Infections

Question 1

Candidiasis

Answer 1

Candidal infection varies from a benign local mucosal membrane infection to disseminated disease; it can involve any organ.
C: Candida spp. are yeast-like fungi. They may be part of the normal body flora, or may become an invasive pathogen.
Risk factors - Broad-spectrum antibiotics, central venous catheters, DM, immunocompromised, protheses, ICU, GI surgery, radiotherapy.
S: Oral - white patches on the inner cheeks, tongue, roof of the mouth, and throat, redness/soreness, pain, loss of taste.
Vaginal - itching, soreness, discharge, coital pain.
Invasive - fever and chills, spread to heart, brain, eyes, bones, or joints.
D: Clinical diagnosis. Swabs.
T: Oral - miconazole oral gel first-line for 7 days (or nystatin suspension). If severe, oral fluconazole 50 mg a day for 7 days.
Vaginal - intravaginal antifungal cream or pessary (clotrimazole, econazole, miconazole, or fenticonazole) or an oral antifungal (fluconazole or itraconazole). If there are vulval symptoms, consider prescribing a topical Clotrimazole or Ketoconazole.

Question 2

E.coli

Answer 2

E. coli strains are common in the human intestine, most are harmless but some produce toxins which cause severe disease.
C: E.coli VTEC O157 can be spread through contaminated food, contact with farm animals, person-to-person, infected water.
S: Asymptomatic, abdominal cramps, bloody diarrhoea, painful defecation.
Hemolytic Uremic Syndrome - AKI, haemolytic anaemia and thrombocytopenia.
Thrombotic thrombocytopenic purpura - with neuro involvement.
D: Stool sample, FBC, U&Es, electrolytes.
T: Early fluid resuscitation. Monitor for features of HUS. Avoid antidiarrheal drugs and opioid analgesics. Good personal hygiene in infected households
Stay at home until 48 hours have elapsed after passing their first normal stool.

Question 3

Salmonella

Answer 3

Most common forms of food poisoning worldwide.
C: Their pathogenicity is conferred due to the ability to invade intestinal mucosa and produce toxins.
Risks - contaminated food, eggs from abroad, inadequate thawing, faeco-oral route, acid-suppressing drugs, IBS, immunosuppression, poor sanitation.
S: Diarrhoea (may be bloody), vomiting, nausea, fever, dehydration may occur.
D: Stool culure, PCR testing
T: Oral/IV rehydration, Racecadotril is an intestinal antisecretory enkephalinase inhibitor, meticulous washing, Loperamide (antimotility agent) may be used in special circumstances.
Exclusion for 48 hours after last episode of D&V.

Question 4

Shigellosis

Answer 4

Aerobic Gram-negative bacilli that are highly contagious. Cause intestinal inflammation and symptoms of gastroenteritis with dysentery.
C: Drinking water contaminated with human faeces, or eating food washed with contaminated water.
Risk factors - children, elderly, poor sanitation, anal sex, swimming in infected water.
S: Acute watery diarrhoea which may be accompanied by mucus, pus or blood, abdo pain, tenesmus, fever, malaise, increased bowel sounds, dehydration.
D: Stool sample, FBC, U&Es.
T: Oral rehydration, antipyretic medication, return to work/school 48 hours after last episode of D&V.

Question 5

Threadworms

Answer 5

Common nematode infection.
C: Infection with Enterobius vermicularis - female lays eggs in anus/vulva/vagina, area is scratched and can re-infect if gets back into mouth.
S: Pruritus ani or pruritus vulvae, especially at night, loss of sleep, vaginal discharge, worms may be seen at night-time.
D: PR exam, adhesive tape test for eggs - microscopy.
T: Hygiene - Tight underwear at night, change and wash underwear, fingernails short and clean, rinse toothbrush.
Mebendazole is the drug of choice in adults and in children older than 2 years. It is given as a single oral dose, and is best repeated after two to three weeks in case re-infection has occurred.

Question 6

Hookworms

Answer 6

Parasitic nematode worm that lives in the small intestine of its host.
C: Either Ancylostoma duodenale and Necator americanus. Passed through stool or soil.
On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs, and are then swallowed.
S: Asymptomatic, nausea, abdominal pain and intermittent diarrhoea, iron-deficiency anaemia, ground itch in skin, respiratory symptoms, swelling of skin.
D: Stool sample, FBC, CXR.
T: Local cryotherapy when it is still in the skin.
Albendazole or mebendazole are effective both in the intestinal stage and during the stage the parasite is still migrating under the skin.
Iron supplements.
Surgical removal in severe cases.

