- Demonstrate knowledge in the importance of vaccines in reducing antimicrobial resistance
- Understand why self-limiting bacterial or viral infections are unlikely to benefit from antimicrobials
- Demonstrate knowledge of when not to prescribe antimicrobials, and use of alternatives, such as the removal of invasive devices (e.g. intravenous or urinary catheters and incision and drainage of abscesses [source control]).
- Demonstrate an understanding of the rationale and use of perioperative prophylactic antimicrobials to prevent surgical site infection
- Describe narrow spectrum antimicrobials
What is the importance of vaccines in preventing antimicrobial resistance/ why is resistance inevitable?
- Antimicrobial resistance an inevitable consequence of antimicrobial usage
- If we can vaccine prevent a disease we should
- Vaccine preventable bacterial infections •Vaccine preventable viral infections that pre-dispose to bacterial infections
- Vaccine preventable viral infections that are inappropriately treated with antibiotics
•Bacteria are excellent at adapting to, and colonising new and hostile environments•Antibiotics are a hostile environment for bacteria, therefore resistance is inevitable•Resistance encouraged by ‘sub-lethal’ doses of antibiotics•Microbiome organisms exposed to antibiotics are encouraged to express resistance genes
What are vaccine preventable bacterial infection?
Many of the organisms in the UK vaccine schedule are bacteria
-Many cause severe infection, with the 3 main causes of bacterial meningitis included Neisseria Meningitidis, Haemophilus Influenzae (B), Streptococcus pneumoniae
Some other bacteria on the schedule cause toxin mediated disease: Corynebacterium diphtheriae, Clostridium tetani, Toxoid vaccines illicit immune response against the Toxin, rather than the bacterial cell
Vaccine preventable viral infections that predispose to bacterial infections
Vaccine preventable viral infections that pre-dispose to bacterial infections- influenza virus has primary infection, viral upper respiratory tract infection
•Influenza is associated with secondary bacterial infections
Pneumonia
Otitis media
•‘Flu vaccines not perfect, but do reduce numbers of severe infections and deaths
•Antigenic drift in Influenza viruses mean annual vaccination needed•Inactivated (dead) and attenuated (live) ‘flu vaccines used in UK
Viral infections that look like bacterial infections
- Symptoms and signs of viral and bacterial infections can be similar
- Upper respiratory tract infections are good examples
- Otitis media
- Pharyngitis/ tonsillitis
- Microbiological tests are often not available in time to guide prescribers
- Some vaccine preventable viral diseases could present like bacterial infections
Rotavirus, mumps, influenza are three viral infections that can be vaccine prevented. Each of them they cause a clinical condition which in some cases would lead to antibiotics being prescribed. Prevention of these infections can therefore reduce the pressure to prescribe antibitoics.Rotavirus: acute gastroenteritis;Mumps: orchitis and parotitis (inflammation of the gonads and parotid salivary 8
glands;Influenza: upper respiratory tract infection
Examples of bacterial causes of
Bordetella pertussis (whooping cough)-given as part of ‘6 in 1’. Haemophilus influenzae (incapsulated type B) A gram negative coccus that causes respiratory infection and meningitis. Aactuallywe sometimes call it a gram negative cocco-bacillus. ‘Bacillus’ is an older word for ‘rod’ and H. Influenzae looks sometime like a really short rod. I prefer the word rod over bacillus when describing gram stain appearances. This is because there are a genus gram of positive aerobic spore forming bacteria called Bacillus (e.g. Bacillus anthracis, the cause of Anthrax), and that can cause confusion. Streptococcus pneumoniae. Cause of pneumonia, other respiratory infections and meningitis. Gram positive coccus in pairs and short chains. Neisseria meningitidis. Cause of meningitis. Gram negative coccus.Corynebacterium diphtheriae: gram positive rod, causes Diphtheria via action of an exotoxin6 Clostridium tetani: anaerobic spore forming gram positive rod. Causes Tetanus via action of a neurotoxin: tetanospasmin.Toxoids are inactivated toxins. So toxoid vaccines are seeking to illicit an immune reaction to the toxin, rather than the bacteria that makes the
Why self-limiting bacterial or viral infections are unlikely to benefit from antimicrobials
