Wk6 - clinical microbiology 1 Flashcards

Question

Cephalosporins - MOA of Cephalopsporins

Answer 1

Initially isolated from Sardinian sewage outflow Found to have good activity against Gram +ves and Gram –ves Less susceptible to beta-lactamases than penicillins (due to them having more side chains) Multiple generations of cephalosporins Gram negative spectrum increases with each generation Some loss of Gram positive activity Recent introduction of MRSA active cephalosporins e.g. Ceftriaxone - broad spectrum MOA: Attaches to penicillin-binding-proteins on forming bacterial cell walls. This inhibits transpeptidase enzyme which cross-links the bacterial cell wall. Failure to cross-link induces bacterial cell autolysis. Less susceptible to beta-lactamases than penicillins - Provides both gram-positive and gram-negative cover

Answer 2

Ultra-broad spectrum beta-lactam antibiotics developed during search for beta-lactamase inhibitors Excellent spectrum of activity against Gram +ves and Gram –ves No activity against MRSA Resistant to beta-lactamases New beta-lactamases are emerging which lyse carbapenems e.g. Meropenem

Answer 3

``` Aztreonam only member of the monobactam class Beta-lactam antibiotic but no cross reactivity to penicillins so can be given to those with penicillin allergy (except anaphylaxis) Only given IV – no oral absorption ``` Only work against gram -ves e.g. Aztreonam

Answer 4

Discovered in 1950s but did not find widespread use until rise of MRSA Inhibits cell wall formation in Gram +ves only (no Gram –ve action) Not dependent on PBP binding so effective against resistant organisms Resistance in clinical isolates is extremely rare 1st drug against MRSA Not absorbed from GI tract so almost always given IV Oral route only used for treatment of C. diff Resistance occurs but is uncommon (esp. Staph) Long half life so loading doses usually given MOA: Bactericidal, inhibiting cell-wall synthesis in gram positive bacteria

Answer 5

``` Nephrotoxicity – more likely with higher doses Red-man syndrome if injected too rapidly Anaphylactoid reaction Very rare now infusion rates slow Ototoxicity - rare ``` Therapeutic drug monitoring undertaken Narrow therapeutic range Aim higher in severe illnesses Main issue with vancomycin in clinical use is underdosing

Answer 6

``` 50S ribosomal subunit: Macrolides Erythromycin Clarithromycin Azithromycin Clindamycin Chloramphenicol ``` 30s Ribosomal subunit: Aminoglycosides - Gentamicin Tetracyclines - Doxycycline

Answer 7

Good spectrum of activity against Gram positives and respiratory Gram –ves Active against “atypicals” (atypical pneummonia) - Legionella - Mycoplasma - Chlamydia Excellent oral absorption: Oral even in severe infection e.g. Clarithromycin - Strep, haemophilus, Atypicals - good for resp. tract infections MOA: Binds to 50s ribosomal subunit Inhibits bacterial protein synthesis

Answer 8

Diarrhoea & Vomiting QT prolongation Hearing loss with long term use

Answer 9

Simvastatin - avoid co-prescription, temporarly stop simvastatin - increases risk of simvastatin toxicity Atrovastatin Warfarin - anticoagulant increases too much

Answer 10

Similar in many respects to macrolides: - Same mechanism of action - Excellent oral absorption - Principle action against Gram positives Some key differences: - No action against aerobic Gram negatives or “atypicals” - Excellent activity against anaerobes Clindamycin highly effective at stopping exotoxin production Added to patients with Gram positive toxin mediated disease: Toxic shock syndrome Necrotising fasciitis Streps, Staphs - sever gram +ve infection Broad anaearobic cover - causes sever destruction of colonic flora --> causes high risk of C.difficile

Answer 11

Antibiotics dramatically alter the colonic flora C. difficile commonly colonises the human colon Forms spores which can be difficult to eradiacate from hospitals Has developed resistance to common antibiotic classes 4Cs: - Clindamycin - Co-amoxiclav - Cephalosporins - Ciprofloxacin All antibiotics cause C. Diff (even those that treat it) Keep antibiotics as narrow spectrum as possible

Answer 12

``` Also inhibits the 50S ribosome Excellent broad spectrum of activity Unfortunately very toxic: - Bone marrow suppression - Aplastic anaemia - Optic neuritis ``` Not used systemically Used topically for eye infections Used for bacterial meningitis with beta-lactam allergy

