Case 43

The number of joint replacements performed in resource-rich countries has increased significantly in the last few decades and has allowed a significant improvement in the quality of life for many patients. Despite preventative measures, a small fraction (around 1% for hip replacements) will become infected. These can present as acute or chronic infections. They can also occur at any time after the primary procedure. Late acute infections are usually via the haematogenous route and often present to the acute medical take or via infection services. A prompt, appropriate medical and surgical management strategy is important.

Case 39

Viral infection in pregnancy can lead to adverse outcomes for both the mother and the foetus. This chapter examines the steps to be taken on exposure to viruses associated with rash illness in pregnancy. Consideration is given to the important points in the history, which viral infections are of concern in pregnancy (varicella-zoster, parvovirus B19, rubella, measles, and Zika), the possible outcomes of infection, diagnostic approaches, and the management of a confirmed case of Parvovirus B19 infection.

Case 38

Post-transplant lymphoproliferative disease (PTLD) is a disorder of lymphoid proliferation seen in recipients of solid organ or haematopoietic transplants as a consequence of immunosuppression. A spectrum of disease is recognized ranging from non-malignant polyclonal proliferation of B cells to monoclonal proliferation of B or T lymphocytes which have features in common with lymphomas. Epstein–Barr virus (EBV) is associated with a majority of cases although it is not a universal feature. Treatment with anti-CD20 antibody in addition to reduction in immunosuppression has become the most common treatment approach.

Case 37

Leishmaniasis is an intracellular protozoan parasitic infection caused by organisms of the genus Leishmania. The parasite is usually transmitted to humans by the bite of Phlebotomine sandflies. A spectrum of illness is seen ranging from localized skin ulceration (which can be self-limiting) to disseminated systemic infection which can be fatal. Different species of Leishmania cause different forms of disease and the species are restricted in their geographic distribution. Host factors also seem to be important in determining how the infection will manifest itself.

Case 28

Nocardia are opportunist pathogens, especially affecting patients with T-cell deficiencies, such as those on prolonged high-dose corticosteroids. They are found in the environment, associated with ornamental fish, and Nocardia asteroids complex is most commonly associated with human disease. Infection may result in a brain abscess, pulmonary infection, or disseminated disease including involvement of the skin. Steriotactic aspiration or via a burr hole to obtain a sample are replacing open craniotomy, unless the brain abscess is large. Previously, laboratory confirmation was dependant on prolonged culture and stains for acid-and alcohol-fact bacilli, but increasingly, molecular techniques are used to diagnose this and other causes of brain abscess. Consensus and clinical experience suggest that co-trimoxazole with or without a carbapenem, are the initial empiric anti-infectives of choice for nocardiosis. Susceptibility testing should be carried out on available isolates as treatment is usually for 6 months or longer.

Case 14

Cryptococcosis is an opportunist infection that should be considered in HIV/AIDS and in other at risk immunosuppressed patients such as those following solid organ transplantation. Cryptococcus neoformans is found in bird droppings and is the commonest cause in temperate climates but C. gattii is increasingly recognized in warmer climates. Diagnosis is usually via antigen detection, microscopy, and culture of blood, respiratory specimens and cerebrospinal fluid (CSF), in addition to histological analysis of appropriate tissue with specialised stains. New antigen assays facilitate point-of-care testing in resource-poor countries. Management includes initial treatment regimens with liposomal amphotericin B (the echinocandins have little activity) followed by follow-up antifungal therapy for up to a year, usually with fluconazole.

Case 13

There is an increasing number of opportunist pathogens that may cause acute pulmonary exacerbations of cystic fibrosis as the patient cohort survives longer. However, it can often be difficult to determine if the isolation of these bacteria represents colonization or true infection. Their identification from sputum samples in the microbiology laboratory is also challenging, requires significant scientific expertise, and is assisted by new technologies such as MALDI-TOF (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry). One such opportunist pathogen is Stenotrophomonas maltophilia, for which risk factors include increasing age and recent oral antibiotics, especially carbapenems. However, it is unclear if this bacterium is transmitted from patient to patient unlike with Pseudomonas aeruginosa, but all patients with cystic fibrosis should be admitted to a single room when hospitalization is required. Controversies exist regarding the optimal treatment which in the future may include a greater reliance on inhaled antibiotics.

Case 12

Lung infiltrates in immunocompromised patients have a broad differential diagnosis. Assessment should include considering host risk factors, the clinical presentation, and imaging. Cross-sectional imaging is very helpful and lower respiratory tract samples should be obtained where possible. Laboratory diagnostic tests should be performed but most have low sensitivity and specificity. The differential diagnosis includes non-infective and infective cause. Effective patient management requires good supportive therapy if in respiratory failure, prompt diagnostics, early empiric antimicrobial treatment, and management of the underlying immunosuppression.

Case 3

Chickenpox is caused by varicella-zoster virus and is predominantly a self-limiting disease of childhood. Chickenpox in adults is more likely to be associated with complications such as varicella pneumonia. Treatment with antivirals is helpful in adults if given early after the onset of rash in uncomplicated disease. In complicated disease such as pneumonia, intravenous treatment is essential to optimize drug levels although an evidence base for this is lacking. Exposure to varicella during pregnancy is a particular concern for non-immune women and passive immunization with varicella immune globulin is indicated.

Case 1

Cellulitis is infection of the dermis and subcutaneous tissues unlike erysipelas which is more superficial and necrotizing fasciitis which involves deeper layers. Cellulitis is most commonly caused by Group A streptococci (GAS) and Staphylococcus aureus, including Panton–Valentine leukocidin-producing isolates. However, most cases are diagnosed clinically and the initial drug of choice is flucloxacillin. Five to ten days of treatment is usually adequate including an early intravenous to oral switch but prophylactic antibiotics may be considered for patients with two or more episodes to prevent further recurrence. There is poor evidence for the benefit of using adjuvant therapy, such as corticosteroids and intravenous immunoglobulin, in more severe cases. Healthcare-associated clusters or outbreaks may be associated with carriage of GAS in a staff member who should be treated if positive.