Efficacy of zidovudine in preventing relapses of Salmonella bacteremia in AIDS

HIV Drugs Inhibit Transfer of Plasmids Carrying Extended-Spectrum β-Lactamase and Carbapenemase Genes

Antimicrobial-resistant (AMR) infections pose a serious risk to human and animal health. A major factor contributing to this global crisis is the sharing of resistance genes between different bacteria via plasmids. The WHO lists Enterobacteriaceae, such as Escherichia coli and Klebsiella pneumoniae, producing extended-spectrum β-lactamases (ESBL) and carbapenemases as "critical" priorities for new drug development. These resistance genes are most often shared via plasmid transfer. However, finding methods to prevent resistance gene sharing has been hampered by the lack of screening systems for medium-/high-throughput approaches. Here, we have used an ESBL-producing plasmid, pCT, and a carbapenemase-producing plasmid, pKpQIL, in two different Gram-negative bacteria, E. coli and K. pneumoniae Using these critical resistance-pathogen combinations, we developed an assay using fluorescent proteins, flow cytometry, and confocal microscopy to assess plasmid transmission inhibition within bacterial populations in a medium-throughput manner. Three compounds with some reports of antiplasmid properties were tested; chlorpromazine reduced transmission of both plasmids and linoleic acid reduced transmission of pCT. We screened the Prestwick library of over 1,200 FDA-approved drugs/compounds. From this, we found two nucleoside analogue drugs used to treat HIV, abacavir and azidothymidine (AZT), which reduced plasmid transmission (AZT, e.g., at 0.25 μg/ml reduced pCT transmission in E. coli by 83.3% and pKpQIL transmission in K. pneumoniae by 80.8% compared to untreated controls). Plasmid transmission was reduced by concentrations of the drugs which are below peak serum concentrations and are achievable in the gastrointestinal tract. These drugs could be used to decolonize humans, animals, or the environment from AMR plasmids.IMPORTANCE More and more bacterial infections are becoming resistant to antibiotics. This has made treatment of many infections very difficult. One of the reasons this is such a large problem is that bacteria are able to share their genetic material with other bacteria, and these shared genes often include resistance to a variety of antibiotics, including some of our drugs of last resort. We are addressing this problem by using a fluorescence-based system to search for drugs that will stop bacteria from sharing resistance genes. We uncovered a new role for two drugs used to treat HIV and show that they are able to prevent the sharing of two different types of resistance genes in two unique bacterial strains. This work lays the foundation for future work to reduce the prevalence of resistant infections.

Emerging concepts in gastrointestinal aspects of HIV-1 pathogenesis and management

GASTROENTROLOGY 2001;120:607-621

Invasive pneumococcal disease in the immunocompromised host

A normal constituent of the human upper respiratory flora, Streptococcus pneumoniae also produces respiratory tract infections that progress to invasive disease at high rates in specific risk groups. The individual factors that contribute to the development of invasive pneumococcal disease in this distinct minority of persons, include immune (both specific and innate), genetic, and environmental elements. Specific defects in host responses may involve age, deficiencies in levels of antibodies and complement factors, and splenic dysfunction. Combinations of these immune defects contribute to the increased rates of invasive pneumococcal disease in patients with sickle cell disease, nephrotic syndrome, neoplasms, and underlying medical conditions such as diabetes and alcoholic liver disease. The number of risk factors are greatest and the rates of invasive disease are highest in patients with HIV-1 infection, which has emerged as a major risk factor for serious S. pneumoniae infection worldwide.

Targeted delivery of antibiotics using liposomes and nanoparticles: research and applications

This review examines current technologies for increasing the bioavailability of antibiotics by means of liposomes or nanoparticles. The main focus is on liposomes. These carriers were preferentially developed because their composition is compatible with biological constituents. Biodegradable polymers in the form of colloidal particles have also been used and show promise for future applications in antimicrobial chemotherapy. The in vivo behaviour of both types of carriers and consequently their therapeutic potential, are determined by their route of administration. Conventional carrier strategies permit the mononuclear phagocyte system to be targeted by intravenous injection of antibiotics. Stealthy strategies avoid major uptake by these cells and extend the systemic presence of these carriers. The purpose of this review is to provide background information in antibiotic targeting gathered from papers published over the last twenty years. It seems clear that such drug carriers (liposomes, nanoparticles) allow increased drug concentration at infected sites but reduce drug toxicity.