Answer 13

30S inhibitors Recommended dose is 3 days. Increased in importance over the last 5 years in UK: Improved dosing regimens Restriction of other broad spectrum antibiotics Use of gentamicin in Glasgow more than doubled Used in severe gram-positive infections (e.g. biliary tract infection, pyleonephritis, HA pneumonia) Some severe gram-positive infecdtions (such as soft tissue infection and endocarditis) MOA: Binds to 30s ribosomal subunit, inhibiting protein synthesis, inducing a prolonged post-antibiotic bacteriostatic effect. Additionally, bacteriocidal action on bacterial cell wall results in rapid killing early in dosing interval and is prominent at high dosese. Also provides a synergistic effect when used alongside other antibiotics (such as flucloxacillin or vancomycin in gram-positive infections)

Answer 14

Binds to 30s ribosomal subunit, inhibiting protein synthesis, inducing a prolonged post-antibiotic bacteriostatic effect. Additionally, bactericidal action on bacterial cell wall results in rapid killing early in dosing interval and is prominent at high doses. Also provides a synergistic effect when used alongside other antibiotics (such as flucloxacillin or vancomycin in gram-positive infections). Poorly understood action on the cell membrane: Bactericidal action Prominent at high concentrations Results in rapid killing early in dosing interval

Answer 15

``` Nephrotoxicity Ototoxicity: Hearing loss Loss of balance Oscillopsia Neuromuscular blockade: Usually only significant in myaesthenia gravis (rare) ```

Answer 16

Give high initial dose to take advantage of rapid killing Leave long dosing interval (24-48hrs) to minimise toxicity Measure trough level to ensure drug not accumulating Give for 3 days only (to prevent toxicity developing)

Answer 17

Gram negatives E.coli Pseudomonas

Answer 18

``` Similar spectrum of activity to macrolides Also active against “atypical” organisms Relatively non-toxic Avoid in children and pregnant women: - Bone abnormalities - Tooth discolouration ```

Answer 19

Staphs, streps, Atypicals

Answer 20

Quinolones - Ciprofloxacin - Levofloxacin Rifampicin

Answer 21

Subtype of DNA repair and replication inhibitors Broad spectrum, bactericidal antibiotics Two quinolones in common clinical use: Ciprofloxacin: good against Gram –ves, weaker against Gram +ves – commonly used in UTI/abdominal infection – urinary tract Levofloxacin: sacrifices some Gram –ve activity for stronger Gram +ve action – respiratory tract Excellent oral bioavailability: can use oral dosing even in severe infection Active against many “atypical” pathogens, inc legionella MOA: Interferes with bacterial DNA replication and repair. Broad-spectrum bactericidal antibiotics; provides both gram-positive and gram-negative cover.

Answer 22

- Gastrointestinal toxicity - QT prolongation - Tendonitis Other therapeutic problems: - Resistance emerging on therapy/tendon damage - C. diff infection (esp. in North America)

Answer 23

Mainly gram negatives | Atypicals

Answer 24

Mainly gram positives - Strep and Staph (use in resp. tract infections) Atypicals

Answer 25

Subtype of DNA repair and replication inhibitors Principally used for two indications in the UK: Tuberculosis (in combination therapy) In addition to another antibiotic in serious Gram positive infection (esp. Staph. aureus) Interactions are very important: Rifampicin is a potent CYP450 enzyme inducer Most drugs that undergo hepatic metabolism affected Important to look up interactions when starting

Answer 26

Isoniazid Rifampicin Pyrazinamide Ethambutol (only bacteriostatic) Toxicity associated with all of them

Answer 27

MOA: Inhibition of folate metabolism pathway leads to impaired nucleotide synthesis and therefore impaired bacterial DNA replication Examples: Trimethoprim Sulfamethoxaole

Answer 28

Orally administered antibiotic Good range of action against Gram +ves and Gram –ves However, resistance a major problem in clinical use Today limited to use in uncomplicated UTI

Answer 29

Elevation of serum creatinine Does not reflect fall in GFR Related to action on proximal tubules Elevation of serum K+ Problematic in patients with chronic renal impairment Rash and GI disturbance relatively uncommon

Answer 30

Combination of Trimethoprim and sulphamethoxazole ``` Significant additional toxicity: Bone marrow suppression Stevens Johnson Syndrome Relatively few advantages: Used in certain uncommon infections by specialists Pneumocystis jirovecii pneumonia ```

