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Question 1
Correct
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Streptococcus pyogenes is commonly implicated in all of the following infective diseases EXCEPT for:
Your Answer: Gas gangrene
Explanation:Gas gangrene is a life-threatening infection caused by toxin-producing Clostridium species, primarily Clostridium perfringens, and characterised by rapidly progressive muscle necrosis, gas production and sepsis.
Gas gangrene is not a notifiable disease. -
This question is part of the following fields:
- Microbiology
- Pathogens
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Question 2
Correct
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A patient presents with a fever, headache and neck stiffness. A CSF sample of someone with meningococcal meningitis typically shows:
Your Answer: All of the above
Explanation:CSF analysis typically shows:
cloudy turbid appearance
raised WCC – predominantly neutrophils
high protein
low glucose (typically < 40% of serum glucose)
Gram-negative diplococci seen under microscopy -
This question is part of the following fields:
- Microbiology
- Pathogens
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Question 3
Correct
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What is the primary route of transmission of Neisseria Gonorrhoeae?
Your Answer: Sexually transmitted
Explanation:Neisseria gonorrhoeae is primarily spread by sexual contact or through transmission during childbirth. It causes gonorrhoea which is a purulent infection of the mucous membrane surfaces.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 4
Correct
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Regarding Clostridium tetani, which of the following statements is CORRECT:
Your Answer: Infection is predominantly derived from animal faeces and soil.
Explanation:Clostridium tetaniis a Gram positive, rod shaped, obligate anaerobic bacterium.
The incubation period is quoted as anywhere between 4-21 days and can occur after several months but symptoms usually occur within the first 7 days after exposure.
Approximately 80% of patients develop generalised tetanus. The commonest presenting feature of generalised tetanus is trismus (lockjaw), occurring in approximately 75% of affected individuals. Other clinical features include:
Facial spasms (risus sardonicus)
Opisthotonus (characteristic body shape during spasms)
Neck stiffness
Dysphagia
Calf and pectoral muscle rigidity
Fever
Hypertension
Tachycardia
Spasms can occur frequently and last for several minutes, they can continue to occur for up to 4 weeks. Current mortality rates are between 10 and 15%.
Tetanic spasms are caused by the exotoxin tetanospasmin. The effects of tetanolysin are not fully understood but it is not believed to have clinical significance.
Localised tetanus is a rare form of the disease, occurring in around 1% of affected individuals. Patients have persistent contraction of muscles in the same anatomic area as the injury. It may precede generalised tetanus. -
This question is part of the following fields:
- Microbiology
- Pathogens
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Question 5
Correct
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You suspected a fungal nail infection in a 50-year-old man who presented with an itchy, scaly rash between his toes and a thicker, discoloured nail on his big toe that has been there for almost one month already. Which of the following tests is most likely to confirm your suspected diagnosis?
Your Answer: Nail clippings for microscopy and culture
Explanation:Nail clippings for microscopy and culture are a diagnostic test for fungal infection. Because some fungi are restricted to the lower parts of the nail, clippings should be taken from the discoloured or brittle parts and cut back as far as possible from the free edge.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 6
Incorrect
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Regarding Clostridium species, which of the following statements is INCORRECT:
Your Answer: They are spore-forming.
Correct Answer: They are facultative anaerobes.
Explanation:Clostridium spp. are obligatory anaerobic spore-forming Gram-positive bacilli. Toxin production is the main pathogenicity mechanism.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 7
Correct
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When a child has chickenpox, how long should he or she be off from school?
Your Answer: Until all vesicles have crusted over
Explanation:To avoid the spread of infection, infected patients should be isolated. All lesions should be crusted over before children return to nursery or school, even if the standard exclusion time is 5 days.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 8
Incorrect
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Regarding Clostridium difficile, which of the following statements is CORRECT:
Your Answer: It has endotoxin-mediated effects causing profuse watery diarrhoea.
Correct Answer: It is normally found in gut flora.
