ORIGINAL ARTICLE The burden of comorbidity is associated with symptomatic polymicrobial urinary tract infection among institutionalized elderly Alice Laudisio 1 • Felice Marinosci 2 • Davide Fontana 1 • Antonella Gemma 3 • Alessandro Zizzo 2 • Anna Coppola 2 • Leonardo Rodano 2 • Raffaele Antonelli Incalzi 1,2 Received: 5 February 2015 / Accepted: 7 April 2015 Ó Springer International Publishing Switzerland 2015 Abstract Background Urinary tract infections (UTIs), often sus- tained by polymicrobial flora (p-UTIs), are a common finding among nursing home patients, and associated with adverse outcomes and increased healthcare costs. P-UTIs have been extensively studied with regard to micro- biological aspects. However, little is known about the characteristics of the host. Aims The aim of this study is to verify to which extent comorbidity characterizes elderly nursing home patients with p-UTIs. Methods We enrolled 299 patients with culture-positive UTI consecutively admitted to the nursing home of the ‘‘Fondazione San Raffaele Cittadella della Carita `’’, Taranto, Italy. P-UTI was diagnosed when two uropatho- gens were simultaneously isolated. The burden of comor- bidity was quantified using the Charlson comorbidity score index. Logistic regression analysis was used to assess the adjusted association of the variables of interest with the presence of p-UTI. Results P-UTIs were detected in 118/299 (39 %) patients. According to logistic regression, the presence of p-UTIs was independently associated with the Charlson index (OR 1.70; 95 % CI 1.06–2.72; P = .026). This association remained also after excluding participants without urinary catheter (OR 1.88; 95 % CI 1.13–3.11; P = .015). Discussion The presence of P-UTIs is associated with the burden of comorbidity, but not with individual diseases. Conclusions Older nursing home patients with comor- bidity should be screened for the presence of p-UTIs; further studies are needed to evaluate the impact of early detection and treatment of p-UTIs on the development of comorbidity. Keywords Elderly Á Nursing home Á Comorbidity Á Urinary infection Á Epidemiology Introduction Urinary tract infections (UTIs) are the most common bacterial infectious diseases afflicting humans, resulting in nearly $2.5 billions health care costs in the year 2000 in the United States alone [1]. These costs will unavoidably rise, due to the advances in therapeutic and preventive medicine that extend life expectancy, increasing the elderly population. Subjects aged C65 years account for approximately 12.6 % of the total population of the United States, yet their care accounts for about one-third of the estimated US health expenditure [2]. Also, mor- tality rates in elderly patients from bacteraemia as a result of UTI can be as high as 33 % [3]. In addition, UTIs are the most common infection in patients living in nursing home, accounting for 20–60 % of all antibiotic prescrip- tion use [3, 4]. Such an approach may contribute to the increasing antibiotic resistance of urinary pathogens. Although UTIs might not result in excess mortality, they significantly burden the health care system by increasing both morbidity and costs [5]. In addition, urine cultures & Alice Laudisio lavoralice@gmail.com 1 Department of Geriatrics, Campus Bio-Medico University, Via A ´ lvaro del Portillo, 200, 00128 Rome, Italy 2 Fondazione San Raffaele-Cittadella della Carita `, Piazzale Mons. G. Motolese, 1, 74123 Taranto, Italy 3 UOS Accesso e Presa in Carico Assistenziale, Azienda Sanitaria Locale Roma E, Borgo S. Spirito, 3, Rome, Italy 123 Aging Clin Exp Res DOI 10.1007/s40520-015-0364-x