Microbiology II Flashcards Preview

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Flashcards in Microbiology II Deck (40):
1

Which of the following is true of human immunodeficiency virus?
(Please select 1 option)
Decreases the risk of opportunistic infection
Induces an increase in CD4 lymphocytes, monocytes and antigen-presenting cells
Is a single stranded DNA retrovirus
Patients can be infective prior to seroconversion illness at about three months
The median survival with AIDS is greater than 10 years

Patients can be infective prior to seroconversion illness at about three months

HIV is a single stranded RNA retrovirus.

It induces immunodeficiency and increases the risk of opportunistic infection (for example, histoplasmosis, Pneumocystis jirovecii) and malignancy (for example, Kaposi's sarcoma).

Patients may have asymptomatic or symptomatic disease for several years before developing AIDS.

The median survival with full AIDS is less than two years.

2

Proteolytic enzymes are released by which one of the following organisms?
(Please select 1 option)
Clostridium botulinum
Mycobacterium tuberculosis
Neisseria meningitides
Salmonella typhi
Streptococcus pyogenes

Streptococcus pyogenes This is the correct answerThis is the correct answer
Virulence factors are important in the bacterial survival in vivo.

In this sense bacterial extracellular proteolytic enzymes can be recognised as the legitimate target for this approach since they are involved either in direct or indirect destruction of an infected/colonised tissue and in dysregulation of many host defence pathways.

The best example of the last is an effect of bacterial proteinases on fibrinolytic, kallikrein-kinin and complement cascades, as well as degradation of immunoglobulins, inactivation of endogenous proteinase inhibitors, and dysregulation of cytokine network system.

Proteolytic enzymes are responsible for the virulence and activity of organisms such as Strep. pyogenes, Staph. aureus, Escherichia coli and Clostridium welchii enabling the necrolytic effects on the skin in cellulitis and gangrene.

3

Micro-organisms that can cause latent infection do not include which of the following?
(Please select 1 option)
Chlamydia trachoma
Cytomegalovirus (CMV)
Hepatitis A
Mycobacterium tuberculosis
Varicella zoster virus

Hep A

Most commonly clinical tuberculosis represents delayed reactivation.

Varicella zoster virus remains dormant in the dorsal root ganglia and can cause latent infections such as shingles.

Over 50% of the adult population have serological evidence of latent infection with CMV, although infection is generally symptomless.

Hepatitis A is self-limiting and usually over in 3-6 weeks.

Chlamydia trachomatis can remain latent for years but can later cause blindness, infertility, and ischaemic heart disease.

4

Recognised virulence factors in bacteria do not include which of the following?
(Please select 1 option)
Beta lactamases
Gonococcal pili
Ig A-proteases
Streptococcal M protein
The capsular polysaccharides in Haemophilus influenzae

Beta lactamases

Virulence factors can be exotoxins or endotoxins (such as the cell wall of Haemophilus influenzae).

M protein on some bacteria prevent phagocytosis pili on gonococcus, allow them to adhere to mucosal surface.

Beta lactamase or penicillaminase hydrolyses penicillin but has no direct effect on host tissue.

5

Which of the following cutaneous manifestations is not correctly paired with its underlying disease?
(Please select 1 option)
Erythema induratum - syphilis
Erythema infectiosum - parvovirus B19
Erythema marginatum - Lyme disease
Erythema multiforme - orf
Erythema nodosum - tuberculosis

Erythema marginatum - Lyme disease

Erythema nodosum. This is characterised by tender red swellings usually over the shins. The most common cause is streptococcal infection. Tuberculosis, sarcoidosis, leprosy, sulphonamides and inflammatory bowel disease are other important causes.

Erythema marginatum. This is a non-itchy, pale red, macular eruption. It is a major criterion for the diagnosis of rheumatic fever but is also seen in acute glomerulonephritis and drug reactions.

Erythema multiforme. This is characterised by cutaneous "target" lesions and mucosal involvement. Children and young adults are more commonly affected. Orf, Mycoplasma and herpes simplex are among the known causes.

