Streptococcus pneumoniae and Legionella pneumophila pneumonia in HIV-infected patients

Legionnaires' Disease Complicated with Rhabdomyolysis and Acute Kidney Injury in an AIDS Patient

Objective

To present a case of an uncommon triad of Legionella pneumonia, rhabdomyolysis, and renal failure, with review of the relevant literature.

Case

A 51-year-old with a history of human immunodeficiency virus (HIV), chronic obstructive pulmonary disease (COPD), and hypertension presented with fever, cough, and shortness of breath over four days. Chest X-ray showed consolidation in left lower lung field; urine was positive for Legionella antigen and myoglobin; creatine kinase was 51092U/L; creatine was 6.9 mg/dL, and his CD4 count was 41 cells/ul. He was managed with azithromycin and levofloxacin and further required dialysis and ventilatory support in the intensive care unit due to renal failure and respiratory failure. He responded well to the treatment and made a complete recovery. Legionella pneumophila infection is a recognized but rare cause of rhabdomyolysis with high morbidity and mortality when there is extrapulmonary involvement. Early diagnosis and appropriate treatment is essential to improve outcomes.

Conclusion

Physicians should consider Legionella pneumonia in patients with rhabdomyolysis, renal failure, and respiratory symptoms. Early diagnosis and treatment have been shown to have good clinical response. Timely intensive care management, together with early and judicious use of dialysis in patients complicated with rhabdomyolysis and renal failure, may lead to good outcomes.

Atypical bacterial pneumonia in the HIV-infected population

Human immunodeficiency virus (HIV)-infected individuals are more susceptible to respiratory tract infections by other infectious agents (viruses, bacteria, parasites, and fungi) as their disease progresses to acquired immunodeficiency syndrome. Despite effective antiretroviral therapy, bacterial pneumonia (the most frequently occurring HIV-associated pulmonary illness) remains a common cause of morbidity and mortality in the HIV-infected population. Over the last few decades, studies have looked at the role of atypical bacterial pneumonia (i.e. pneumonia that causes an atypical clinical presentation or responds differently to typical therapeutics) in association with HIV infection. Due to the lack of available diagnostic strategies, the lack of consideration, and the declining immunity of the patient, HIV co-infections with atypical bacteria are currently believed to be underreported. Thus, following an extensive database search, this review aimed to highlight the current knowledge and gaps regarding atypical bacterial pneumonia in HIV. The authors discuss the prevalence of Chlamydophila pneumoniae, Mycoplasma pneumoniae, Coxiella burnetii, Legionella species and others in the HIV-infected population as well as their clinical presentation, methods of detection, and treatment. Further studies looking at the role of these microbes in association with HIV are required. Increased knowledge of these atypical bacteria will lead to a more rapid diagnosis of these infections, resulting in an improved quality of life for the HIV-infected population.

HIV-associated bacterial pneumonia

Community-acquired bacterial pneumonia (CAP) remains one of the most common opportunistic infections in patients who are infected with the human immunodeficiency virus (HIV). The risk of CAP increases as the CD4 cell count decreases. The common bacterial pathogens that cause CAP in HIV-infected persons are similar to those in HIV-uninfected individuals, with the pneumococcus being the most common pathogen. Prevention of CAP remains critical and necessitates a comprehensive approach addressing, among many other factors, cigarette smoking cessation strategies, antiretroviral therapy adherence, and immunization against those infections for which effective vaccinations are available.

[Bacterial pneumonia in HIV-infected patients (excluding mycobacterial infection)]

Respiratory infections are the most common complications in HIV patients, regardless of the degree of immunosuppression. Even though antiretroviral therapy has a protective effect on the risk of bacterial pneumonia, this still remains high (including those with CD(4)>500/mm(3)). The most frequently isolated bacteria are Streptococcus pneumoniae and Haemophilus influenzae. The clinical and radiological presentations of lower respiratory tract infections in HIV patients are quite variable. The clinical presentation is more severe and the radiological presentation is more atypical if the immunosuppression is severe. The first-line antibiotic therapy is an injectable third-generation cephalosporin (ceftriaxone or cefotaxime) or co-amoxiclav. Pneumococcal vaccination (as well as influenza vaccine) is recommended. Although rare, Nocardia spp. and Rhodococcus equi seem more common among AIDS patients.

Comparisons of clinical characters in patients with pneumococcal and Legionella pneumonia

BACKGROUND/PURPOSE

The etiology of pneumonia is usually unknown, but the availability of urinary pneumococcal and Legionella antigen tests can improve the diagnostic yield. Our aim was to provide clinical clues to help clinicians perform the appropriate urinary antigen tests.

METHODS

A retrospective study of patients admitted to the National Cheng Kung University Hospital between July 2006 and June 2008 was conducted. Patients aged over 18 years presenting with clinical symptoms and signs, radiological findings compatible with pneumonia, and a positive pneumococcal or Legionella pneumophila urinary antigen test, were included. Medical records were reviewed for data collection.

