Answers

The Arthus reaction is a localised antigen-antibody reaction at the site of introduction of antigen in individuals with high circulating levels of the corresponding antibody, e.g. local reaction to tetanus toxoid in individuals who are already immune; farmer's lung

65. A - F B - F Tuberculin skin tests measure cell mediated hypersensitivity C - F D - T Detects circulating penicillin-specific IgE E - F All these tests except B and D are in vitro tests for quantifying antibodies

66. A - F Pathogenic amoebae mainly affect the colon (Entamoeba histolytica) B - F Most species are non-pathogenic, e.g. Entamoeba coli, Entamoeba nana C - T Usually as a result of ruptured amoebic liver abscess D - T E - T

67. A - T B - T C - T D - T E - F

68. A - F B - F C - T The hepatitis D agent (delta agent) can replicate only in the

presence of the hepatitis B virus D - F E - F

69. A - T B - T C - T D - F Hepatocellular carcinoma is associated with hepatitis B E - F Transmitted parenterally or by sexual contact

70. A - F Incubation period ranges from 15 to 45 days B - F Transmission is faeco-oral C - F Recovery is usually complete D - T E - T Formalin-killed vaccine available

71. A - T B - T C - T D - F E - F

72. A - T By direct immunofluorescence B - T By electron microscopy or SDS-PAGE C - T By direct immunofluorescence D - F Cell culture or animal inoculation is required E - T By the presence of characteristic inclusion bodies

73. A - T B - F This belongs to the papovaviridae C - F This belongs to the rhabdoviridae D - T E - T

74. A - T Most cases recover without specific antimicrobial treatment, but

treatment with pyrimethamine is required if there is retinitis or myocarditis

B - T Cats are the primary source of oocysts but many domestic and wild animals can be sources of tissue cysts infective to man

C - F Transmission is by ingestion of tissue cysts or oocysts D - T E - T

75. A - T B - F Inoculation through abraded skin or mucous membranes C - T D - T E - T

76. A - T Rodent reservoir B - F Caused by Coxiella burneti - not a virus C - F D - T Caused by accidental inoculation of a sheep poxvirus E - T Rodent reservoir

77. A - F Antiviral agent sometimes useful in treating respiratory syncytial

virus infection B - F Antiviral agent useful in treating influenza A infection C - T Useful for treating fungal nail infections D - T Oral or parenterally available agent particularly useful for treat­

ment of infections with yeasts such as Candida albicans or Crypto­ coccus spp

E - T Broad-spectrum antifungal agent

78. A - F B - T C - T Cause vesicular pharyngeal lesions called herpangina D - F Cause wart-like lesions E - F

79. A - F These often predispose to Candida infection B - T C - F D - F E - T

80. A - T B - T C - F Gram-positive bacilli D - F As above E - T Gram-negative curved bacilli

81. A - F B - T C - F D - F These are Gram-negative cocci E - F

82. A - T Though more commonly due to type 2 B - F Recurrent infections are not uncommon C - F Is often asymptomatic D - T But treatment must be started early E - F

83. A - F B - T Associated with meat-based foods C - T But very uncommon D - F E - T Associated with cooked rice

84. A - F Detects specific DNA or RNA sequences, not proteins B - F Antimicrobial susceptibility tests require growth of viable whole

organisms. However, certain mutant DNA sequences which confer specific antibiotic resistance may be detected by PCR (e.g. rifampicin resistance in Mycobacterium tuberculosis)

C - T D - T However, RNA is far less stable than DNA and stored tissues are

not suitable for PCR tests based on RNA amplification E - F Is now used increasingly in diagnostic microbiology

