Opportunistic Microbial Infections

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Opportunistic Infections Immmunocompromised patients are vulnerable to opportunistic infections caused by organisms of lower pathogenecity, besides being also susceptible to primary pathogens causing disease among immunocompetent hosts resistant to opportunistic infections. Many opportunistic infections arise from the individual’s own flora or local environment2, at or near the microbes’ normal sites of colonization. Hence, some normal flora species are associated with particular opportunistic infections. For example, Bacteroides fragilis is associated with abdominal infections, Staphylococcus epidermidis with catheter infections, and Escherichia coli with urinary tract infections3. Bacterial Opportunistic Infection Staphylococcus aureus causes the greatest number of pyodermas and soft tissue infections. It is not one of the cutaneous resident flora, however it colonizes the anterior nares in up to 25% of healthy individuals at any one time and more than 50% of chronically ill individuals4. … Once established in the skin, S. aureus invades more deeply into the soft tissue resulting in erysipelas or horizontal spread in lymphatics, and cellulitis or vertical spread into subcutaneous fat. Further, S. aureus is the most common cause of wound infections5. Risk factors for surgical wound infections include host factors such as immune status, diabetes mellitus. surgical factors such as foreign body use and disruption of tissue perfusion accompanying surgical procedure. and staphylococcal factors such as substances that mediate tissue adherence and invasion, or that facilitate staphylococci surviving host defenses and antibiotics in tissues, and antimicrobial prophylaxis. Bacteremia can lead to deposition of S. aureus in the skin, resulting in petechiae, hemorrhages, subcutaneous nodules, soft tissue infections, and pyomyositis6. Parasitic Opportunistic Infection Some chronic parasitic infections that are reactivated in immunocomprised patients include those caused by Strongyloides stercoralis. Weakened cell-mediated immunity in pregnancy, during chemotherapy with corticosteroids, and in organ transplantation, may enable reactivation of toxoplasmosis and congenital infection7. Further, S. stercoralis is able to cause autoinfection giving rise to chronic infestations in the immunocompetent8. Strongyloides stercoralis is an intestinal parasite, and causes strongyloidiasis. The parasite uniquely carries out its entire life cycle within the human body. Hence, in immunocompromised patients, strongyloidiasis can lead to a hyper infection syndrome with high morbidity and mortality due to the accelerated endogenous autoinfection9. Strongyloidiasis that