Answer 31

Miscellaneous antibiotic Enters by passive diffusion and produces free radicals Effective against most anaerobic bacteria Not actinomyces Often added to therapy in intra-abdominal infections, esp abscess Causes unpleasant reaction with alcohol Peripheral neuropathy with long term use

Answer 32

Trimethoprim: Currently first line agent for most cases Avoid in 1st trimester of pregancy (as folate synthesis inhibitor) Penetrates well into prostate so good choice for men Nitrofuratoin: Excellent, broad spectrum of activity Concentrated in urine so no effect on other tissues Failure to concentrate in urine in renal failure – avoid Relatively non-toxic in short courses: - Pulmonary fibrosis with long term use

Answer 33

``` Thought to be safe: Most beta-lactams: Broad spectrum agents may be associated with NEC in premature infants Macrolides (e.g. clarithromycin) Anti-tuberculants ``` ``` Not considered safe: Tetracyclines - Bone/tooth abnormalities Trimethoprim - Neural tube defects (1st Tri) Nitrofurantoin - Haemolytic anaemic (3rd Tri) Aminoglycosides - Ototoxicity (2nd/3rd Tri) Quinolones - Bone/joint abnormalities, tendon problems ``` Always need to consider risks vs benefits

Answer 34

Inherently resistant antibiotics lack a pathway or target which a drug interacts with, or the drug is unable to gain access to the target. Acquired resistance is where a drug which was previously sensitive has gained some genetic material encoding for resistance. Examples of inherent resistance include vancomycin against Gram negative bacteria. These do not update the antibiotic meaning it has no opportunity to act on the cell wall. Also metronidazole against aerobic bacteria. It need anaerobically reduced to its active form meaning it is not activated by aerobes and therefore has no activity. It is these mechanisms of acquired resistance which we’ll be focussing on today.

Answer 35

* They can produce enzymes that inactivate or modify antimicrobials. Examples of these include the beta-lactamases which we’ll talk more about later. * They change change the drug target so that the antibiotic no longer has any effect. Examples of target modification include methylation of the 23S ribosomal subunit resulting in resistance to erythromycin. * Decreasing the permeability of the cell to the drug, meaning that the concentration required for the drug to be effective is not achieved, for example porins which permit drug to pass into a cell can be down regulated. * The final mechanism is where bacteria are able to export the drug from inside the cell. Examples of this mechanism includes the production of multi-drug resistance efflux pumps, bacteria such as Pseudomonas can produce these allowing them to become resistant to may drugs through a single mechanism. The drug is usually exchanged for protons.

Answer 36

1. Chromosomal mutation 2. Acquisition of a mobile piece of DNA such as plasmid, integron or transposon 3. DNA uptake can occur through transformation 4. Pieces of DNA can be transferred between bacteria by viruses

Answer 37

Vertical gene transfer is where genetic information is transferred from parent cell to progeny via binary fission. Horizontal gene transfer is where genes are transferred other than through traditional reproduction. Importantly it is the primary reason for antibiotic resistance. If these mechanisms for genetic exchange didnt occur antibiotic resistance wouldnt be the significant problem that it is. ``` 4 methods: Spontaneous mutation - vertical transmission Conjugation - horizontal Transduction Transformation - horizontal ```

Answer 38

Spontaneous mutation - once a mutation coding for antibiotic resistance has occurred in a cell, they will transfer this mutation to all their progency - vertical transmission of resistance. Conjugation: Requires cell to cell contact between two bacteria Small pieces of DNA called plasmids are transferred. Most important mechanism of horizontal gene transfer.

Answer 39

Plasmids are pieces of circular double stranded DNA Genetic information that can be carried on plasmids can include resistance to antibiotics, heavy metals, UV light. Can carry genes which encode pili and mediate adherence and can encode toxins. As well as carrying genes of interest to the host cell they also carry genetic information to allow themselves to replicate and pass between cells. Can either exist free within the cell or become integrated into the host chromosome Plasmids are the most important mechainsm of 'horizontal' gene transfer. They are found in Gram positives and Gram negatives and several different types of plasmids can exist within a single cell. Plasmids are a very effective way of spreading resistance, they can multiply in high numbers have a high rate of cell to cell transfer and can be picked up by different species.

Answer 40

Transduction - This is where small pieces of DNA are transferred between bacteria by a virus Bacteriophages are viruses which infect bacteria Transformation - is the changing of a bacterial cell wall or other proteins within the bacteria, causing resistance to drugs which act against these properties. Do an MRSA Screen: MRSA (like MSSA) likes to live in moist areas of the body. MRSA screen consists of a swab of the nose and perineum (nose, axilla, groin). Usually takes 1-2 days for a result.

Answer 41

Usually plasmid encoded These are enzymes which are able to hydrolyse the beta-lactam ring of not only penicillins but also cephalosporins Options for treatment include ciprofloxacin, temocillin, gentamicin and meropenem.

Answer 42

Narrow spectrum where possible Follow the empirical prescribing guidance Short courses e.g. 3 days for UTI, 5-7 days for LRTI

Answer 43

Primary: inherited Exposure in utero to environmental factors Rare Secondary: Underlying disease state Treatment for disease Common

Answer 44

