Community acquired urinary tract infection : etiology and bacterial susceptibility 1

PURPOSE: Urinary tract infections (UTI) are one of the most common infectious diseases diagnosed. UTI account for a large proportion of antibacterial drug consumption and have large socio-economic impacts. Since the majority of the treatments begins or is done completely empirically, the knowledge of the organisms, their epidemiological characteristics and their antibacterial susceptibility that may vary with time is mandatory. OBJECTIVE: The aim of this study was to report the prevalence of uropathogens and their antibiotic susceptibility of the community acquired UTI diagnosed in our institution and to provide a national data. METHODS: We analyzed retrospectively the results of urine cultures of 402 patients that had community acquired urinary tract infection in the year of 2003. RESULTS: The mean age of the patients in this study was 45.34 ± 23.56 (SD) years. There were 242 (60.2%) females and 160 (39.8%) males. The most commonly isolated organism was Escherichia coli (58%). Klebsiella sp. (8.4%) and Enterococcus sp.(7.9%) were reported as the next most common organisms. Of all bacteria isolated from community acquired UTI, only 37% were sensitive to ampicillin, 51% to cefalothin and 52% to trimethoprim/sulfamethoxazole. The highest levels of susceptibility were to imipenem (96%), ceftriaxone (90%), amikacin (90%), gentamicin (88%), levofloxacin (86%), ciprofloxacin (73%), nitrofurantoin (77%) and norfloxacin (75%). CONCLUSION: Gram-negative agents are the most common cause of UTI. Fluoroquinolones remains the choice among the orally administered antibiotics, followed by nitrofurantoin, second and third generation cephalosporins. For severe disease that require parenteral antibiotics the choice should be aminoglycosides, third generation cephalosporins, fluoroquinolones or imipenem, which were the most effective.


INTRODUCTION
Urinary tract infections (UTI) are one of the most common infectious diseases diagnosed in outpatients as well as in hospitalized patients, and can lead to significant mortality 1 .UTI account for a large proportion of antibacterial drug consumption and have large socio-economic impacts 2 .
Since the majority of the treatments begins or is done completely empiricall, the knowledge of the organisms, their epidemiological characteristics and their antibacterial susceptibility is mandatory.These data are essential to optimize the treatment and avoid the emergence of bacterial resistance 3 , which is responsible for the increasing number of therapeutic failure 4,5 .Temporal and local variables can modify these data so they need to be constantly re-evaluated.There are few publications about urinary tract pathogens in Brazil [6][7][8][9][10] .
The aim of this study was to report the information about the uropathogens and their antibiotic susceptibility of the community acquired UTI diagnosed in our institution and to provide a recent national data.

METHODS
We analyzed the results of urine cultures of 402 patients that had community acquired urinary tract infection [³ 10 5 colony-forming units (CFU/ mL) 11 ] and had urine sampled in the Hospital das Clínicas -FMRP-USP from January to June of 2003.

Demographic data
The mean age of the patients in this study was 45.34 ± 23.56 (SD) years; (range 3 months to 95 years).There were 242 (60.2%) females and 160 (39.8%) males.The prevalence of UTI in the females was more homogenous between age groups, considering intervals of 10 years, with small difference after the third decade, and few children was diagnosed.Fifty percent of the male patients were older than 60 years and the distribution was almost constant in the younger decades (Table 1).

Pathogens
The most commonly isolated organism was Escherichia coli (58%).Klebsiella sp.(8.4%) and Enterococcus sp.(7.9%) were reported as the next most common organisms.The others bacteria are summarized in Table 2.

