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Microbiology Flashcards

1
Q

One way bacteria can be classified as gram positive and gram negative. What do these terms mean?

A

Gram positive: cell walls are composed of thick peptidoglycan. They stain purple when subject to gram stain procedure.
Gram negative: Thin cell wall of peptidoglycan. Stain pink when subject to gram stain procedure as they do not retain the purple.

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2
Q

Clinical implication of difference between gram neg and gram pos bacteria

A

Gram positive bacteria have a cell wall that is easier to penetrate even though it is thicker. Due to this they tend to be susceptible to more antibiotics whereas gram negative bacteria are often less susceptible.

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3
Q

What is MRSA and what is its implication in healthcare?

A

Methicillin resistant staphlococcus aureus. It is a strain of bacteria with antibiotic resistance, particularly to B-lactams, gentamycin, tetracycline and erythromycin. It can cause a variety of problems in healthcare settings:

  • sepsis
  • pneumonia
  • joint replacements which can be irreparably damaged
  • surgical site infections
  • death
  • bloodstream infections
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4
Q

A mother brings her 18 month child to General Practice complaining of having seen small white “threads” in the nappy. What is the likely cause and the most appropriate treatment?

A

Threadworms - Mebendazole

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5
Q

What is the commonest condition associated with Mycobacteria? What term is used to describe these bacteria which is relevant to detecting them in the labs?

A

Tuberculosis - Acid-fast meaning they are resistant to discolouration by standard lab processes and require specific tests to be requested.

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6
Q

What are the five properties of a virus?

A
  1. They grow only inside living cells
  2. They possess only one type of nucleic acid, RNA or DNA
  3. They have no cell wall structure but have an outer protein coat. Some viruses have a lipid envelope
  4. Inert outside the host cell, but carry enzymes that function inside the cell
  5. They have protein receptors on their surface to allow attachment to susceptible host cells
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7
Q

Name three of the ways that viruses can cause disease

A
  • Damage by direct destruction of host cells
  • Damage by modification of host cell structure or function
  • Damage involving ‘over-reactivity’ of the host as a response to infection
  • Damage through cell proliferation and cell immortalisation
  • Evasion of both extracellular and intracellular host defences
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8
Q

What viral vaccine has been introduced to the UK programmme and what cancer is it designed to prevent?

A

HPV given to all girls’ routine vaccines designed to protect against cervical cancer

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9
Q

What is the commonest causative organism in fungal nail infection? Name three other possible differential diagnoses of fungal nail infection.

A

Trichophyton rubrum - dermatophyte is the commonest type.

Other differential diagnoses include: Psoriasis, Lichen planus, Trauma, Eczema, Yellow nail syndrome, Periungual squamous cell carcinoma/Bowens disease

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10
Q

A patient presents with fever and recent travel overseas to Africa. What protozoal illness should be top of your differential diagnosis and what is the key diagnostic test?

A

Malaria. Blood test with giemsa stain.

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11
Q

Summarise what an antibiotic is and how it works

A

An antibiotic is medication which stops or inhibits the growth of microorganisms (bacteria). They do this by binding a target site on the bacteria. Target sites are defined as points of biochemical reaction crucial to the survival of the bacterium and these sites will vary with the antibiotic class and bacterium.

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12
Q

Give four possible clinical situations that might indicate a need for an HIV test

A
  • Prolonged episodes of herpes simplex
  • Persistent frequently recurrent candidiasis
  • Recurrent infections
  • Oral candida
  • Indicators of immune dysfunction
  • Odd looking mouth lesions
  • New onset abnormal skin lesions (Kaposi’s sarcoma)

In summary suspect in any medical condition that is recurrent, severe or unexplained.

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13
Q

Difference between gram neg and gram pos bacteria

A

Gram positive bacteria have a thick peptidoglycan layer and no outer lipid membrane so they stain purple

Gram negative bacteria have a thin peptidoglycan layer and have an outer lipid membrane so they stain pink

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14
Q

Name a catalase pos and catalyse neg aerobic, gram positive cocci

A

Catalase pos = staphylococcus

Catalase neg = enterococcus and streptococcus

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15
Q

What are the 3 ways in which bacterial genetic variation occurs?

