Antimicrobial resistance in Shigella species isolated in Dakar, Senegal (2004-2006).

From May 2004 to October 2006, a prospective study was carried out in Dakar, Senegal, to update information about the antimicrobial susceptibility of Shigella spp. isolated from stool specimens. Among the 165 non-duplicate strains collected, 81 (49%) were identified as Shigella flexneri, 75 (45%) as Shigella sonnei, 5 (3%) as Shigella boydii, and 4 (2%) as Shigella dysenteriae. Disk diffusion testing revealed that the majority of isolates were resistant to sulphonamides, trimethoprim-sulfamethoxazole, streptomycin, and tetracycline (respective overall resistance rates: 90, 90, 96, and 94%). More than half of the S. flexneri isolates were resistant to amoxicillin, amoxicillin-clavulanic acid, and chloramphenicol (respective resistance rates: 59, 58, and 52%), and almost all of the S. sonnei isolates were susceptible to these antimicrobials (respective resistance rates: 4, 1, and 4%). Only one isolate (belonging to the species S. sonnei) was resistant to nalidixic acid and displayed reduced susceptibility to ciprofloxacin.

Analysis of topoisomerase mutations in fluoroquinolone-resistant and -susceptible Campylobacter jejuni strains isolated in Senegal.

In this study, topoisomerase mutations in ciprofloxacin-resistant and -susceptible Campylobacter jejuni were analysed by DNA sequencing. In certain ciprofloxacin-resistant C. jejuni, the mechanism of resistance was complex. The Thr86-Ala substitution in the GyrA protein appears to play a role in increasing the minimum inhibitory concentration of nalidixic acid only. In addition, isolates with this amino acid change and those resistant to quinolones but lacking a mutation in the GyrA quinolone resistance-determining region could be derived from two different clones. Based on gyrA and gyrB polymorphisms, C. jejuni isolates from the Dakar region of Senegal appeared to be less diverse than those from other countries. Moreover, C. jejuni isolates in Senegal appeared to differ from European isolates by lack of a silent mutation at codon 120 of the gyrA gene.

Campylobacter coli isolates derived from chickens in Senegal: Diversity, genetic exchange with Campylobacter jejuni and quinolone resistance.

We used the multilocus sequence typing (MLST) method to study the genetic diversity of Campylobacter coli isolated from chickens in Senegal, and to check the presence of genetic exchange with Campylobacter jejuni. In addition, we assessed the resistance of the isolates to ciprofloxacin and nalidixic acid, and their gyrA sequences. MLST revealed a low level of diversity and the absence of lineages among C. coli isolates. In addition, an exchange of alleles with C. jejuni was found. Twenty percent of the ciprofloxacin-resistant isolates lacked mutations within the quinolone resistance-determining region (QRDR) of GyrA. There was no link between quinolone resistance and sequence type (ST).

Antimicrobial resistance in outpatient Escherichia coli urinary isolates in Dakar, Senegal.

BACKGROUND: Data regarding the evolution of antimicrobial resistance are needed to suggest appropriate empirical treatment of urinary tract infections (UTI) in developing countries. To assess the antimicrobial susceptibility of Escherichia coli, the predominant pathogen in community-acquired UTI, a prospective multicenter study was carried out in Dakar, Senegal. METHODOLOGY: From February 2004 to October 2006, 1010 non-duplicate E. coli strains were collected from four centres. Antimicrobial susceptibility testing was performed using disk diffusion method according to the recommendations of the CA-SFM (2004). RESULTS: Most of the isolates were resistant to amoxicillin (73.1%), amoxicillin-clavulanic acid (67.5%), cephalothin (55.8%), and trimethoprim/sulfamethoxazole (68.1%). Extended spectrum beta-lactamase was detected in 38 strains. The overall resistance rates to nalidixic acid, norfloxacin and ciprofloxacin were 23.9%, 16.4% and 15.5%, respectively. Most of the strains were susceptible to gentamicin, nitrofurantoin and fosfomycin (respective susceptibility rates, 93.8%, 89.9%, and 99.3%). During this period, a significant decrease in sensitivity was observed for cephalothin, fluoroquinolones and trimethoprim/sulfamethoxazole (p<0.001). CONCLUSIONS: These data suggest that trimethoprim/sulfamethoxazole may no longer be used as empirical treatment for community-acquired UTI in Dakar. In order to preserve the activity of fluoroquinolones for future years, alternatives such as fosfomycin or nitrofurantoin should be considered.

