Recurrent Salmonella typhimurium bacteremia associated with the acquired immunodeficiency syndrome

Oxidative stress activates transcription of Salmonella pathogenicity island-2 genes in macrophages

The type III secretion system encoded in the Salmonella pathogenicity island-2 (SPI-2) gene cluster facilitates intracellular growth of nontyphoidal Salmonella by interfering with the maturation of Salmonella-containing vacuoles along the degradative pathway. SPI-2 gene products also protect Salmonella against the antimicrobial activity of reactive oxygen species (ROS) synthesized by the phagocyte NADPH oxidase 2 (NOX2). However, a potential relationship between inflammatory ROS and the activation of transcription of SPI-2 genes by intracellular Salmonella is unclear. Here, we show that ROS engendered in the innate host response stimulate SPI-2 gene transcription. We found that the expression of SPI-2 genes in Salmonella-sustaining oxidative stress conditions involves DksA, a protein otherwise known to regulate the stringent response of bacteria to nutritional stress. We also demonstrate that the J and zinc-2-oxidoreductase domains of DnaJ as well as the ATPase activity of the DnaK chaperone facilitate loading of DksA onto RNA polymerase complexed with SPI-2 promoters. Furthermore, the DksA-driven transcription of SPI-2 genes in Salmonella experiencing oxidative stress is contingent on upstream OmpR, PhoP, and SsrB signaling events that participate in the removal of nucleoid proteins while simultaneously recruiting RNA polymerase to SPI-2 promoter regions. Taken together, our results suggest the activation of SPI-2 gene transcription in Salmonella subjected to ROS produced by the respiratory burst of macrophages protects this intracellular pathogen against NOX2-mediated killing. We propose that Salmonella have co-opted inflammatory ROS to induce SPI-2-mediated protective responses against NOX2 host defenses.

Failure of CD4 T Cell-Deficient Hosts To Control Chronic Nontyphoidal Salmonella Infection Leads to Exacerbated Inflammation, Chronic Anemia, and Altered Myelopoiesis

Immunocompromised patients are more susceptible to recurrent nontyphoidal Salmonella (NTS) bacteremia. A key manifestation of HIV infection is the loss of CD4 T cells, which are crucial for immunity to Salmonella infection. We characterized the consequences of CD4 T cell depletion in mice where virulent Salmonella establish chronic infection, similar to chronic NTS disease in humans. Salmonella-infected, CD4-depleted 129X1/SvJ mice remained chronically colonized for at least 5 weeks, displaying increased splenomegaly and more severe splenitis than infected mice with CD4 T cells. Mature erythrocytes, immature erythroid cells, and phagocytes accounted for the largest increase in splenic cellularity. Anemia, which is associated with increased mortality in Salmonella-infected humans, was exacerbated by CD4 depletion in infected mice and was accompanied by increased splenic sequestration of erythrocytes and fewer erythropoietic elements in the bone marrow, despite significantly elevated levels of circulating erythropoietin. Splenic sequestration of red blood cells, the appearance of circulating poikilocytes, and elevated proinflammatory cytokines suggest inflammation-induced damage to erythrocytes contributes to anemia and splenic retention of damaged cells in infected animals. Depleting CD4 T cells led to increased myeloid cells in peripheral blood, spleen, and bone marrow, as well as expansion of CD8 T cells, which has been observed in CD4-depleted humans. This work describes a mouse model of Salmonella infection that recapitulates several aspects of human disease and will allow us to investigate the interplay of innate and adaptive immune functions with chronic inflammation, anemia, and susceptibility to Salmonella infection.

Definitive Cefazolin Therapy for Stabilized Adults with Community-Onset Escherichia coli, Klebsiella Species, and Proteus mirabilis Bacteremia: MIC Matters

Background: Cefazolin is in vitro active against wild isolates of Escherichia coli, Klebsiella species, and Proteus mirabilis (EKP), but clinical evidence supporting the contemporary susceptibility breakpoint issued by the Clinical and Laboratory Standards Institute (CLSI) are limited. Methods: Between 2010 and 2015, adults with monomicrobial community-onset EKP bacteremia with definitive cefazolin treatment (DCT) at two hospitals were analyzed. Cefazolin minimum inhibitory concentrations (MICs) were correlated with clinical outcomes, including primary (treatment failure of DCT) and secondary (30-day mortality after bacteremia onset, recurrent bacteremia, and mortality within 90 days after the end of DCT) outcomes. Results: Overall, 466 bacteremic episodes, including 340 (76.2%) episodes due to E. coli, 90 (20.2%) Klebsiella species, and 16 (3.6%) P. mirabilis isolates, were analyzed. The mean age of these patients was 67.8 years and female-predominated (68.4%). A crude 15- and 30-day mortality rate was 0.7% and 2.2%, respectively, and 11.2% experienced treatment failure of DCT. A significant linear-by-linear association of cefazolin MICs, with the rate of treatment failure, 30-day crude mortality, recurrent bacteremia or 90-day mortality after the DCT was present (all γ = 1.00, p = 0.01). After adjustment, the significant impact of cefazolin MIC breakpoint on treatment failure and 30-day crude mortality was most evident in 2 mg/L (>2 mg/L vs. ≤2 mg/L; adjusted hazard ratio, 3.69 and 4.79; p < 0.001 and 0.02, respectively). Conclusion: For stabilized patients with community-onset EKP bacteremia after appropriate empirical antimicrobial therapy, cefazolin might be recommended as a definitive therapy for cefazolin-susceptible EKP bacteremia, based on the contemporary CLSI breakpoint.

