Correlation between antibiotic consumption and bacterial resistance as quality indicator of proper use of these drugs in inpatients

Background/Aim. Antibiotics are the most frequently used medications in Serbian hospitalized patients. Information about antibiotic utilization and sensitivity among inpatients in Serbia is scanty, and there are no available publications on the topic. The aim of this study was to investigate the correlation between antibiotic use and bacterial resistance in the Clinical Center Niš, one of the biggest hospitals in Serbia. Methods. The data on antibiotics use in inpatients were obtained from the database of the Department of Pharmacotherapy and expressed as defined daily doses per 100 bed-days (DBD), during 2003–2007. Bacterial resistances were given as percentages of resistant isolates. Results. During the investigation period, the overall consumption of antibiotics had a significant decrease in 2007, by 22.99% (62.23 : 47.92 DBD; p < 0.05). The most frequently used antibiotics were cephalosporins, followed by penicillins, aminoglycosides and quinolones. Hospital aminoglycosides consumption was reduced in 2007 to 59.9% (13.4 : 5.53 DBD) while the resistance to amikacin was reduced from 40.88% to 32.1%. However, utilization of ciprofloxacin had a significant increase in 2007 (120.7%). There was an alarming increase in the level of resistance to ciprofloxacin in our hospital (from 13.5% to 28.3 % in Escherichia coli and from 11.1 to 30.09% in Proteus mirabilis). Reduction of E coli resistant to amoxicillin+clavulanic acid correlated significantly with their utilization, while the resistance for all isolates decreased from 52.16% to 24.40%. Conclusions. These results confirm an association between the use of antibiotics and the prevalence of resistance. This methodology could provide good quality indicators of rational drug use and serve for local monitoring of antibiotics use and resistance, as well as for external comparison.


Introduction
Antibiotics are the most frequently used medications in hospitalized patients (15-30% of all prescribed drugs).It has been estimated that 30-50% of hospitalized patients receive antimicrobial agents, and that up to 50% of prescribed antimicrobial agents are not prescribed optimally [1][2][3] .It has been shown that inappropriate antibiotic use significantly contributes to increasing rates of resistant pathogens 4,5 .Bacteral resistance is now being recognized as a major factor determining morbidity, mortality and costs in the hospital.It has been generally recognized that the prevalence of bacterial resistance among bacteria is an unavoidable consequence of antibiotics use and that it correlates with the overall use of antimicrobial drugs 2,5 .Several lines of evidence suggest that there is a causal association between the use of antimicrobial agents and the prevalence of drug resistance in microorganisms [6][7][8] .Taking into account this escalation in bacterial resistance and the large body of evidence considering the overuse of antibiotics a rational approach is a strict control of antibiotic use.Factors that promote the emergence of resistance include frequent use of broad-spectrum antimicrobial agents, prolonged use of antimicrobial agents, more frequent use of invasive devices and procedures 9,10 .However, there are reasons for optimism, as studies in various centers show rapid reversal of resistance 7,8 .The 1998 European Conference entitled "The Microbial Threat" emphasized the importance of collecting and comparing data of antibiotic use and bacterial resistance from different countries 11,12 .Information about antibiotic utilization and sensitivity among inpatients in Serbia is scanty, and there are no available publications on the topic.The purpose of this study was to investigate the extent of antimicrobial usage and to evaluate the bacterial resistance in the Clinical Center Niš, one of the biggest hospitals in Serbia.This study generally used the World Health Organization (WHO) Anatiomical Therapeutic Chemical (ATC) Classification System and the volume unit -Defined Daily Doses (DDD) 13,14 .