Question 7

Epstein-Barr Virus

Answer 7

Virus targets circulating B lymphocytes (lifelong latent infection) and squamous epithelial cells of the oropharynx.
C: EBV spreads most commonly through bodily fluids, especially saliva. However, EBV can also spread through blood and semen during sexual contact, blood transfusions, and organ transplantations.
S: Infectious mononucleosis (glandular fever) in 50% of primary infection in adults.
Fever, sore throat, anorexia, lymphadenopathy, palatal petechiae, jaundice, malaise, splenomegaly, hepatomegaly.
D: Blood film, antibody tests, serology, reverse transcriptase viral PCR.
T: Supportive - analgesia, hygiene, rest. To limit spread of the disease by avoiding kissing and sharing eating or drinking utensils, and to thoroughly clean all items that may have been contaminated by saliva.
Admission if dehydrated, struggling to breathe, stridor.

Question 8

Herpes simplex

Answer 8

Includes HSV1 and HSV2.
Present on lip border, genitals, eyes, throat, skin, phalanx, brain.
C: Viruses multiply in epithelial cells of mucosal surface producing vesicles or ulcers.
Lifelong latent infection when virus enters sensory neurons at infection site. Can then reactivate, replicate and infect surrounding tissue.
S: Subclinical or sensory nerve prodrome (tingling) then vesicles and then shallow ulcers, fever, malaise, lymphadenopathy. Heals within 8-12 days.
D: Clinical diagnosis. Viral PCR of CSF, vesicle scraping, culture, immunofluorescence, serology.
T: Acyclovir - decreased symptoms and viral shredding.
Give IV if HSV encephalitis suspected as mortality rates are high in untreated cases.

Question 9

Mumps

Answer 9

Acute generalised infection
C: A paramyxovirus, usually in children and young adults. Usually affects the salivary glands (parotid) and, less often, the pancreas, testis, ovary, brain, mammary gland, liver, kidney, joints and heart.
Highly infectious with transmission by droplets spread in saliva.
S: Can be asymptomatic.
Non-specific symptoms lasting a few days, such as fever, headache, malaise, myalgia and anorexia.
Pain in the jaw. Hot and swollen over gland.
D: Notify Health Protection Unit. Oral fluid sample - Salivary immunoglobulin M for mumps. RT-PCR and mumps genotyping. High-resolution colour Doppler ultrasound.
T: Supportive - maintain good fluid intake (mostly self-limiting within 1-2 weeks).
Paracetamol and ibuprofen may give symptomatic relief.
If signs of Meningitis or Epididymo-orchitis - seek advice.

Question 10

Roseola

Answer 10

Common in children 6 months to 2 years.
C: Caused by a virus called human herpesvirus type 6 (HHV-6). It may also be caused by human herpesvirus type 7 (HHV-7). Spread via airborne droplets.
S: Fever, rash (small pink spots), sore throat, swollen glands.
D: Clinical diagnosis
T: Paracetamol or ibuprofen to lower a temperature
Good fluid intake
Once a child has had this they will be immune.

Question 11

Rubella

Answer 11

A viral infection once seen mainly in spring and early summer.
C: An RNA virus (genus Rubivirus, family Togaviridae). Transmitted as airborne droplets between close contacts.
S: Prodromal - low-grade fever, headache, mild conjunctivitis and anorexia with rhinorrhoea. Rash - pink discrete macules that coalesce, starting behind the ears and on the face, spreading to the trunk and then the extremities. Cervical, suboccipital and postauricular lymphadenopathy.
D: Serological and/or polymerase chain reaction testing. FBC.
T: Notify HDU. Antipyretics. Stay off work for at least 5 days after the initial development of the rash. If pregnant, Refer urgently to obstetrics for risk-assessment and counselling (risk of congenital rubella syndrome).

Question 12

Measles

Answer 12

Childhood infection - can be trivial or life-threatening.
C: Single-stranded RNA Morbillivirus from the paramyxovirus family. Spread by airborne transmission. Once infected, the person develops lifelong immunity.
S: Rash for at least 3 days, fever, cough, coryza, conjunctivitis, diarrhoea, swelling around the eyes, photophobia.
D: Salivary swab or serum sample for measles-specific immunoglobulin M, RNA detection.
T: Identify HPU. Uncomplicated - fluids, paracetamol, ibruprofen.
Vulnerable contacts (infants, pregnant women and immunocompromised individuals) should be identified for post-exposure prophylaxis where appropriate - administer MMR vaccine within 72 hours of initial measles exposure, or immunoglobulin (IG) within six days of exposure.