``` Improved survival at extremes of life Improved cancer treatment Developments in transplant techniques Developments in intensive care Management of chronic inflammatory conditions Steroids ```

Answer 45

Neutropenia: Cytotoxic chemotherpay therapeutic irradiation (TBI) --> Dec. proliferation of haemopoietic progenitor cells --> depletion of marrow reserves --> Neutropenia DEfine as <0.5x10^9/L

Answer 46

DEc. chemotaxis, phagocytic activity, intracellular killing

Answer 47

``` Inherited immunodeficiency disorder 1/200,000 X linked most common Defect in gene coding for NADPH oxidase > deficient production of oxygen radicals > defective intracellular killing ``` Recurrent bacterial and fungal infections --> abscesses in lung, lymph nodes, skin Inflammatory responses with widespread granuloma formation.

Answer 48

DiGeorge syndrome (primary deficiency, rare) Malignant lymphoma Cytotoxic chemotherapy Extensive irradiation Immunosuppressive drugs - corticosteroids - cyclosporin – immunosuppressant used to prevent organ rejection - tacrolimus – more potent than cyclosporin - alemtuzumab – anti-CD52 monoclonal - rituximab – anti-CD20 monoclonal - purine analogues eg fludarabine – causes profound lymphopaenia Allogeneic stem cell transplantation especially if GVHD Infections – HIV, mycobacterial infections, measles, EBV, CMV

Answer 49

Bruton agammaglobulinaemia (primary, rare) Antibody production  in lymphoproliferative disorders - CLL, multiple myeloma Usually preserved in acute leukaemia Intensive radiotherapy and chemotherapy will ultimately cause hypogammaglobulinaemia

Answer 50

``` Skin Conjunctivae Mucous membranes - gut, - respiratory tract - GU tract ```

Answer 51

Gram +ve - Streptococcus, Staphylococcus, Enterococcus Gram -ve - E.coli, Neisseria (meningitis, gonorrhoea), Haemophilus, Pseudomonas Anaerobes - Clostridium (gram +ve), Bacteriodes (gram -ve)

Answer 52

High mitotic index - affected by chemotherapy & irradiation Gi lymphoid tissue responds with inflammatory response --> Mucositis --> Pain, dysphagia, xerostoma, ulceration --> Impairment of GI function Alterations in permeability --> Altered nutritional status H2 antagonists, PPIs Antibiotics Diarrhoea --> Altered microbiome

Answer 53

<75% ideal body weight OR Rapid weight loss + Hypoalbuminaemia

Answer 54

1. Produce enzymes that inactivate/modify the antibiotics e.g. beta-lactamases 2. Change the drug target so the antibiotic no longer has any affect 3. Decreasing permeability of the cell to the drug e.g. porins which permit drugs into the cell can be down-regulated 4. Bacteria can deevlop mechanisms to export the drug from inside the cell to the outside e.g. pseudomonas can develop this mechanism. The drug is usually exchanged for protons

Answer 55

1. Conjugation - requires cell to cell contact between 2 bacteria. Plasmids are transferred. Most important mechanism of horizontal gene transfer 2. Transduction - this is where small pieces of DNA are transferred between bacteria by a virus. Bacteriophages are viruses which infect bacteria 3. Transformation - when bacteria die, they release some naked DNA into the environment. Some bacteria are capable of up taking this naked NA and utilising it e.g. strep pneumoniae uses this method to become resistant to penicillin

Answer 56

Inhibits 50S ribosomal subunit

Answer 57

Trimethoprim

Answer 58

is a prodrug that undergoes reductive activation in anaerobic bacteria, leading to the formation free radicals and cytotoxic-intermediate products.

Answer 59

disrupts peptide elongation by binding to the 16S ribosomal RNA.

