URINARY TRACT INFECTION in THE IMMUNOCOMPROMISED HOST

R.A.S HEMAT, MB;BCh, FRCSI, DUL.

Once UTI is established, immunocompromised differ than normal hosts. The most common route of seeding of the urinary tract is the ascending route. Bacteriuria and leukocytouria do not always go in parallel. Diuresis must be taken into consideration when evaluating bacteriuria.
In patients with indwelling catheters, the cumulative risk for UTI is 4-7.5% per day. Mobile bacteria are able to ascend against a flow of urine of 25 ml/min, and urinary stasis may facilitate bacterial adhesion and invasion.
Patients with chronic renal failure have several risk factors for UTIs, including infrequent voiding with low flow rates and impaired concentrating capacity of the kidneys.
Factors predisposing to UTIs in diabetics include poor control of glucose levels, diabetic neuropathy with neurogenic bladder and chronic urine retention, older age, female sex, prior instrumentation of the urinary tract, recurrent vaginitis, diabetic microangiopathy, large-vessel renal vascular disease, and impairment in leukocyte function. Once UTI is established in diabetics, renal parenchymal damage is more extensive.
UTIs are common in men with HIV. E. coli is the predominant pathogen in these cases. Symptomatic UTI may represent a relevant cause of morbidity for men with AIDS.

Bacterial infections are common after renal transplantation, particularly UTI, wound infections and RTI. Immunosuppressive therapy affects multiple functions of polymorphonuclear leukocytes. Oxidative burst from polymorphonuclear cells are inhibited by methyl-prednisolone, prednisolone, and dexamethasone. The impaired oxidative burst by leukocytes may contribute to impaired microbial killing. In the first week after transplantation there are mainly bacterial and candidal infections. One to six months after transplantation the greatest risk of life-threatening infections is cytomegalovirus (CMV) infection. Bacterial infections in the transplant patient can be divided into: 1-those identical to normal population, 2- those related to technical mishaps, 3- those related to GIT, 4- opportunistic infections. Urinary tract infections are the most common bacterial infection in the renal transplant recipient (6-85%).

Factors associated with an increased risk for bacterial invasion:
1- Female patient.
2- History of UTI.
3- Polycystic kidney disease.
4- Diabetes mellitus.
5- Chronic viral infections.
6- Increased urinary aluminium excretion.
7- Urinary catheters.
8- Antirejection treatment.
9- Chronic uraemia.

Turbulent flow in the female urethra increases the risk of bacterial infection. Even though the urethra is only 3-4 cm long, flow is frequently not linear, but turbulent. So, the urine will be washed back into the bladder, increasing the risk of contamination. Urinary tract is the source of sepsis in 40-60% in transplant recipients, and 7% of UTI are complicated with sepsis. Factors associated with increased risk for opportunistic infections are poor allograft function, antirejection therapy, chronic viral diseases and low socioeconomic status.
UTI in cardiac transplant recipients receiving cyclosporine and prednisone is highest within the first 3 weeks after transplantation
UTI accounts for 2-7% of all infections in neutropenic patients and 5% of infections in bone marrow transplant recipients.

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Dr. R.A.S HEMAT declares no conflicts of interest or financial interests in any product or service mentioned in this article, including grants, employment, stock holdings, gifts, or honoraria.