A

Transformation: horizontal gene transfer where bacteria take genetic material from environment

Transduction: requires bacteriophage to inject DNA into bacterial cell

Conjugation: transfer of plasmid through pilus transferring info from one bacteria to another

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16
Q

What bacteria am I describing?

  • Gram positive
  • Cocci
  • Blood agar shows golden colonies
  • Non-motile and non spore forming
  • Catalase positive so they foam up when hydrogen peroxidase is applied
A

Stpahylococcus aureus

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17
Q

If S. aureus invades the epidermis what condition can be caused?

A

Impetigo

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18
Q

If S. aureus invades the dermis what condition can be caused?

A

Cellulitis

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19
Q

How does s aureus infection in the blood stream lead to sepsis?

A

Infection into the bloodstream = septic thrombophlebitis (infected blood clot) which can lead to bacteremia → widespread immune reaction → blood vessels → hypotension and poor perfusion to organs → SEPSIS.

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20
Q

How can S aureus affect the heart?

A

Infection into heart = causes clumps called vegetation which damage the heart valves → infective endocarditis

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21
Q

How can S aureus affect the CNS?

A

Infection into CNS = bacterial meningitis or epidural abscess in the spine

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22
Q

How can s aureus affect the lungs?

A

Infection into lungs = severe pneumonia

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23
Q

When treating MRSA, which antibiotics are chosen?

A

clindamycin or vancomycin

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24
Q

What are strains of s aureus with complete resistance called?

A

VRSA

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25
Q

Which bacteria am I describing?

  • cocci
  • live on epidermis of skin and part of normal flora
  • gram positive
  • catalase positive
  • urease positive (turn urea agar broth and phenol red into pink)
  • coagulase negative so fibrinogen won’t break down and clump
A

Staphyloccocus epidermidis

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26
Q

What bacteria is the most dominant bacteria on the skin and colonises the nose, scalp, face, axilla?

A

S epidermidis

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27
Q

Which bacteria is a common cause of prosthetic valve endocarditis and prosthetic joint infections?

A

S epidermidis

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28
Q

Treatment for an infected prosthetic joint with s epidermidis?

A

vancomycin with rifampicin can be added and infected device removed

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29
Q

What bacteria is the causative agent of strep pharyngitis, scarlet fever, impetigo and necrotising fasciitis?

A

Streptococcus pyogenes

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30
Q

Diagnosis of s pyogenes?

A

rapid strep test for throat infections

definitive cultures from affected site

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31
Q

treatment for s pyogenes?

A

penicillin G

ceftriaxone alternative

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32
Q

what is a complication of strep throat/pharyngitis?

A

Following pharyngitis there may be acute rheumatic fever due to M protein that mimic the structure of proteins which make up tissues in the body (myosin of heart muscle and smooth muscle cells). The immune system then activates a type II hypersensitivity reaction releasing IgM and IgG antibodies aimed at destroying the M protein but instead attack the heart muscle (myocarditis, heart valves and causing infective endocarditis or pericarditis)

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33
Q

what is post-streptococcal glomerulonephritis? What are the signs?

A
  • Complication causing acute inflammation of the kidneys’ glomeruli commonly seen after impetigo about 2 weeks post infection due to a type III hypersensitivity reaction
  • Facial oedema
  • Dark red urine because glomerular damage allows RBC’s to pass into the urine
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34
Q

What is the most common infection that strep pneumoniae causes? What other infections can it cause?

A

Pneumonia

Others

  • meningitis
  • pneumococcal endocarditis
  • septic arthritis
  • rhinosinusitits
  • otitis media
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35
Q

What role does the spleen play in immunity?

A

the spleen plays an important role in fighting against encapsulated organisms and therefore, those with spleen problems, will be more susceptible to these types of infections

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36
Q

What bacteria would you suspect to be the causative agent in food poisoning where food has been cooked in big batches and kept warm for a long time such as in buffets?

