Bacteriological profile and antimicrobial susceptibility patterns of urine culture isolates from patients in Ndjamena, Chad

Bacteriological profile and antimicrobial susceptibility patterns of urine culture isolates from patients in Ndjamena, Chad

Michel Kengne^1,&, Amon Todjimbaide Dounia^1,2, Julius Mbekem Nwobegahay^1,3

 

¹Department of Medical Microbiology and Immunology, School of Health Sciences-Catholic University of Central Africa, Yaoundé, Cameroon, ²Ndjamena General Hospital of National Reference, Chad, ³Yaoundé Military Hospital, Cameroon

 

 

^&Corresponding author
Michel Kengne, Department of Medical Microbiology and Immunology, School of Health Sciences-Catholic University of Central Africa, Yaoundé, Cameroon

 

 

 

 

Urinary tract infections (UTIs) are the third most common infection in human with an estimated annual global incidence of at least 250 million in developing country [1-3]. Different microorganisms can cause UTIs, E. coli which accounts approximately for 75% of isolates is the most common pathogen isolated from community and hospital acquired UTIs [4]. Other uropathogens such as Klebsiella spp. and S. saprophyticus have also been frequently isolated [5, 6]. The management of UTIs is usually empirical, based on the predictable spectrum of etiologic agents and their susceptibility patterns. Due to the emergence of antimicrobial resistance among uropathogens, the effectiveness of empirical therapy has been affected [7]. In Chad, antimicrobial susceptibility among pathogens involved in UTIs is poorly investigated. Therefore, it is important to obtain information on local antimicrobial resistance rates to provide adequate treatment to community and hospital acquired UTIs in this country. In this study, we investigated the bacteriological profile and the antimicrobial susceptibility patterns of urine culture isolates among patients in Ndjamena General Hospital of National Reference.

 

 

Patients: the study participants were both inpatients and outpatients attending the Ndjamena General Hospital of National Reference from July to November 2014. Six hundred and sixty patients to whom a cytobacteriological examination of urine was prescribed and who had not received antimicrobials within the previous fifteen days were eligible for inclusion.

 

Bacterial isolation, identification procedures and antimicrobial susceptibility testing: a freshly midstream morning urine sample of 2-5ml was collected in sterile container from the selected patients. Aseptic measures were maintained during samples collection. Immediately after sampling, urine was spread on Eosin Methylene Blue agar media and incubated at 37°C for 24h. A growth of > 105 CFU/ml of one type of organism was considered as significant bacteriuria. Identification of the pathogens and antimicrobial testing were performed using Vitek 2 compact automated system (bioMérieux, Marcy l’étoile, France) according to the manufacturer’s instructions.

 

The results were recorded as susceptible (S), susceptible dose dependent (SDD) and resistant (R). The following antibiotics purchased from bio-Mérieux (France) were used: amoxicillin/ clavulanic acid (20/10µg), ampicillin (10µg), oxacillin (5µg), ceftriaxone (30µg), ceftazidime (30µg), cefotaxime (30µg), aztreonam (30µg), imipenem (10µg), gentamycin (15µg), amikacin (30µg), nalidixic acid (30 µg), ciprofloxacin (5µg), ofloxacin (5µg). The reference strain used as quality control was E. coli (ATCC 25922).

 

Data analysis: data were entered and analyzed using SPSS version 12.0 for windows (SPSS, Inc., Chicago, IL). Discrete variables were expressed as frequencies and percentages.

 

Ethics: permission to collect samples was obtained from the Ndjamena General Hospital of National Reference. Informed consent was obtained from all participants ≥ 18 years, while assent consent was obtained from participant teenagers via a proxy.

 

 

From July to November 2014 (05 months study period), 660 urine samples were obtained from patients (age range: 10-90 years) and analyzed. 216 (32.7%) samples had significant bacteriuria among which 94 (43.5%) positive samples were from women and 122 (56.5%) were from men (sex ratio M/F: 1.29). Bacteriuria was more present in inpatients 152/216 (70.4%) compared to outpatients 64/216 (29.6%). The most frequent pathogen was E. coli 128 (59.2%), followed by K. pneumonia 28 (13.0%) and E. cloacae 11 (5.1%) which altogether accounted for 77.3% of the total isolates (Table 1). Bacterial uropathogen isolates from patients revealed the presence of high level of single and multiple antimicrobial resistances against commonly prescribed drugs. The total isolates displayed a resistance rate of > 60% to the antibiotics used excepted imipéneme, amikacin, aztreonam and gentamicin for which the resistance rates were 2.7%, 19.4%, 30.5% and 49.5% respectively. E.coli which is the predominant cause of UTIs in this study was susceptible to imipeneme 96.1%, aztreonam 67.1%, amikacin 62.5% and gentamycin 50%. As E. coli, K. pneumonia and E. cloacae were the most important uropathogens isolated and their susceptibility rates are displayed in Table 2.