Prevalence and antibiotic-resistance of Salmonella isolated from beef sampled from the slaughterhouse and from retailers in Dakar (Senegal).

A study was made of Salmonella contamination in beef sampled from a slaughterhouse and from retailers in Dakar, Senegal. The serotypes as well as antibiotic-resistance patterns of the Salmonella isolates were determined. A total of 435 meat samples (236 from the slaughterhouse, 199 from retailers) were tested. Among them, 275 (63%) were positive for Salmonella, 43% (101/236) from the slaughterhouse and 87% (174/199) from the retailers. Furthermore, 97% of the investigated retailers had at least one beef sample contaminated by Salmonella. The 286 Salmonella isolates were divided into 51 serotypes. The most prevalent serotypes were Salmonella bredeney (25%), S. muenster (8%), S. waycross (7%), S. corvallis (4%) and S. kentucky (4%). About 62% of the isolates were resistant to nitrofurans. Resistance rates were lower to streptomycin (22%), sulfamethoxazole (15%), spectinomycin (1%), chloramphenicol (1%), and tetracycline (0,4%) while low-level resistance to quinolones was detected. About 16% of the Salmonella strains were multiresistant to two or more antibiotic families. Finally, ten resistance profiles have been identified. This study shows the huge spread of Salmonella in the beef production chain in Dakar, Senegal. Finally, this study provides the very first data about Salmonella prevalence in sub-saharian Africa.

Genetic diversity and quinolone resistance in Campylobacter jejuni isolates from poultry in Senegal.

We used the multilocus sequence typing (MLST) method to evaluate the genetic diversity of 46 Campylobacter jejuni isolates from chickens and to determine the link between quinolone resistance and sequence type (ST). There were a total of 16 ST genotypes, and the majority of them belonged to seven clonal complexes previously identified by using isolates from human disease. The ST-353 complex was the most common complex, whereas the ST-21, ST-42, ST-52, and ST-257 complexes were less well represented. The resistance phenotype varied for each ST, and the Thr-86-Ile substitution in the GyrA protein was the predominant mechanism of resistance to quinolone. Nine of the 14 isolates having the Thr-86-Ile substitution belonged to the ST-353 complex. MLST showed that the emergence of quinolone resistance is not related to the diffusion of a unique clone and that there is no link between ST genotype and quinolone resistance. Based on silent mutations, different variants of the gyrA gene were shown to exist for the same ST. These data provide useful information for understanding the epidemiology of C. jejuni in Senegal.

In vitro susceptibility of quinolone-resistant Enterobacteriaceae uropathogens to fosfomycin trometamol, in Dakar, Senegal.

We conducted a study in order to confirm the eligibility of fosfomycin trometamol as an alternative treatment to quinolones for urinary tract infections. Among 102 quinolone-resistant Enterobacteriaceae strains, resistance rates to first line-prescribed antibiotics were above 77%. The resistance rate to fosfomycin was 2%.

Risk factors for antibiotic-resistant Escherichia coli isolated from community-acquired urinary tract infections in Dakar, Senegal.

OBJECTIVES: To assess overall resistance rates and risk factors for resistance to ampicillin, co-amoxiclav, nalidixic acid, fluoroquinolones and trimethoprim/sulfamethoxazole in Escherichia coli strains isolated from outpatients with acute urinary tract infection in Dakar (Senegal). PATIENTS AND METHODS: From June 2001 to June 2003, a prospective study was performed among Senegalese outpatients consulting at the Institut Pasteur of Dakar for urine analysis. Evaluated risk factors were: age, gender, prior hospitalization, antibiotic exposure, urinary tract infection and urinary catheter. RESULTS: A total of 398 non-duplicate, consecutive, biologically significant E. coli were isolated. The levels of antibiotic resistance in Dakar appeared dramatic and worrisome with resistance rates ranging from 18.6% for fluoroquinolones to 73.6% for ampicillin. With the exception of the presence of urinary catheter, the risk factors identified were consistent with data previously reported in developed countries. CONCLUSIONS: We hope our results will assist medical authorities in the development of appropriate control strategies.