CRTAM Shapes the Gut Microbiota and Enhances the Severity of Infection

Gut lymphocytes and the microbiota establish a reciprocal relationship that impacts the host immune response. Class I-restricted T cell-associated molecule (CRTAM) is a cell adhesion molecule expressed by intraepithelial T cells and is required for their retention in the gut. In this study, we show that CRTAM expression affects gut microbiota composition under homeostatic conditions. Moreover, Crtam-/- mice infected with the intestinal pathogen Salmonella exhibit reduced Th17 responses, lower levels of inflammation, and reduced Salmonella burden, which is accompanied by expansion of other microbial taxa. Thus, CRTAM enhances susceptibility to Salmonella, likely by promoting the inflammatory response that promotes the pathogen's growth. We also found that the gut microbiota from wild-type mice, but not from Crtam-/- mice, induces CRTAM expression and Th17 responses in ex-germ-free mice during Salmonella infection. Our study demonstrates a reciprocal relationship between CRTAM expression and the gut microbiota, which ultimately impacts the host response to enteric pathogens.

Adaptive Immune Responses during Salmonella Infection

The interaction betweenSalmonella and its host is complex and dynamic: the host mounts an immune defense against the pathogen, which in turn acts to reduce, evade, or exploit these responses to successfully colonize the host. Although the exact mechanisms mediating protective immunity are poorly understood, it is known that T cells are a critical component of immunity to Salmonella infection, and a robust T-cell response is required for both clearance of primary infection and resistance to subsequent challenge. B-cell functions, including but not limited to antibody production, are also required for generation of protective immunity. Additionally, interactions among host cells are essential. For example, antigen-presenting cells (including B cells) express cytokines that participate in CD4+ T cell activation and differentiation. Differentiated CD4+ T cells secrete cytokines that have both autocrine and paracrine functions, including recruitment and activation of phagocytes, and stimulation of B cell isotype class switching and affinity maturation. Multiple bacterium-directed mechanisms, including altered antigen expression and bioavailability and interference with antigen-presenting cell activation and function, combine to modify Salmonella's "pathogenic signature" in order to minimize its susceptibility to host immune surveillance. Therefore, a more complete understanding of adaptive immune responses may provide insights into pathogenic bacterial functions. Continued identification of adaptive immune targets will guide rational vaccine development, provide insights into host functions required to resist Salmonella infection, and correspondingly provide valuable reagents for defining the critical pathogenic capabilities of Salmonella that contribute to their success in causing acute and chronic infections.

Bacteremia as a cause of fever in ambulatory, HIV-infected Mozambican adults: results and policy implications from a prospective observational study

Fever is typically treated empirically in rural Mozambique. We examined the distribution and antimicrobial susceptibility patterns of bacterial pathogens isolated from blood-culture specimens, and clinical characteristics of ambulatory HIV-infected febrile patients with and without bacteremia. This analysis was nested within a larger prospective observational study to evaluate the performance of new Mozambican guidelines for fever and anemia in HIV-infected adults (clinical trial registration NCT01681914, www.clinicaltrials.gov); the guidelines were designed to be used by non-physician clinicians who attended ambulatory HIV-infected patients in very resource-constrained peripheral health units. In 2012 (April-September), we recruited 258 HIV-infected adults with documented fever or history of recent fever in three sites within Zambézia Province, Mozambique. Although febrile patients were routinely tested for malaria, blood culture capacity was unavailable in Zambézia prior to study initiation. We confirmed bacteremia in 39 (15.1%) of 258 patients. The predominant organisms were non-typhoid Salmonella, nearly all resistant to multiple first-line antibiotics (ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole). Features most associated with bacteremia included higher temperature, lower CD4+ T-lymphocyte count, lower hemoglobin, and headache. Introduction of blood cultures allowed us to: 1) confirm bacteremia in a substantial proportion of patients; 2) tailor specific antimicrobial therapy for confirmed bacteremia based on known susceptibilities; 3) make informed choices of presumptive antibiotics for patients with suspected bacteremia; and 4) construct a preliminary clinical profile to help clinicians determine who would most likely benefit from presumptive bacteremia treatment. Our findings demonstrate that in resource-limited settings, there is urgent need to expand local microbiologic capacity to better identify and treat cases of bacteremia in HIV-infected and other patients, and to support surveillance. Data on the prevalence and susceptibility patterns of important pathogens can guide national formulary and prescribing practices.

