Focal infections due to non-typhi Salmonella in patients with AIDS: report of 10 cases and review

Comparison of the clinical and laboratory features of muscle infections caused by Salmonella and those caused by other pathogens

Muscle infections caused by Salmonella constitute an uncommon complication of extraenteric salmonellosis. The aim of this study was to compare the clinical features of Salmonella muscle infections with those reported in several large series of typical, both tropical and non-tropical, pyomyositis, caused mostly by Staphylococcus aureus. A literature survey of Salmonella muscle infections was carried out by using MEDLINE files 1966 through 2000, and cross-references from the selected articles, as well as major reviews of Salmonella infections and of pyomyositis. The survey yielded 32 cases suitable for analysis. The sex distribution, duration of symptom at presentation, degree of fever, involvement of multiple muscle groups, and leukocyte counts were not significantly different between patients with muscle infections caused by Salmonella and typical pyomyositis patients. In contrast, the median age of the patients with Salmonella muscle infections, and the rate of underlying conditions, were significantly higher than those in typical pyomyositis. Psoas muscle was involved more commonly in Salmonella infections than in typical pyomyositis, and the yield of positive blood cultures and, particularly, the mortality rate, were substantially higher in Salmonella muscle infections than in typical pyomyositis. We conclude that patients with Salmonella muscle infections seem to have some different characteristics with respect to typical pyomyositis, such as older age, and higher rates of associated conditions, psoas muscle involvement, bacteremia, and mortality.

Foodborne Illnesses

Foodborne illnesses cause a substantial human and financial burden. Despite sanitary infrastructure improvements, the incidence of foodborne bacterial infections due to non-typhoidal salmonellae (NTS), Campylobacter jejuni, and enterohemorrhagic Escherichia coli (EHEC) has risen over the last two decades. Overall, viruses account for two thirds of all foodborne illness. Most foodborne illnesses are self-limited. Supportive therapy with rehydration and the correction of electrolyte abnormalities is usually sufficient. Antibiotics play a beneficial role in the treatment of patients with certain foodborne diseases, such as listeriosis and typhoid fever, and all patients with tissue invasive or bloodstream infections. Immunocompromised patients should be treated presumptively. Antibiotics are of variable efficacy for the treatment of many infections limited to the gastrointestinal tract, and recommendations differ between pathogens. Antibiotics are generally helpful for shigellosis and cholera, and possibly beneficial for campylobacteriosis. However, antibiotics are potentially harmful in uncomplicated NTS and EHEC gastroenteritis and generally should not be used. Toxin-mediated food poisoning usually does not require specific therapy. The exception is botulism, for which botulinum antitoxin is highly efficacious if used early in the course of illness. Empiric therapy for gastroenteritis is possibly beneficial, though the magnitude of benefit is modest and incurs the risk of inadvertently treating NTS or EHEC. The choice of antibiotic should be based on local resistance patterns and the results of susceptibility testing.

Oxygen-dependent anti-Salmonella activity of macrophages

Numerous observations have established a crucial role for phagocytic cells in host resistance to Salmonella. Activated macrophages rely on a complex array of oxygen-dependent antimicrobial molecules to inhibit or kill intracellular Salmonella. An initial oxidative bactericidal phase, which is dependent on the respiratory burst phagocyte oxidase (phox) is succeeded by a prolonged nitrosative bacteriostatic phase, which is dependent on inducible nitric oxide synthase (iNOS). The sequential contribution of phox and iNOS to anti-Salmonella innate immunity has been demonstrated both in vitro and in vivo. The temporal progression from the predominant production of reactive oxygen species to the production of nitrogen oxides could optimize the initial reduction in microbial burden while minimizing the immunopathological consequences of the host inflammatory response.

