Apr 28, 2008 - 5 (3%) as Shigella boydii, and 4 (2%) as Shigella dysenteriae. ... and almost all of the S. sonnei isolates were susceptible to these ...
Jpn. J. Infect. Dis., 61, 307-309, 2008
Short Communication
Antimicrobial Resistance in Shigella Species Isolated in Dakar, Senegal (2004 - 2006) Jean-Marie Sire*, Edgard Adam Macondo1, Jean-David Perrier-Gros-Claude, Tidiane Siby1, Ibrahim Bahsoun, Abdoulaye Seck and Benoit Garin Laboratoire de Biologie Médicale, Institut Pasteur, and 1Laboratoire Bio24, Dakar, Senegal (Received October 1, 2007. Accepted April 28, 2008) SUMMARY: 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. by disk diffusion according to the guidelines of the Antibiogram Committee of the French Society for Microbiology (CA-SFM) (4). Strains were tested against the following antimicrobial disks (Bio-Rad): amoxicillin (10 μg), amoxicillin-clavulanic acid (20 μg/10 μg), ticarcillin (75 μg), cephalothin (30 μg), cefotaxime (30 μg), nalidixic acid (30 μg), ciprofloxacin (5 μg), chloramphenicol (30 μg), sulphonamides (300 μg), trimethoprim-sulfamethoxazole (cotrimoxazole) (1.25 μg/23.75 μg), streptomycin (10 μg), gentamicin (15 μg), and tetracycline (30 μg). Inhibition zone diameters were measured with an automated zone size reader (Osiris; Bio-Rad) and isolates were classified as susceptible, intermediate, or resistant according to the annual report of the CA-SFM (4). Isolates with intermediate susceptibility were categorized as resistant for further analysis. Multidrug resistance was defined as resistance to three or more antimicrobial agents among the following antibiotics: amoxicillin, chloramphenicol, streptomycin, sulphonamides, and tetracycline. The minimal inhibitory concentration (MIC) of ciprofloxacin was determined in case of nalidixic acid resistance, using the agar dilution method according to the CASFM recommendations (4). E. coli ATCC 25922 was used as the control strain for both antimicrobial susceptibility testing and MIC determination. Among the 165 Shigella isolates, 81 (49%) were identified as Shigella flexneri, 75 (45%) as Shigella sonnei, 5 (3%) as Shigella boydii, and 4 (2%) as Shigella dysenteriae. It is well established that S. flexneri is the most commonly isolated species in developing countries, and its presence has been associated with inadequate sanitation; in contrast, S. sonnei predominates in developed countries (3). In this study, we found similar proportions of S. flexneri and S. sonnei isolates as well as infrequent isolates of S. dysenteriae and S. boydii, corroborating a previous report performed in our laboratory between 2000 and 2002 (5). This particular trend could be attributed to the fact that most of the patients attending the two participating laboratories belonged to the upper and middle classes, and probably benefitted from better hygiene conditions than those of the population at large. Further in-
Shigellosis is recognized by the World Health Organization as a major global public health concern. It is a main cause of death in pediatric patients in developing countries (1). Shigella infection can lead to a variety of symptoms ranging from watery diarrhea to severe dysentery. Appropriate antimicrobial therapy shortens the duration of symptoms and can prevent life-threatening complications. Moreover, treatment reduces the duration of intestinal carriage, thus limiting the spread of infection (2). Unfortunately, Shigella spp. have become resistant to commonly used and inexpensive antimicrobials, drastically reducing therapeutic possibilities. As antimicrobial resistance patterns vary considerably from place to place and over time, updating the empirical antimicrobial susceptibility data is periodically necessary for adopting new clinical treatments (3). Hence, a prospective study was undertaken for a period of two and a half years in order to document the distribution and the antimicrobial susceptibility of Shigella spp. isolated from diarrhea samples obtained in Dakar, the capital of Senegal. From May 2004 to October 2006, a total of 165 Shigella strains were consecutively isolated in two clinical laboratories in Dakar. Duplicate samples were excluded, and only a single isolate from epidemiologically related cases was included. All patients included in the study lived in Dakar, or in nearby suburbs, and none were hospitalized at the time of stool collection. The median patient age was 17 years old (range,