Answer 60

inhibits bacterial DNA-dependent RNA polymerase.

Answer 61

Oropharynx

Answer 62

Rhinovirus

Answer 63

human herpes virus 8

Answer 64

Gastroenteritis & Toxic Shock Syndrome

Answer 65

Panton-Valentine leucocidin

Answer 66

Campylobacter jejuni

Answer 67

Beta-lactams - are bacteriostatic as inhibit cross-linking of cell wall peptidoglycan, so therefore cause lysis of bacteria Protein synthesis inhibitors - either inhibit 50S or 30S ribosomes, preventing production of necessary proteins. Gentamicin, for example, reversibly binds to 30S ribosome, causing bacteriostatic effect, however has also been seen to have bacteriocidal action as well.

Answer 68

Beta-lactams - usually well tolerated however can cause GI toxicity with N&V, diarrhoea and cholestasis. Can also cause infection (candida or c.diff) due to effect on normal gut flora. Hypersensitivtity an occur (either type I or IV) Vancomycin - nephrotoxicity, Red-man syndrome (if injected too quickly - anaphylactic reaction) Macrolides - D&V, QT prolongation, hearing loss with long term Chloramphenicol - bone marrow suppresion, aplastic anaemia, optic neuritis Aminoglycosides - nephrotoxicity, ototoxicity (hearing loss, loss of balance), neuromuscular bloackade Quinolones - GI toxicity, QT prolongation, Tendonitis, C.diff infection Rifampicin - potent CYP450 enzyme inducer so therefore most drugs which under hepatic metabolism are effected Trimethoprim - elevation of serum creatinine, elevation of serum K+ is problematic which chronic renal impairment

Answer 69

C diff can be treated using the 4 Cs - Clindamycin, Co-amoxiclav, Cephalosporins, Ciprfloxacin UTIs: Uncomplicated --> Trimethoprim Complicated --> Ciprofloxacin Severely unwell --> Amoxicillin and Gentamicin Abdo infections - ciprofloxacilin Respiratory tract infections - Levofloxacin TB requires long duration (6/12) as difficult to reach granuloma due to inadequate blood supply - Rifampicin

Answer 70

• Urinalysis to look for microscopic haematuria and proteinuria. • Full blood count and biochemistry (urea and electrolyte, liver function tests). • Any other relevant cultures – perhaps sputum and urine culture? • Chest X - ray. Blood cultures. - Echocardiogram -

Answer 71

* 3 sets of blood cultures * Taken from peripheral veins * 10 mls of blood in each bottle * Meticulous sterile technique * Taken prior to antibiotics (taking 3 sets of blood cultures with the first and the last cultures at least 1 hour apart)

Answer 72

* Blood cultures – prior to the administration of any antimicrobial agent * Urine culture * Urea & Electrolytes * Liver function tests * Amylase * CRP * Full blood count & platelets * Repeat lactate * Chest X-ray

Answer 73

Water control Rodent control Isolation

Answer 74

``` TB: Respiratory tract Salmonella: Faeces Norovirus: vomit Blood borne viruses - cuts and injuries Enterovirus: Conjuctival secretions ```

Answer 75

Direct - Direct contact; Droplet spread Indirect - Airborne, Vehicle borne (food, water fomites); Vectorborne (mechanical or biologic)

Answer 76

Respiratory tract Mucous membranes Skin - non-intact Mouth (faecal-oral)

Answer 77

``` Infectious agent Reservoirs Portal of exit Means of transmission Portal of entry Susceptible host ```

Answer 78

Contact - isolation, cleaning, gloves, apron Droplet - surgical mask and eye protection Airborne - FFP3 masks (to stop you breathing it in) - TB, Pandemic flu, Aerosol Generating Procedures for resp pathogens, measles varciella zoster