Erythema induratum. Cutaneous tuberculosis. Otherwise known as Bazin's disease.

Erythema infectiosum. "Slapped cheeks", caused by parvovirus B19.

Erythema chronicum migrans. An expanding annular lesion occurring in Lyme disease.

Erythema gyratum repens. Erythema forming repeated concentric rings. Often there is an underlying malignancy.

6

The germination of tetanus spores in a wound is inhibited by which of the following?
(Please select 1 option)
Antiseptic dressings
Normal oxygen levels
Injection of anti-toxin
Intravenous metronidazole
Therapeutic immunisation of toxoid

Normal oxygen levels

Germination occurs in damaged tissue where damage to the blood supply has reduced the supply of oxygen.

Early careful debridement of devitalised tissue and removal of foreign bodies is a useful preventative measure.

Antitoxin should be promptly administered in all cases of suspected tetanus. It is ineffective when the toxin is already fixed in the central nervous system.

Because spores of C. tetani are so widely distributed the only effective way to control tetanus is by prophylactic immunisation with tetanus toxoid.

7

Which of the following is true regarding subphrenic abscesses?
(Please select 1 option)
Are commonly associated with hiccups
Are commonly asymptomatic
Are associated with lung consolidations
Cause splenomegaly
Require laparotomy and thorough peritoneal lavage

Are commonly associated with hiccups

Subphrenic abscesses are associated with a swinging fever and marked toxaemia.

Hiccups are common and are usually distressing.

The liver is usually pushed down by the diaphragm and is therefore palpable. They are not associated with splenomegaly.

On chest x ray pleural effusions are commonly seen as well as air in the subphrenic space, and occasionally an air-fluid level.

Most subphrenic abscesses can be treated with ultrasound guided drainage and systemic antibiotics.

8

Which one of the following is true of radiological imaging in a septic patient?
(Please select 1 option)
A chest radiograph is of little use in suspected intra-abdominal sepsis
A CT should be performed as soon as the diagnosis of severe acute pancreatitis is made
An indium-111 labelled white cell scan has a good sensitivity for identification of occult abscesses
Diagnostic ERCP is the investigation of choice in suspected obstructive biliary disease
Ultrasound is the investigation of choice to diagnose appendicitis

An indium-111 labelled white cell scan has a good sensitivity for identification of occult abscesses

An indium-111 labelled white cell scan has a good sensitivity for identification of occult abscesses

9

Which of the following is true regarding C-reactive protein (CRP)?
(Please select 1 option)
Is functionally analogous to immunoglobulin G (IgG)
Is increased when a patient is taking non-steroidal anti-inflammatory drugs (NSAIDs)
Is produced primarily in the affected tissue
Shows a less intense increase than the erythrocyte sedimentation rate (ESR) in acute inflammation
Synthesis is initiated by the release of adrenocorticotropic hormone (ACTH)

Is functionally analogous to immunoglobulin G (IgG

CRP is an abnormal protein produced by the liver during an acute inflammatory response.

Antigen-immune complexes to infecting agents and trauma initiate the synthesis of CRP.

Although functionally analogous to IgG it is not antigen specific.

CRP is more sensitive and responds more rapidly than ESR.

NSAIDs reduce the CRP response.

10

Which of the following is true regarding deep surgical site infections?
(Please select 1 option)
Are not related to rough handling of the tissues
Are usually asymptomatic
Can result in life threatening sequelae
Occur within sixty days of surgery if no implant is present
Rarely occur at the time of surgery

Can result in life threatening sequelae

They occur within 30 days of operation without an implant or up to one year with an implant.

The infecting organism usually originates from the patient's own skin or from the theatre staff. They are usually associated with a fever (greater than 38°C) and pain.

Deep infections in a laparotomy wound can result in a spontaneous dehiscence.

Rough handling of the tissues results in tissue necrosis with subsequent infection.

11

In acute osteomyelitis, which of the following is correct?
(Please select 1 option)
Blood cultures are rarely positive
C-reactive protein changes slowly with the course of the disease
Joint aspiration should never be attempted
MR is the investigation of choice
Plain radiographs lag the clinical picture by 10 days

Plain radiographs lag the clinical picture by 10 days This is the correct answerThis is the correct answer
Blood cultures are positive in approximately 50% of patients.