Fever of undetermined origin in patients with the acquired immunodeficiency syndrome in Brazil: report on 55 cases

The medical records of patients with AIDS admitted to a general hospital in Brazil from 1989 to 1997 were reviewed retrospectively with the aim at defining the frequency and etiology of fever of undetermined origin (FUO) in HIV-infected patients of a tropical country and to evaluate the usefulness of the main diagnostic procedures. 188 (58.4%) out of 322 patients reported fever at admission to hospital and 55 (17.1%) had FUO. Those with FUO had a mean CD4+ cell count of 98/ml. A cause of fever was identified for 45 patients (81.8%). Tuberculosis (32.7%), Pneumocystis carinii pneumonia (10.9%), and Mycobacterium avium complex (9.1%) were the most frequent diagnoses. Other infectious diseases are also of note, such as cryptococcal meningitis (5.5%), sinusitis (3.6%), Salmonella-S. mansoni association (3.6%), disseminated histoplasmosis (3.6%), neurosyphilis (1.8%), and isosporiasis (1.8%). Four patients had non-Hodgkin's lymphoma (7.3%). We conclude that an initial aggressive diagnostic approach should be always considered because biopsies (lymph node, liver and bone marrow) produced the highest yield in the diagnosis of FUO and the majority of the diagnosed diseases are treatable. The association of diseases is common and have contributed to delay the final diagnosis of FUO in most cases. In our study area the routine request of hemocultures for Salmonella infection and the investigation of cryptococcal antigen in the serum should be considered.

Diarrheal diseases associated with HIV infection

Diarrhea is a major complication of HIV infection and adversely impacts health care costs, quality of life, and even survival of patients. There is a wide variety of potential causes of diarrhea in HIV-infected patients, and the number of pathogens found continues to increase with time. In addition, there is some controversy concerning the role of some organisms in the pathogenesis of diarrhea and the appropriate diagnostic evaluation of affected patients. This article reviews our current understanding of these pathogens and some of the diagnostic and therapeutic approaches for diarrhea associated with HIV infection.

Fever in patients with HIV infection

Fever is a common sign during the course of HIV infection, usually represents a superimposed opportunistic infection, and is almost always a treatable condition. Proper management generally requires detection of the underlying cause, and the diagnostic evaluation is largely driven by the clinical symptoms, associated conditions such as injection drug use, and stage of disease based largely on the absolute CD4 cell count. This article provides guidelines for the management of fever in the patient with HIV infection.

The impact of bacteraemia on HIV infection. Nine years experience in a large Italian university hospital

The object of this case control study was to evaluate the frequency, the risk factors, the microbiological spectrum and the outcome of 249 cases of bacteraemia observed in 209 HIV-infected patients, most them affected by AIDS. The rate of bacteraemia in the total yearly HIV-related admissions increased from 4% in 1985 to 13% in 1993. The more common aetiological agents of bacteraemia were: Staphylococcus aureus (29.7%), non-typhoidal species of Salmonella (14.1%), Staphylococcus epidermidis (10.9%), Streptococcus pneumoniae (8.4%) and Pseudomonas aeruginosa (7.6%). A mixed flora was found in 14% of the episodes. Multivariate analysis of predisposing factors indicated that a low CD4+T-cell count (<0.2 x 10(9)/l) (P=0.01), use of central venous catheters (CVC) (P=0.01) and neutropenia (polymorphonuclear neutrophils <1.0 x 10(9)/l) (P=0.04) were independent risk factors for the development of bacteraemia. Logistic regression did not reveal any association of bacteraemia with intravenous drug abuse (on univariate analysis P=0.04). The response (31.8%). Recurrences to specific therapy was favourable in 170 episodes (68.2%); death occurred in 79 (31.8%). Recurrences arose in 40 patients, 17 (42.5%) of them died. The outcome of bacteraemia was influenced by a low number of CD4+T-cells (P<0.001) but not of polymorphonuclear cells. Our findings suggest that bacteraemia is a relatively common event in HIV-infected patients, especially under particular conditions (e.g. intravenous drug abuse, use of CVC, neutropenia and a low CD4-T-cell count). It requires special attention from physicians who must recognise and treat the condition promptly at an early stage.