Explanation:C. difficile is normally found in the gut flora but its growth is normally suppressed by more dominant anaerobes. It has exotoxin-mediated effects causing profuse diarrhoea. Oral clindamycin (a broad spectrum antibiotic) is commonly implicated in precipitating C. difficile colitis; first line treatment is with oral metronidazole. Tetanolysin is a toxin produced by Clostridium tetani bacteria.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 9
Correct
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Regarding dermatophytes, which of the following statement is CORRECT:
Your Answer: Diagnosis is made from microscopy and culture of skin scrapings, hair samples or nail clippings.
Explanation:Diagnosis is made from microscopy and culture of skin scrapings, hair samples or nail clippings depending on the site of infection. The lesions of ringworm typically have a dark outer ring with a pale centre. Tinea capitis is ringworm affecting the head and scalp. Spread is via direct skin contact. Treatment is usually topical, oral antifungals are reserved for refractory infection.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 10
Correct
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Which of the following statements concerning hepatitis D is TRUE:
Your Answer: It can only be transmitted with, or to somebody who is infected with, Hepatitis B.
Explanation:Hepatitis D virus (HDV) is an RNA virus that was discovered in 1977 and is structurally unrelated to the hepatitis A (HAV), hepatitis B (HBV), and hepatitis C (HCV) viruses. HDV causes a unique infection that requires the assistance of HBV viral particles to replicate and infect hepatocytes. Its clinical course is varied and ranges from acute, self-limited infection to acute, fulminant liver failure. Chronic liver infection can lead to end-stage liver disease and associated complications (including accelerated fibrosis, liver decompensation, and hepatocellular carcinoma).
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 11
Correct
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How is measles primarily transmitted:
Your Answer: Respiratory droplet route
Explanation:Measles belongs to the paramyxoviridae group of viruses. The incubation period is 7-18 days (average 10) and it is spread by airborne or droplet transmission. The classical presentation is of a high fever with coryzal symptoms and photophobia with conjunctivitis often being present. The rash that is associated is a widespread erythematous maculopapular rash. Koplik spots are pathognomonic for measles, and are the presence of white lesions on the buccal mucosa.
Differential diagnoses would include:
Rubella
Roseola infantum (exanthem subitom)
Scarlet fever
Kawasaki disease
Erythema infectiosum (5thdisease)
Enterovirus
Infectious mononucleosis
Diagnosis can be confirmed by the following means:
Salivary swab for measles specific IgM
Serum sample for measles specific IgM
Salivary swab for RNA detection
Possible complications include:
Otitis media
Febrile convulsions
Pneumonia
Bronchiectasis
Diarrhoea
Meningitis
Encephalitis
Immunosuppression
Subacute sclerosing panencephalitis
Death -
This question is part of the following fields:
- Microbiology
- Pathogens
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Question 12
Correct
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Regarding hepatitis C, which of the following statements is INCORRECT:
Your Answer: Anti-HCV IgG antibodies are diagnostic of acute infection.
Explanation:Anti-HCV IgG antibodies indicate exposure to hepatitis C but this could be acute, chronic or resolved infection. If the antibody test is positive, HCV RNA should be tested for, which if positive indicates that a person has current infection with active hepatitis C.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 13
Incorrect
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Diagnosis of HIV is predominantly made through which of the following:
Your Answer: Viral PCR
Correct Answer: Antibody detection
Explanation:Diagnosis of HIV is predominantly made through detection of HIV antibody and p24 antigen. Viral load (viral PCR) and CD4 count are used to monitor progression of disease.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 14
Correct
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An outbreak of acute pneumonia occurs in military recruits living in one barrack and only in those persons located near the air conditioner. Epidemiologic surveillance results in isolation of the causal organism from the patients and from the drip pans of the air conditioner. The organism is weakly Gram-negative. The most likely organism is:
Your Answer: Legionella pneumophila
Explanation:Legionella pneumophilais a Gram negative bacterium that is found in natural water supplies and in the soil, transmitted predominantly via inhalation of aerosols generated from contaminated water (direct person-to-person spread of infected patients does not occur). It is the cause of Legionnaires’ disease. Outbreaks of Legionnaires’ disease have been linked to poorly maintained air conditioning systems, whirlpool spas and hot tubs.