Answer 79

``` Isolation Screening Cohorting Standard and transmission based precautions Surveillence Antimicrobial stewardship ```

Answer 80

Reduce activity in the area Keep exposure of a susceptible site to a minimum Check sterile packs for evidence of damage or moisture Ensure all fluids material in date. Do not re-use single use items Hand decontamination prior to the procedure Protect uniform/clothing with a disposable apron. Use sterile gloves. Appropriate waste disposal.

Answer 81

3 sets of blood cultures Taken from peripheral veins 10 mls of blood in each bottle Taken prior to antibioitics The volume of blood collected is the most significant factor in indentifying microorganisms from blood cultures. Endocarditis leads to sustained bacteraemia and this is best established by taking 3 sets of blood cultures with the first and last cultures at least 1 hour apart. The need for culture prior to antibiotic administration is self-evident. In BE, bacteraemia is almost constant, which has 2 implications: There is no rationale for delaying blood sampling to coincide with peaks of fever; and virtually all blood cultures are positive. As a result a signle positive blood culture should be regarded cautiously for eastablishing the diagnosis of BE

Answer 82

Echocardiogram is required. IE is an infection of the endocardial surface of the heart valves. It can involve previously normal valves, a valve damaged as a result of prior endocarditis, rheumatic heart disease r a degenerative process, or a prosthetic valve. Fibrin and platelets attach to the surface of damaged heart vlaves producing a sterile thrombotic endocarditis. Certain bacteria can adhere to lthese lesions on the valvular surface and initiate an inflammatory response that leads to further fibrin deposition, thus leading to maturation of the lesions. Such masses of fibrin and bacteria are termed 'vegetations'. The heart and its appendages are easily viewed by an echocardiogram. A TTE is a non-invasive procedure that defines both the structure and the function of the heart. Unfortunately, TTE is not as sensitive as TOE. The heart is more clearly visualised by placing the transducer in the oesophagus. TOE is more invasive, and patients need to be sedated before the procedure. TTE is more commonly doen for IE

Answer 83

IV Vancomycin with IV Gentamicin

Answer 84

Alpha-haemolytic streptococci: - Streptococcus pneumoniae - Streptococus viridans (most common Streptococcus species associated with BE Beta-haemolytic streptococci: - Group A streptococcus (Streptococcus pyogenes) - Group B streptococcus (Streptococcus agalactiae) - Group D streptococcus (Enterococcus) Gamma (Non) - Haemolytic Streptococci

Answer 85

Duke's criteria 2 of the major criteria - Sustained bacteraemia with a typical organism and an echocardiogram that is consistent with endocarditis

Answer 86

A commonly used regimen for treatment of streptococcal endocarditis of a native valve is 4 weeks of benzylpenicilllin combined with gentamicin for th first 2 weeks. Although streptococci are intrinsically resistant to gentamicin, benzylpenicillin disrupts the cell wall and allows gentamicin to penetrat inside the cell. Thus, they are synergestic when used in combination. The nature and duration of treatment depend upon the organism isolated and also the nature of the valve - native or prosthetic - and thus it is important to refer to the appropriate guideline. Often 4 weeks IV antibiotics. Should monitor renal function as gentamicin is a nephrotoxic drug. Regular trough levels of gentamicin need to be ascertained. A high trough level correlates with increased toxicity. Single day dosing of gentamicin has become common in serious infection, but this has not been validated for Tx of endocarditis

Answer 87

Intravenous fluids - as dehydrated Urinary catheter Oxygen mask to maintain sats at >95% IV antibiotics - e.g. Amoxicillin, Gentamicin and Metronadizole (Take blood culture, lactate, urine output) Likely to be referred to the surgical team (as is intraabdominal)

Answer 88

Gallbladder infections usually result from gallstone formation and impaction in the cystic duct, with impaired biliary drainage leading to: Infection, oedema, compressive effects on the local blood supply which may lead to gangrene of the gallbladder Infection within the gallbladder may lead to: Bloodstream infection, cholangitis, liver abscess formation

Answer 89

``` SIRS is 2 or more of: Temperature >30 or <36 Tachycardia >90 Tachypnoea RR >20/min WBC >12 x10^9/L ``` Young fit patients can look well at first - as they can compensate for severe illness in the early stages

Answer 90

``` Cellulitis Necrotising fasciitis Myositis Osteomyelitis DVT (unlikely in young man) Abscess (IVDU?) ```

Answer 91

FBC (looking at WCC), U+Es, Lactate, CRP, Doppler ultrasound of leg, Blood cultures ECG as is tachycardic

Answer 92

The patient requires admission. Given his SIRS status, IV antibioitcs are warranted. Students should follow local prescribing policy, but an initial regime of IV Flucloxacillin and Benzylpenicillin would be reasonable (Vancomycin could be an option if has penicillin allergy). LMWH should be given. Analgesia would be appropriate (e.g. co-codamol) - NSAIDs have been associated with increased risk of developing necrotising fasciitis from cellulitis, and should be withheld. The area of erythema should be marked and closely monitored overnight.

Answer 93