Immunity to salmonellosis

Salmonella enterica is a genetically broad species harboring isolates that display considerable antigenic heterogeneity and significant differences in virulence potential. Salmonella generally exhibit an invasive potential and they can survive for extended periods within cells of the immune system. They cause acute or chronic infections that can be local (e.g. gastroenteritis) or systemic (e.g. typhoid). In vivo Salmonella infections are complex with multiple arms of the immune system being engaged. Both humoral and cellular responses can be detected and characterized, but full protective immunity is not always induced, even following natural infection. The murine model has proven to be a fertile ground for exploring immune mechanisms and observations in the mouse have often, although not always, correlated with those in other infectable species, including humans. Host genetic studies have identified a number of mammalian genes that are central to controlling infection, operating both in innate and acquired immune pathways. Vaccines, both oral and parenteral, are available or under development, and these have been used with some success to explore immunity in both model systems and clinically in humans.

[Intraabdominal infection in inmunodepressed patients]

Diseases of the gastrointestinal system frequently complicate immunosuppressed patients. Endogenous flora is the principal source of infection in humans, especially in patients with dysfunction of the digestive epithelial barrier due to various factors. Bacterial translocation, traumatisms, ischemia and surgery are frequent events in the general population. In addition, important risk factors for abdominal infections in specific patients include tumoral infiltration, mucositis complicating chemotherapy and/or radiotherapy, hypoproteinemia, neutropenia and lymphocyte deficiency. Clinical pictures vary according to patients' baseline condition and the environmental setting, including nosocomial infections. The differential clinical characteristics of abdominal infections observed in distinct types of immunosuppressed patients are reviewed.

Th17 cytokines and the gut mucosal barrier

Local immune responses serve to contain infections by pathogens to the gut while preventing pathogen dissemination to systemic sites. Several subsets of T cells in the gut (T-helper 17 cells, gammadelta T cells, natural killer (NK), and NK-T cells) contribute to the mucosal response to pathogens by secreting a subset of cytokines including interleukin (IL)-17A, IL-17F, IL-22, and IL-26. These cytokines induce the secretion of chemokines and antimicrobial proteins, thereby orchestrating the mucosal barrier against gastrointestinal pathogens. While the mucosal barrier prevents bacterial dissemination from the gut, it also promotes colonization by pathogens that are resistant to some of the inducible antimicrobial responses. In this review, we describe the contribution of Th17 cytokines to the gut mucosal barrier during bacterial infections.

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.

Th17 cytokines and host-pathogen interactions at the mucosa: dichotomies of help and harm

The mucosal surfaces are often the first site of interaction between pathogenic microorganisms and the host. Activation of the mucosal immune response has the important function of containing an infection and preventing dissemination of pathogens to systemic sites (barrier function). Numerous lines of evidence suggest that the barrier function is orchestrated by a subset of cytokines (interleukin (IL-)17 and IL-22), which belong to the Th17 family. IL-17 and IL-22 induce expression of antimicrobial peptides and neutrophil chemoattractants at mucosal sites, and thus play an important role in controlling mucosal infections. However, there is increasing evidence that mucosal pathogens achieve greater colonization during inflammation because they are resistant to a subset of these antimicrobial responses. In this review we compare the antimicrobial responses elicited by Th17 cytokines during mucosal infections with four different pathogens: Klebsiella pneumoniae, Citrobacter rodentium, Candida albicans and Salmonella typhimurium. We will then discuss which responses may constitute the mucosal barrier, thus providing a benefit to the host, and which ones may promote the colonization of pathogens, thereby providing a benefit to the microbes.