Diarrheogenic bacterial enteritis in acquired immune deficiency syndrome: a light and electron microscopy study of 52 cases

Diarrhea, the etiology of which often is obscure, is a major complication of human immunodeficiency virus (HIV) disease. Diarrheogenic bacterial infections (eg, enteropathogenic Escherichia coli) are diagnosed traditionally by stool analysis rather than by examination of endoscopic biopsy specimens. Although E coli rarely have been associated with diarrhea in HIV/acquired immunodeficiency syndrome (AIDS) patients, neither have they routinely been sought. Endoscopic ileal and colorectal biopsy specimens from AIDS-positive patients with chronic diarrhea were analyzed by light and transmission electron microscopy (TEM). The surface epithelium of many large intestinal biopsy specimens previously diagnosed with, for example, nonspecific colitis, regularly showed disarray, degeneration, and necrosis, often with polymorphonuclear neutrophils (PMNs) and eosinophils, irregular cell aggregates, cell shedding, and defects. The crypts were not involved nor were consistent changes noted in the lamina propria. Closer scrutiny of 52 of these biopsy specimens showed gram-negative coliform bacteria intimately associated with histopathology in four distinct patterns. In 22 biopsy specimens, including two from infants, four morphological types of bacilli were observed that adhered to and effaced the brush border in the classic manner with cytoskeletal rearrangement and pedestals. Other bacterial morphologies and/or patterns of epithelial interaction also were observed (ie, thin bacilli intercalated between microvilli [n = 7], loosely associated bacilli [n = 21], and enterocyte invasion by long rods [n = 2]). Three patients also had minor ileal involvement. Infection was greatest in the right colon and coinfections (eg, microsporidia, Mycobacterium avium complex, adenovirus, and especially cytomegalovirus) were documented in 37% (19 of 52) of specimens. Diarrheogenic bacterial infections, some of the E coli type, may be an important cause of diarrhea in HIV disease. Their precise characterization is needed so that stool samples, not endoscopic biopsy specimens, can be used for diagnosis.

Non-typhoid Salmonella subdural empyema in a patient with AIDS

In AIDS patients, non-typhoid salmonella metastatic abscesses in lung and brain due to bacteremia have been described previously. Here we present a case in which a group B Salmonella, serotype Copenhagen, caused right parietal subdural empyema. The etiologic diagnosis was based on culture of pus obtained from the lesion. The patient was treated for bacterial meningitis and made a good recovery. He is at present reasonably well and is taking ciprofloxacin as prophylaxis against salmonella relapse.

In vitro activity of zidovudine alone and in combination with ciprofloxacin against Salmonella and Escherichia coli

The in vitro antibacterial activity of zidovudine alone and in combination with ciprofloxacin was investigated. Zidovudine showed a good activity against Escherichia coli and Salmonella (MIC range 0.5-8 micrograms/ml and 1.5-62 micrograms/ml respectively) isolated from biological samples of HIV-infected patients. These strains proved to be extremely susceptible to ciprofloxacin alone. The interaction between zidovudine and ciprofloxacin ranged from additive activity to indifference. No antagonism was observed: the FIC index for every combination resulted < or = 1.5. The addition of AZT 1 mg/l (clinically achievable plasma concentration after therapeutic doses of 1200 mg/day) did not affect the bactericidal activity of ciprofloxacin; on the contrary, in some cases we observed an increase of bactericidal effect of the quinolone. These data have to be considered in patients with AIDS who can be treated concomitantly with zidovudine and ciprofloxacin.

