Silvano Esposito1, Renato Gioia1, Giuseppe De Simone1, Silvana Noviello1, Domenico Lombardi2, Vincenzo Giuseppe Di Crescenzo3, Amelia Filippelli4, Maria Rosaria Rega5, Angelo Massari5, Maria Giovanna Elberti6, Lucilla Grisi6, Giovanni Boccia7, Francesco De Caro7 and Sebastiano Leone1
1 Division of Infectious Diseases, University of Salerno, Italy
2 Division of Surgery, University of Salerno, Italy
3 Division of Thoracic Surgery, University of Salerno, Italy
4 Pharmacology Unit, University of Salerno, Italy
5 Microbiology Unit,“San Giovanni di Dio e Ruggi d’Aragona Hospital”, Salerno, Italy
6 Pharmacy Unit,“San Giovanni di Dio e Ruggi d’Aragona Hospital”, Salerno, Italy
7 Hygiene Unit, University of Salerno, Italy
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Objectives: Surgical infections represent an increasingly important problem for the National Health System. In this study we retrospectively evaluated the bacterial epidemiology and antimicrobial susceptibility of the microorganisms concerned as well as the utilization of antibiotics in the General and Emergency Surgery wards of a large teaching hospital in southern Italy in the period 2011-2013.
Methods: Data concerning non-duplicate bacterial isolates and antimicrobial susceptibility were retrieved from the Vitek 2 database. The pharmacy provided data about the consumption of antibiotics in the above-reported wards. Chi-square or Fisher’s exact test were used.
Results: In all, 94 Gram-negative were isolated in 2011, 77 in 2012, and 125 in 2013, Escherichia coli, Acinetobacter baumannii and Pseudomonas aeruginosa always being the most frequently isolated microorganisms. A. baumannii showed high rates of resistance to carbapenems (with values of 100% in 2011 and 2012) and low rates of resistance to tigecycline, colistin, and amikacin. In the same years, there were respectively 105, 93, and 165 Gram-positive isolated. The rate of MRSA isolates ranged from 66% to 75% during the study period.
Conclusions: Our results show no significant increase in antimicrobial resistance over the period in question, and a higher rate of both MRSA isolates and resistance to carbapenems in A. baumannii compared with other European data.
The considerable progress that occurred in the last century in treating post-operative infections led many authors to underestimate the problem of antibiotic resistance in the surgical field. This caused the re-emergence of the problem in the late 1990s and at the beginning of the new millennium, with a growing demand for multicenter studies that would contextualize the problem of either the epidemiology of these infections and the increasing antibiotic resistance or the increasingly innovative mechanisms put in place by pathogens to evade the action of antibiotics. Currently, the main problems related to antibiotic resistance consist in the increasing prevalence of extended-spectrum beta-lactamases (ESBLs) producing Enterobacteriaceae, and in the increasing intra-hospital presence of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), even though the spread of multi-drug resistant (MDR) bacteria greatly differs according to the geographic areas.[2-5] Knowledge of the local epidemiology of antibiotic resistance may help to develop therapeutic strategies and stewardship of more effective measures to optimize therapeutic outcomes and reduce the length of hospital stay.[6-9] In this study we retrospectively examined the bacterial epidemiology of the major Gram-negative and Gram-positive pathogens isolated in the Departments of General Surgery and Emergency Surgery of the Salerno University Hospital “San Giovanni di Dio e Ruggi d'Aragona” in the period 2011-2013, paying special attention to the antibacterial susceptibility profile of Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii and Staphylococcus aureus.
Materials and methods
Data concerning non-duplicate Gram-positive and Gram-negative microorganisms isolated from different clinical specimens of patients hospitalized in the period 2011-2013 at the General Surgery and Emergency Surgery of "San Giovanni di Dio e Ruggi d’Aragona", a university hospital having 900 bed capacity with major programs in a broad range of clinical specialties located in Salerno (Italy), were retrieved from the database of the Laboratory of Bacteriology of the same hospital. Overall, the number and type of admission to the hospital did not change over time in the study period. In these wards, mainly patients undergoing major elective and urgent/emergency abdominal procedures are admitted. Microbial isolates are labelled as clinically relevant (both community- and healthcare-acquired) according to the information as detailed in the laboratory request form. We also focused on the evaluation of any change over time of the main expressions of resistance, with particular regard to the microorganisms considered to be the most difficult to treat in surgical wards, i.e., K. pneumoniae, A. baumannii, P. aeruginosa and S. aureus. In particular, we analyzed rates of resistance to carbapenems (imipenem, meropenem, and ertapenem), amikacin, tigecycline, and colistin in the Gram-negative and of methicillin-resistance in S. aureus. Microbial identification and antibiotic susceptibility testing were performed by the fully automated system VITEK 2 (bioMérieux, Marcy l'Etoile, France). Colleagues at the Department of Pharmacy provided data on consumption, in the years 2011-2013, of antibiotics with a spectrum of activity mainly directed against Gram-negative microorganisms, i.e., imipenem, meropenem, ertapenem, amikacin, tigecycline, and colistin. Antibiotic usage was evaluated using defined daily doses (DDDs). Indeed, in our study, we defined the consumption of drugs as DDD/100 bed days. Chi-square or Fisher’s exact test were used to analyze possible significant differences in isolation rate. Statistical significance was established at a two-tailed level of <5%.
|Table 1. Epidemiology of Gram-negative bacteria in the Departments of General Surgery and Emergency Surgery in the period 2011-2013*|
|Table 2. Epidemiology of Gram-positive bacteria in the Departments of General Surgery and Emergency Surgery in the period 2011-2013*.|
|Table 3. Rates of resistance of the main Gram-negative microorganisms in the Departments of General Surgery and Emergency Surgery in the period 2011-2013.|
|Table 4. Rates of resistance of the main Gram-positive microorganisms in the Departments of General Surgery and Emergency Surgery in the period 2011-2013.|
|Table 5. Antibiotics usage rates in the Departments of General Surgery and Emergency Surgery in the period 2011-2013.|