``` Disproportionate pain NSAID use Mild preceding trauma SIRS/sepsis Rapid progress over several hours Dusky discolouration ```

Answer 94

I - Synergistic infection with anaerobes (e.g. bacteriodes, peptostreptococcus) and anaerobes (strep, enterobacteriaciae). More common in elderly diabetic patients. This is why very broad antibiotic cover is required. II - Infection with Group A Streptococci (S.pyogens or occassionally S.aureus), mediated by toxin production. III - Vibrio vulnificus - after trauma in sea water) IV - Fungal

Answer 95

The patient requires urgent surgical/plastics/ortho review for wide debridement of all the infected tissue. Tissue from theatre should be sent to microbiology urgently for gram stain and culture. IV antibiotics are important at this stage, but are unlikely to work whilst the necrotic tissue is present: this is avascular and full of organisms. Very broad cover is needed here - a common combination is IV Flucloxacillin (for Staph), IV Benzylpenicillin (for Strep), IV Gentamicin (for gram negatives), IV Metronidazole (for anaerobes) and PO/IV Clindamycin (for anaerobes/reduction in toxin production). If penicillin allergy/MRSA positive Vancomycin can be used. He is hypotensive (BP 95/80) and requires IV fluids rapidly, and catheterisation for monitoring of his urine output Will most likely have to go to ITU post-op

Answer 96

Surgical prophylaxis appropriate to cover MRSA should include a glycopeptide e.g. vancomycin or teicoplanin

Answer 97

Gentamicin

Answer 98

Increases the risk of CDI

Answer 99

A diarrhoeal stool sample needs to be sent to microbiology

Answer 100

The severity of the CDI should be assessed and appropriate treatment initiated i.e. a decision made as to whether to start metronidazole or vancomycin. Any unnecessary antibiotics should be stopped (e.g. cefuroxime) The laxatives and any PPIs should be stopped. Standard infection control precautions need to be in place as well as isolation of the patient and appropriate hand hygiene with soap and water and not alcohol gels.. Oral metronadizole (?)

Answer 101

The primary cause of death is large bowel perforation secondary to toxic megacolon secondary to Clostridium infection. An MRSA wound infection is also a contributing factor. Yes the procurator fiscal should be informed as the patient has died as a direct consequence of a Hospital Acquired Infection (HAI) It is good practice to inform the patients GP that the patient has dies. Should also inform the infection control team. The medical director should also be informed as there may be issues regarding the competence of the doctors who were looking after the patient which need urgently to be addressed.

Answer 102

A constant desire to defacate

Answer 103

Date of last sex Establish facts about practice rather than questions about orientation What gender was the partner What type of sex: insertive or receptive, oral or anal or vaginal Was a condom used? Have they ever had a sexual health check-up and/or HIV test? Question style: Non-judgemental approach/Open questions Language they understand Question examples: "Tell me a bit about the last time you had any type of sex with anyone" "Was that a male or female partner?" "Did he use a condom all the way through?" "Did you discuss HIV status at all?" "Have you noticed anything else wrong with your health recently?" - Start a symptoms screen for HIV: - acute seroconversion e.g. fever, rash, headache, myalgia, sore throat, swollen glands - chronic HIV

Answer 104

Blood test for HIV and syphilis NAAT (nucleic acid amplification test) for gonorrhoea and chlamydia. Tests are taken from relevant anatomical sites (e.g. anal, pharayngeal swabs and urine) Hepatitis B should eb tested for in MSM (blood test) as it can be sexually transmitted and vaccination offered

Answer 105

HSV can be shed on about 1 day in 50 with no symptoms at all: many people do not understand the risk of 'asymptomatic shedding' - therefore important to discolse to future partners

Answer 106

Proctitis = inflammation of the anus lining ``` Pain - tenesmus Bleeding - bloody stools Discharge Constipation Other - rectal fullness, 'pencil-shaped' stools ```

Answer 107

Gonorrhoea is naturally transformable so can easily acquire plasmids and genetic material between resistant and sensitive organisms. Rapid accurate diagnosis (microscopy, NAAT) Avoidance of blind therapy with inappropriate drugs Partner notification to limit the onward spread of resistant infection Epidemiological monitoring of and policy reaction to resistance data.

