Antimicrobial Resistance in Hospitalized Patients with Community Acquired Urinary Tract Infection in Isfahan, Iran

Sayed Nassereddin Mostafavi, MD1,2*; Soodabeh Rostami, PhD3*; Yasamin Rezaee Nejad, MD1; Behrooz Ataei, MD1; Sina Mobasherizadeh, PhD3; Aazam Cheraghi, MSc4; Somayeh Haghighipour, MD1; Samereh Nouri, MSc5; Arezoo Pourdad, MSc6; Parisa Ataabadi, MSc6; Nasser Almasi, DMLS7; Leila Heidary, MSc7; Kourosh Naderi, MSc7; Setareh Korangbeheshti, BSc7; Shiva Navabi, BSc8; Laleh Masssah, MSc8; Zohreh Norouzi, MSc8; Mehrnoush Bakhtiyaritabar, BSc8; Saeed Moayednia, DMLS5; Dariush Shokri, PhD3; Mahin Mikhak, DMLS7; Majid Rahmani, DMLS8; Mohammad Hashemi, MD9; Reza Etminani, MD4; Nasrin Ahmadi, BSc4; Roya Kelishadi, MD2


Introduction
Urinary tract infection (UTI) is a worldwide bacterial infection with significant mortality, morbidity, and health expenses in all ages. 1 The main bacterial etiology of the infection includes Escherichia coli, Proteus sp., Pseudomonas aeruginosa, Acinetobacter spp., Klebsiella spp., Enterobacter sp., Citrobacter sp., Staphylococcus saprophyticus, Enterococcus sp., and Staphylococcus epidermidis. 2 Clinical manifestations vary largely from asymptomatic or mild dysuria to high fever, vomiting, back pain, and even bacteremia, sepsis or death. 3 Treatment of patients with severe or complicated disease requires hospital admission and prompt intravenous antibiotic therapy before obtaining the results of urinary culture. 4,5 Unfortunately, during recent years, the increasing resistance of microorganisms to antibiotics has become a global concern; urinary pathogens are not an exception. 6,7 In addition, the susceptibility pattern of uro-pathogens differs in various geographic locations and different settings, i.e. outpatient versus hospitalized, community acquired hospitalized patients versus hospital-acquired hospitalized patients. [6][7][8] Therefore, periodic evaluation of susceptibility pattern of uro-pathogens in each area and in different settings is necessary to select the best antibiotics for empiric treatment of UTIs. [6][7][8][9] According to our literature review, few studies have been performed on antibiotic susceptibility of microorganisms causing UTI in hospitalized patients all around the world, and none of them have specifically studied the community-acquired cases. [9][10][11][12][13] The aim of this study is to determine the etiology and total antibiotic susceptibility of community-acquired uropathogens in patients who were admitted to three large hospitals which participate in the Isfahan Antimicrobial resistance Surveillance-1(IAS-1) study.

Study Design
The study was designed to report the results of antibiotic susceptibility patterns of pathogens in patients who were admitted to hospitals because of community-acquired UTI. They were recruited during the time period of March 2016 to March 2018 and participated in the IAS-1 project which is a cross-sectional study planned to investigate the antimicrobial susceptibility profile of clinically important microorganisms, conducted in Isfahan, Iran. 14 Indications for admission of the patients include hemodynamic instability, complicating factors (such as urinary stones), severe symptoms, intolerance of oral antibiotics, and poor adherence to medications. The IAS-1 study was planned to investigate the main microorganisms and antibiotic susceptibility profile of infections in cases who were admitted to three large medical centers in Isfahan city, Iran (Project No: 194042). In addition to recording antibacterial resistance of clinical isolates, it aimed to eliminate contaminant isolates, and determine healthcare/ community source of the infection by cooperation of skilled infectious control nurses and physicians in the enrolled hospitals. The study aimed to help the clinicians in selecting the most appropriate antibiotic for treatment of infections in the area. The medical centers that participate in the research were the main large hospitals of Isfahan city, i.e. Al-Zahra, Dr. Shariati and Dr. Gharazi hospitals. The laboratories of these medical centers attained Quality Credit for microbiological report from the Iranian Ministry of Health and collaborated in the Global Antimicrobial Resistance Surveillance System (GLASS) program of the World Health Organization (WHO). 15 Organism Identification and Antibiotic Susceptibility Testing Urine samples were obtained from patients with suspected UTI. UTI was defined as presence of pyuria in urine analysis (≥10 WBC/mL of urine) in addition to growth of ≥10 5 colony count of a single urinary pathogen in one urine sample or single non-urinary pathogens in 2 urine specimen with the same resistance profile. Patients with healthcare-associated UTI were excluded from the study. Data on age, sex, nosocomial or community acquisition of the infection as well as the etiological agent and susceptibility profile of the isolated bacteria were prepared using the WHONET software.
For detection of uro-pathogens, urine samples were collected according to local hospital guidelines and were inoculated with a standard wire loop onto sheep blood agar and MacConkey agar or eosin-methylene blue agar and were incubated overnight at 37°C. Isolation of uropathogens (E. coli, Proteus spp., Klebsiella spp., Enterobacter spp., Citrobacter spp., P. aeruginosa, Acinetobacter spp., Enterococcus spp., S. saprophyticus and S. epidermidis) was done by routine conventional methods such as catalase and oxidase test, sugar fermentation, growth on selective media, susceptibility or resistance to specific agents and other standard microbiology tests.
Statistical Analysis Data on age group (≤20 years, >20 years), sex, etiology and antibiotic susceptibility were extracted from the WHONET version 5.6 software in each laboratory and analyzed with SPSS version 18.0. Chi-square and Fisher exact tests were applied for analysis of the study variables. P value of < 0.05 was considered as significant.