A

Clostridium perfringens
- these bacteria thrive in anaerobic conditions so when they are exposed to oxygen they form spores and when conditions are right, they develop into bacteria again (such as when cooling foods or storing them) and can cause food poisoning

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37
Q

These symptoms are suggestive of what condition?

  • abdominal cramping
  • watery diarrhoea
  • vomiting

Symptoms improve within a day

A

Food poisoning

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38
Q

Treatment for food poisoning?

A

Usually no abx, treatment focuses on keeping hydrated

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39
Q

Clostridium botulism can cause what syndrome in babies? What food is thought to be a potential vector for transmitting this bacteria to babies?

A

Floppy baby syndrome where it causes botulism and causes a flaccid paralysis.
Honey is thought to be a vector so should be avoided in the first 12m of life.

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40
Q

Which bacteria am I describing?

  • gram positive bacilli
  • forms spores
  • thrives in deep compact soil
  • produces toxins which affect the nervous system causing muscle spasm and rigidity
A

Clostridium tetani

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41
Q

What is the tetanic triad?

A
  1. locked jaw
  2. risus sardonicus (facial muscle spasm causing grin)
  3. opisthotonos (severe spasm of all muscles in body simultaneously)
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42
Q

Treatment for tetanus?

A

Tetanus immune globulin - anti-toxin that binds to circulating tetanospasmin

  • muscle relaxants
  • pain meds
  • supportive measures
  • tetanus vaccine for prevention
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43
Q

Which bacteria am I describing

  • gram negative (stains pink)
  • rod shaped
  • encapsulated
  • anaerobe
  • catalase positive (foams when hydrogen peroxide is added to colony)
  • lactose fermenting (turns phenol into yellow)
  • when cultivated on eosin methylene blue agar it grows into black colonies with greenish-black metallic sheen
A

E coli

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44
Q

STEC (EHEC) causes what characteristic sign when someone is infected?

A

bloody, watery diarrhoea

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45
Q

Does ETEC cause bloody diarrhoea or watery diarrhoea?

A

Watery diarrhoea

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46
Q

Uropathogenic E coli (UPEC) causes 90% of what infection?

A

Causes 90% of community acquired UTIs and 50% of hospital acquired UTIs

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47
Q

What condition are these symptoms a sign of?

  • high sustained fever
  • abdo pain
  • constipation followed by diarrhoea
  • rose coloured spots on chest and abdomen
  • hepatomegaly and splenomegaly as infection spreads
  • dehydration, weakness, headaches and confused mental state
A

Typhoid fever

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48
Q

What is the 3rd most common causative agent of UTI and can also cause pneumonia? what type of urinary stones are formed by this bacteria and why?

A

Klebsiella pneumoniae
Causes struvite stones as klebsiella use urease to convert urea into ammonia and CO2 and this can combine and form ammonium which increases urine pH (more alkaline). Alkaline urine promotes precipitation of phosphate, calcium and magnesium which can combine to form struvite stones.

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49
Q

The symptoms described below are of which condition which can be caused by klebsiella?

  • high fever
  • chest pain
  • chills
  • SOB
  • productive cough with blood-tinged sputum
A

Lobar pneumonia

50
Q

these symptoms are characteristic of which condition

  • dysuria
  • urinary frequency
  • urinary urgency
A

UTI

51
Q

these symptoms are characteristic of which condition

  • flank pain
  • fever
  • nausea or vomiting
A

pyelonephritis

52
Q

these symptoms are characteristic of which condition

  • fever
  • chills
  • swollen, tender prostate on palpation
A

prostatitis

53
Q

how is shigella transmitted?

A

faecal to oral (contaminated water, flies, water, sexual contact)

54
Q

If shiga toxin reaches the mucosal cells lining blood vessels, it can damage them allowing toxin to enter blood stream causing what condition?
What can then happen once the infection is in the blood stream?