Endocarditis due to rare and fastidious bacteria

The etiologic diagnosis of infective endocarditis is easily made in the presence of continuous bacteremia with gram-positive cocci. However, the blood culture may contain a bacterium rarely associated with endocarditis, such as Lactobacillus spp., Klebsiella spp., or nontoxigenic Corynebacterium, Salmonella, Gemella, Campylobacter, Aeromonas, Yersinia, Nocardia, Pasteurella, Listeria, or Erysipelothrix spp., that requires further investigation to establish the relationship with endocarditis, or the blood culture may be uninformative despite a supportive clinical evaluation. In the latter case, the etiologic agents are either fastidious extracellular or intracellular bacteria. Fastidious extracellular bacteria such as Abiotrophia, HACEK group bacteria, Clostridium, Brucella, Legionella, Mycobacterium, and Bartonella spp. need supplemented media, prolonged incubation time, and special culture conditions. Intracellular bacteria such as Coxiella burnetii cannot be isolated routinely. The two most prevalent etiologic agents of culture-negative endocarditis are C. burnetti and Bartonella spp. Their diagnosis is usually carried out serologically. A systemic pathologic examination of excised heart valves including periodic acid-Schiff (PAS) staining and molecular methods has allowed the identification of Whipple's bacillus endocarditis. Pathologic examination of the valve using special staining, such as Warthin-Starry, Gimenez, and PAS, and broad-spectrum PCR should be performed systematically when no etiologic diagnosis is evident through routine laboratory evaluation.

Typhoid fever and HIV infection: a rare disease association in industrialized countries

Typhoid fever is still a global health problem, mainly in tropical and subtropical areas of the world and in developing countries, where relatively elevated morbidity and mortality rates still are present, mostly because of persisting poor hygienic conditions. In the majority of Mediterranean regions, including Italy, the disease is constantly present, though with a low prevalence rate, as a result of an endemic persistence of Salmonella typhi infection.1-4 On the other hand, in industrialized countries, most cases of S. typhi infection are related to foreign travel or prior residence in endemic countries.4-6 In the United States, 2445 cases of typhoid fever have been reported in the decade 1985 to 1994, and the annual number of cases remained relatively stable over time: over 70% of episodes were acquired in endemic countries (mostly Mexico and India).6 The persisting morbidity of S. typhi also may be supported by the increasing resistance rate of this pathogen against a number of commonly used antimicrobial compounds. For instance, 6% of 331 evaluable S. typhi strains were resistant to ampicillin, chloramphenicol, and cotrimoxazole, and 22% of isolates were resistant to at least one of these three agents in a recent survey performed in the United States.6 The spread of antibiotic resistance among S. typhi isolates is emerging in many countries, and multidrug-resistant strains have been isolated, as well as isolates with poor susceptibility to fluoroquinolones,3-5,7-9 so that in vitro susceptibility should be determined for all cultured strains, and antimicrobial treatment should be adjusted accordingly. Nevertheless, fluoroquinolones (e.g., ciprofloxacin and pefloxacin) or third-generation cephalosporins, still represent the best choice for empirical treatment,2,4,6-8,10 and mortality remains rare in Western countries (less than 1% of episodes), although it is expected to be greater in developing areas of the world. The aim of this report is to describe two cases of typhoid fever that occurred in patients with human immunodeficiency virus (HIV) infection, a rarely reported disease association in industrialized countries.

The compromised traveler

Compromised travelers represent a diverse and challenging group of individuals. They include HIV-infected patients who are at risk for potentially adverse reactions to immunizations, and new exposures to enteric water-borne opportunistic pathogens associated with chronic infections. Such travelers may encounter unfamiliar opportunistic fungi and classical tropical infections, such as leishmaniasis, whose pathogenesis can be enhanced by the presence of prior HIV infection. Other immunocompromised groups include those who are functionally or anatomically asplenic, and patients who are iatrogenically immunosuppressed from medications utilized for solid organ transplantation, chemotherapy, or treatment of malignancies. This population of travelers also includes those with diabetes mellitus who may require adjustments in their dosing, administration, and possibly even the types of insulin used on their trips. These patients are also at greater risk for acquisition of tuberculosis, severe community-acquired pneumonia, urinary tract infections, and pyomyositis. Older travelers present both the infectious disease and travel medicine specialist with issues such events, malignancy-related infections, myocardial infarction, and other forms of cardiopulmonary compromise, which the authors address in this article.