RESULTS

Overall, 55 adults with pneumonia, including 42 with pneumococcal pneumonia (PP) and 13 with Legionella pneumonia (LP), were enrolled. On admission, patients with PP tended to be older (73.5 years vs. 59.1 years; p=0.001), had lower body weights (52.0 kg vs. 69.7 kg; p < 0.001), more frequent respiratory symptoms (59.5%vs. 0%; p < 0.001), and lower systolic (123.0 mmHg vs. 141.0 mmHg; p=0.004) and diastolic blood pressures (68.3 mmHg vs. 81.7 mmHg; p=0.008), compared with patients with LP. However, those with LP had higher body temperatures (39.0°C vs. 37.5°C; p < 0.001), a higher incidence of relative bradycardia (45.5%vs. 0%; p < 0.001), diarrhea (15.4%vs. 0%; p= 0.053), and lower platelet counts (178.5 × 10(3)/mm(3)vs. 233.7 × 10(3)/mm(3); p= 0.026). Radiological findings showed that the major abnormality, lobar consolidation, was indistinguishable between LP and PP. The percentage of patients requiring intensive care (35.7%vs. 38.5%) or ventilator support (31%vs. 23.1%) and in-hospital crude mortality rates (9.5%vs. 7.7%) was similar in both groups.

CONCLUSION

Some clinical and laboratory characteristics may be regarded as important clues indicating the need for an appropriate urinary antigen test in patients with pneumonia.

Molecular pathogenesis of infections caused by Legionella pneumophila

The genus Legionella contains more than 50 species, of which at least 24 have been associated with human infection. The best-characterized member of the genus, Legionella pneumophila, is the major causative agent of Legionnaires' disease, a severe form of acute pneumonia. L. pneumophila is an intracellular pathogen, and as part of its pathogenesis, the bacteria avoid phagolysosome fusion and replicate within alveolar macrophages and epithelial cells in a vacuole that exhibits many characteristics of the endoplasmic reticulum (ER). The formation of the unusual L. pneumophila vacuole is a feature of its interaction with the host, yet the mechanisms by which the bacteria avoid classical endosome fusion and recruit markers of the ER are incompletely understood. Here we review the factors that contribute to the ability of L. pneumophila to infect and replicate in human cells and amoebae with an emphasis on proteins that are secreted by the bacteria into the Legionella vacuole and/or the host cell. Many of these factors undermine eukaryotic trafficking and signaling pathways by acting as functional and, in some cases, structural mimics of eukaryotic proteins. We discuss the consequences of this mimicry for the biology of the infected cell and also for immune responses to L. pneumophila infection.

[Management of the Legionella-link risk in a multicentre area's hospital: lessons learned of a six-year experience]

To reduce the Legionella-linked risk in the several sites of Sud-Francilien Hospital, following a hospital-acquired legionellosis case, a multidisciplinary working group performed an action plan monitored through Legionella pneumophila counts in hot water supply. From 2003 to the first half year 2009, positive points for Legionella pneumophila in the main sites of the hospital decreased from 85.71 to 28.00%, representing a significant reduction of 67.33%. Similar results were observed for three of the four establishments, whereas the last did not describe a pronounced reduction of Legionella pneumophila counts and showed constantly serogroup 1 strains. During this period, investigations of additional cases of legionellosis demonstrated a nosocomial transmission in one case in this last site. Multidisciplinary mobilization in management of Legionella-linked risk contributed to these results.

Hyponatremia in pediatric community-acquired pneumonia

Studies focusing on serum sodium disorders in children with community-acquired-pneumonia (CAP) are nearly entirely lacking, though clinical experience suggests that at least hyponatremia (HN) might be rather common. We evaluated the incidence of hypo- and hypernatremia, in relation to other clinical, laboratory and etiological findings, in pediatric CAP. Serum sodium concentration was measured in 108 ambulatory and hospitalized children with radiologically confirmed CAP of variable severity. The etiology of CAP was revealed by serology in 97 patients. HN (serum sodium < 135 mmol/l) was present in 49 (45.4%) children, and it was mild (> 130 mmol/l) in 92% of the cases. On admission, hyponatremic patients had higher body temperature (38.96 degrees C vs 38.45 degrees C, P = 0.008), white blood cell count (21,074/microl vs 16,592/microl, P = 0.008), neutrophil percentage (78.93% vs 69.33%, P = 0.0001), serum C-reactive protein (168.27 mg/l vs 104.75 mg/l, P = 0.014), and serum procalcitonin (22.35 ng/ml vs 6.87 ng/ml, P = 0.0001), and lower calculated osmolality (263.39 mosmol/l vs 272.84 mosmol/l, P = 0.0001) than normonatremic ones. No association was found with plasma glucose, type of radiological consolidation or etiology of CAP. HN is common but usually mild in children with CAP. HN seems to be associated with the severity of CAP, assessed by fever, need of hospitalization and serum non-specific inflammatory markers.

The evidence for using conjugate vaccines to protect HIV-infected children against pneumococcal disease

Pneumococcal conjugate vaccines (PCVs) are a potentially useful complement to existing treatment strategies in HIV-infected children, for whom pneumococcal infections are common and serious. This Review summarises available data on the burden of pneumococcal disease and the safety and efficacy of PCVs in HIV-infected children. The data demonstrate that children with HIV have significantly increased risk of pneumococcal disease compared with uninfected children; the serotypes included in currently licensed or near-licensure conjugate vaccines include most serotypes that cause invasive pneumococcal disease (IPD) in HIV-infected children and adults; PCVs provide substantial protection against IPD and clinical pneumonia when given to HIV-infected infants; and HIV-infected adults gain an indirect benefit when children in the community are vaccinated. PCV should be considered as an important intervention for improving the lives of HIV-infected children.