Percentage of susceptible micro-organisms
Of all bacteria isolated from community acquired urinary tract infection, only 37% were sensitive ABSTRACT -Purpose: Urinary tract infections (UTI) are one of the most common infectious diseases diagnosed.UTI account for a large proportion of antibacterial drug consumption and have large socio-economic impacts.Since the majority of the treatments begins or is done completely empirically, the knowledge of the organisms, their epidemiological characteristics and their antibacterial susceptibility that may vary with time is mandatory.Objetive: The aim of this study was to report the prevalence of uropathogens and their antibiotic susceptibility of the community acquired UTI diagnosed in our institution and to provide a national data.Methods: We analyzed retrospectively the results of urine cultures of 402 patients that had community acquired urinary tract infection in the year of 2003.Results: The mean age of the patients in this study was 45.34 ± 23.56 (SD) years.There were 242 (60.2%) females and 160 (39.8%) males.The most commonly isolated organism was Escherichia coli (58%).Klebsiella sp.(8.4%) and Enterococcus sp.(7.9%) were reported as the next most common organisms.Of all bacteria isolated from community acquired UTI, only 37% were sensitive to ampicillin, 51% to cefalothin and 52% to trimethoprim/sulfamethoxazole.The highest levels of susceptibility were to imipenem (96%), ceftriaxone (90%), amikacin (90%), gentamicin (88%), levofloxacin (86%), ciprofloxacin (73%), nitrofurantoin (77%) and norfloxacin (75%).
Conclusions: Gram-negative agents are the most common cause of UTI.Fluoroquinolones remains the choice among the orally administered antibiotics, followed by nitrofurantoin, second and third generation cephalosporins.For severe disease that require parenteral antibiotics the choice should be aminoglycosides, third generation cephalosporins, fluoroquinolones or imipenem, which were the most effective.

DISCUSSION
Urinary tract infection occurs in every age and in both genders.According to the demographic data, it is more frequent in woman 12 .
The present study is retrospective, using the results of our routine diagnostic and susceptibility analysis.These data are from a tertiary hospital, the patients are screened in the primary and secondary level of healthy system and prone to associated conditions and diseases.These factors may influence the patterns of the data herein presented.We are concerned about the necessity of periodical re-evaluation of bacterial etiology and antibiotic resistance in each health unit and of a national surveillance to avoid the rise of the antimicrobial resistance.
In the community, it is important to guide the general practitioners that generally treat empirically the UTI, for what they need to be aware of the locally prevalent strains and their sensitivity pattern.Geographic variations in pathogen occurrence and susceptibility profiles require frequent monitoring to provide information to guide the therapeutic options.Unfortunately, there is few studies published on the prevalence of strains and their antimicrobial susceptibilities in Brazil.
We found that E. coli is the predominant bacterium in urine samples, corresponding to 58% of the cases.This is in accordance with previous studies [13][14][15] , however in a study from Norway 16 E. coli caused 81.5% of UTI in outpatients compared to 58% in the present study.A lower proportion of UTI was caused by Klebsiella sp (8.4%) and Enterococcus sp (7.9%), which is in accordance to others 12,13,15 .
In summary, fluoroquinolones remains the choice among the orally administered antibiotics, followed by nitrofurantoin, second and third generation cephalosporins.To treat severe illness one may use the injectable antibiotics, and among then, we should choice aminoglycosides, third generation cephalosporin, fluoroquinolones or imipenem, which were the most effective ones.The high resistance patterns to ampicillin, cephalotin and TMP-SMX should be remembered.

CONCLUSION
The most common community acquired UTI is caused by negative-Gram agents.Fluoroquinolones remains the choice among the orally administered antibiotics, followed by nitrofurantoin, second and third generation cephalosporins.For severe disease that require parenteral antibiotics the choice should be aminoglycosides, third generation cephalosporin, fluoroquinolones or imipenem, which were the most effective.

INTRODUCTION
Hospitalized patients are predisposed to a variety of nosocomial infections, especially with multidrug-resistant organisms 1 .Urinary tract infection (UTI) is the most frequent nosocomial infection and has been suffering a shift in the etiology and antimicrobial susceptibility, as common as other infections detected in the last decade [2][3][4][5] .Since most of treatments began empirically, prior knowledge of the bacterial prevalence as well as the resistance patterns in a particular setting is essential.
Informations on the etiology and bacterial susceptibility of nosocomially acquired UTI in Brazil are scarce which makes the decisions on antibiotic choice almost entirely dependent of international data 6 .As both geographic and temporal factors can influence these data, they need to be constantly and locally re-evaluated.
The aim of this study was to determine the local prevalence of bacterial strains and the antibiotic susceptibility of the nosocomially acquired UTI in our institution to guide antibiotic choice and to achieve a maximal clinical response in empiric treatment while the antibiotic susceptibility of the pathogen is still unknown.

TABLE 1 -
Incidence of UTI in the sex groups, divided in decades.

TABLE 2
Micro-organisms isolated in urine