title: Increasing spectrum in antimicrobial resistance of Shigella isolates in Bangladesh: resistance to azithromycin and ceftriaxone and decreased susceptibility to ciprofloxacin.
abstract: Antimicrobial resistance of Shigella isolates in Bangladesh, during 2001-2002, was studied and compared with that of 1991-1992 to identify the changes in resistance patterns and trends. A significant increase in resistance to trimethoprim-sulphamethoxazole (from 52% to 72%, p < 0.01) and nalidixic acid (from 19% to 51%, p < 0.01) was detected. High, but unchanged, resistance to tetracycline, ampicillin, and chloramphenicol, low resistance to mecillinam (resistance 3%, intermediate 3%), and to emergence of resistance to azithromycin (resistance 16%, intermediate 62%) and ceftriaxone/cefixime (2%) were detected in 2001-2002. Of 266 recent isolates, 63% were resistant to > or =3 anti-Shigella drugs (multidrug-resistant [MDR]) compared to 52% of 369 strains (p < 0.007) in 1991-1992. Of 154 isolates tested by E-test in 2001-2002, 71% were nalidixic acid-resistant (minimum inhibitory concentration [MIC] > or =32 microg/mL) and had 10-fold higher MIC90 (0.25 microg/mL) to ciprofloxacin than that of nalidixic acid-susceptible strains exhibiting decreased ciprofloxacin susceptibility, which were detected as ciprofloxacin-susceptible and nalidixic acid-resistant by the disc-diffusion method. These strains were frequently associated with MDR traits. High modal MICs were observed to azithromycin (MIC 6 microg/mL) and nalidixic acid (MIC 128 micdrog/mL) and low to ceftriaxone (MIC 0.023 microg/mL). Conjugative R-plasmids-encoded extended-spectrum beta-lactamase was responsible for resistance to ceftriaxone/cefixime. The growing antimicrobial resistance of Shigella is worrying and mandates monitoring of resistance. Pivmecillinam or ciprofloxacin might be considered for treating shigellosis with caution.
authors.affiliation: Laboratory Sciences Division, ICDDR,B GPO Box 128, Dhaka 1000 (Mohakhali, Dhaka 1212), Bangladesh. mahbubur@icddrb.org
authors.forename: Mahbubur
authors.initials: M
authors.lastname: Rahman
authors.forename: Shereen
authors.initials: S
authors.lastname: Shoma
authors.forename: Harunur
authors.initials: H
authors.lastname: Rashid
authors.forename: Shams
authors.initials: S
authors.lastname: El Arifeen
authors.forename: A H
authors.initials: AH
authors.lastname: Baqui
authors.forename: A K
authors.initials: AK
authors.lastname: Siddique
authors.forename: G B
authors.initials: GB
authors.lastname: Nair
authors.forename: D A
authors.initials: DA
authors.lastname: Sack
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology; D001459:Bangladesh; D002443:Ceftriaxone / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D015169:Colony Count, Microbial; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D004405:Dysentery, Bacillary / Q000188:drug therapy*; D006801:Humans; D008826:Microbial Sensitivity Tests; D018571:Sentinel Surveillance; D012760:Shigella / Q000187:drug effects*; D013045:Species Specificity; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D002443:Ceftriaxone; D017963:Azithromycin