CRP is the biochemical parameter of choice to monitor the condition.

Plain radiographs are usually normal in the early stages.

A three-phase bone scan is the investigation of choice.

The diagnosis is confirmed by culturing organisms from aspirated fluid or from operative samples.

12

In osteomyelitis which of the following statements is correct?
(Please select 1 option)
In the neonate it is commonly caused by anaerobes from the birth canal
Is frequently due to local blunt trauma
Is more common in the elderly
Is usually monofocal
Typically affects the epiphysis of the long bones

Is usually monofocal

In neonates the usual causative organisms are Streptococcus (group B), Staphylococcus aureus, and Gram positive bacteria.

Local blunt trauma causing subperiostal haematoma plays a small role, however, these haematomas then become infected by haematogenous spread (which is the commonest cause).

The most common age group affected is children aged 3 - 15 years.

It can also be multifocal, affecting multiple bones simultaneously.

The metaphyses of the long bones are most often affected due to the convoluted arrangement of end-arterioles trapping bacteria.

13

Which of the following is true regarding hepatitis C?
(Please select 1 option)
Can be prevented by vaccination
Carries a transmission risk of 30 - 40% following a needle stick injury
Has prevalence in the UK of

Has prevalence in the UK of

14

Which of the following is true regarding occupational infection with HIV?
(Please select 1 option)
Can occur rarely by percutaneous exposure
Is not related to the donor's stage of disease
Is possible through aerosolisation of infected material
Is related to the population prevalence
Occurs more commonly in surgeons than other health care workers

Is related to the population prevalence

HIV is not contagious and therefore transmission does not occur by casual or social contact.

Percutaneous exposure to HIV-infected blood is the main route of occupational transmission.

Most reported cases of occupational acquisition of HIV have come from countries where there is a high prevalence of infected patients. Nurses and laboratory staff account for 71% of the reported cases.

The higher the viral load in the patient, the greater the risk of transmission.

15

Which one of the following is the normal flora found in the particular anatomical site?
(Please select 1 option)
Female genital tract: lactobacilli
Nasopharynx: Propionibacteria
Skin: Haemophilus spp
Stomach: sterile
Urinary tract: Escherichia coli

Female genital tract: lactobacilli

The normal flora found are:

Female genital tract: Flora of the large bowel plus Lactobacilli, Staphylococcus epidermidis, Streptococci, diphtheroids.
Nasopharynx: Staphylococci, Streptococci (including Pneumococci), Haemophilus spp., anaerobes.
Skin: Staphylococci, Streptococci, Propionibacteria.
Stomach: The acid content reduces the bacterial load, however, organisms can persist, for example, Helicobacter pylori.
Urinary tract: Normally sterile.

16

Which one of the following is untrue regarding hydradenitis suppurativa?
(Please select 1 option)
Can result in sterile abscesses
Complete excision of the affected tissue down to the deep fascia can be curative
Due to an antigen-antibody reaction
Occurs more often in overweight women
Represents an infection of the paracrine sweat glands

Represents an infection of the paracrine sweat glands This is the correct answerThis is the correct answer
This is a condition of the apocrine sweat glands. It is thought that it is an antigen-antibody complex clump that blocks excretion from the gland. The condition affects the axillae and perineum most often in overweight women.

Abscesses are commonly sterile and when pathogens are present they may represent commensal organisms.

The surgery can often be extensive and debilitating.

17

Which of the following is correct of Fournier's gangrene?
(Please select 1 option)
Is diagnosed by acute cellulitis with crepitations
Is not related to urinary tract instrumentation
Rapidly involves the testes
Responds rapidly to aggressive systemic antibiotics if given early
The penis is spared

Is diagnosed by acute cellulitis with crepitations

Fournier's gangrene is a severe synergistic infection arising in the scrotum or perianal tissues and requires radical debridement of the subcutaneous tissues. Crepitations precede gangrene by 12 hours.

