Risk of recurrent non-typhoid Salmonella bacteraemia after early discontinuation of ciprofloxacin as secondary prophylaxis in AIDS patients in the era of highly active antiretroviral therapy

Invasive nontyphoidal Salmonella disease: epidemiology, pathogenesis and diagnosis

PURPOSE OF REVIEW

This review highlights and discusses important publications over the past 12 months providing new insights on invasive nontyphoidal Salmonella (iNTS) disease.

RECENT FINDINGS

There have been informative new estimates of the burden of iNTS in Asia and in high-resource, low-incidence settings. Important information has emerged in the last year about the relationships between HIV, malaria, iNTS and typhoid fever in adults and children in Africa. HIV causes susceptibility to iNTS disease, but has been shown to be protective against typhoid fever. Clinical guidelines for presumptive diagnosis frequently fail to identify iNTS disease in Africa, and there remains a need for improved diagnostic tools. Experimental studies in humans have helped us to understand the intracellular pathogenesis of iNTS and to direct the search for appropriate protein vaccine targets.

SUMMARY

The most important remaining gap in our knowledge is probably an understanding of how NTS is transmitted, and the nature of the relationship between diarrhoeal disease, carriage and invasive disease in Africa, so that diagnostic and prevention tools can be appropriately directed.

Antimicrobial therapy for the treatment of opportunistic infections in HIV/AIDS patients: a critical appraisal

The widespread use of antiretroviral therapy (ART) has entirely changed the management of human immunodeficiency virus (HIV) infection and dramatically reduced the rates of opportunistic infections (OI). However, OI continue to cause significant morbidity and mortality in both developed countries, where presentation with advanced HIV infection is common, and also in developing countries where ART is less widely available. Evidence to direct OI guidelines is partly limited by the fact that many large-scale studies date from the pre-ART era and more recent studies are sometimes poorly powered due to the falling rates of OI. Treatment of OI is now known to be as much about antimicrobials as about immune reconstitution with ART, and recent studies help guide the timing of initiation of ART in different infections. OI have also become complicated by the immune reconstitution inflammatory syndrome phenomenon which may occur once successful immune recovery begins. Trimethoprim-sulfamethoxazole has long been one of the most important antibiotics in the treatment and prevention of OI and remains paramount. It has a broad spectrum of activity against Pneumocystis jiroveci, toxoplasmosis, and bacterial infections and has an important role to play in preventing life-threatening OI. New advances in treating OI are coming from a variety of quarters: in cytomegalovirus eye disease, the use of oral rather than intravenous drugs is changing the face of therapy; in cryptococcal meningitis, improved drug formulations and combination therapy is improving clearance rates and reducing drug toxicities; and in gut disease, the possibility of rapid immune restitution with ART is replacing the need for antimicrobials against cryptosporidia and microsporidia.

Lack of fluoroquinolone resistance in non-typhoidal salmonella bacteremia in HIV-infected patients in an urban US setting

Non-typhoidal salmonella (NTS) bacteremia is a significant cause of morbidity and mortality in HIV-infected individuals worldwide. Recent reports have noted increasing resistance of NTS isolates to fluoroquinolones, the recommended first-line therapy for NTS bacteremia. The outcomes and risk factors for NTS bacteremia in HIV-infected patients in an urban US setting were evaluated. From January 2002 to December 2006, 26 episodes of NTS bacteremia were identified in 16 patients. The risk factors for NTS bacteremia were low CD4 count, high viral load, and lack of antiretroviral therapy (ART). Recurrences appeared related to lack of immune reconstitution in patients not on ART. Unlike reports from Asia, no fluoroquinolone resistance was identified in any of the Salmonella strains isolated in this setting. Optimal treatment of NTS in the HIV-infected patient in the United States should include therapy with fluoroquinolones as well as attaining complete viral suppression and immune reconstitution with ART.

Reduced morbidity and mortality in the first year after initiating highly active anti-retroviral therapy (HAART) among Ugandan adults

OBJECTIVE

To evaluate the effect of highly active anti-retroviral therapy (HAART) and cotrimoxazole prophylaxis on morbidity after HAART eligibility.

METHODS

Between 1999 and 2006, we collected morbidity data from a community-based cohort of HAART-eligible patients, comparing patients initiating HAART and those non-HAART. Patients aged 15 years or older visited the clinic every 6 months and when ill. Baseline data on patients' characteristics, WHO stage, haemoglobin and CD4+ T-cell counts, along with follow-up data on morbidity (new, recurrent and drug-related), were collected for the first year after initiating HAART or becoming HAART-eligible. We estimated the overall effect of HAART on morbidity; adjusted for the effect of cotrimoxazole prophylaxis by Mantel-Haenszel methods. A negative binomial regression model was used to assess rate ratios (RR) after adjustment for other confounders, including cotrimoxazole.

RESULTS

A total of 219 HAART patients (median age 37 years; 73% women; 82% using cotrimoxazole prophylaxis, median haemoglobin 11.7 g/dl and median CD4+ 131 cells/microl) experienced 94 events in 127 person-years. 616 non-HAART patients (median age 33 years; 70% women; 26% using cotrimoxazole prophylaxis, median haemoglobin 11.2 g/dl and median CD4+ 130 cells/microl) experienced 862 events in 474 person-years. The overall morbidity during the first year of HAART was 80% lower than among non-HAART patients (adjusted RR = 0.20, 95% CI: 0.12-0.34). Cotrimoxazole prophylaxis also reduced morbidity (adjusted RR = 0.65, 95% CI: 0.45-0.94).