Methods
In this survey antibiotic consumption and bacterial susceptibility were monitored in the period 2003-2007.The results were analyzed in the Clinical Center Niš, a 1460-bed, 3rd tertiary health care university hospital in Serbia, that comprises departments covering all major specialties except for infectious diseases, kidney transplantation, hematology, oncology, surgery and tuberculosis.The study period extended from 2003 -2007.In 2003 -2005, the Clinical Center had 417 357, 452 993 bed-days per year.
As this study did not collect any data on individual patients and surveillance was a part of quality assurance, an approval by Ethical Committee was not considered necessary.
Utilization of antibiotics in Clinical Center Niš in the period followed was obtained from the computerized database of the Department of Pharmacotherapy and expressed as DDD per 100 bed/days (DBD).Defined Daily Doses of anti-bacterial agents for systemic use listed in the ATC Index with DDD in the period from 2003 to 2007 were used.Thirty-five different antibiotic drugs were used in our hospital.
Until April 2005, there was no antibiotic restriction policy in the hospital and every physician could prescribe any antibiotic, so misuse or overuse of antibiotics was common.There has been the Pharmacotherapy Department here since 2005.Routine monitoring of the use of antibiotic drugs and antibacterial resistance was started in the Clinical Center Niš in 2005 with the aim to prevent an increase in bacterial resistance and the costs of treatment.Following implementation of restriction policy in 2005, prescription of aminoglycosides, third-and fourth-generation cephalosporins, carbapenems, piperacillintazobactam and vancomycyn were placed under the control of the clinical pharmacologist.These agents may only be prescribed after consultation with the clinical pharmacologist or following an approval by the medical director.Some surgical departments have their own guidelines for surgical prophylaxis, which were developed in collaboration with a microbiologist and a clinical pharmacologist.Occasional lectures on rational antimicrobial drug use are given in some departments.
The hospital has three clinical pharmacologists surveying and analyzing drug utilization and bacterial resistance, while one of them is a president of the Drug and Therapeutics Committee (DTC), within the hospital.
The bacteriological laboratory of the Institute for Public Health Niš routinely screens bacterial resistance/sensitivity for all patients requiring antibiotic therapy except for prophylactic use.Bacterial strains were isolated from the clinical material of the hospitalized patients and susceptibility to antibiotics was assessed by the disc diffusion method.
The process of testing the susceptibility of bacteria to antibacterial medicines and the creation of antibiogram are conducted according to recommendations of the American National Committee for Clinical and Laboratory Standards 14,15 and according to the recommendation of the European Committee for Antimicrobial Susceptibility Testing (EUCAST) and the European Association of Clinical Microbiology and Infectious Diseases (ESCMID).For the interpretation of the zones of inhibition the standards were used.Strains were classified as susceptible or resistant (intermediate zones of inhibition were considered resistant).Bacterial resistances were given as percentages of resistant isolates.The hospital specialist in infectious diseases and the clinical pharmacologist analyzed the data provided by the microbiology unit and based on that created a hospital profile.
The number of the assays performed by the bacteriological laboratory was comparable for the years 2003 (2865), 2004 (2968), 2005 (3120), 2006 (2671) and 2007 (3534).The burden of resistance for each antibiotic was calculated as percentage of all resistance + intermediate among all tested isolates from all patients samples (blood, urine, sputum, etc).
For testing the significance of resistance development and changes in antibiotics utilization a linear analysis was used.The Chi-square test was used to compare antibiotic use in different time periods.Pearson's correlation was used to determine the relationship between the use of antibiotics and the bacterial resistance.A statistical significance was accepted at the 5% level.The WHONET software developed by the WHO was utilized for data management 16 .The antibiotic resistance data were obtained and presented with the DBD segment in tables and figures.The data were visualized as a diagram combining drug utilization (DBD) and resistance.

Results
The consumption of antibiotics in our hospital is shown in Table 1.During the investigation period a total consumption of antibiotics had a significant decrease (p < 0.01) from 62.23 DBD in 2003 to 47.92 DBD in 2007.
The most frequently used antibiotics were cephalosporins, followed by penicillins, aminoglycosides and quinolones.In 2003, ceftriaxone was the most frequently prescribed antibiotic and made up a quarter of the use (Figure 1).
Escherichia coli was a most frequently isolated bacteria (15.71-19.19%),followed by Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and other gram-negative bacilli.The types and frequency of isolated bacterial strains per each year of the followed period are described in Table The rates of resistance of frequently isolated bacteria in our hospital are presented in Table 3.
Reduction of E. coli resistant to amoxicil-lin+clavulanic acid correlated significantly with their utilization (r = 0,944, p < 0.05), while the resistance for all isolates was reduced from 61.58% to 46.36%.The dependence of the reduction of E. coli resistance to amoxicil-lin+clavulanic on their utilization in Clinical Center Niš is shown in Figure 2. A significant correlation was found (r = 0.924; p < 0.05).
During the same period, there was a substantial decrease in the use of ceftriaxone, while the resistance for all isolates was reduced from 58.2% to 48.86%.

Fig. 2 -Correlation between the consumption of amoxicillin+clavulanic acid and the resistance to E. coli
There was an alarming increase in the level of resistance to ciprofloxacin in our hospital (from 13.5% to 28.3% to E. coli and from 11,1 to 30.09% to P. mirabilis).The dependence of the development of E. coli resistance to ciprofloxacin on their utilization in the Clinical center Niš is shown in Figure 3.A significant correlation was found (r = 0.827, p = 0,025).