A

Haemolytic uremic syndrome
From the bloodstream, shiga toxin can enter the kidneys and bind to the endothelial cells lining the glomerulus making them apoptose = protein leaks through causing proteinuria.
Damage to the endothelial cell causes clotting using a high number of platelets and therefore, thrombocytopenia.
Clots obstruct the small arterioles and cause fragmented RBC (schistocytes) and destruction causes anaemia.
Reduced blood supply to organs such as kidneys lead to build up of urea (blood not being filtered properly) and leads to uraemia.

Triad: haemolytic anaemia, kidney failure, thrombocytopenia.

55
Q

Where is legionella commonly found? How is it commonly transmitted?

A

hot water tanks, cooling towers, large air conditioning systems and hot tubs
Transmission: inhaling infected aerosols

56
Q

These symptoms are a sign of which disease?

  • severe pneumonia
  • high fevers
  • GI upset
  • neurological symptoms (headache and confusion)
A

Legionnaires disease

57
Q

Identification of Legionella?

Treatment?

A

Cultures from respiratory tract secretions
Urinary antigen test detect legionella lipopolysaccharide antigen in urine
Treatment: azithromycin

58
Q

H pylori is found in the stomach of what percentage of the population?

A

50%

59
Q

Is H pylori gram neg or gram pos curved rod?

A

gram neg curved rod

60
Q

Which cells in the stomach secrete hydrochloric acid?

  • chief cells
  • parietal cells
  • G cells
  • foveolar cells
A

Parietal cells

chief cells secrete pepsinogen to digest proteins and G cells secrete gastrin which stimulates parietal cells among other things. foveolar cells secrete mucus

61
Q

How is h pylori spread?

A

faecal oral, gastro-oral and oral-oral transmission from one infected person to another (contaminated food, water or direct contact with faecal matter, vomit or saliva)

62
Q

Explain how h pylori causes infection in the stomach and can cause gastric ulcers.

A
  • When H pylori reaches the stomach, it uses it’s flagella to propel towards the stomach lining and usually travel to places like the antrum where there are less parietal cells and therefore, lower pH
  • Adhesin proteins are used to stick to the surface of foveolar cells where it can release a number of virulence factors which help it both survive and thrive, and cause damage to the mucosa.
  • One of the most important enzymes for their survival is aurease because it converts urea in the gastric juices to carbon dioxide and ammonia. Ammonia, which is basic, locally neutralises the acidic gastric environment and protects H. pylori from the harsh, acidic environment of the stomach.
  • H pylori does not itself go into the epithelial cells but some virulence factors it secretes do and these cause extensive damage to epithelial cells interfering with the mucus layer and increases the risk of gastric ulceration and cancers
63
Q

What is of concern with H pylori infection and ulceration besides the higher risk of gastric cancers?

A

Erosion through the duodenum and into the underlying blood vessels causing perforation.

64
Q

In a lot of patients, h pylori infection does not cause symptoms. In those who do get symptoms, what sort of things do they experience?

A

Heartburn
SOB
Loss of appetite with or without weight loss
Pain in the abdomen above the stomach which worsens a few hours after eating
If erosion = bleeding and blood in vomit or stools
Air can collect under the diaphragm if there is perforation and can lead to irritation of the phrenic nerve causing referred pain to the shoulder
Chronic infection can also cause iron deficiency anaemia as the bacteria sequester iron

65
Q

How can we diagnose h pylori?

A

faecal antigen test
urease breath test
Blood titres
Biopsy from upper GI endoscopy

66
Q

How do we treat h pylori infection?

A

Triple therapy using 2 antibiotics (amoxicillin and clarithromycin) and a PPI (omeprazole)

67
Q

What gram negative rod shaped organism is the most common cause of bacterial gastroenteritis worldwide? Where is it commonly found?

A

Campylobacter jejuni
commonly found in poultry and unpasteurised milk - children at risk as there is a risk of spread from direct contact with infected pets

68
Q

Infection with which bacteria is the most common risk factor for GBS?

A

Campylobacter jejuni

69
Q

Describe the microbiology of Neisseria meningitidis. What test do we use to distinguish between N meningitidis and N gonorrhoea?