Question 13

Varicella zoster virus

Answer 13

Primary infection transmitted by respiratory droplets.
C: Invades the respiratory mucosa, replicates in the lymph nodes. Disseminates via mononuclear cells to infect skin epithelial cells. Leads to virus containing vesicles. Virus then remains dominant in sensory nerve roots. Reactivation is dermatomal.
S: Chicken pox - fever, malaise, headache, abdominal pain, pruritic rash with erythematous macules that become vesicles.
Shingles - painful, hyperaesthetic area, then macular to vesicular rash in dermatomal distribution.
D: Clinical diagnosis. Viral PCR, culture, immunofluorescence.
T: Oral acyclovir/valaciclovir for uncomplicated chicken pox/shingles in adults, aim to give within 48 hours of rash.
IV acyclovir if immunosuppressed, pregnant, severe/disseminated disease (including ocular).

Question 14

Erythema infectiosum

Answer 14

Common infection in children.
C: Parvovirus B19 spread via respiratory droplets, bone marrow transplant, other blood products and from mother to baby via the placenta.
S: Can be asymptomatic.
Prodrome - headache, rhinitis, sore throat, low-grade fever and malaise. Symptom-free for 7-10 days. ‘Slapped cheek’ rash. An erythematous macular/morbilliform rash develops on the extremities, mainly on the extensor surfaces. May or may not be itchy. Symmetrical arthropathy.
D: Not necessary. B19-specific IgM (current infection). B19-specific IgG (immunity).
T: Symptomatic treatment
Prevention of transmission - reduce contacts, washing

Question 15

Amoebiasis

Answer 15

Protozoan disease.
C: Entamoeba histolytica. Infection occurs by ingestion of mature cysts in food or water, or on hands contaminated by faeces. Invade the epithelial cells of the large intestines, causing flask-shaped ulcers, then infection can spread to other areas.
S: Intestinal - loose stools with fresh blood, abdominal pain in iliac fossae, low fever, flatulence, abdominal mass, may lead to perforation, appendicitis, peritonitis.
Hepatic - pyrexia, painful right hypochondrium, epigastrium and intercostal spaces, weight loss, anaemia, painful dry cough, epigastric mass.
D: FBC, ESR, LFTs, stool sample, Cultures, antigen testing and PCR, serology, Ultrasound, CT and MRI, Proctoscopy, sigmoidoscopy or colonoscopy.
T: Fluid and electrolyte replacement, gastric suction and blood transfusion may be required.
Diloxanide furoate is the drug of choice for asymptomatic patients.
Metronidazole is the first choice for treatment of acute invasive amoebic dysentery, followed by 10 day course of Diloxanide furoate.

Question 16

Cryptococcosis

Answer 16

Severe opportunistic infection is caused by two serotypes in patients with defective T-cell mediated immunity.
C: Cryptococcus neoformans var grubii (serotype A - causes the large majority) and Cryptococcus neoformans var neoformans (serotype D).
Abundant in soil contaminated by pigeon droppings.
Risk factors - HIV infection, organ transplant recipient, DM, hepatic cirrhosis, haematological malignancies, corticosteroid therapy, sarcoidosis, connective tissue disorders.
S: May be asymptomatic, lethagy, weight loss.
Meningitis or meningoencephalitis - headache, confusion, altered mental state, coma, seizures, neurological signs such as diplopia, ataxia and aphasia.
Pulmonary cryptococcosis - cough and pleuritic chest pain, dyspnoea.
D: CSF, blood, and urine cultures, FBC, U&Es, LFTs, radiology.
T: Induction (initial therapy) - usually amphotericin B. Consolidation (clearance therapy) - fluconazole orally for 8 weeks. Maintenance (suppression therapy) - lower dose oral fluconazole for 6-12 months.

