Community acquired urinary tract infection: etiology and bacterial susceptibility

Infecção urinária comunitária: etiologia e sensibilidade bacteriana

ARTIGO ORIGINAL

Community acquired urinary tract infection: etiology and bacterial susceptibility¹

Infecção urinária comunitária: etiologia e sensibilidade bacteriana

José Anastácio Dias Neto^I; Antonio Carlos Pereira Martins^II; Leonardo Dias Magalhães da Silva^I; Ricardo Brianezi Tiraboschi^I; André Luis Alonso Domingos^I; Adauto José Cologna^II; Edson Luis Paschoalin^III; Silvio Tucci Jr^II

^IMedical resident of Hospital das Clínicas – FMRP-USP

^IIProfessor and Assistants of FMRP-USP

^IIIPostgraduation alumni of the Department of Surgery – FMRP-USP

^{Correspondence}

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.

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.

Key Words: Urinary tract. Infection. Community. Bacteria. Antibiotic. Susceptibility.

RESUMO

INTRODUÇÃO: Devido a freqüência a infecção do trato urinário (ITU) responde por consumo elevado de antibióticos e tem impacto sócio-economico elevado. Como a escolha do antimicrobiano no início do tratamento ou para o tratamento completo é geralmente empírica, o conhecimento da prevalência bacteriana e sua sensibilidade, que podem variar no tempo, é mandatoria.

OBJETIVO: O objetivo do trabalho é relatar a freqüência das cepas bacterianas diagnosticadas em nossa instituição, bem como a sensibilidade aos antimicrobianos, e prover dados nacionais.

MÉTODOS: Foram analisados retrospectivamente os resultados de cultura de urina de 402 pacientes com ITU adquirida na comunidade e tratados em nossa instituição.

RESULTADOS: A idade média dos pacientes foi de 45,3±23,5 anos, 242 (60,2%) dos quais eram mulheres e 160 (39,8%) eram homens. A bactéria mais freqüente foi a E. coli (58%) seguida de Klebsiella sp. (8,4%) e Enterococcus sp. (7,9%). Das bactéria isoladas somente 37% apresentavam sensibilidade à ampicilna, 51% à cefalotina e 52% ao trimxazol. As maiores taxas de sensibilidade ocorreram para o imipenem (96%), ceftriaxone (90%), amicacina (90%), gentamicina (88%), levofloxacina (86%), ciprofloxacina (73%), nitrofurantoina (77%) e norfloxacina (75%).

CONCLUSÃO: As bactérias Gram-negativas são a causa mais comum de ITU comunitária. Os antimicrobianos de escolha para tratamento oral são as fluoroquinolonas, nitrofurantoina, cefalosporinas de segunda e terceira geração. Para quadros graves que requerem antibiótico parenteral a escolha recai sobre os aminoglicosídeos, cefalosporinas de terceira geração e imipenem.

Descritores: Trato urinário. Comunidade, infecção. Bactéria. Antibiótico, sensibibilidade.

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 mortality¹. UTI account for a large proportion of antibacterial drug consumption and have large socio-economic impacts².

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 resistance³, 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^6-10.

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 [³ 10⁵ colony-forming units (CFU/mL)¹¹] and had urine sampled in the Hospital das Clínicas – FMRP-USP from January to June of 2003.

RESULTS

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.

Bacterial susceptibility

The comparison of the susceptibility pattern of organisms to various antimicrobial agents from all the specimens was shown in Table 3. Escherichia. coli showed high susceptibility to aminoglycosides: amikacin (97%) and gentamicin (94%); to nitrofurantoin (89%); fluoroquinolones: norfloxacin (81%), ciprofloxacin (78%) and levofloxacin (91%); second and third generation cephalosporins and imipenem. There was a low susceptibility pattern of E. coli to ampicillin (41%), trimethoprim-sulfamethoxazole (TMP-SMX) (50%) and cephalothin (58%).