A
  • Gram negative - stains pink
  • Round bacterium
  • N meningitidis typically lives in pairs - diplococci
  • Non motile
  • Non spore forming
  • Obligate aerobes (they need O2 to survive)
  • Catalase and oxidase positive

Use maltose test to distinguish - NM causes solution to go yellow, NG makes the solution stay red.

70
Q

diagnosis of n meningitidis

A

blood cultures

lumbar puncture for CSF analysis and culture

71
Q

treatment of meningitis?
treatment for close contacts?
prevention?

A

Prompt administration of Ceftriaxone.

Following results of antibiogram → can be switched to Penicillin G

Prophylactic ceftriaxone, rifampin or ciprofloxacin should be given to close contacts of affected individual

Vaccinate high risk individuals

72
Q

How is N gonorrhoea commonly transmitted? If the infection spreads up the Cervix and into uterus and Fallopian tubes in a woman, what complication could it cause?

A

Sexual contact

Can cause pelvic inflammatory disease

73
Q

If gonorrhoea infects a pregnant woman, what can the baby be born with?

A

Early neonatal conjunctivitis

74
Q

Symptoms of gonorrhoea infection in men and women?

What can occur if the infection spreads to the joints?

A

Can be asymptomatic in up to 50% of women

Females = thick, white, purulent discharge from vagina or urethra which can turn bloody and urethritis. Can cause inflammation of Fallopian tubes.

Men = Burning sensation when peeing, clear urethral discharge which can become purulent and bloody

Can cause gonococcal arthritis where joints become painful, swelling of wrists, ankles and elbows.

75
Q

How do we diagnose gonorrhoea?
Treatment?
Prevention?

A

Vaginal or urethral swab sent for gram stain and biochem tests
Nucleic acid amplification can also be done to reveal bacteria

Treatment: ceftriaxone
Prevention: condoms during sex

76
Q

What are the 2 major forms of fungal infection?

A

Skin infection - ring worm

Mucosal infection - usually female genital or mouth and easy to treat but beware of repeated infections

77
Q

Name 2 common fungal skin infections

A

Athletes foot

Ring worm

78
Q

What are 2 things we can focus on targeting in anti-fungal treatments to make them effective?

A

Fungal cells have cell walls which humans dont and their plasma membrane is made of ergosterol rather than cholesterol that we have so we mainly focus on these things to target fungi.

79
Q

What 2 drug groups have we got for fungal infections?

A

Azoles

Echinocandins - choice for severe candida infection

80
Q

What is the most common causative agent of fungal nail?

How is it treated?

A

Trichophyton rubrum
Treatment is difficult, main therapy is systemic itraconzaole or terbinafine (take a long time to work - few months) and have high failure rates.

81
Q

Mycobacteria are slow growing, gram positive, immobile bacteria and due to their special staining characteristics under the microscope, they are know as?

A

Acid-fast

82
Q

What infective organism remains to be the single biggest infectious killer worldwide?

A

M tuberculosis

83
Q

Why do 90% of people with TB not know they have it?

A

TB remains dormant in the body and when a patient becomes immunocompromised or older, the bacteria can re-appear and cause disease.

84
Q

In terms of microbiology, what are M tuberculosis like?

shape, aerobe or anaerobe, motility, spores, staining

A 
curved, rod shaped beaded bacilli
Strict aerobes
non-spore forming
Non motile
Waxy cell wall so don't dye = acid fast positive using Ziehl Neelson stain
Very slow generation time
85
Q

How is TB transmitted?

A

Usually from patients with active, infectious pulmonary TB

Via droplets in air (coughing or sneezing) and entry into the lungs

86
Q

Why can TB survive in the lungs

A
  • When in the lung, there is initial contact made with alveolar macrophages and macrophages engulf TB bacilli which the bacilli use to proliferate
  • In the macrophage, bacilli are trafficked to a phagolysosome which has hydrolytic enzymes to create a very acidic environment which would typically kill bacteria. TB however, can resist fusion with the lysosome which allows the bacterium to survive and proliferate and create localised infection
87
Q

A few weeks after primary infection with TB, cell mediated immunity begins and form a granuloma around the site of infection to seal it off. This leads to the death of the inside cells known as?