CONCLUSION

These results confirm the reduction in morbidity due to HAART, and the additional protection of cotrimoxazole prophylaxis.

Risk of Recurrent Nontyphoid Salmonella Bacteremia in HIV-Infected Patients in the Era of Highly Active Antiretroviral Therapy and an Increasing Trend of Fluoroquinolone Resistance

BACKGROUND

Risk of recurrent nontyphoid Salmonella (NTS) bacteremia and trends of antimicrobial resistance of NTS remain unknown in human immunodeficiency virus (HIV)-infected patients receiving highly active antiretroviral therapy (HAART).

METHODS

Ninety-three patients who received a diagnosis of NTS bacteremia from June 1994 through June 2006 were prospectively followed up. Incidence of recurrent NTS bacteremia was compared between the pre-HAART era (June 1994-March 1997) and the HAART era (April 1997-June 2006). Prevalence of antimicrobial resistance was compared among the NTS isolates obtained in the pre-HAART era, the early HAART era (April 1997-June 2002), and the late HAART era (July 2002-June 2006).

RESULTS

Compared with patients enrolled in the pre-HAART era, patients who received HAART had an incidence of recurrent NTS bacteremia that was significantly reduced by 96%; the incidence of recurrent NTS bacteremia was 2.56 cases per 100 person-years in the HAART era, compared with 70.56 cases per 100 person-years in the pre-HAART era (rate ratio, 0.036; 95% confidence interval, 0.012-0.114; P<.001). In the HAART era, the incidence of recurrent NTS bacteremia did not increase among patients receiving fluoroquinolone prophylaxis for <or=30 days (1.69 cases per 100 person-years), compared with among patients receiving fluoroquinolones for >30 days (3.95 cases per 100 person-years), with a rate ratio of 0.43 (95% confidence interval, 0.07-2.58). Although resistance to ampicillin, cotrimoxazole, and chloramphenicol decreased, the proportion of NTS isolates resistant to fluoroquinolones increased from 0% in the pre-HAART era to 6.2% in the early HAART era and 34.2% in the late HAART era (P=.002).

CONCLUSIONS

The risk of recurrent NTS bacteremia decreased significantly in the HAART era, although NTS isolates obtained from HIV-infected patients were increasingly resistant to fluoroquinolones.

Gamma irradiation or CD4+-T-cell depletion causes reactivation of latent Salmonella enterica serovar Typhimurium infection in C3H/HeN mice

Upon infection with Salmonella, a host develops an immune response to limit bacterial growth and kill and eliminate the pathogen. Salmonella has evolved mechanisms to remain dormant within the body, only to reappear (reactivate) at a later time when the immune system is abated. We have developed an in vivo model for studying reactivation of Salmonella enterica serovar Typhimurium infection in mice. Upon subcutaneous infection, C3H/HeN (Ity(r)) mice showed an increase in bacterial numbers in livers and spleens, which reached a peak on day 19. After full recovery from the infection, these mice were irradiated or depleted of CD4(+) T cells. The mice displayed a secondary infection peak in livers and spleens with a course similar to that of the primary infection. We concluded that CD4(+) T cells are involved in active suppression of S. enterica serovar Typhimurium during latency. The role of CD4(+) T cells during primary infection with S. enterica serovar Typhimurium is well established. This is the first study to describe a role of CD4(+) T cells during the latent phase of S. enterica serovar Typhimurium infection.

Non-typhoidal salmonella bacteraemia--an under-recognized feature of AIDS in African adults

Non-typhoidal salmonella (NTS) infections are severe, invasive and recurrent in the HIV-infected adult, and NTS are the commonest cause of hospital admission with bacteraemia in sub-Saharan Africa. NTS bacteraemia typically presents in patients with HIV/AIDS once the CD4 count falls below 200 cells/microL. In-patient mortality is 35%-60%, and is highest in patients with confusion or severe anaemia. Among survivors, 25%-45% may have single or multiple recurrences of NTS bacteraemia 1-6 months after the first illness, requiring retreatment. Diagnosis relies on blood culture, so in many areas this disease cannot be definitively diagnosed, and must be empirically treated. Treatment is guided by local antibiotic sensitivities; fluoroquinolones are particularly useful for initial treatment if there is multidrug reistance to other agents, and may result in lower recurrence rates than other agents. Where possible, long-term secondary chemoprophylaxis to prevent recurrence is advisable. Successful ARV treatment also prevents recurrence. There is inadequate knowledge about the epidemiology of carriage and transmission among at-risk populations.

Impact of highly active antiretroviral therapy on incidence and management of human immunodeficiency virus-related opportunistic infections

We review the changes in incidences of HIV-related opportunistic infections and the safety of discontinuation of primary and secondary prophylaxis for HIV-related opportunistic infections in patients achieving immune restoration after the introduction of highly active antiretroviral therapy (HAART). HIV-related opportunistic infections continue to occur in patients who are newly diagnosed with HIV infection, those in the early course of HAART or non-adherent to HIV care and HAART, and those in whom non-HIV-related infections have emerged as a significant cause of morbidity and mortality in the post-HAART era. Clinical studies of patients with tuberculosis and HIV co-infection are reviewed to provide appropriate regimen combinations of rifamycins and antiretrovirals, which have varying degrees of drug-drug interactions that have posed challenges in the management of tuberculosis as well as HIV infection.