The Etiology of Lower Respiratory Tract Infections in People with Diabetes
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REVIEW Renata Barbara Klekotka1, Elżbieta Mizgała2, Wojciech Król1 1Department of Microbiology and Immunology, Medical University of Silesia in Katowice, Zabrze, Poland 2Department of Family Medicine, Medical University of Silesia in Katowice, Zabrze, Poland The etiology of lower respiratory tract infections in people with diabetes The authors declare no financial disclosure Abstract Patients with diabetes mellitus (DM) are likely to develop many types of infections, which affect the transport of glucose into tissues. Diabetes increases the susceptibility to different kinds of respiratory infections, is often identified as an independent risk factor for developing lower respiratory tract infections. Pulmonary infections caused by Mycobacterium tuberculosis, Staphylococ- cus aureus, gram-negative bacteria and fungi may occur with an increased frequency, whereas infections due to Streptococcus pneumonia or influenza virus may be associated with increased morbidity and mortality. During lung infection, there are changes in the local and ciliary epithelial lining. Increased susceptibility to pneumococcal infection by people with diabetes is the result of reduced defense capability of antibodies to protein antigens. The relationship between diabetes and pulmonary tuberculosis is well known, and the incidence of tuberculosis in diabetic individuals is 4−5 times greater than among the non-diabetic population. It is thought that malfunction of monocytes in patients with diabetes may contribute to the increased susceptibility to tuberculosis and/ or a worse prognosis. Hospitalization of patients with diabetes due to influenza virus or flu-like infections is up to 6 times more likely to occur compared to healthy individuals, also diabetic patients are more likely to be hospitalized due to infection complications. Im- munization with influenza and anti-pneumococcal vaccines is recommended to reduce hospitalizations, deaths, and medical expen- ses. Diabetes, especially the uncontrolled one, predisposes to fungal infection, the most common candidiasis and mucormycosis. Key words: diabetes mellitus, Streptococcus pneumoniae, influenza, tuberculosis, mycosis Pneumonol Alergol Pol 2015; 83: 401–408 Introduction can Thoracic Society (ATS), the Infectious Diseases Society of America (IDSA) and the British Thoracic Lower respiratory tract infections (LRTI) are Society (BTS) presented comprehensive guidelines the most common diseases in the world [1]. In the [3]. Some of the most common respiratory tract United States, the incidence of lower respiratory infections in diabetics includes: acute bronchitis, tract infections and associated mortality rate are sinusitis, otitis media, pneumonia. Etiological higher than of other infectious diseases. According factors are bacterial, viral and fungal. Respiratory to the WHO report, LRTI accounted for 6.9% of all tract infections are the cause of increased hospita- deaths in 2002 [2]. High rates of lower respiratory lizations in diabetic individuals compared to those tract infections contributed to the development of without diabetes [4−6]. guidelines for the diagnosis and treatment of lower respiratory tract infections by European countries Immunodeficiency in diabetes and the USA. These guidelines are subject to regu- lar evaluation, which is based on review of multiple The complement system is one of the main medical and epidemiological studies. The Ameri- mechanisms of humoral immunity. It contains Address for correspondence: Renata Klekotka, Department of Microbiology and Immunology, Medical University of Silesia in Katowice, Jordana 19, 41−808, Zabrze, Poland, tel: +48 32 272 25 54, e-mail: [email protected] DOI: 10.5603/PiAP.2015.0065 Received: 29.04.2015 Copyright © 2015 PTChP ISSN 0867–7077 www.pneumonologia.viamedica.pl 401 Pneumonologia i Alergologia Polska 2015, vol. 83, no. 5, pages 401–408 plasma proteins and cell surface proteins whose HbA1c < 8.0% results in the proliferative activity main functions are to promote opsonization and of T helper cells (CD4 +) and their response to phagocytosis of microorganisms by macrophages antigens. Glycation of immunoglobulin occurs in and neutrophils and induction of lysis of micro- diabetic patients in proportion with the increase in organisms. Induction of the complement system HbA1c, and this may harm the biological function mediates a B cell antibody production. Lowering of the antibodies (Table 1) [4]. In addition, infec- the content of C4 in patients with DM may be tious diseases in patients with DM may result in associated with dysfunctional neutrophils and metabolic complications such as hypoglycemia, decreased response to cytokines. Mononucle- ketoacidosis, and