Question 17

Histoplasmosis

Answer 17

C: Histoplasma capsulatum var. capsulatum lives in soil that contains large amounts of bird or bat droppings.
Risk factors - immunosuppression, infants, over 55s.
S: May be asymptomatic, fever, chills, cough, fatigue, headache, chest pains, body aches.
D: Enzyme immunoassay and culture on urine and/or serum, or cerebrospinal fluid or bronchoalveolar lavage fluid.
T: Treatment is indicated for moderate to severe acute pulmonary, chronic pulmonary, disseminated, and central nervous system (CNS) histoplasmosis.
Antifungal agents proven to be effective are amphotericin B (including liposomal and lipid formulations) and itraconazole (for mild-to-moderate infections and step-down therapy).

Question 18

Pneumocystis

Answer 18

A serious infection that causes inflammation and fluid buildup in your lungs.
C: P. jirovecii. It can cause a transient infection in an immunocompetent host.
Risk factors - HIV, AIDS, patients taking immunosupressants, haematological malignancy, organ transplant recipients, severe malnutrition, pre-existing lung disease.
S: Non-productive cough, exertional dyspnoea, fever, tachypnoea, chest pain, crackles/wheeze, low O2. Extrapulmonary disease may manifest as hepatosplenomegaly, lymphadenopathy or ocular disease.
D: Elevated lactate dehydrogenase, ABG (hypoxia, hypocarbia), CXR, CT, sputum sent for routine and mycobacterial culture, pulmonary function test.
T: High-dose co-trimoxazole (trimethoprim-sulfamethoxazole). If unable to tolerate, use Atovaquone suspension, Dapsone with trimethoprim or Clindamycin with primaquine. With oral prednisolone or parenteral hydrocortisone alongside.

Question 19

Rabies

Answer 19

Viral infection affecting the peripheral and central nervous system.
C: Lyssavirus Rhabdoviridae . Most commonly transmitted in saliva by the bite of an infected mammal.
S: Pain and paraesthesia around the wound or inoculation site, malaise, fever, headache, weakness in bitten limb, itching at wound site, hydrophobia, hallucinations and behavioural disturbance, ascending flaccid paralysis with sensory disturbances and coma.
D: Virus antigens in skin, brain, saliva or concentrated urine sample.
Nuchal skin biopsy - fluorescent antibody testing.
T: Wound cleansing and active and passive immunisation - Rabies vaccine and human rabies-specific immunoglobulin (HRIG). No treatment.

Question 20

Cytomegalovirus

Answer 20

May cause a mononucleosis infection in healthy individuals but can cause severe illness in congenital infection and in an immunocompromised host.
C: Human cytomegaloviruses. Spread via body fluids, such as saliva, urine, blood, tears, semen, and breast milk.
S: Mononucleosis syndrome - febrile illness with splenomegaly, impaired liver function and abnormal lymphocytes in the blood.
In immunocompromised host - pneumonia, hepatitis, encephalitis, colitis, uveitis, retinitis and neuropathy.
In newborns - low birth weight, fever, hepatitis with jaundice, haemorrhagic manifestations, hepatosplenomegaly, thrombocytopenia, chorioretinitis, microcephaly, blindness, deafness, seizures.
D: Antibody blood test, amniocentesis in a pregnant patient. Regular monitoring for CMV complications will include testing for vision and hearing problems.
T: Cannot be cured. To stop it from getting worse - ganciclovir and foscarnet. Ganciclovir ca be delivered in the form of an intravitreal implant.

Question 21

Tetanus

Answer 21

A bacterial toxin that affects your nervous system.
C: Clostridium tetani. Found in soil, house dust and both animal and human faeces.
Risk factors - wounds contaminated with garden soil or manure and those caused by rusty metals, lack of immunisation, poverty, drug addiction, >60.
S: Lockjaw, risus sardonicus, neck stiffness, swallowing difficulties, abdominal muscle rigidity, muscle spasms.
D: Clinical diagnosis. The spatula test is useful: touching the back of the pharynx with a spatula elicits a bite reflex in tetanus, instead of a gag reflex.
T: Give human tetanus immunoglobulin (antitoxin) intravenously (IV). Local debridement. Metronidazole may be given. Prophylactic sedation and intubation. Benzodiazepines are often administered to prevent or control spasms.
Botulinum toxin may reduce tetanus symptoms.