Klebsiella sp was highly susceptible to aminoglycosides: gentamicin (91%) and amikacin (84%); to cephalosporins: cefoxitin (96%), cefotaxime (90%) and ceftriaxone (88%). Nevertheless, there was a decreased susceptibility to nitrofurantoin (50%), norfloxacin (68%), ciprofloxacin (71%), cefalothin (58%), TMP-SMX (58%) and ampicillin (6%).

Enterococcus sp. showed high sensibility to nitrofurantoin (100%), penicillin G (100%), vancomycin (100%) e ampicillin (96%) The resistance to TMP-SMX was high, approximately 70% (Table 3).

Percentage of susceptible micro-organisms

Of all bacteria isolated from community acquired urinary tract infection, only 37% were sensitive to ampicillin, 51% to cefalothin and 52% to TMP-SMX. The highest levels of susceptibility were to imipenem (96%), ceftriaxone (90%), amikacin (90%), gentamicin (88%), levofloxacin (86%), cefoxitin (80%) nitrofurantoin (77%), norfloxacin (75%) and ciprofloxacin (73%)-(Table 3).

DISCUSSION

Urinary tract infection occurs in every age and in both genders. According to the demographic data, it is more frequent in woman¹².

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^13-15, however in a study from Norway¹⁶E. 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.

E. coli exhibited resistance to the commonly used antibiotics, and the most effective in-vitro agents were found to be aminoglycosides: amikacin (97%) and gentamicin (94%) among the injectables; and fluoroquinolonas: norfloxacin (81%), ciprofloxacin (78%) and levofloxacin (91%) among the orally administered ones. Other useful oral antibiotic is nitrofurantoin (89%). The organisms showed resistance to common used urinary antibiotics like ampicillin (59%), TMP-SMX (50%) and cephalothin (42%), in disagreement with data published by others^13,17,18.

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.

References

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• 3. Magree JT, Pritchard EL, Fitzgerald KA. On behalf of the Welsh Antibiotic Study Group. Antibiotic prescribing and antibiotic resistance in the community practice: retrospective study, 1996-8. BMJ 1999; 319:1239-40.
• 4. Grunberg RN. Changes in urinary pathogens and their antibiotic sensitivities, 1971-1992. J Antimicrob Chemother 1994;33: 1-8
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• 11. Kass EHFM. Assymptomatic infections of the urinary tract. Trans Assoc Am Physicians 1956; 69: 56-64.
• 12. Prais D, Strussberg R. Bacterial susceptibility to oral antibiotics in community acquired urinary tract infection. Arch Dis Child 2003; 88: 215-8.
• 13. Ladhani S, Gransden W. Increasing antibiotic resistance among urinary tract isolates. Arch Dis Child 2003; 88: 444-5.
• 14. Andrews JM. The developmentof the BSAC standardized method of disc diffusion testing. J Antimicrob Chemother 2001; 48(suppl S1): 29-45.
• 15. Mangioarotti P, Pizzini C, Fanos V. Antibiotic prophylaxis in children with relapsing urinary tract infections. J Chemother 2000; 12: 115-23.
• 16. Kristiansen B-E. Uriveispatogene bakterier. Frekvens og resistensforhold. Tidsskr Nor Laegeforen 1983; 103: 1684-6.
• 17. Vromen M, van der Ven AJ. Antimicrobial resistance patterns in urinary isolates from nursing home residents. Fifteen years of data reviewed. J Antimicrob Chemother 1999; 44: 113-6.
• 18. Zhanel GG, KarlowskyJA, Harding GKM. A Canadian national surveillance study of urinary tract isolates from out patients: Comparison of the activities of trimethoprim-sulfametaxazole, ampicilin, mecillinam, nitrofurantoin, and ciprofloxacin. Antimicr Agents Chemother 2000; 44: 1089-92.

Correspondence to

Antonio Carlos Pereira Martins

Hospital das Clínicas – Departamento de Cirurgia

Av. Bandeirantes, 3.900, 9º Andar

Ribeirão Preto, SP

CEP: 14048-900

1

This research was developed at Hospital das Clínicas – FMRP-USP

Publication Dates

• Publication in this collection
  29 Apr 2004
• Date of issue
  2003