coma. Table 2 shows the effect of ar cells and monocytes of DM patients release diabetes on the immune dysfunction in diabetics. lower amounts of interleukin-1 (IL-1) and in- terleukin-6 (IL-6) in response to stimulation by Community and hospital-acquired pneumonia lipopolysaccharide (LPS), which is activated in the process of phagocytosis [7, 8]. The increased Community-acquired pneumonia (CAP) is glycosylation may inhibit IL-10 production by one of the most common infections of the lower lymphocytes and macrophages. Additionally, the respiratory tract and accounts for 5−12% of amount of interferon gamma (IFN-g) released by all LRTI [9]. In Europe, the incidence of com- T cells and NK cells, and tumor necrosis factor munity-acquired pneumonia is estimated to be (TNF-a) released by T cells and macrophages is 5−12 per 1,000 persons per year. Mortality of reduced. The process of glycation also reduces the outpatients with CAP does not exceed 1% of myeloid cells expression of surface major histo- hospitalized cases [10]. Pathogens that cause compatibility complex class I (MHC), which impa- CAP are viruses, bacteria and other unusual mi- irs cell-mediated immunity [7, 8]. Hyperglycemia crobes. The microbial composition is complex reduces the mobilization of polymorphonuclear and often depends on the geographical area, leukocytes, chemotaxis and phagocytic activity. population and seasonal changes. The most Hyperglycemic environment also prevents the common CAP pathogens include Streptococcus antibacterial functions of the immune system, pneumoniae, Mycoplasma pneumoniae, Chla- resulting in inhibition of glucose-6-phosphate mydophila pneumoniae, Legionella pneumophila (G6PD), which in turn stimulates apoptosis of and Haemophilus influenzae. A high percentage leukocytes and reduces the transmigration of le- of CAP cases in adults is due to mixed bacterial ukocytes across the endothelium. In tissues that and atypical pathogens [10, 11]. CAP caused do not consume insulin, hyperglycemic environ- by methicillin-resistant Staphylococcus aureus ment increases the intracellular concentration of (MRSA) is still rare, however, it accounts for an glucose, which is then metabolized using NADPH increasing number of cases reported in the Uni- as a cofactor. The decrease in concentration of ted States [12, 13]. It is generally accepted that NADPH prevents the action of molecules that play MRSA causes more frequently infections of the a key role in the mechanisms of antioxidant func- skin and soft tissue than of the respiratory tract. tions of a cell, which leads to an increase in tissue CAP caused by Escherichia coli and Klebsiella sensitivity to oxidative stress. With respect to the pneumoniae is significantly more frequent in mononuclear cells, some studies have shown that patients over 50 years of age [14]. Table 1. Pathophysiological changes resulting from infection in patients with diabetes mellitus Diabetes mellitus Hyperglycaemia/ un- Related metabolic Molecular and Impaired immunological defense controlled diabetes consequences immunologic events HbA1c > 8.0% Glycation, cells Inhibit: interleukin 10 Polymorphonuclear dysfunction and reduction of C4 compo- Glycosuria hypoglycemia, keto- (IL-10) interferon gamma nent reduces major histocompatibility complex class I (MHc) acidosis, coma (IFN-g) tumor necrosis fac- decreased function of the antibodies and T lymphocytes rere- tor (TnF-a) lower amounts sponse abnormalities in neutrophil function, such as impaired of interleukin-1 (IL-1) and chemotaxis, phagocytes, and bacterial killing interleukin-6 (IL-6) increase in tissue sensitivity to oxi- dative stress 402 www.pneumonologia.viamedica.pl Renata Barbara Klekotka et al., The etiology of lower respiratory tract infections in people with diabetes Table 2. Pathophysiology of infections associated with diabetes mellitus Diabetes mellitus Decrease T lymphocytes respon- Hyperglycemia: increased Large number of medical in- GIT-gastrointestinal tract: se, decrease neutrophil function, virulence of infectious micro- terventions, neuropathy, dysmotility lower secretion of inflammatory organisms and apoptosis of angiopathy cytokines, anti-oxidant system polymorphonuclear leukocytes . depression, disorder of humoral Glycosuria. immunity. Hospital-acquired pneumonia (HAP) is lung and more so among non-diabetic patients: adju- inflammation that occurs at least 48 hours after sted 30-day MRRs for glucose level ≥ 14 mmol/l hospital admission. This group of diseases refers were 1.46 (1.01–2.12) and 1.91 (1.40–2.61), to pneumonia infections associated with me- respectively. In 60.2% of diabetic and 59.7% chanical lung ventilation, i.e. it is inflammation of other patients with pneumonia at least one occurring 48−72 hours of mechanical ventilation blood culture was isolated [5]. Streptococcus in patients,