Genetic relatedness of ciprofloxacin-resistant Shigella dysenteriae type 1 strains isolated in south Asia.
OBJECTIVE
The aim of the present study was to determine the clonal relationships of ciprofloxacin-resistant Shigella dysenteriae type 1 strains isolated from south Asia, and S. dysenteriae 1 strains associated with epidemics in 1978, 1984 and 1994.


METHODS
The antimicrobial susceptibilities were examined by NCCLS methods. Molecular epidemiological characterization was performed by plasmid profiling, pulsed-field gel electrophoresis (PFGE) and mutation analysis of the quinolone resistance-determining region (QRDR) of gyrA by sequencing.


RESULTS
Plasmid patterns of the current ciprofloxacin-resistant strains from India, Nepal and Bangladesh were very similar to those of the 1978, 1984 and 1994 epidemic isolates of S. dysenteriae 1, except for the presence of a new plasmid of approximately 2.6 MDa, which was found in one recent ciprofloxacin-resistant strain isolated in Bangladesh. PFGE analysis showed that the ciprofloxacin-resistant strains isolated in Bangladesh, India and Nepal belonged to a PFGE type (type A), which was possibly related to that of the 1984 and 1994 clone of S. dysenteriae 1, but different from 1978 epidemic strains. The current ciprofloxacin-resistant strains belong to five subtypes (A3-A7), all of which were found in India, but in Bangladesh and Nepal, only A3 existed. Mutation analysis of the QRDR of gyrA revealed that amino acid substitutions at positions 83 and 87 of ciprofloxacin-resistant strains isolated in Bangladesh were similar to those of the strains isolated in Nepal, but different (at position 87) from ciprofloxacin-resistant strains isolated in India.


CONCLUSIONS
PFGE and mutation analysis of gyrA showed differences between the current ciprofloxacin-resistant S. dysenteriae 1 strains isolated in south Asia and those associated with epidemics in 1978, 1984 and 1994.
Talukder
Kaisar A
KA
Enteric Microbiology Laboratory, ICDDR, B: Centre for Health and Population Research, GPO Box-128, Dhaka-1000, Bangladesh. kaisar@icddrb.org
Khajanchi
Bijay K
BK
Islam
M Aminul
MA
Dutta
Dilip K
DK
Islam
Zhahirul
Z
Safa
Ashrafus
A
Khan
G Y
GY
Alam
Khorshed
K
Hossain
M A
MA
Malla
Sarala
S
Niyogi
S K
SK
Rahman
Mustafizur
M
Watanabe
Haruo
H
Nair
G Balakrish
GB
Sack
David A
DA
D019943:Amino Acid Substitution; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001208:Asia / Q000453:epidemiology; D002939:Ciprofloxacin / Q000494:pharmacology*; D016172:DNA Fingerprinting; D027081:DNA Gyrase / Q000235:genetics; D004252:DNA Mutational Analysis; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial / Q000187:drug effects* / Q000235:genetics; D004405:Dysentery, Bacillary / Q000453:epidemiology* / Q000382:microbiology; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D012762:Shigella dysenteriae / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D027081:DNA Gyrase