Increased sensitivity to Salmonella enterica serovar Typhimurium infection in mice undergoing withdrawal from morphine is associated with suppression of interleukin-12

We have shown previously that withdrawal from morphine induces immunosuppression in mice. The present study reports the effects of morphine withdrawal on infection with Salmonella enterica serovar Typhimurium. Mice were made dependent on morphine by the implantation of a slow-release morphine pellet for 96 h. Controls received a placebo pellet. Withdrawal was induced by pellet removal. Mice were inoculated intraperitoneally with Salmonella 24 h postwithdrawal. Morphine withdrawal sensitized mice to Salmonella infection, as evidenced by increased mortality, shortened mean survival time, and increased bacterial load in the blood, spleen, and liver. Examination of the levels of a panel of proinflammatory cytokines in sera of infected, morphine-withdrawn mice showed that morphine withdrawal inhibited the elevation of interleukin-12p70 (IL-12p70). The production of IL-12p40 in morphine withdrawal mice was also suppressed. The administration of exogenous IL-12 significantly decreased the bacterial burden in morphine-withdrawn mice. These studies show a correlation between the suppression of IL-12 production and a heightened susceptibility to Salmonella infection in mice undergoing withdrawal from morphine.

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.

Risk Factors for Recurrent Bacteremia in Adult Patients with Nontyphoid Salmonellosis

BACKGROUND

This study sought to find the risk factors for recurrent bacteremia in adult patients with nontyphoid salmonellosis.

METHOD

Retrospective chart review.

RESULT

Between September 1984 and December 2003, 235 adult (age > or = 18 years old) patients with bacteremia with nontyphoid salmonellosis were admitted to our hospital. Among them, 130 patients (55%) had immunodeficiency, 31 patients (13%) had systemic lupus erythematosus, 26 patients (11%) had hematologic malignancies, 50 patients (21%) had solid organ cancers, and 39 patients (17%) had endovascular infections. Thirty-seven patients had recurrent bacteremia during the study period. Both univariate and multivariate analysis showed that immunodeficiency was the only predictor of recurrent bacteremia (odds ratio, 2.79; P = 0.013). The overall hospital mortality rate was 26%: 8% for patients with recurrent bacteremia and 29% for patients without recurrence. The independent risk factors of hospital death were old age, not recurrent infection, and solid organ cancers.

CONCLUSION

Old age, systemic lupus erythematosus, malignancies, and immunodeficiency were common in adult patients with nontyphoid Salmonella bacteremia. The incidence of recurrent bacteremia was 16%. Immunodeficiency predisposed patients to recurrent bacteremia. Recurrent bacteremia was associated with a lower hospital mortality rate, however.

Salmonella meningitis in adults infected with HIV: case report and review of the literature

We report a case of Salmonella infantis meningitis in a patient infected with HIV who was successfully treated with 4 weeks of therapy and has had no relapses after 12 months of follow-up. Only 10 episodes of Salmonella species meningitis in patients infected with HIV are reported in the literature.

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.

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

GASTROENTROLOGY 2001;120:607-621

Ultrastructure of the polymorphonuclear leucocytes in human immunodeficiency virus infection

The ultrastructure of polymorphonuclear leucocytes (PMNL) was studied in 16 patients infected with the human immunodeficiency virus (HIV). PMNL were isolated from HIV-infected patients with CD4+ lymphocytes counts > 200/mm3 (without signs of active infection) (n = 12) (group 1), or < 200/mm3 (n = 4) (group 2), and from 16 healthy volunteers (group 3). Immunoelectron microscopy staining using an anti-beta 2 integrin antibody (anti-CD18) was performed on PMNL from three individuals of group 2 and of three individuals of group 3, before and after incubation with N-formyl-methionyl-leucylphenylalanine (f-MLP). The radical oxygen intermediates (ROI) production of PMNL was investigated by luminol-mediated chemiluminescence. A number of ultrastructural abnormalities in PMNL were found in a higher proportion in HIV-infected patients. These were: (a) an increase in the size of the Golgi apparatus and in the number of mitochondria, and in the quantity of endoplasmic reticulum; (b) some dysplastic features including large cytoplamic vacuoles, whorl of myelin, and nuclear pockets; (c) an increase prevalence of multivesicular bodies compared with control PMNL; (d) some cylindrical confronting cisternae and tubuloreticular structures. After anti-CD18 staining, gold particles were seen on the plasma membrane and more rarely inside the cytoplasm of PMNL from each group but no decrease in this staining was noted in HIV PMNL. Incubation with f-MLP similarly increased the immunostaining of the PMNL in each group. In vitro ROI production was significantly depressed for HIV PMNL compared with control PMNL. Some ultrastructural abnormalities observed in this study could support the possibility that one of the mechanisms underlying the qualitative functional defects of PMNL from HIV-infected patients may be related to some cytopathic effect.

Gram-negative bacillary bacteremia in human immunodeficiency virus type 1-infected children

BACKGROUND

HIV-infected children are particularly susceptible to serious bacterial infections including Gram-negative bacillary bacteremia (GNB). However, the information available on GNB in these children is limited.