Results
A total number of 5844 urine specimens were received for culture from March 21, 2016 to March 20, 2018, of which 3586 (61.4%) samples showed no growth, 284 Resistance of Inpatient Uro-pathogens (4.9%) samples were positive for fungus and yeast, 511 (8.7%) samples were considered as contamination, and 283 (4.8%) cases were nosocomial acquired. Of 1180 isolates from patients with confirmed CAI-UTI, 488 (41.4%) belonged to males and 295 (25.0%) were less than 20 years old.

Discussion
Our study reveals that E. coli is the most common cause of community-acquired UTI in patients who need hospitalization. Furthermore, it shows a high bacterial resistance rate to several antibiotics including cefotaxime, ceftriaxone, ceftazidime, cefepime, trimethoprimsulfamethoxazole, and ciprofloxacin. In addition, it demonstrates a high susceptibility rate of causative agents to imipenem, meropenem and amikacin.
To the best of our knowledge, no earlier investigation has reported common pathogens and their sensitivity profile in hospitalized patients with community-acquired UTI. Recognition of the antibacterial susceptibility patterns of uropathogens in these patients is an essential factor for selecting a proper empirical antimicrobial treatment in each area. 6,7 Previous studies on the resistance pattern of uropathogens all around the world usually did not exclude the cases of contamination 8,10 or outpatient isolates from the analysis. 10,12 A few investigations which were performed in hospitalized patients did not exclude the cases of healthcare-associated UTIs from their studies. [8][9][10][11][12][13] To decrease the rate of contamination in final analysis, we excluded the urinary isolates with no concomitant pyuria in urinalysis. Moreover, we recognized community source of the isolates with help from experienced infectious control nurses at the bed of patients in enrolled hospitals. 14 The sex pattern of patients in our study reveals relatively equal distribution in both sexes. Approximately 41% of admitted patients in our study were males. This finding is in accordance with findings of previous researches in hospitalized patients with UTI. 8,9 In our study, consistent with some other investigations, the most frequent bacterium in the UTI cases was E. coli, accounting for 68.1% of the isolates. The percentage of the isolate is comparable to those reported in several former investigations. 10 Enterococcus spp. was the second most common organism followed by Klebsiella spp. and Staphylococcus spp. Our study is different from some researches that reported Klebsiella spp. or other Gram-  negative rods as the second most prevalent urinary pathogen. As we included only hospitalized patients with community-acquired UTI in the analysis, the finding could be different from other investigations that had included outpatient cases 12,13 or nosocomial hospitalized individuals. 10,11,12,16 Our study, in accordance with findings of some previous investigations, shows that non-E. coli uro-pathogens were significantly more common in male 8,9,10 and younger (<20 years) UTI cases. 8 The most effective antibiotics in our study were carbapenems (imipenem, meropenem) and amikacin. This finding can suggest them as the first line for empiric treatment of hospitalized UTI patients with severe symptoms in the area.
Carbapenems are effective drugs for multidrug resistant (MDR) Enterobacteriaceae, and our results are in agreement with the frequency of resistance to these antibiotics from earlier studies in Canada, Greece, and India (less than 10%). [10][11][12] However, due to the frequent administration of the drugs in recent years, resistance to this class of antibacterial medications is growing. 17 Therefore, carbapenems should be kept for empiric therapy of severely ill patients with UTI. However, after obtaining the culture results, another appropriate antibiotic might be started.
