Changing prevalence and antibiotic susceptibility patterns of different shigella species in Tehran, Iran
M Rahbar, M Deldari, M Hajia
M Rahbar, M Deldari, M Hajia. Changing prevalence and antibiotic susceptibility patterns of different shigella species in Tehran, Iran. The Internet Journal of Microbiology. 2006 Volume 3 Number 2.
During the 3 years of study period (April 2002 to April 2005) 220 strains of shigella isolated from fecal samples of patients having acute diarrhea. Shigella sonnei with 157 (78.5%) isolates had the highest frequency of isolation. Resistance to Ampicillin and Trimethoprime/sulphamethoxazole was observed in 88.5% and 98% isolates respectively. 11.5% of isolates were resistant to nalidixic acid and 5.5% to ceftriaxone. Resistance to Chloramphenicol and Ciprofloxacin was 2.5% and 1% respectively.
Shigelosis is an acute gastroenteritis caused by Shigella specis, including
Material and Methods
All patients admitted to the Milad hospital in Tehran during 3 years from 2003 to 2005 with history of diarrhea of less than 7 days duration were included in this study. A total 4351 patients were admitted. Individual case records of these patients were scrutinized. A special Performa was designed to collect information regarding epidemiological variables such as age, sex, date of admission;other information such as the result of faecal cultures were also included. Incomplete records were excluded. for enteric pathogens. Samples of faeces were collected in sterile wide mouth containers and rectal swabs were transported in Cary- Blair transport medium and were processed within 2 hours of collection. The samples were examined microscopically for pus cells, RBCs, leukocyte , cysts and ova of parasites. The samples were inoculated directly on the MacConky agar, Xylose-lysine desoxycholate (XLD), Hekton Enteric agar (HE) and, Salmonella Shigella agar (SS). Enrichment was done on selient F broth and incubated for 6 hours. After the 6 hours subculture was done on SS agar. All plates incubated at 35°C for overnight. All specimens were also processed for other enteropathogens by using standard laboratory procedures. For isolation of Yersinia
All isolated enteric pathogens were identified by conventional bacteriological methods (4,5). Colonies resembling to shigella species were identified by biochemical reaction and confirmed by slide agglutination test using polyvalent and monovalent antisera (Bahar Afshan, Tehran Iran ). Susceptibility testing for shigella spp isolates were performed by disk diffusion methods as recommended by NCCLS. (6) Commercially manufactured disks of antimicrobial agents and their concentration were as follows.Ampicllin10µg, ceftriaxone 30µg, chloramphenicol 30 µg, nalidixic acid 30µg , ciprofloxacin 5 µg , trimethprim-sulfamethoxazole 1.25/2375µg
4351 stool samples were sent to microbiology laboratory of Milad hospital for culture and susceptibility testing. In total 464 (10.15%) Enteropathogens were isolated. The rate of isolation was: Shigella spp 220 (46. 5% ) isolates salmonella spp120(26.3%), Enteropathogenic
Result of susceptibility testing of Shigella spp to various antibiotics were as follows: Resistance to Ampicillin and Trimethoprime / sulphamethoxazole was observed in 88.5% and 98% isolates respectively. 11.5% of isolates were resistant to nalidixic acid and 5.5% to ceftriaxone. Resistance to Chloramphenicol and Ciprofloxacin were 2.5% and 1% respectively.
The isolation rate of Shigella species from stool specimens in our study was 5% .Among entropathenic isolated bacteria, Shigella species accounted 46.5% of isolation, and
The result of present study were compared with that previous studies in Tehran. In a study that carried out by Moez_Ardalan
Antimicrobial therapy is recommended for shigellosis because it can shorten the severity and duration of illness, reduce shedding of the organism, and prevent secondary complication and death. However antimicrobial resistance occurred among shigella spp, since the 1940s, when sulfonamide resistance among shigella organism was first recognized in Japan( 12) .In our study more than 88.5% of isolates were multiple drug resistant. The previous studies also showed that 87.8% of shigella multiple resistant. Resistance to nalidixic acid as s first line drug is going to increase in our country, In a study by Nikkah et al during 1984-1985 in Tehran ,all isolates of shigella were susceptible to nalidixic acid( 8 ) and in a report by Moez Ardalan in 2002-2003 only 1% of shigella spp were resistant to nalidixic acid.(7) In our study this figure was 11 .5 %. In other countries like India resistance of
The relative antimicrobial susceptibility of different Shigella spp may vary geographically. It may be due to pattern of antibiotic using for treatment of shigellosis. Further studies on the antibiotic resistance mechanism and genetic relatedness of isolates are required to understand the progression of antibiotic resistance in shigella.