METHODS

Retrospective review of hospital charts of HIV-infected children with GNB diagnosed between 1980 and 1997. The association between bacteremic episodes, degree of immunosuppression, HIV severity, medical treatment and clinical outcome was assessed.

RESULTS

Of 680 HIV-infected children, 72 (10.6%) had 95 episodes of GNB. Statistical analyses were restricted to data from the first episode. The mean age (+/-SD) at diagnosis of GNB was 2.5 +/- 2.7 years (median, 1.6). The predominant organisms were Pseudomonas aeruginosa (26.4%), nontyphoidal Salmonella (15.3%), Escherichia coli (15.3%) and Haemophilus influenzae (12.5%). The relative frequency, per 5-year interval, of P. aeruginosa bacteremia steadily increased from 13% during 1980 through 1984 to 56% during 1995 through 1997. There were no cases of H. influenzae bacteremia after January 1, 1990. Eighty percent of GNB developed in children with AIDS and 72.2% developed in those with severe immunosuppression. Hypogamma-globulinemia and neutropenia were present in only 4.9 and 10.4% of first episodes, respectively. The overall case-fatality rate of GNB was 43.0%, and in children younger than 12 months it was 54.2%.

CONCLUSIONS

A diagnosis of AIDS and/or severe immunosuppression was associated with increased risk of GNB, especially among younger children. Because of the high mortality of GNB, a broad spectrum antimicrobial therapy that effectively covers these organisms should be promptly instituted when bacteremia is suspected in HIV-infected children.

Impaired antibody response after immunization of HIV-infected individuals with the polysaccharide vaccine against Salmonella typhi (Typhim-Vi)

Infections with Salmonella species, including Salmonella typhi, are more frequently observed in HIV-infected individuals than in healthy individuals. HIV-infected individuals were vaccinated with polysaccharide vaccine against Salmonella typhi (Typhim-Vi) which is assumed to be a T-cell-independent antigen. We found that the antibody response in patients with < 200 x 10(6)/l CD4+ T lymphocytes was significantly lower compared with patients with > or = 200 x 10(6)/l CD4+ T lymphocytes and healthy controls. The antibody response after vaccination with the polysaccharide salmonella Vi-antigen was correlated with the number of CD4+ T lymphocytes and therefore Typhim-Vi can be considered to be a T-cell-independent type 2 antigen. The results of this study indicate that after vaccination the proportion of HIV-infected individuals with protective antibody concentrations against Salmonella typhi will be lower than in healthy controls.

Salmonella septic arthritis in systemic lupus erythematosus and other systemic diseases

Salmonella infection is an important problem in immunocompromised patients. The synovium is a particular metastatic focus of Salmonella infection and can result in many disabilities of life. Systemic lupus erythematosus (SLE) patients were highly susceptible to Salmonella infection. In the past 6 years, 41 patients with Salmonella septic arthritis have been treated in our hospital. Eleven patients had an underlying systemic disease of SLE which presented with a distinctive clinical course. Alcoholic liver disease (six cases) was another common underlying systemic disease. The most frequent predisposing articular factor was avascular necrosis (16 cases). The hip joint was the most commonly involved site. Salmonella group B was the most common serotype (30/41). Seventy-three per cent (8/11) of the SLE group had involvement of two or more joints compared with only three out of 30 patients in the non-SLE group. The sex differentiation shows a predominance of young females (10/11) in the SLE group and middle-aged males in the non-SLE group. Moreover, in the SLE group, all 11 patients shared the risk of lupus nephritis and steroid use. Ten patients had Salmonella group B bacteraemia and five had urinary tract infections simultaneously. In the non-SLE group, there were 10 patients with a history of steroid use, three with antecedent enteritis, 12 with bacteraemia, and three with necrotising fasciitis. Seven patients in each of the groups had a recurrent course. However, three patients in the non-SLE group had died during the episode of septic arthritis.

Salmonella lung involvement in patients with HIV infection

STUDY OBJECTIVE

To determine the frequency, clinical features, and outcome of lung involvement in HIV-infected patients having nontyphoid strains of Salmonella bacteremia.

DESIGN

A retrospective clinical study.

PATIENTS AND SETTING

We studied the records of all HIV-infected patients with Salmonella bacteremia diagnosed at a university tertiary hospital from January 1987 to December 1995.