In vitro activities of nucleoside analog antiviral agents against salmonellae

Zidovudine (ZDV) has antibacterial activity against many members of the family Enterobacteriaceae, including Salmonella species, and may be responsible for a decrease in the frequency of salmonellosis in persons infected with human immunodeficiency virus (HIV). Other nucleoside analogs, such as didanosine (2',3'-dideoxyinosine [ddI]) and zalcitabine (2',3'-dideoxycytidine [ddC]), which have undefined anti-salmonella activity, increasingly are being used in the treatment of HIV infection. To evaluate the anti-Salmonella activity of the antiviral agents ZDV, ddI, ddC, and acyclovir (ACV), we determined MICs for 39 nontyphoidal Salmonella blood isolates. ZDV (MIC for 50% of strains tested [MIC50], 0.5 microgram/ml; MIC range, 0.125 to 4 micrograms/ml) and ddI (MIC50, 8 micrograms/ml; MIC range, 2 to 125 micrograms/ml) had concentration-dependent activity. Anti-Salmonella activity was not observed for ddC or ACV. Nine Escherichia coli blood isolates were inhibited by ZDV (MIC50, 0.125 microgram/ml; MIC range, 0.031 to 1 microgram/ml) to a greater degree than they were by ddI (MIC50, 62.5 micrograms/ml; MIC range, 31 to > 62.5 micrograms/ml). Inoculum size affected susceptibility to ZDV and ddI for Salmonella and E. coli isolates. Resistance to ZDV or to ddI could be induced in vitro in Salmonella isolates, but cross-resistance was not observed. These results indicate that at concentrations achieved during the treatment of HIV infection, ZDV has activity against nontyphoidal salmonellae, although resistance can develop. ddI, ddC, and ACV at currently used dosages would not be expected to be effective in the prevention or treatment of Salmonella infections.

Low-dose trimethoprim-sulfamethoxazole alone and in association with zidovudine for prevention and treatment of murine Pneumocystis carinii pneumonia

Low-dose trimethoprim-sulfamethoxazole (TMP-SMX) alone was found to be as effective as low-dose TMP-SMX plus zidovudine and standard-dose TMP-SMX alone in preventing and treating Pneumocystis carinii pneumonia (PCP) in an immunosuppressed-rat model. Zidovudine alone had no preventive or curative effect on PCP. We conclude that the initially reported reduced incidence of PCP in human immunodeficiency virus-infected patients treated with zidovudine alone is not due to anti-P. carinii activity of zidovudine. Furthermore, the clinical efficacy of low-dose TMP-SMX for the prevention and treatment of PCP should be further investigated.

Intracellular activity of zidovudine (3'-azido-3'-deoxythymidine, AZT) against Salmonella typhimurium in the macrophage cell line J774-2

The antibacterial effect of zidovudine (AZT) has been demonstrated both in vitro and in vivo with experimental models of gram-negative bacterial infections. It has been associated with the absence or low occurrence of nontyphoid Salmonella infections in AIDS patients treated with AZT. Using the macrophage cell line J774-2, we demonstrate the inhibition of intracellular growth of Salmonella typhimurium by AZT. This effect is obtained with one-half of the MIC (1 microgram/ml) of AZT for S. typhimurium. Inhibition of intracellular growth is observed after 4 h of incubation and persists at 24 h. Maximal inhibition is shown at a concentration of 128 micrograms/ml, and no further effect is observed with higher concentrations. When the inhibitory effect of AZT is compared with that of pefloxacin or that of ceftriaxone at half their MICs (0.2 and 0.02 microgram/ml, respectively), AZT and pefloxacin give better results than ceftriaxone. In this study, using an intracellular model, we show that AZT is able to inhibit the intracellular multiplication of S. typhimurium at a minimal effective concentration lower than the MIC, indicating its potential for antibacterial accumulation in the macrophages.