Ífi^n÷]<‹äœ÷] –25% of serious infections in developing countries, with some of these bacteria not being susceptible to any licensed antibacterial agent. Some antimicrobial resistance mechanisms are difficult to detect with routine microbiological testing leading to inappropriate treatment. Biofilm formation by MDRo (mainly Staphylococci, Acinetobacter and Pseudomonas) increases the difficulty of management of infective endocarditis. Clear understanding of biofilm development, antibiotic pharmacokinetics, antimicrobial resistance mechanisms, institution of infection control measures and antibiotic stewardship are the mainstay of controlling this growing problem. Diagnostic Approach to Primary Immunodeficiency Dr. Salim Al-Tamimi Clinical Immunology & Allergy, Sultan Qaboos University Hospital, Muscat, Oman Host immune defense is accomplished by innate immunity and adaptive immunity; both of these are essential in order to fight infections and prevent autoimmune diseases. Innate immunity includes naturally occurring barriers, mucociliary clearance, peristalsis, secretions, cells and protein enzymes that do not involve the production of immunologic memory for their function. Adaptive immune responses are both humoral and cellular and depend on immunologic memory for antigen recognition. Patients who are immunodeficient present mainly with recurrent or severe infections. Immunodeficiency can be separated into primary and secondary states and the type of infection suggests the particular component of the system involved. Examples that can cause secondary immunodeficiency are HIV, drugs (e.g. cytotoxic agents, steroids) protein losing states. Primary immunodeficiency results from absence or malfunction of bone marrow precursor stem cells, various blood cells, and soluble molecules that make up the immune system which can lead to compromise of the host defense system. Over the last two decades, many genes have been discovered that are responsible for disease status in the immune system. These genes either fail to produce specific proteins (immunoglobulins in X-linked agammaglobulinaemia) or produce altered proteins (truncated common gamma chain of the interleukin-2 receptor in X-linked severe combined immunodeficiency), and enzyme deficiency, as seen in adenosine deaminase deficiency. Conventionally, immunodeficiency is classified into four major host defense mechanisms (B-cell immunity, T-cell immunity, phagocytic cells, and complement pathways). Immunodeficiency usually presents with unusual severe or recurrent infections, the following are the most warning signs of primary immunodeficiency: 1) a family history of immunodeficiency disease; 2) two new ear infections within 1 year; 3) two serious sinus infections within 1 year; 4) two months on antibiotics with little effect; 5) two pneumonias within 1 year; 6) two deep-seated infections, such as meningitis, sepsis or osteomylitis; 7) need for IV antibiotics to clear infections; 8) recurrent deep skin or organ abscesses; 9) failure to thrive; 10) persistent thrush in mouth or fungal infection on skin. When an immunodeficiency is suspected, the following screening tests should be performed and may be tailored according to the clinical information with respect to the immune system arm likely to be involved: antibody mediated immunity; quantitative immunoglobulins (IgG, A, M, E); isohaemagglutinins; functional antibodies e.g. diphtheria/ tetanus titers, T-cell immunity; total lymphocyte count; T and B cells numbers; lymphocyte proliferation assay; lateral chest X-ray; HIV, neutrophil, cell count and differential nitro blue tetrazolium test (NBT); dihydrorhodamine 1,2,3 test; complement, total haemolytic complement test, C3 and C4 concentration. Further specialised functional immunological tests may be required to establish an accurate diagnosis; these tests are not available in all laboratories, for example phagocytic assays and cytotoxic assays. Genetic studies are more commonly used now. Update on Zygomycosis Dr. Saleh Al-Azri Senior Consultant Medical Microbiology, Central Public Health Laboratories, Ministry of Health, Muscat, Oman Zygomycosis is one of the most rapidly progressing forms of mould infections, which usually begins in the nose and paranasal sinuses. This infection produces angioinvasive disease with tissue necrosis and is prone to dissemination. Diabetes and immuno-suppression are major risk factors. Recent reports showed an increased incidence of zygomycosis. The presentation and diagnosis are usually challenging and the treatment is even more so. Zygomyces are resistant to most commonly used antifungal medications, but high dose liposomal amphotericin followed by posaconazole are considered in most cases. The clinical outcome is closely related to the patient’s overall health and control of the underlying diseases. 310 | SQU Medical Journal, May 2011, Volume 11, Issue 2 Oman International Conference on Laboratory Medicine – Part II Sultan Qaboos University Prosthetic Joint Infections Dr. Fatma M. Al-Rashdi Specialist, Khoula Hospital, Muscat, Oman Since its development in the late 1960s, total hip and knee replacement has increased from an infrequent procedure to one that is commonly performed. The success of these procedures is hampered in part by the development of joint infections. The rate of infection in most centres ranges between 0.5 to 1.0 % for hip replacements, 0.5 to 2 % for knee replacements, and less than 1 % for shoulder replacements. Prosthetic joint infections can be classified according to the time of onset (early, delayed and late) or the pathogenic mechanism causing infection. Any microorganism can cause prosthetic joint infection and the distribution of organisms varies with the time from implantation and source of infection. Diagnosis of prosthetic joint infections always requires obtaining samples of joint fluid or tissue. Treatment usually involves both medical and surgical measures. The type and timing of such therapies is dependent upon the cause and timing of the infection and the condition of the host. Molecular Epidemiology of Tuberculosis in Oman Dr. J. P. N. Singh Specialist Bacteriologist, National TB Reference Laboratory, Central Public Health Laboratories, Ministry of Health, Muscat, Oman Tuberculosis continues to be a major cause of morbidity and mortality throughout the world with 8.8 million new cases and 1.6 million deaths in 2005 (WHO fact sheet, 2007). Rapid detection, adequate treatment, and contact tracing to arrest further transmission are the key factors in the control of this infectious disease. Various developments in DNA technology and molecular biology have led to methods to trace tuberculosis transmission routes by the differentiation of clinical isolates based on polymorphism in genomic DNA of Mycobacterium tuberculosis. This presentation gives a brief introduction to molecular epidemiology and its applications, and then focuses on the molecular characterisation of Omani M. tuberculosis isolates by spoligotyping, a study performed by our laboratory. We identified 265 different spoligotypes among the 786 M. tuberculosis isolates. The designation of the spoligotype was attributed by comparison of the pattern to those contained in a SpolDB4 database. Out of these, 124 spoligotypes (containing 573 isolates) showed matching with SpolDB4 database, while 141 spoligotypes (containing 213 isolates) were not found in SpolDB4 database and an ST number could not be assigned for them. Most unidentified spoligotypes were orphan (n = 109), however, 104 clustered spoligotypes (without ST numbers) were roughly assembled into the Unknown group 1 to 32. Over all clustering was observed in 77.2% (n = 607) isolates, whereas 22.8% (n = 179) clinical isolates harboured unique profiles. This study gives an outline of the M. tuberculosis strains circulating in Oman, and describes the distribution of the major phylogenetic families. It contributes towards a better understanding of the current trend of TB epidemiology in a low-incidence Middle Eastern country.