 

Furthermore, the remainder of this report will consider only these organisms. Betalactame-type enzymes production which determines variable phenotypes of betalactamines resistance was observed among the isolates. Extended spectrum betalactamases (ESBLs) that hydrolyze extended-spectrum cephalosporins (cefotaxime, ceftriaxone, ceftazidime) and monobactams (aztreonam) were present in 68/105 (64.7%) of betalactamines resistant isolates followed by cephalosporinase overproducing phenotype 27/105 (25.7%). Aminoglycosides resistance through enzymatic production was also recorded. Aminglycoside-acetyltransferases AAC(3)-I and AAC(6’)-I phenotypes were found respectively in 16/36 (44.4%) and 20/36 (55.6%) of aminoglycosides resistant isolates, thereby explaining the resistance phenotypes observed with gentamycin and amikacin. On the other hand, phenotypes associated with quinolones resistant isolates were produced through natural resistance and acquired resistance through non enzymatic drug resistance mechanisms. Resistance of isolates to quinolones was mainly due to an association of target modification (gyrA and parC), porin reduction and/or efflux mechanism which was present in 107/213 (49%) of quinolones resistant isolates, wild type phenotype was found in 60/213 (28%) of quinolone resistant isolates (Table 3).

 

 

Knowledge of the etiology and the antimicrobial resistance patterns of the agents involved in UTIs may help clinicians to choose appropriate antimicrobial treatments. The present study determined the bacteriological profile and antimicrobial susceptibility patterns of urine culture isolates among patients in Ndjamena General Hospital of National Reference, Chad. In this study, 216 (32.7%) on 660 urine samples met the criteria for urinary tract infection. This data contrasts with those presented by other surveillance studies. Irenge et al. [8] among 2,724 urine samples processed in a tertiary care hospital in south Kivu Province (Democratic republic of Congo) found a rate of 23.6%. Beyene and Tsegaye [9] obtained a bacteriuria of 9.2% from 228 cultured urine specimens in Jimma University Specialized Hospital in Southwest Ethiopia whereas Villar et al. [10] recorded a result of 25.5% from 3.105 urine samples collected from male outpatients in Argentina. The data reported in this study showed a high bacteriuria in inpatients compared to outpatients. This result is in line with that of Gupta et al. [11] and might reflect infections acquired during hospitalization. E. coli is the major etiological agent involved in urinary tract infections accounting for up to 90% of cases [5]. E. coli was the most common bacteria isolated from urine samples in both inpatients and outpatients of both sexes and this finding is in agreement with other studies [1,12-14]. In contrary to another study where the second reported isolate was Proteus mirabilis [15], in this study, it was K. pneumonia followed by E. cloacae which is in agreement with the findings of Ghorbani et al. [1].

 

Resistance to antimicrobial agents has been noted since the first use of these agents and is an increasing worldwide problem [16]. The Infectious Diseases Society of America guidelines suggest that 10-20% resistance warrants a change in the recommended antibiotic used as the first line therapy [17]. In the present study, only imipeneme (94.9%) displayed satisfactory activity against pathogens. High antibiotic-resistance rate was observed with other antimicrobial drugs. Resistance of isolates to betalactamines was mainly due to production of ESBLs. It has been found that the increasing frequency of ESBL phenotypes is an emerging problem due to the enormous potential for multidrug resistance from strains that produce these enzymes [18]. Acetylation of aminoglycosides by acetyltransferases is one of the major mechanisms of acquired resistance to these compounds [19, 20]. The 3-N-aminoglycoside acetyltransferases (AAC(3) enzymes) and the 6’-N- aminoglycoside acetyltransferases (AAC(6’) enzymes) were found to be among the modifying enzymes most commonly encountered in clinical isolates [19, 21]. The AAC(3)-I enzymes confer resistance to gentamycin, sisomicin and astromicin and are widespread among Enterobacteriaceae [21, 22]. These findings were also observed in the current study. The involved mechanisms of resistance to quinolones were alterations in the targets of quinolones, decreased accumulation due to impermeability of the membrane and/or an over expression of efflux pump systems and an association of many of these. This result agrees in some respect with other studies [23, 24].

 

The decreased susceptibility rates found for many agents in the current study is worrisome, since some of them are currently prescribed in Ndjamena as first line agents for treating hospital or community acquired infections such as UTIs. The current data may reflect the extensive use of prescribed agents. This over use may select for multidrug resistant strains, harboring the potential to disseminate within a specific region.

 

 

E. coli remains the most common bacterial uropathogen responsible for UTIs in Ndjamena. This study confirms the presence of antibiotic-resistant uropathogens in this study area. As drug resistance is an evolving process, routine surveillance and monitoring studies should be conducted to provide physicians with knowledge about the most effective empirical treatment of UTIs.

 

 

The authors declare no competing interests.

 

 

Michel Kengne: conceived, designed, financed the study and produced the first draft of this manuscript. Amon Todjimbaide Dounia performed the sample collection, the laboratory assays and the data analysis and interpretation. Julius Mbekem Nwobegahay corrected the research proposal before the study and did a thorough review of the manuscript. All authors have read and agreed to the final manuscript.

 

 

Special thanks are due to the participants who provided the specimen and to the Director of the Ndjamena General Hospital of National Reference in Chad who granted the research authorization for this study.

 

 

Table 1: distribution of uropathogens in patients

Table 2: percentage of resistance of isolates to antibiotics

Table 3: resistance mechanism/phenotype of resistant isolates

 

 

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