The clinical features of the pneumonic form of Legionnaires’ disease include:
Mild flu-like prodrome for 1-3 days
Cough (usually non-productive and occurs in approximately 90%)
Pleuritic chest pain
Haemoptysis
Headache
Nausea, vomiting and diarrhoea
Anorexia
Legionella pneumophilainfections can be successfully treated with macrolide antibiotics, such as erythromycin, or quinolones, such as ciprofloxacin. Tetracyclines, such as doxycycline, can also be used.
The syndrome of inappropriate antidiuretic hormone secretion (SIADH) can occur with Legionnaires’ disease and will result in hyponatraemia as is seen in this case.
Legionella pneumophilainfections are resistant to amoxicillin but can be successfully treated with macrolide antibiotics, such as erythromycin, or quinolones, such as ciprofloxacin. Tetracyclines, such as doxycycline, can also be used. The majority of cases of Legionnaires’ disease are caused by Legionella pneumophila, however many other species of Legionella have been identified.
Legionella longbeachae is another less commonly encountered species that has also been implicated in outbreaks. It is predominantly found in soil and potting compost, and has caused outbreaks of Pontiac fever, the non-respiratory and less severe variant of Legionnaires’ disease. -
This question is part of the following fields:
- Microbiology
- Pathogens
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Question 15
Incorrect
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Regarding Clostridium tetani, which of the following statements is CORRECT:
Your Answer: Tetanolysin is predominantly responsible for its neurotoxic effects.
Correct Answer: Germination and outgrowth of clostridial spores depends on anaerobic conditions.
Explanation:Clostridium tetani is found in normal human intestinal flora, although infection is predominantly exogenous. Tetanospasmin, an exotoxin produced by C. tetani is responsible for the neurotoxic effects of tetanus, largely by preventing the release of the inhibitory neurotransmitter GABA, resulting in prolonged excitation. Clostridium tetani is an obligate anaerobe, with an incubation period of about 3 – 21 days (average 10 days).
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 16
Incorrect
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Regarding the varicella zoster virus, which of the following statements is CORRECT:
Your Answer: The varicella zoster vaccine is part of routine childhood immunisation.
Correct Answer: Contracting chickenpox infection while pregnant is associated with a higher risk of developing varicella pneumonitis.
Explanation:Chickenpox infection in neonates, adults/adolescents and pregnant women is associated with more severe disease. Varicella zoster pneumonitis typically occurs in pregnant women or immunocompromised individuals and is associated with a high mortality. A live attenuated-virus vaccine is available and recommended for non-immune healthcare workers but is not part of the routine childhood immunisation schedule. Antiviral treatment is not typically recommended in childhood chickenpox but is indicated for shingles.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 17
Correct
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Infection with Campylobacter jejuni is one of the most common risk factors for which of the following conditions?
Your Answer: Guillain-Barre syndrome
Explanation:One of the most common risk factors for GBS is infection with Campylobacter jejuni, which causes diarrhoea.
Guillain-Barré syndrome (GBS) is a rare autoimmune disorder in which the body’s immune system attacks the nerves, resulting in muscle weakness and paralysis.
Infection with Streptococcus pyogenes can cause acute glomerulonephritis and rheumatic fever.
Haemolytic uraemic syndrome is commonly linked to E. coli infection.
Following measles infection, subacute sclerosing panencephalitis develops.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 18
Incorrect
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Which patients are particularly susceptible to infection with herpes simplex, those with:
Your Answer: Neutropaenia
Correct Answer: T-cell deficiency
Explanation:Cell-mediated immunity, especially the action of cytotoxic T-cells, is essential in the control of herpesvirus infections and patients with T-cell deficiency are at particular risk of reactivation and severe infection. T-cell deficiency may follow HIV infection, chemotherapy, corticosteroid therapy or organ transplantation.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 19
Incorrect
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The percentage of patients with hepatitis B that develop chronic infection is about:
Your Answer: 30%
Correct Answer: 10%
Explanation:With hepatitis B, about 90% of people will develop lifelong immunity after clearing the infection. Chronic hepatitis develops in about 10% of patients and this may be complicated by cirrhosis or hepatocellular carcinoma. There is a very high risk of chronic infection and hepatocellular carcinoma when there is congenital infection. The risk of this in healthy adults is only about 5%.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 20
Correct
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Regarding Escherichia coli, which of the following statements is INCORRECT:
Your Answer: It is a predominant member of the normal flora of the skin.