85. A - F The Schick test may be used for detecting immunity, but is not of

diagnostic value in suspected cases B - F Diagnosis is made by serology C - T Mantoux, Heaf or Tine tests D - F Diagnosis is based on blood culture or stool culture E - T But this test is of low sensitivity and specificity and is no longer

used. More sensitive and specific serological tests are now available

86. A - T In verotoxin-producing strains, e.g. Escherichia coli 0157 B - T Disease is due to exotoxin released by the bacterium in the con­

taminated food C - F D - T Diphtheria toxin causes local tissue necrosis as well as systemic

toxicity including myocardiotoxicity E - T

87. A - F Usually associated with lung infections and disseminated

infections in immunocompromised patients B - F As in A C - T D - F Usually associated with meningitis and disseminated infections in

immunocompromised patients E - T

88. A - T B - T C - F D - F E - T

89. A - T By ingestion of faecally-contaminated water B - T By swimming in water infested with infected snails C - T As in A, but the source of contamination is often cattle D - T By contact with water fouled by infected animals E - F

90. A - F Caused by Clostridium difficile B - T Mucosal damage is caused by a cytotoxin secreted by the

organism C - F The disease is very rare in children even though the organism may

be often present in the gut D - T E - F Vancomycin or metronidazole is given orally in severe cases

91. A - T B - T C - F D - F E - T

92. A - T B - F Viral infections do not usually elicit a CRP response; bacterial

infections often do C - T Secreted by hepatocytes D - T It is a useful objective parameter for monitoring progress E - F Does not involve the complement system

93. A - F Once every 5 years is adequate B - F Made from capsular polysaccharide antigen of several serotypes C - F Given intramuscularly D - T E - F Often effective in the elderly

94. A - T B - F C - F D - F E - T

95. A - T Enables the organism to adhere to the site of infection B - T C - T Are by far the most important pathogens infecting prosthetic heart

valves, joint replacements, indwelling vascular catheters, etc D - F Coagulase production is a property of coagulase-positive staphylo­

cocci (Staphylococcus aureus) E - T

96. A - T The mucoid forms are particularly difficult to treat. Other

pathogens involved in cystic fibrosis include Staphylococcus aureus, Haemophilus influenzae and Pseudomonas cepacia

B - T C - T D - F Pseudomonas septicaemias are more likely to occur in granulo-

cytopaenic patients E - F Third-generation cephalosporins and other ß-lactam antibiotics

such as piperacillin, azlocillin, etc are active against most strains of Pseudomonas aeruginosa

97. A - F Erythromycin is the preferred antibiotic B - F There is no asymptomatic carrier state in pertussis C - F Pernasal swabs are preferred D - F Immunity declines rapidly over the course of a few years E - F Infection in early infancy is not uncommon

98. A - T Particularly in the elderly B - F These do not produce partial (green) haemolysis C - T D - F Is generally much less susceptible than other streptococci E - F

99. A - F Protective levels of antibody persist for at least 5 years after

successful immunisation. B - T Live vaccines in general should be avoided in all patients with

severe T-cell deficiency C - T D - F Universal immunisation including boys is necessary to achieve

eradication. This is current policy in the UK using the MMR (mumps, measles and rubella) vaccine

E - T

100. A - T The commonest cause B - T An uncommon but important cause C - F D - T Another common cause E - F Chlamydia trachomatis is a rare cause of hospital acquired

pneumonia in neonates. However, Chlamydia pneumoniae, a newly recognised organism, is increasingly recognised as a cause of community-acquired pneumonia

101. A - T The tissue necrosis at the site of infection and the cardiotoxic

effects are mediated by the diphtheria toxin B - F Infection may occasionally present as necrotic ulcers at other sites C - T D - F There is no invasion of deep tissue by the pathogen, Coryne-

bacterium diphtheriae. Clinical disease is due to the effects of the exotoxin

E - F Though rare, toxigenic strains of Corynebacterium diphtheriae are still occasionally isolated in the UK. Clinical cases of diphtheria, however, have only been due to imported infections in recent years, particularly from countries of the former Soviet Union

102. A - F This is not a live vaccine B - F The risks of delaying the treatment are much higher than the

teratogenic risks of the chemotherapy C - F D - T Dental discolouration in baby; maternal hepatotoxicity. E - F All live vaccines should be avoided in pregnancy

103. A - T B - T But the mainstay of laboratory diagnosis is virus isolation from

throat swab or stool sample C - T But the faeco-oral route is by far the most important D - T E - F It is used in situations where live vaccines are contraindicated, e.g.