The testes are not involved due to their proximal blood supply and separation from the fascia by the tunica vaginalis.

The spreading gangrene rapidly involves the penis.

The condition usually occurs in older men who have recently undergone urological or perianal surgery.

18

Which of the following is true regarding perianal abscess?
(Please select 1 option)
Are more common in ulcerative colitis than in Crohn's disease
Are relatively common in children
Has an incidence of 5% in the diabetic population
Position is predicted by Goodsall's rule
With the presence of aerobic bacteria in the pus implies a fistula

Has an incidence of 5% in the diabetic population

Goodsall's rule predicts the position of the internal opening of a perianal fistula.

The presence of bowel flora is associated with a fistula, aerobic bacteria would imply that the sepsis was derived from the skin.

The incidence is less than 0.1% with boys less than 2 years being affected more often.

Crohn's patients present more often with perianal sepsis and that may be the presenting symptom. Therefore all patients presenting with a perianal abscess need to be screened for diabetes.

19

Which one of the following conditions requires operative management?
(Please select 1 option)
Cellulitis
Dyshidrosis
Erysipelas
Fournier's gangrene
Lymphangitis

Fournier's gangrene

Cellulitis, lymphangitis and erysipelas are non-localised infections and should be treated with immobilisation, elevation and antibiotics.

Dyshidrosis is a type of dermatitis presenting as small fluid filled or pus filled bumps on the hands and feet.

Fournier's gangrene is produced by mixed infections producing rapidly spreading subcutaneous and fascial necrosis. Treatment is by excision of the entire area of fascia and skin involved.

20

With which of the following are Pseudomonas infections associated?
(Please select 1 option)
Faeculent-like odour
Grape-like odour
Red exudates
Sloughy exudates
Urea-like odour

Grape-like odour

Pseudomonas spp. is an ubiquitous facultative anaerobe.

Proteus infections are associated with urea-like odours.

Bacteroides, Fusobacteria and Clostridia infections produce a faeculent odour.


21

Which one of the following pathogens is uncommonly isolated from intra-abdominal pus?
(Please select 1 option)
Actinomyces
Clostridia
Escherichia coli
Enterococci
Klebsiella spp.

Actinomyces

The commonest aerobic bacteria in descending order are

Escherichia coli
Enterococci
Proteus and
Klebsiella spp.
The commonest anaerobic bacteria in descending order are

Bacteroides
Clostridia and
Peptostreptococci.
Commonly found in breast abscesses are

Actinomyces and
Bacillus anaerobes.

22

In surgical infection, which of the following is true?
(Please select 1 option)
Antibiotics are only advised once a septic focus has been drained
Primary refers to a planned surgical trauma
There is rarely a focus
Tissue necrosis is rarely an association
Tissue necrosis results in inflammation

Tissue necrosis results in inflammation This is the correct answerThis is the correct answer
Primary surgical infections refer to surgical wounds which appear spontaneously, for example, a skin abscess.

Surgical wounds differ from non-surgical wounds in that they always have a source of infection which can be drained surgically.

Tissue necrosis results from trauma or through a pathophysiological process.

Inflammation leads to the events visible at the surface.

Once the source of infection has been drained antibiotics are usually unnecessary unless the surrounding tissues are infected.

23

To which of the following is failure of wound healing in a surgical wound not related?
(Please select 1 option)
Cicatrisation
Hypertrophic scarring
Incisional hernia
Superficial wound disruption
Wound dehiscence

Hypertrophic scarring

Superficial wound disruption usually results from a superficial wound infection.

Incisional hernias result when the deeper layers (usually the rectus) give way but the skin remains intact.

Hypertrophic scarring occurs in individuals predisposed to the condition.

Cicatrisation occurs when wounds have broken down or been left to close by secondary intention.

Wound dehiscence occurs when the deep layer and the skin break down.

24

Which of the following is correct regarding anastomotic leakage?
(Please select 1 option)
Detected by clinical means is roughly equal to radiologically detected leaks
In colorectal surgery results in a threefold increase in post-operative mortality
Is reduced by excessive tension in the ligatures
Is reduced if the anastomosis is formed below the peritoneal reflection
The investigation of choice to confirm the diagnosis is barium enema

In colorectal surgery results in a threefold increase in post-operative mortality

Most colorectal anastomotic leaks present late (after the patient has recommenced oral feeding).