Performance evaluation of automated depolarization analysis for detecting clinically unsuspected malaria in endemic countries.

This prospective study evaluated the efficiency of automated depolarization analysis for recognition of unsuspected malaria by haemozoin detection during routine full blood count (FBC) screening of 676 randomly selected out-patients in a malaria hypoendemic area of Senegal. An additional 123 patients with clinically suspected malaria were studied for comparison. Of the 799 samples, 648 (81.1%) were categorized as malaria-negative, 83 (10.4%) as malaria-positive, and 68 as treated (early convalescence) or subclinical malaria (indirect evidence of infection). At a discrimination level of one or more atypical pigment-containing monocytes (PCM), negative and positive agreement was found to be 95.6% and 91.6% respectively for all malaria-negative and parasite-positive samples combined. Increasing the discriminator to two or more PCM events improved the overall agreement to 97.5%. Multivariate analysis showed that the only significant risk factor for the presence of PCM (odds ratio>200) was malaria infection. In the randomly selected group of 676 patients, 41 unsuspected cases of malaria infection were detected using the panel of reference diagnostic tests, and 37 (90.2%) of these had atypical PCM. The detection of clinically unrecognized malaria infection as part of a routine FBC procedure is a potentially useful extended application for laboratories in countries with endemic malaria.

Identifying relapsing fever Borrelia, Senegal.

We describe a nested polymerase chain reaction for the identification of Borrelia species from serum of patients with unidentified fevers. This technique, based on single nucleotide polymorphisms of the 16S ribosomal RNA gene, was used to test blood samples from 7,750 patients, 33 of whom were diagnosed with spirochete infections. Borrelia crocidurae was the only species identified.

Characterization of extended-spectrum-beta-lactamase (CTX-M-15)-producing strains of Salmonella enterica isolated in France and Senegal.

Three clinical isolates of Salmonella enterica recovered between 2000 and 2003 in France and Senegal were found to produce extended-spectrum beta-lactamase CTX-M-15. The two isolates from Senegal were recovered from stool of a hospitalized patient with gastroenteritis in 2000 and from an urine specimen of an out-patient with urinary tract infection in 2001. These S. enterica isolates belonged to serotype Kentucky and were clonally related as determined by pulsed-field gel electrophoresis and automated ribotyping. The third isolate of serotype Typhimurium was recovered from a patient hospitalized in France for an acute gastroenteritis acquired in Lebanon. The bla(CTX-M-15) gene was located on two different transferable plasmids, one of which also carried bla(TEM-1), bla(OXA-30), aminoglycoside-, tetracycline-, and sulfamethoxazole-trimethoprim resistance genes. ISEcp1 element was found to be located upstream of bla(CTX-M-15) in the same position as reported previously in CTX-M-15-producing Escherichia coli from India and Turkey. This is the first report of bla(CTX-M-15) in the genus Salmonella.

Increasing prevalence of antimicrobial resistance among Enterobacteriaceae uropathogens in Dakar, Senegal: a multicenter study.

To assess antibiotic susceptibility among Enterobacteriaceae isolated in urine from outpatients in Dakar, Senegal, a prospective multicenter study involving 3 laboratories had been conducted between June and October 2001. During this period, 300 strains were isolated and susceptibility testing was performed against antibiotics commonly used in treatment of community-acquired urinary tract infections (UTI). E. coli and K. pneumoniae represented 89% of isolates. The overall resistance rates of ampicillin, amoxicillin-clavulanic acid, nalidixic acid, fluoroquinolones and cotrimoxazole were respectively 77.3%, 34.7%, 14.7%, 13.3%, and 55%. In the light of these results, a re-evaluation of first line therapies and prudent use of fluoroquinolones is advised. At the same time a continued surveillance of antimicrobial resistance should be developed in Senegal in order to control the emergence of multidrug resistant strains and to establish a national therapeutic guideline for treatment of UTI.

Fluoroquinolone susceptibility of Campylobacter strains, Senegal.

To assess fluoroquinolone susceptibility of Campylobacter strains in Senegal, skin samples were collected from 250 chicken carcasses from January 2001 to October 2002. Among 205 isolated Campylobacter strains, 59% and 41% were identified as Campylobacter jejuni and C. coli, respectively; the overall ciprofloxacin-resistance rate was 34%.