Answer 108

This is a classic rash of secondary syphilis involving the palms. In this case the sexual history is a large clue. A key differential is acute HIV infection although the rash is not typical this can be a co-infection alongside syphilis. HIV and syphilis antibody tests can take up to three months to be positive. However currently available HIV tests look for HIV p24 antigen and will detect the great majority of individuals who have been infected with HIV at 4 weeks after specific exposure Primary syphilis can take up to 90 days and secondary syphilis up to 6 months to present as treponemes (the causative agent) are slowly growing with a long division time of several days. Infection can only become apparent once the organism is present in sufficient numbers to disturb the host.

Answer 109

This reaction is caused by the penicillin lysing cell walls of the organism which can only happen at the time of cell division. The cell fragments released lead to an escalating immune response triggering release of pro-inflammatory cytokines. In severe cases such as neurosyphilis this can be life-threatening.

Answer 110

Food history - classic culprits for gastroenteritis include undercooked poultry, reheated rice and frozen food that has been incompletely defrosted prior to cooking. Ill contacts - many forms of gastroenteritis are passed from person to person. This is particularly important when thinking about viral gastroenteritis where contact with others (often children) with diarrhoea and vomiting is common. Travel history - should include questions about pre-travel vaccinations and food and water precautions when traveling. Travel to more exotic locations increases the risk of parasitic causes of gastroenteritis and changes the spectrum of possible pathogens Past medical history - important when thinking about a non-infectious aetiology for a patients diarrhoea. If patient reports several years of recurrent loose stool or 'irritable bowel syndrome' then exacerbation of a more chronic bowel disease should be considered. PmHx should also include an assessment of the patients medication. Many drugs can include diarrhoea as a side effect. Risk factors for CDI - the main risk factors are age >65y, recent hospitalisation and a recent course of antibiotics. The presence of two of these three risk factors should prompt the consideration of CDI as a cause of the patients diarrhoea.

Answer 111

IBD (UC & Crohn's), bowel cancer, diverticular disease, chronic pancreatitis, HIV infection and ischaemic bowel. Non GI infection can also present with diarrhoea as this can be a manifestation of sepsis syndrome (e.g. pneuomococal bacteraemia)

Answer 112

FBC, U&Es, Blood culture Sample of diarrhoea for culture to try and identify the causative organism. It is best to obtain more than one stool sample as culture of bacterial organisms associated with gastroenteritis can be difficult

Answer 113

She is dehydrated (can tell as has raised urea). Should be rehydrated with oral fluids (if she can tolerate them and ideally oral rehydration salts) or with IV fluids. Antibiotics are not indicated - they have little clinical use in gastroenteritis as they only reduce the length of diarrhoea by a short period of time. An exception is when the patient has signs of sepsis (SIRS criteria) or there is concern about CDI 1. Rehydration 2. Antibiotics - if c.diff - quinolones (e.g. ciprofloxacin) 3. Infection control - most causes of gastroenteritis are transmissible from person to person. Need to be careful about hand washing - if work as food handler cannot return to work until she has been symptom free for 48 hours

Answer 114

Herpes simplex virus - 1/2 Varicella zoster virus (e.g. chicken pox) Enterovirus (e.g. Hand, foot and mouth disease (HFMD))

Answer 115

Polymerase chain reaction (PCR) should be requested on a vesicle swab

Answer 116

Exposure to on set of the rash is an average of 14-16 days (range 10-21 days). Varicella is contagious for 48 hours before the onset of the rash until every lesion has crusted over: 1. Respiratory transmission - coughs, sneezes, droplets are inhaled or acquired via surfaces contaminated by infected droplets 2. Contact with vesicle fluid

Answer 117

Patients with severe primary immunodeficiency e.g. SCID, Wiskott-Aldrich sydrome Patients being treated for malignant disease with immunosuppressive chemotherapy or radiotherapy, and for at least 6 months after terminating the Tx. Patients who have received a solid organ transplatn and are currently on immunosuppressive Tx. Patients who have received a solid organ transplant until at least 12 months after finishing all immunosuppressive Tx Patients receiving systemic high-dose steroids until at least 3 months after Tx has stopped.

Answer 118

Significant exposure to chickenpox or herpes zoster A clinical condition that increases the risk of severe varicella; this includes immunosuppressed patients, neonates and pregnant women. No antibodies to varicella zoster virus If unsuccessful: Treatment of varicella-zoster is aciclovir 10mg/kg IV every 8 hours in the immunocompromised. If the patient is well enough for oral therapy valaciclovir 1g TDS daily continued for 2 days after crusting of lesions.

Wk6 - clinical microbiology 1 Flashcards

(143 cards)