Self limiting infections
•Benefit and risk balance
•Antimicrobials
Self- limiting infecitons- Innate immune system acts fast against invaders
Barriers
Mucosal antibody (IgA)
Clearance mechanisms such as muco-ciliary escalator
Phagocytes such as macrophages and neutrophils
Fever
Benefit and risk balance- Antibiotics are good drugs, but overuse limits their usefulness
Antibiotic benefit is for the individual but risk of resistance is to the population - RESISTANCE
Increasingly aware of risks to individual taking antibiotics also
C. diff in elderly
Microbiome dysfunction in young- IBS, childhood astmha, obesity, cancer
Longer and higher doses of antibiotics are more toxic
Benefit and risk balance
Benefit and risk balance- Antibiotics are good drugs, but overuse limits their usefulness
Antibiotic benefit is for theindividual but risk of resistance is to the population - RESISTANCE
Increasingly aware of risks to individual taking antibiotics also
C. diff in elderly
Microbiome dysfunction in young- IBS, childhood astmha, obesity, cancer
Longer and higher doses of antibiotics are more toxic
Antimicrobials
Many classes of antibiotics, divided according to their site of action in the bacterial cell
We want antibiotics that have Selective Toxicity
The majority of agents act on the Cell wall The mechanisms of bacterial protein synthesis is another major target
Beta lactam drugs and the peptidoglycan cell wall
Beta lactam drugs and the peptidoglycan cell wall
Beta lactams are the commonest prescribed antibiotics
Penicillin-type agents are the commonest beta-lactams Eukaryotes have no cell wall-so a good antibiotic target Cell wall madeof Peptidoglycan Beta-lactams inhibit cross linking of Peptidoglycan chains
- Monomers of n-acetyl muramic acid (NAMA) and n-acetyl glucosamine (NAG) form a complex polymer called Peptidoglycan
- These monomers are formed into chains
- The chains are ‘cross-linked’ by the action of the transpeptidase enzyme. This enzyme catalyses binding between amino acids on NAMA monomers on adjacent chains. The effect is a net structure. These nets stack on top of one another to form a multi-layered cell wall.
- The transpeptidase enzyme is also known as the penicillin binding protein: This enzyme is inhibited by allbeta lactam drugs
- The penicillin structure has the 4-membered beta-lactam ring at its centre. All beta-lactam antibiotics have this ring at their core.
- Beta-lactam drugs therefore stop bacterial cells from making cell walls
Demonstrate knowledge of when not to prescribe antimicrobials, and use of alternatives, such as the removal of invasive devices (e.g. intravenous or urinary catheters and incision and drainage of abscesses [source control]).
- Don’t treat Self limiting and viral infections
- Consider the Source of the infection
- Drain Abscess and collections
- Remove Implantable or temporary medical devices
Abscesses and collections
Abscess: a localised collection of pus surrounded by inflamed tissue
Some bacteria particularly associated with abscess
-Streptococcus pyogenes
-Staphylococcus aureus
A containment measure, leading tor elease of pus outside the body
Antibiotics NOT good for collections-drainage is primary treatment
Control the SOURCE
Biofilm on medical devices
Many devices used in medicine
E.gs Some temporary such as catheters
Some permanent like pacemakers and joint prostheses
Temporary devices tend to be colonised with bacteria in Biofilm
Antibiotics NOT good against biofilm
Control the SOURCE
Demonstrate an understanding of the rationale and use of perioperative prophylactic antimicrobials to prevent surgical site infection
- Many surgeries will inevitably result in infection •Prophylactic antimicrobials are reasonable because of the high chance of postoperative infection
- Antibiotics immediately prior to surgery are shown to reduce post operative infection.
The measures taken to prevent infection are essential to surgery
Ventilated operating theatres
Gloves and gowns
Sterile instruments
Skin preparation
Antibiotic prophylaxis
Surgical infection remains a critical and frequent adverse effect of surgery
Describe narrow spectrum antimicrobials
- What do we mean by spectrum of activity of antimicrobials
- Intention is to give the most narrow spectrum we can
- Good clinical practice, knowledge of microbiology and good diagnostics allow us to give narrow spectrum antimicrobials
- Start Smart then Focus approach