RESULTS

Lung involvement was found in 18 (35.3%) of 51 HIV-infected individuals with Salmonella bacteremia. Six of 18 (33.3%) were diagnosed as having definite Salmonella pulmonary infection by isolation of Salmonella from respiratory specimens, while probable Salmonella lung disease was considered in two patients who developed lung abscesses without the identification of any pathogen. Predisposing factors for focal disease, such as prior lung disease or Salmonella serotype, were equally prevalent regardless of the presence of Salmonella pulmonary involvement. Cavitary infiltrates or abscess formation were seen in five of the eight patients. With the exception of one patient coinfected with Nocardia asteroides who died 1 month later, all patients were cured with antibiotic treatment. Superinfection with other pulmonary pathogens (10 cases, 56%) was more frequent than Salmonella pneumonia; the most frequent alternative diagnosis was Pneumocystis carinii pneumonia (5 cases, 28%), pyogenic bacterial infection (17%), and tuberculosis (11%).

CONCLUSIONS

In HIV-infected patients with Salmonella bacteremia, lung involvement is frequent, although there were no significant factors to explain this association. Cavitary disease was the most common radiologic pattern, and focal lung disease due to Salmonella does not seem to be associated with a worse prognosis. Coinfection and superinfection with other respiratory pathogens are more common than isolated Salmonella lung disease, and therefore, additional diagnostic procedures must be considered in the evaluation of these patients.

Bacterial infections

Non-opportunistic bacterial infections are an important cause of morbidity and mortality for HIV-infected adults and children. Factors associated with increased risk of these include altered B- and T-cell function; altered phagocytic cell function; skin and mucous membrane defects; and use of indwelling vascular catheters, antibiotics, or cytotoxic agents. The pathogens encountered most frequently are S. aureus, S. pneumoniae, H. influenzae, Salmonella sp., and Pseudomonas aeruginosa. Less commonly encountered organisms include Rhodococcus equi, Listeria monocytogenes, Shigella sp., and Nocardia asteroides, Strategies for prevention as well as diagnosis and treatment of these are discussed.

Non-typhoidal Salmonella bacteraemia: clinical features and risk factors

A case control study was conducted to determine the risk factors of non-typhoidal Salmonella bacteraemia. Eighty adult patients with non-typhoidal Salmonella bacteraemia admitted to Siriraj Hospital from January to December 1993 served as the cases. The controls comprised 3 groups: group 1, 80 adult in-patients with Escherichia coli bacteraemia; group 2, 80 adult in-patients who did not have bacteraemia and had been admitted to the hospital during the same period as the cases; group 3, 80 in-patients who did not have Salmonella bacteraemia and matched the cases in terms of gender, age, hospital services and admission date. AIDS and corticosteroid use were the major risk factors for acquiring non-typhoidal Salmonella bacteraemia with an odds ratio of 7.27 to 12.31 (95% confidence interval of 3.39 to 29.40). Almost all patients with non-typhoidal Salmonella bacteraemia presented with a fever for a median duration of 7 days. AIDS patients usually had concomitant opportunistic infections. Salmonella group D was the most common serogroup. Most patients were treated with co-trimoxazole, quinolones, ceftriaxone and ampicillin. Localized suppurative complications were observed in 14% of the patients; the overall mortality rate was 36.3%, 12% of whom died prior to receiving appropriate antibiotics for Salmonella.

Recovery of uncommon bacteria from blood: association with neoplastic disease

Table 6 is a summary of the organisms discussed with a listing of the environmental source, the endogenous source, the predisposing factors including neoplasms, and the postulated mechanisms by which the organism can gain access to the circulation. The evidence considered indicates that the entrance of one of these microorganisms into the bloodstream of a human being depends on the presence of multiplicity of predisposing factors. In the majority of cases of bacteremia due to one of these unusual organisms, two or more predisposing factors are present. Certain predisposing factors, such as cancer chemotherapy or intravenous catheterization, often provide a barrier break, while others, such as liver disease, may render the host immune system less capable of clearing organisms from the circulation. For organisms such as Campy-lobacter, Listeria, and Salmonella spp., attributes that allow the invasion of a healthy host are present and seem to be enhanced by the simultaneous presence of a predisposing condition, such as liver disease, in the host. Although somewhat fragmentary, a number of individual case reports describe bacteremia due to one of these organisms occurring weeks to years after surgery and after other therapeutic measures had effected a supposed cure of a cancer. It may be speculated that cancer patients, even after a cure, are still susceptible to bloodstream invasion by one of the aforementioned organisms by virtue of the presence of one or more predisposing metabolic, physiologic, or immunologic factors, even though these factors may be cryptic. The predominance of hematologic malignancies among cases of bacteremia due to these unusual organisms is also apparent. Although, as pointed out by Keusch (169), the reduction in the performance of immune function in hematologic malignancies compared with solid tumors is likely to be responsible, other associations of certain organisms with specific neoplasms warrant further examination. The frequency of bloodstream infections of Salmonella typhimurium and Capno-cytophaga canimorsus in Hodgkin's disease patients seems likely due to a particular mechanism which infection by these species is favored. The specific nature of these mechanisms remains to be determined. The recovery of any unusual bacterium from blood should warrant a careful consideration of the possibility of underlying disease, especially cancer. Microbiologists should advise clinicians of the unusual nature of the identified organism and provide the counsel that certain neoplastic processes, often accompanied by neutropenia, render the human host susceptible to invasion by almost any bacterium. The recovery of such organisms as C. septicum or S. bovis should prompt the clinician to aggressively seek to identify an occult neoplasm if one has not yet been diagnosed.