A

Caseous necrosis

88
Q

In TB, the triad of hilar lymph node involvement, granulomas and caseating necrosis is known as?

A

Primary complex formation

89
Q

What can we use to detect latent TB?

A

TB skin test

90
Q

What is the leading cause of death in those living with HIV?

A

TB infection

91
Q

How do we diagnose TB?

A

Nucleic acid detection is the hallmark testing for TB endemic countries
Mantoux TB skin test - does not differentiate between active and latent TB, CXR used to look for active TB

92
Q

Treatment for TB?

A

Isoniazid, rifampicin, pyrazinamide and ethambutol and treatment times are long as they have a lipid rich cell wall which is hard to penetrate.

Resistance to TB drugs is becoming a problem

93
Q

Name some viruses which are linked to cancers

A

EBV - glandular fever and lymphoma
Hep B/C - hepatocellular carcinoma
HPV - cervical and anal cancer

94
Q

What are the 5 things needed for viruses to replicate?

A 
Attachment
Cell entry
Host cell interaction and replication
Assembly of virus
Release of new virus particles
95
Q

How do viruses cause disease? (5)

A
  1. direct destruction of host cells - polio
  2. modification of host cell - rotavirus changing villi etc in SI causing diarrhoea
  3. over-reactivity of the immune system (hep B infecting hepatocytes)
  4. damage through cell proliferation (HPV)
  5. evasion of immune response - staying latent in the body VZV for example or antigenic variability like influenza & HIV
96
Q

What is the pre-patent period in relation to worm infections?

A

The interval between infection and the appearance of eggs in the stool.

97
Q

What are the 3 groups of helminths?

A

Nematodes - round worms
Trematodes - flat worms
Cestodes - tape worms

98
Q

What is the only common helminth in the UK? What is their appearance, transmission, clinical presentation, diagnosis and treatment?

A

Threadworm
They have a white, threadlike appearance
Transmission: faeco-oral route when threadworms are ingested

Clinical presentation

  • Pruritis ani - very itchy around the perianal region typically worse at night time
  • Commonly affects whole families
  • Appendicitis
  • Vaginal penetration

Diagnosis and treatment

  • Microscopy of sellotape strip applied to perianal region first thing in the morning and observed for eggs.
  • Drugs - mebensazole and hygiene measures
  • Treat whole family simultaneously
99
Q

What condition can be passed on through the tsetse fly bite and is usually seen in the tropics?

A

Sleeping sickness - African trypanosomiasis

Causes flu like symptoms, CNS involvement, cognitive impairment

100
Q

how is giardiasis usually spread, symptoms, diagnosis and treatment?

A

face-oral spread from non-drinking water
causes diarrhoea, cramps, bloating and flatulence
diagnosis by finding it in stools
treated with metronidazole

101
Q

how is entamoeba histolytica spread? how can it present?

A

faeco-oral by contaminated water supplies (more common in LEDC’s) can present with bloody stools

102
Q

How is malaria spread?

Which species of malaria is the most fatal?

A

Bite of female anopheles mosquito

Plasmodium falciparum is most likely to be fatal and require hospitalisation (SE Asia and Africa)

103
Q

How do we diagnose malaria? What are the symptoms and signs?

A

Blood film - found inside RBCs

Malaria Symptoms

  • FEVER
  • May also have chills, headache, myalgia, fatigue, diarrhoea, vomiting, abdo pain

Malaria Signs

  • Anaemia
  • Jaundice
  • Hepatosplenomegaly
  • Black water fever - blood in urine causing black coloured urine
104
Q

Describe the malaria cycle

A
  1. Mosquito bites and takes blood meal
    - release of sporozoites in the salivary glands
  2. These sporozoites enter the human which goes to the liver cell to infect it - ABDO PAIN
  3. Schizonts are relased from the liver cells and these enter the RBC’s
  4. Trophozoites feed on the RBC and grow and more schizonts are formed releasing the schizonts which infect more RBC - cyclic fever, haemolytic, anaemia, jaundice and haemoglobinuria
105
Q

Treatment for malaria?