Low anastomoses have a higher leak rate therefore most surgeons divert the faecal flow with a temporary proximal stoma. The clinical leak rate underestimates the true incidence of leakage.

Excessive tension leads to tissue necrosis and leakage of the anastomosis.

Barium is toxic in the peritoneal cavity therefore the investigation of choice is a gastrograffin enema.

25

Which of the following is true regarding a wound infection?
(Please select 1 option)
In a dirty wound requires intravenous antibiotics only
Producing pus should have the pus discarded as it is usually contaminated
Should be irrigated with chlorhexidine
Should be opened to allow adequate drainage
Should be treated empirically with intravenous antibiotics

Should be opened to allow adequate drainage

Use antibiotics only if specifically indicated, for example, cellulites or septicaemia.

Opening a wound distally will allow for adequate drainage of pus. Wounds should be irrigated with sterile water. Chlorhexidine is not licensed for this indication.

Pus culture identifies the infecting organism and antibiotic sensitivity.

Dirty wounds (faecal contamination) require formal surgical exploration to identify the source.

26

Which one of the following wound classifications is correct?
(Please select 1 option)
Emergency abdominal aortic aneurysm repair - contaminated
Emergency femoral hernia repair - clean
Girdlestone's procedure - clean
Hartmann's procedure performed for peritonitis - potentially contaminated
Open cholecystectomy for a mucocele of the gallbladder - potentially contaminated

Open cholecystectomy for a mucocele of the gallbladder - potentially contaminated This is the correct answerThis is the correct answer
While the femoral hernia repair is being performed as an emergency there is a high risk of strangulation and possible perforation; therefore this wound should be considered as potentially contaminated.

There is always a risk of bile/mucus spillage during the procedure.

Emergency and elective abdominal aortic aneurysm should be considered clean procedures.

Girdlestone's procedure (excision of the femoral head and arthrodesis) is usually performed for infection and should be considered to be potentially contaminated.

An emergency Hartmann's procedure is usually performed for a sigmoid colon perforation due to diverticular disease or cancer.

27

Which one of the following is not considered to be a risk factor for post-operative wound infection?
(Please select 1 option)
Chronic obstructive airways disease
Diabetes mellitus
Haematoma formation
Incorporation of a synthetic mesh
Rough handling of the tissues

Incorporation of a synthetic mesh

Poor haemostasis results in haematoma, which can readily become infected and cause a wound breakdown.

Diabetic patients are more likely to develop a wound infection due to impaired white cell function.

Incorporation of synthetic material does not increase the risk of wound infection but if they become infected they may form a chronically discharging wound.

Rough handling of tissue is more likely to result in tissue necrosis predisposing to wound infection. Tissue hypoxia increases the risk of poor wound healing and subsequent infection.

28

Which one of the following is untrue of skin preparation?
(Please select 1 option)
Application of alcoholic solutions chlorhexidine gluconate or povidone-iodine gives better disinfection
Alcohol pooled in the umbilicus must be removed
Chlorhexidine gluconate 4% w/v is a clear solution
Chorhexidine and cetrimide (Savlon) is advised when disinfecting the vagina and perineum
Povidone-iodine has a broader spectrum and persists longer than chorhexidine gluconate

Povidone-iodine has a broader spectrum and persists longer than chorhexidine gluconate This is the correct answerThis is the correct answer
Pure chlorhexidine is a clear solution which has a pink dye added to enable the surgeon to see which areas of the skin which have been painted.

Chlorhexidine is more rapidly active, broader spectrum and persists longer than povidone-iodine.

Alcoholic based solutions give better disinfection when rubbed on until the skin is dry. Alcohol may ignite if used in the presence of diathermy.

Cetrimide is used when a detergent effect is required.