Small intestinal manifestations of HIV infection

The small intestine is a common site of involvement in patients infected with the human immunodeficiency virus (HIV). Although there are numerous mechanisms by which small intestinal disease may occur in HIV infected patients, the resulting clinical manifestations of these disorders are remarkably similar and include the development of diarrhoea, weight loss and nutrient deficiencies. In fact, the original designation of AIDS in African countries as the 'slim disease' underlines the importance of small intestinal involvement (most likely secondary to parasitic infections) which commonly occurs in Third World Countries. The current review will provide a clinically oriented overview of small intestinal disease in patients infected with HIV. Because specific data on treatment of small intestinal diseases in AIDS is often lacking, some presented information is based on the author's experience and opinions.

Recurrent Salmonella enteritidis meningitis in a patient with AIDS

The profound impairment of cellular immunity associated with HIV infection predisposes to salmonella infections with recurrent bacteremia as a well recognized opportunistic infection in patients with AIDS. However, salmonella meningitis is extremely rare in this group of patients and only 4 cases have been reported so far. We present 1 case of recurrent Salmonella enteritidis meningitis in an AIDS patient. The infection recurred despite prolonged antimicrobial therapy. Treatment of salmonella infections in AIDS patients may be very difficult and, in some cases, lifelong maintenance therapy may be required.

Salmonella osteomyelitis and arthritis in sickle cell disease

Salmonellosis is one of the most frequent serious infections in sickle cell patients and remains a significant cause of morbidity and mortality in this population. Capillary occlusion secondary to intravascular sickling may devitalize and infarct the gut, permitting Salmonella invasion. Reduced function of the liver and spleen, together with interference with reticuloendothelial system function due to erythrophagocytosis, suppresses clearing of these organisms from the blood stream. Abnormal opsonizing and complement function probably also play a role. The expanded bone marrow with sluggish flow leads to an ischemic focus for salmonella localization. The majority of Salmonella infections in sickle cell patients involve bones (especially long bones) and joints and occur most frequently in early childhood. Multiple sites, often symmetrical, are usually involved. It is imperative to distinguish Salmonella osteomyelitis from bone infarctions. While clinical and hematologic data may be suggestive, radionuclide bone imaging studies, particularly combined technetium and gallium scintigraphy and technetium sulphur colloid bone marrow scans, and magnetic resonance imaging appear more sensitive and specific. Salmonella osteomyelitis is best managed medically. Chloramphenicol, ampicillin, and trimethoprim/sulfamethoxazole have been used most frequently; however, newer beta lactams and quinolones are more active. Septic arthritis carries a poorer prognosis and often requires aggressive surgical intervention.

Salmonella infections in a cancer center

Data concerning 40 patients hospitalized in a cancer center and Salmonella infection were analyzed. Hematological malignancy was present in 24 patients (60%) and solid tumor in 14 patients (35%). Among the predisposing factors, antineoplastic chemotherapy was the most frequent (60%) followed by antacid use (47.5%), corticosteroids (37.5%), granulocytopenia below 500 neutrophils/microliters (15%), surgery (10%) and splenectomy (2.5%). Bacteremia was the most frequent clinical syndrome accounting for 42.5% of the patients. Focal infection, enteritis and carrier state accounted for the remaining 30%, 20% and 7.5% respectively. Salmonella typhimurium and S. dublin represented 65% of the isolates, with clear association between serotype dublin and bacteremia. All S. dublin isolates were resistant to chloramphenicol. Among dublin and typhimurium serotypes, 20% the isolates were resistant to the traditional antibiotics used in salmonellosis (ampicillin, chloramphenicol, cotrimoxazole). All strains were susceptible in vitro to cephalosporins. The frequency of relapse was 15% and the overall mortality (within 30 days) attributed to Salmonella infection was 15%.

Cerebral Salmonella typhimurium abscess in a patient with a stroke

A 59-year-old woman with renal failure was admitted in a coma with seizures. Computerized tomography (CT) revealed a frontal mass in the right cerebral hemisphere and on day 12 new low density areas had appeared in both the right and left hemisphere. Blood cultures on day 13 grew Salmonella typhimurium, and the patient died the next day. An autopsy showed cerebral infarction with abscess formation. The elusive features of non-typhoid Salmonella infections make it advisable to obtain blood and faecal cultures from susceptible patients with fever or focal disorders of unknown aetiology.