A

Complicated malaria = IV artesunate, supportive measures

106
Q

What are the targets for the 4 different classes of antibiotics?

A
  1. Cell wall synthesis
  2. Nucleic Acid synthesis
  3. Protein synthesis
  4. Folate synthesis
107
Q

How do beta-lactam antibiotics work? give examples of beta lactic antibiotics why are beta lactic antibiotics more effective in gram positive bacteria?

A
  • All of these antibiotics target peptidoglycan (much bigger in gram positive so more effective).
  • Beta lactam antibiotics bind to peptidoglycan layer in bacteria and disrupt the peptidoylgycan production causing cell wall disruption
  • This results in a hypo-osmotic or iso-osmotic environment which stops the cell carrying out it’s normal function
  • As the peptidoglycan layer is thicker in gram positive bacteria, the Beta lactams are much more effective in treatment of gram-positive bacteria.
  • Additionally, gram-negative have additional lipopolysaccarhide layer that decreases antibiotic penetration

Examples: penicillins, cephalosporins, carbapenems

108
Q

Give an example of antibiotics which target nucleic acid synthesis

A

rifampicin
metronidazole
fluoroquinolone

109
Q

Difference between bacteriostatic and bactericidal antibiotics?

A

Bacteriostatic: prevents growth of bacteria killing 90% within 24h by. inhibiting protein synthesis, DNA replication or metabolism

Bactericidal: kill all bacteria inhibiting cell wall synthesis

110
Q

What is the Minimum Inhibitory Concentration of an antibiotic?

A

The concentration of antibiotic needed to stop the bacteria growing.

111
Q

What are the 2 major determinants of antibacterial effects?

A

Concentration - how high above the MIC

Time - time that the antibiotic remains on the binding sites for

112
Q

Difference between intrinsic and acquired antibiotic resistance

A

Intrinsic: inherent features of the bacteria such as mycoplasma being resistant to b-lactams and glycopeptides because they don’t have a peptidoglycan cell wall

Acquired: when a previously susceptible bacteria are no longer susceptible to an antibiotic due to spontaneous mutation or horizontal gene transfer

113
Q

What is an important gram positive resistant micro-organism?

A

MRSA (resistance to all beta lactase in addition to methicillin) and VRE (resistance to vancomycin)

114
Q

How do we manage patients in a hospital at risk of CRE or CPE?

A

Keep them in a side room and monitor their gut microbiota for CPE and CRE, need a few negative rectal swabs to be negative for them to be clear

115
Q

What are the consequences of antibiotic resistance? (3)

A
  1. increased mortality
  2. increased morbidity
  3. increased cost (length of stay, more expensive newer drugs)
116
Q

what are some factors to consider when deciding if an abx is safe to prescribe?

A
  • Intolerance / Allergy / Anaphylaxis
  • Side effects
  • Age
  • Renal and liver function
  • Pregnancy and breast feeding
  • Drug interactions
  • Risk of C Diff - causing severe diarrhoea because of broad spectrum abx
117
Q

How do beta-lactams work? Which type of bacteria do they work best against and why?

A

They target the peptidoglycan cell wall. They work best against gram positive as gram pos have very thick peptidoglycan cell walls whereas gram neg do not.

118
Q

What is the first line treatment for skin and soft tissue infection caused by s aureus, group A,C,G strep?

A

Flucloxacillin

119
Q

First line treatment for bacterial tonsillitis caused by group a,c,g strep?

A

PO penicillin V or IV benzylpenicillin

120
Q

What can we use to treat staph MRSA infection?

A

Glycopeptides - vancomycin IV

121
Q

In terms of UTIs, when do we send a culture?

What’s the first line treatment for lower UTI?

A

Only send culture if we think the person is at risk of having a resistant strain of bacteria or if they are pregnant.

First line: nitrofurantoin 100mg for 3 days women, 7 days men.

Core (7 decks)

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