Question 22

Cholera

Answer 22

An acute diarrhoeal infection.
C: Caused by enterotoxin subunit-A of Vibrio cholerae. Water-borne infection caught through ingestion of faecally contaminated water or shellfish.
S: May be asymptomatic. Sudden onset of profuse, watery diarrhoea with nausea and vomiting.
Dehydration - sunken eyes and possibly impaired level of consciousness, skin will be dry and lacking turgor, pulse will be fast but weak, low blood pressure indicating haemodynamic instability.
D: Stool specimen, FBC, U&Es.
T: Oral or IV fluid replacement, Tetracycline, doxycycline or ciprofloxacin used for moderate-to-severe dehydration. Vaccine is given to aid workers helping in disaster relief or refugee camps or backpackers travelling to remote areas.

Question 23

Diphtheria

Answer 23

Acute upper respiratory tract infection, can affect the skin.
C: Corynebacterium diphtheriae. Spread is via respiratory droplets or contact with exudate from skin lesions.
Risk factors - poor hygiene and living conditions, lack of booster immunisations.
S: Similar to the common cold, nasal discharge that can become purulent and blood-stained, sore and crusted nostril, difficulty swallowing.
Skin - vesicles or pustules that quickly rupture to form a ‘punched-out’ ulcer on the lower legs, feet and hands.
D: Positive culture from respiratory tract secretions or cutaneous lesions, and a positive toxin assay.
Blood tests.
T: The antibiotics of choice are usually erythromycin, azithromycin, clarithromycin or penicillin.
Booster - a single reinforcing dose of a diphtheria-containing vaccine according to their age.

Question 24

Atypical mycobacterial disease

Answer 24

Infections caused by a species of mycobacterium other than Mycobacterium tuberculosis.
C: Many types of Mycobacterium. Can cause pulmonary disease, lymphadenitis, skin and soft tissue disease, disseminated disease.
S: Avium-intracellulare - fever, swollen lymph nodes, diarrhoea, fatigue, weight loss and shortness of breath.
Kansasii - fever, swollen lymph nodes and lung crackles and wheezing.
Marinum - a single lump or pustule that breaks down to form a crusty sore or abscess.
Ulcerans - solitary, painless and sometimes itchy nodule that will develop into an ulcer.
Chelonae - fever, lung disease, joint infection, eye disease and other organ infections.
Abscessus - skin infection after puncture wounds, tattoos, skin trauma or surgery.
Fortuitum - local cutaneous disease, osteomyelitis, joint infections and ocular disease.
D: Biopsy, culture, PCR testing.
T: Depends on the mycobacterium - rifampicin, ethambutol, isoniazid, minocycline, ciprofloxacin, clarithromycin, azithromycin and cotrimoxazole. Surgery for infected lymph nodes and skin lesions.

Question 25

Toxoplasmosis

Answer 25

Infection caused by a parasite.
C: Toxoplasma gondii, an intracellular protozoan parasite carried in cat faeces. May be ingested by secondary hosts (humans, cattle, sheep, pigs, rodents and birds).
Transmission - handling of cat faeces, uncooked meat, maternal-to-fetal transmission, organ transplantation.
S: Acquired - asymptomatic, lymphadenopathy, changes in behaviour/personality, myocarditis, pericarditis, pneumonitis, hepatitis or encephalitis.
Ocular - reduced visual acuity, focal retinochoroiditis.
Congenital - hydrocephalus, microcephaly, sight impairment, developmental delay, epilepsy, miscarriage or fetal abnormalities.
D: IgG and IgM tests, PCR, Enhanced Immunohisto-staining, CT/MRI, ultrasonography for pregnancy.
T: Patients may require stabilisation and treatment of acute symptoms such as seizures, respiratory failure and cardiovascular compromise.
Pyrimethamine, sulfadiazine and folinic acid for 4-6 weeks.

Question 26

Malaria

Answer 26

A protozoan parasite widespread in the tropics and subtropics.
C: P. falciparum, P.ovale, P.malariae, P.knowlesi and P.vivax. Transmitted by the bite of infected female Anopheles mosquitoes.
S: An abrupt onset of fever, tachycardia and rigors, followed by profuse sweating some hours later.
This may be accompanied by anaemia and hepatosplenomegaly.
D: Thick (detect malaria parasites) and thin blood film (parasite identification and for quantification). Blood tests - full blood count, urea, creatinine and electrolytes, liver function tests and blood glucose.
T: Uncomplicated falciform malaria - treated with artemisinin combination therapy (ACT). Parenteral artesunate and quinine accompanied by doxycycline 200 mg orally.
Non-falciform malaria - CT or chloroquine.