The Salmonella typhimurium virulence plasmid increases the growth rate of salmonellae in mice

The virulence plasmids of Salmonella typhimurium and other invasive Salmonella serovars have long been associated with the ability of these bacteria to cause systemic infection beyond the intestines in orally inoculated animals. Genetic analysis of virulence genes on the high-molecular-weight plasmids has revealed that no more than five genes spanning a 6.2-kb region are sufficient to replace the entire plasmid for conferring virulence. However, the exact virulence function(s) encoded by these genes has not been elucidated. In this report, we measured the possible effect of the virulence plasmid on the growth rate of S. typhimurium in mice by two complementary procedures. The first procedure used segregation of a temperature-sensitive plasmid in vivo to provide a measure of bacterial divisions and the number of recovered marker plasmid-containing salmonellae as a measure of killing. In the second procedure, aroA deletions were transduced into virulence plasmid-containing and plasmid-cured S. typhimurium. Since AroA- salmonellae are inhibited for growth in vivo, if the virulence plasmid affected only growth rate, no difference in the recoveries of the paired AroA- strains would be seen. Virulence plasmid-containing S. typhimurium segregated the marker plasmid more rapidly than did the virulence plasmid-cured strain, and AroA- derivatives of both strains were recovered equally from mice. Therefore, the S. typhimurium virulence plasmid increased growth rate but had no detectable effect on killing or bacterial movement into deep tissues. To examine whether the plasmid accomplished this function by affecting the intracellular/extracellular location of bacteria, orally infected mice were injected with gentamicin to kill the extracellular bacteria. Wild-type and plasmid-cured S. typhimurium strains were equally resistant to gentamicin in vivo and hence most likely located intracellularly to equal degrees. When wild-type and plasmid-cured S. typhimurium strains were sequestered within peritoneal chambers in mice, the resulting extracellular growth was equal. Therefore, the virulence plasmid increases the growth rate of S. typhimurium in mice, probably within mouse cells.

Neisseria spp. and AIDS

Neisseria meningitidis from various serogroups and two commensal neisseriae (N. sicca and N. perflava) were isolated from 15 patients at various stages of human immunodeficiency virus infection in this clinical and bacteriological study. The cases were grouped into the following three classes: (i) infections with an N. meningitidis strain of a serogroup known to be pathogenic (A, B, or C) and apparently independent of the human immunodeficiency virus infection, (ii) infections with a N. meningitidis strain of a serogroup which is normally either commensal or poorly pathogenic (serogroups Y, X, Z, and Z,29E), (iii) pulmonary and disseminated infections occurring in the course of the clinical evolutionary stage of AIDS, in two cases of which commensal neisseriae (N. sicca and N. perflava) were isolated from blood cultures.

Medical management of AIDS patients. Bacterial and fungal infections

The rapid and thus far generally inexorable rise in HIV infections has led to a series of opportunistic infection that includes those caused by bacteria, yeasts, and members of the Eumycetes. The infections range in prevalence from occasional to highly prevalent, in severity from trivial to fatal, and in anatomic areas involved from local to disseminated. They occur as isolated, concurrent, or sequential infections with regard to other opportunistic diseases. Some vary in their geographic distribution. They may be newly acquired or reactivated and occur early or late in the course of HIV infection. Bacterial infections are usually easily treated, although they frequently disseminate and often recur after seemingly appropriate treatment. In contrast, all but the mildest fungal infections are difficult to treat and even more difficult or impossible to eradicate. The diagnosis of bacterial and fungal infections begins with clinical suspicion and involves relatively standard methodology. Treatment of the systemic mycoses and some bacterial infections in HIV infected patients is punctuated by exaggerated side effects of therapy, frequent relapses, and the need for maintenance suppressive therapy.

The management of HIV-related illness in the emergency department

As the AIDS epidemic progresses, the number of ED patients with HIV-related illness will continue to increase. As reviewed in this article, much of the existing clinical research in HIV-related illness has an impact on the diagnostic and management issues that arise in the ED. Many of the patterns of disease, subtleties of diagnosis, and therapies unique to AIDS patients have already been greatly elucidated. However, as the recognition of this disease goes into only its second decade, many questions remain. Further studies are needed, for example, to improve physician assessment of HIV risk, to further identify discriminators of PCP and bacteremia, and to optimize strategies for disposition and outpatient management. In the future, in the areas of research and clinical care, emergency medicine will play an increasing important role in the front-line attack on this modern epidemic.