Amongst aminoglycosides, we found that amikacin had high activity against urinary pathogens, as described in previous studies. 9,11,12 More than 90% of the isolates showed susceptibility to this medication in disk diffusion test. Amikacin has a dose-dependent bactericidal activity, achieves enough concentrations in renal parenchyma and can be administered via the intramuscular route; thus, it could be a good suggestion for treatment of patients who cannot tolerate oral medications and are planned to be treated in an outpatient setting. 18,19 However, because of the nephrotoxicity of this medication, administration of amikacin for treatment of renal infections has decreased in recent years. 18,19 In our study, the sensitivity of isolates to gentamicin was about 64%. This finding is in concordance with the study in Bosnia 13 and in contrast to previous studies in Iran and Canada that reported more than 90% susceptibility of urine pathogens to this antibiotic. 9,10 These differences are probably due to difference in year of the research or difference in antibiotic prescription in different societies. 20 Our analysis revealed that urinary isolates were highly resistant to cefotaxime (60.0%), ceftriaxone (58.2%), ceftazidime (52.8%), and cefepime (47.3%), therefore making these antibiotics unsuitable for empiric treatment of UTI in severely ill inpatient cases. These findings should be considered in spite of the fact that cephalosporins are amongst the most commonly prescribed medications for treatment of UTI all around the world. This high resistance rate to cephalosporins was also reported in previous studies conducted in Iran. 9 However, reports from the USA, Canada, and Greece have shown susceptibility rates of greater than 90% in urinary isolates; this might be because of the difference in the study time or geographical settings. 8,10,11 Ciprofloxacin and other fluoroquinolones are broadly prescribed for treatment of upper and lower UTIs in recent years. 21 We found a low susceptibility rate of uropathogens to ciprofloxacin (38.6%). Therefore, this agent is not appropriate for empirical treatment of inpatient UTI cases and should be reserved for de-escalation therapy, after confirmation of sensitivity of uropathogen to it, based on the opportunity of its oral usage. 21 This finding is consistent with previous researches performed in Iran and Bosnia, 9,13 and in contrast to reports from the USA and Canada. 8,10 In our study, most of the isolates (68.7%) showed resistance to trimethoprim-sulfamethoxazole, as reported in previous investigations in Iran, India, and Bosnia. 9,12,13 Extensive use of this antibiotic in outpatients with urinary or respiratory tract infections could explain this high level of resistance in different communities. 20,21 However, as this medication has an oral formulation, it would be a good choice for de-escalation therapy and for completion of the duration of therapy. This high level of resistance to trimethoprim-sulfamethoxazole was previously reported from a study in Bosnia. 13 In some earlier studies, urinary isolates had better susceptibility to this agent, probably due to the time and location of the research 8,10,11 or inclusion of outpatient cases in the final analysis. 10 Our study had some limitations. First, our investigation was performed in three referral and large hospitals; thus, generalization of the results to all hospitalized patients with UTI should be done with caution. The second limitation is that the study was laboratory-based and information on previous antibiotic administration or anatomical abnormalities of the patients is lacking. Such data could provide meaningful clues to allow a better understanding of the sensitivity pattern of causative bacteria in clinical settings. The third is that our data were extracted from the routine work of the clinical laboratories and all antibiotic disks and strips were not available at the time of isolation of the bacteria. So, all microorganisms were not tested by all antibiotic disks and strips.

Conclusion
Our data revealed that E. coli, Enterococcus spp. and K. pneumonia were the predominant isolates among hospitalized patients with community-acquired UTI. In addition, we found a high susceptibility rate of uropathogens to imipenem, meropenem, and amikacin, suggesting them as good choices for empiric therapy of complicated or severe infections. Moderate sensitivity to gentamicin, cefepime, and ceftazidime suggests them as acceptable initial therapy in non-severe cases; while low susceptibility to cefotaxime, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole makes them unsuitable for empiric therapy of inpatients with communityacquired UTI in the area.