Multidrug-resistant Bloodstream Infections in Internal Medicine

Results from a Single-Center Study

Edoardo Pace, MD; Christian Bracco, MD; Corrado Magnino, MD; Marco Badinella Martini, MD; Cristina Serraino, MD; Chiara Brignone, MD; Elisa Testa, MD; Luigi Maria Fenoglio; Massimo Porta


South Med J. 2022;115(5):333-339. 

In This Article

Abstract and Introduction


Objectives: Infections due to multidrug-resistant organisms (MDROs) are expanding globally and are associated with higher mortality rates and hospital-related costs. The objectives of this study were to analyze the trends of MDRO bacteremia and antimicrobial resistance rates in Internal Medicine wards of our hospital and to identify the variables associated with these infections.

Methods: During a 6-year period (July 1, 2011–June 30, 2017), patients with positive blood culture isolates hospitalized in the Internal Medicine wards in the Santa Croce and Carle Hospital in Cuneo, Italy, were assessed. We performed an analysis taking into consideration the time trends and frequencies of MDRO infections, as well as a case-control study to identify clinical-demographic variables associated with MDRO bacteremias.

Results: During the study period a total of 596 blood cultures were performed in 577 patients. The most frequently identified organism was Escherichia coli (33.7%), followed by Staphylococcus aureus (15.6%) and S epidermidis (7.4%). The percentage of resistance to methicillin among S aureus isolates showed a decreasing trend, whereas rates of extended-spectrum β-lactamase-producing Enterobacteriaceae and carbapenemase-producing Klebsiella pneumoniae increased during the study period. Multivariate analysis showed that the nosocomial origin of the infection, hospitalization during the previous 3 months, residence in long-term care facilities, presence of a device, antibiotic exposure during the previous 3 months, and cerebrovascular disease were independently associated with bacteremia by resistant microorganisms.

Conclusions: Our analysis reveals a concerning microbiological situation in an Internal Medicine setting, in line with other national and regional data. The risk variables for infection by MDRO identified in our study correspond to those reported in the literature, although studies focused on Internal Medicine settings appear to be limited.


Antibiotic resistance is one of the most important issues in modern medicine.[1] The onset and spread of new resistance mechanisms limit our ability to fight infections, leading to longer hospitalizations, increased mortality, and related costs.[2,3] At the beginning of the 2000s, the development of bacterial resistance, together with inadequate treatment and prevention strategies, created the conditions for a discouraging new scenario for therapy, to the point of prefiguring a catastrophic "end of the antibiotic era."[4] A 2019 report[1] showed concerning estimates on multidrug-resistant organism (MDRO) infections in Europe in 2015: 700,000 infections with resistant microorganisms, with an incidence of 131/100,000 inhabitants and a mortality rate of 6.34/100,000 inhabitants. The future scenery is not reassuring, either, because by 2050, 10 million lives per year are expected to be at risk along with a cumulative expenditure of $20 to $35 billion in Organization for Economic Cooperation and Development countries.[4,5]

It is essential to identify patients at risk of MDRO infection as early as possible, to establish broad-spectrum empirical antibiotic therapy while waiting for the results of blood cultures and antibiograms. Several studies[6–8] have tried to identify risk factors for MDRO infections. These risk factors include severity of the underlying disease before hospitalization, nosocomial origin of the infection, immunosuppression, neutropenia,[9] diabetes mellitus, cirrhosis, autoimmune diseases, and malignancies. Other important risk factors are the presence of invasive devices,[10] such as central venous catheters (CVCs), bladder catheters, prosthetic valves, joint replacements, and pacemakers. Some studies have focused on certain MDROs, particularly methicillin-resistant Staphylococcus aureus (MRSA),[11–14] extended spectrum β-lactamase-producing Enterobacteriaceae (ESBL),[9,15–17] and carbapenemase-resistant Enterobacteriaceae.[18–20] Studies focusing on Internal Medicine settings are limited in the literature, however.

The objectives of this study were to analyze the trends of MDRO bacteremia and antimicrobial resistance rates in the Internal Medicine wards of the Santa Croce and Carle Hospital in Cuneo, northwest Italy, and to identify the variables associated with these infections.