Explanation:Escherichia coli is a Gram-negative bacilli that is an important member of the intestinal flora. It is the most common cause of UTI in adults (about 70 – 95% of cases), followed by Staphylococcus saprophyticus (about 5 – 10% of cases), and an important cause of neonatal meningitis. E. coli O157 strain is implicated in the development of dysentery associated with haemolytic uraemic syndrome characterised by haemolytic anaemia, thrombocytopenia and acute renal failure.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 21
Correct
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A 18 year old university student develops facial swelling and dark frothy urine. Urine dipstick demonstrates haematuria and proteinuria. Approximately 3 weeks ago, he was treated with oral antibiotics for a sore throat. His condition is most likely to be secondary to infection with:
Your Answer: Streptococcus pyogenes
Explanation:Post-streptococcal glomerulonephritis is a postinfectious immune-mediated reaction secondary to infection with Streptococcus pyogenes. It typically occurs 2 weeks or more after acute/initial infection, and presents with haematuria, reduced urine output, peripheral oedema, proteinuria, and hypertension. Permanent kidney damage is rare.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 22
Correct
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Streptococcus pneumoniae is commonly implicated in all of the following infectious diseases EXCEPT for:
Your Answer: Impetigo
Explanation:Impetigo is a highly contagious infection of the superficial epidermis that most commonly affects young children but can occur in any age group. In children it is the most common bacterial skin infection and it is the third most common skin disease overall, behind dermatitis and viral warts.
The commonest causative organism is Staphylococcus aureus. Streptococcus pyogenesis the second commonest and causes fewer cases, either alone or in combination withS. aureus.The streptococcal form tends to be commoner in warmer, more humid climates. (Hirschmann JV. Impetigo: etiology and therapy. Curr Clin Top Infect Dis. 2002;22:42–51.)
Impetigo is most commonly spread by direct person-to-person contact, and can spread rapidly through families and school classes. It can also, less commonly, be spread by indirect contact.
There are two main forms of impetigo:
Non-bullous impetigo – lesions usually start as tiny pustules or vesicles that evolve rapidly into honey-crusted plaques that tend to be under 2 cm in diameter. These can be itchy but are rarely painful.
Bullous impetigo – lesions have a thin roof and tend to rupture spontaneously. This type is more likely to be painful and may be associated with systemic upset. -
This question is part of the following fields:
- Microbiology
- Pathogens
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Question 23
Incorrect
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Regarding Campylobacter gastroenteritis, which of the following statements is INCORRECT:
Your Answer: Bloody diarrhoea is a typical feature.
Correct Answer: Infection usually requires antibiotic treatment.
Explanation:Campylobacter jejuni is the primary human pathogen, typically causing dysentery (bloody diarrhoea illness) following ingestion of contaminated meat, especially poultry. Infection is typically self-limiting and does not require antibiotic therapy. Campylobacter gastroenteritis is associated with the immune-mediated complications of Guillain-Barre syndrome, reactive arthritis and Reiter’s syndrome.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 24
Correct
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Herpes simplex virus is transmitted most commonly through which of the following routes:
Your Answer: Direct contact spread
Explanation:Herpes simplex virus is the most common cause of infective encephalitis and has a predilection for the temporal lobes. Herpes simplex is transmitted through direct contact. It invades skin locally producing skin vesicles by its cytolytic activity.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 25
Correct
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When a child has mumps, how long should he or she be off from school?