Discussion
Utilization of antibiotics in Serbia is among the highest in Europe, mostly due to overuse of cephalosporines and aminoglycosides.The European Surveillance of Antibiotic Consumption (ESAC) found large differences in antibiotic use in inpatients.Utilization of antibiotics in the world varied greatly, from the extremely high in Croatia and Greece, next rate in France and to the lowest one was in the Netherland.In this study we found high antibiotic utilization and high resistance rates in our hospital compared with other countries 1,11,12,18 .A survey carried out at three university hospitals, in another country, showed lower total antibiotic consumption to that found at our hospital l6, 19 .Unfortunately, no resistance data were included in these studies.
We found high rate of resistance among the most commonly used antibiotics (aminoglycosides, cephalosporines, fluoroquinolones) 20 .Here it was found that resistance of P. aeruginosa to gentamicin, was changed from 75.9% of resistant strains in 2005, to 53.5% in 2007.This means that for P. aeruginosa infections change led to improved sensitivity, though it is clear that gentamicin cannot be used for this kind of infection 1,17 .Goryachkina et al. 11 showed the decreased resistance level for gentamicin (80% to 40%) in Russia from 2003-2005.
At the same time, we showed a decreased resistance level for amoxicillin+clavulanic acid (61.58 to 46.36%; same strains were tested).This provides an overall impression on coincidence of resistance and antibiotic overuse.The resistance of E. coli was decreased significantly from 52.16% of resistant strains in 2005, to 24.40% in 2007.
At the beginning of this study, utilization of ciprofloxacin was low in our hospital (2.12 DBD).The resistance of E.coli in inpatients was at a level of 15.5%.In the study period ciprofloxacin utilization increased significantly (p < 0.001).Bacte-rial resistance followed this trend very closely and reached 28.3% in 2007.This is a result of the increased consumption of ciprofloxacin from 2005 2007, the single most prescribed drug.Now, the increased levels of resistance to fluoroquinolones among nosocomial isolates like P. aeuriginosa, Serratia sppecies and Klebsiella sppecies have been reported worldwide.
The influence of hospital antibiotic policy is responsible for this delay.Ciprofloxacin was not placed on restricted antibiotics list in the same period in our hospital.Fluoroquinolone resistance to E.coli is emerging as a significant problem in hospitals.Urbanek et al. 5 have shown a correlation between the increased use of fluoroquinolones and the increase in E.coli resistance.Results of numerous studies show the impact of fluoroquinolone utilization on bacterial resistance and support the need for controlled use of these effective antibiotics 5,19,21 .Periods of extensive ciprofloxacin use were associated with a significant increases in resistance.Similarly to our results, the resistance of E.coli to ciprofloxacin in Spain was increased from 13.8% in 2001, to 23.4% in 2005 [10][11][12] .A total ciprofloxacin use was an independent predictor of the burden of ciprofloxacin resistance in E. coli in hospitals [21][22][23] .Our data support the concept that a written antibiotic policy which balances the use of various antibiotic classes may help to avoid disturbances of a hospital′s microbial sensitivity patterns [21][22][23][24][25] .As antibacterial resistance is a multifactorial problem, a multisectoral effort is needed to control it.The problem of antibacterial resistance needs to be addressed in a continuous proccess of actions.The key areas of community recommendations for the control of bacterial resistance are surveillance of antibiotic consumption and resistance rates, optimizing antibiotic use, education, prevention and control 2,3,26,27 .

Conclusion
These results confirm an association between the prevalence of bacterial resistance and use of antibiotics.Monitoring of bacterial resistance can serve as an indicator of quality of antibiotic use.A combined presentation of antibiotic utilization and bacterial resistance provides clear indication on both problems in relation to each other.This methodology seems to be beneficial for external comparisons as well as local regulation of antibiotics use and resistance.Programs for the management of bacterial resistance usually include modifications of antibiotic use, especially in the decreased use of ciprofloxacin and the third-generation cephalosporins.Physicians training should be an important part of efforts against antibiotic resistance.National guidelines on this topic, as well as good diagnostic and therapeutic protocols are important.A rational and strict antibiotic policy is, thus, of great importance for the optimal use of these agents.
The obtained results are the basis for further analysis of bacterial resistance in correlation with antibiotic consumption in the Clinical Center Niš in Serbia.

SFig. 3 -
Fig. 3 -Correlation between the consumption of ciprofloxacin and the resistance to E. coli