29

Which of the following is true concerning high risk patients?
(Please select 1 option)
Are patients who are at high risk of being MRSA positive
Infected with hepatitis B virus can transmit the virus by splash contamination into the operator's conjunctiva
Requires the surgeon to double glove (wearing the inner glove a half-size larger than the surgeon's usual size)
Should be placed at the end of an operating list to avoid infecting any subsequent patients
Should have their skin cleaned at least four times with chlorhexidine

Infected with hepatitis B virus can transmit the virus by splash contamination into the operator's conjunctiva

Stating that a patient is high risk allows the surgeon to modify his technique to avoid sharp injuries.

High risk patients do not pose a risk of infection to subsequent patients on the operating list, placing them last is discriminatory.

The patient's skin is cleaned in the normal way.

Eye protection must always be worn when operating on a high risk patient.

Wearing two pairs of the surgeon's usual size gloves will constrict the blood flow to the fingers and reduce dexterity. Usually surgeons prefer to wear their larger glove on the inside.

30

Which one of the following is untrue of sterilisation?
(Please select 1 option)
Ethylene oxide should only be used when heat sterilisation of an item is not possible
Flash autoclaving at 147°C and 40 lb/square inch is the preferred method of sterilisation by steam
Hot air sterilisation is the preferred method to treat surgical instruments with fine cutting edges
Sterilisation by ethylene oxide has a broad-spectrum -cidal action against bacteria, spores and viruses
Unwrapped instruments may be sterilised in theatre using a portable steam steriliser

Flash autoclaving at 147°C and 40 lb/square inch is the preferred method of sterilisation by steam

Hot-air ovens have the benefit of not causing corrosion in non-stainless metals and not damaging fine cutting edges in delicate instruments.

Under optimal conditions of concentration, temperature and exposure time, ethylene oxide has a broad spectrum -cidal action. Ethylene oxide is toxic, irritant, mutagenic and carcinogenic, therefore its use requires extreme caution.

Flash autoclaving is no longer recommended or available for safety reasons; the preferred setting is 132°C (30 lb in-2) held for three minutes. This method is a convenient way to deal with dropped instruments.

31

What is the mechanism of resistance for penicillin resistant Streptococcus pneumoniae?
(Please select 1 option)
Alteration in cell wall permeability
Alteration of penicillin binding proteins (PBPs)
Alteration of the DNA dependent RNA transcriptase
Efflux
Production of the inactivating enzyme penicillinase

Alteration of penicillin binding proteins (PBPs)

Penicillin is a bactericidal antibiotic which acts by inhibiting cell wall synthesis.

Mutations in PBPs, enzymes required for cell wall synthesis, result in penicillin resistance.

32

What is the mechanism of resistance for rifampicin resistant Mycobacterium tuberculosis?
(Please select 1 option)
Alteration in cell wall permeability
Alteration of penicillin binding proteins (PBPs)
Alteration of the DNA dependent RNA transcriptase
Efflux mechanism
Production of the inactivating enzyme penicillinase

Alteration of the DNA dependent RNA transcriptase

Rifampicin is a bacteriostatic antibiotic which acts by inhibiting protein synthesis.

Mutations in rpoB gene cause alterations in the bacterial DNA dependent RNA transcriptase which prevents the binding of rifampicin.

33

What is the mechanism of action of gentamicin, when used synergistically with benzylpenicillin to treat an infective endocarditis caused by Streptococcus viridans?
(Please select 1 option)
Cell wall inhibition
Inhibition of folic acid metabolism
Inhibition of protein synthesis (transcription)
Inhibition of protein synthesis (translation)
Interference with DNA replication

Inhibition of protein synthesis (translation)

Gentamicin is synergistic to the action of benzylpenicillin.

Benzylpenicillin is bactericidal, inhibiting cell wall synthesis, enabling gentamicin to enter the bacterial cell.

It acts at the level of the ribosome, inhibiting protein synthesis.

34

What is the mechanism of action of glycopeptides (for example, vancomycin)?
(Please select 1 option)
Cell wall inhibition
Inhibition of folic acid metabolism
Inhibition of protein synthesis (transcription)
Inhibition of protein synthesis (translation)
Interference with DNA replication

Cell wall inhibition

Glycopeptides inhibit cell wall synthesis through steric hindrance of peptidoglycans, components of the bacterial cell wall.