Your Answer: 5 days from onset of swelling
Explanation:To avoid the spread of infection, infected patients should be isolated. Patients should avoid going to school, childcare, or job for five days after the swelling has occurred.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 26
Correct
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Regarding threadworms, which of the following statements is CORRECT:
Your Answer: First line treatment of threadworms is with mebendazole.
Explanation:First line treatment of threadworms is with mebendazole, with treatment of the whole family, and a repeat treatment after 2 weeks. Threadworms live in the large bowel, but direct multiplication of worms does not occur here. Threadworms most commonly infect children, and may be symptomatic or cause pruritus ani.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 27
Incorrect
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Which of the following could denote a diagnosis of acquired immunodeficiency syndrome (AIDS) in a patient infected with HIV:
Your Answer: Oral candidiasis
Correct Answer: CD4 count < 200 cells/uL
Explanation:A diagnosis of AIDS can be made in a patient infected with HIV if the patient has a CD4 count < 200 cells/uL, or an AIDS-defining illness. Antiretroviral treatment should be considered in patients with CD4 counts < 350 cells/uL.
Oral candidiasis is not an AIDS defining illness – candidiasis of the bronchi, trachea, lungs or of the oesophagus is an AIDS defining illness.
A positive p24 antigen test seen in early HIV infection and does not indicate the development of AIDS.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 28
Correct
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An elderly man with chronic heart and lung disease develops Legionnaires' Disease. By what route was the infection most likely to have been acquired:
Your Answer: Inhalation of aerosolised contaminated water
Explanation:Legionella pneumophilais a Gram negative bacterium that is found in natural water supplies and in the soil, transmitted predominantly via inhalation of aerosols generated from contaminated water (direct person-to-person spread of infected patients does not occur). It is the cause of Legionnaires’ disease. Outbreaks of Legionnaires’ disease have been linked to poorly maintained air conditioning systems, whirlpool spas and hot tubs.
The clinical features of the pneumonic form of Legionnaires’ disease include:
Mild flu-like prodrome for 1-3 days
Cough (usually non-productive and occurs in approximately 90%)
Pleuritic chest pain
Haemoptysis
Headache
Nausea, vomiting and diarrhoea
Anorexia
Legionella pneumophilainfections can be successfully treated with macrolide antibiotics, such as erythromycin, or quinolones, such as ciprofloxacin. Tetracyclines, such as doxycycline, can also be used.
The syndrome of inappropriate antidiuretic hormone secretion (SIADH) can occur with Legionnaires’ disease and will result in hyponatraemia as is seen in this case.
Legionella pneumophilainfections are resistant to amoxicillin but can be successfully treated with macrolide antibiotics, such as erythromycin, or quinolones, such as ciprofloxacin. Tetracyclines, such as doxycycline, can also be used. The majority of cases of Legionnaires’ disease are caused by Legionella pneumophila, however many other species of Legionella have been identified.
Legionella longbeachae is another less commonly encountered species that has also been implicated in outbreaks. It is predominantly found in soil and potting compost, and has caused outbreaks of Pontiac fever, the non-respiratory and less severe variant of Legionnaires’ disease. -
This question is part of the following fields:
- Microbiology
- Pathogens
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Question 29
Correct
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About what percentage of patients with hepatitis A develop chronic infection:
Your Answer: None
Explanation:Chronic hepatitis and carrier state does not occur in hepatitis A infection and complete immunity is attained after infection.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 30
Incorrect
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Which of the following statements regarding hookworm is FALSE:
Your Answer: Hookworm larvae mature into adult worms in the small intestine.
Correct Answer: Transmission of hookworm is via ingestion of contaminated food and water.
Explanation:The hookworm life cycle begins with the passage of eggs from an adult host into the stool. Hookworm eggs hatch in the soil to release larvae that mature into infective larvae. Infection is usually transmitted by larval penetration into human skin (duodenal infection may also be transmitted by the oral route). From the skin, larvae migrate into the blood vessels and are carried to the lungs, where they penetrate the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed.
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This question is part of the following fields:
- Microbiology
- Pathogens
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SESSION STATS - PERFORMANCE PER SPECIALTY