35

What is the mechanism of action of trimethoprim?
(Please select 1 option)
Cell wall inhibition
Inhibition of folic acid metabolism
Inhibition of protein synthesis (transcription)
Inhibition of protein synthesis (translation)
Interference with DNA replication

Inhibition of folic acid metabolism

Trimethoprim interferes with the action of dihydrofolic reductase (DHFR), which is an enzyme that converts dihydrofolic to tetrahydrofolic acid, an essential stage in bacterial purine and, ultimately DNA synthesis.

36

What is the mechanism of action of ciprofloxacin?
(Please select 1 option)
Cell wall inhibition
Inhibition of folic acid metabolism
Inhibition of protein synthesis (transcription)
Inhibition of protein synthesis (translation)
Interference with DNA replication

Interference with DNA replication This is the correct answerThis is the correct answer
Ciprofloxacin interferes with DNA synthesis by disrupting the function of DNA gyrase.

37

A multiple drug resistant Escherichia coli was isolated from the urine of a patient with severe sepsis.
What is the likely mechanism of resistance?
(Please select 1 option)
Alteration of drug target
Drug efflux
Drug impermeability
Extended spectrum beta-lactamase (ESBL) production
Penicillinase production

Extended spectrum beta-lactamase (ESBL) production

Some Escherichia coli isolates produce an ESBL that inactivates second and third generation cephalosporins.

The class of drugs that will most reliably treat these infections are the carbapenems.

38

Gentamicin, 7 mg/kg once daily, is administered to an elderly patient with severe urosepsis.
Twenty-four hours post administration gentamicin levels are more than 2 mg/L.
Which of the following complications would you expect?
(Please select 1 option)
Hepatotoxicity IncorrectIncorrect answer selected
Nephrotoxicity This is the correct answerThis is the correct answer
Ototoxicity
Peripheral neuropathy
Retinopathy

Nephrotoxicity

Prolonged exposure to gentamicin is likely to cause nephrotoxicity, particularly in elderly patients with renal impairment. This is more likely to develop if gentamicin accumulates over a course of treatment, and is usually due to acute tubular necrosis. It is therefore important to dose gentamicin according to body weight, and monitor levels, the frequency of which depends on which dosing schedule is being used. In this situation the next dose of gentamicin should not be given if the gentamicin trough exceeds 2 mg/L.

Gentamicin is also a vestibulotoxin, which can result in permanent loss of equilibrioception. This usually develops if gentamicin is taken at high doses for prolonged periods, although there are case reports where this developed within three to five days. This side effect can be used for therapeutic benefit in severe Meniere's disease.

Hepatotoxicity, peripheral neuropathy and retinopathy are not classically associated with gentamicin.

39

A patient with multiple drug resistant (MDR) TB is receiving prolonged treatment with moxifloxacin.
Which side effect is likely to occur as a result of prolonged administration?
(Please select 1 option)
Achilles tendinitis
Hepatotoxicity
Nephrotoxicity
Peripheral neuropathy
Retinopathy

Achilles tendinitis

This is an idiosyncratic reaction associated with prolonged use of quinolones.

The risk of tendon abnormalities with fluoroquinolone use is 0.1-0.4% overall, however the risk is thought to increase with prolonged use. The rate of tendon rupture is 1.9 times the general population risk.

Hepatotoxicity is less often associated. Nephrotoxicity is usually only seen in overdose.

Only one study has shown an association with peripheral neuropathy.

Chloroquine, but not moxifloxacin, is associated with retinopathy

40

A patient with TB is receiving the following drugs as induction phase during treatment:
Ethambutol
Isoniazid
Pyrazinamide
Pyridoxine
Rifampicin.
Which drug is most likely to cause peripheral neuropathy?
(Please select 1 option)
Ethambutol
Isoniazid
Pyrazinamide
Pyridoxine
Rifampicin

Isoniazid

Supplementation with pyridoxine, vitamin B6, reduces the risk.