Plasmid-mediated high-level ceftriaxone resistance in a Salmonella enterica serotype typhimurium isolate.
OBJECTIVE
To present the first documented case of acute infectious gastroenteritis caused by high-level ceftriaxone-resistant Salmonella enterica serotype typhimurium in Kuwait.


METHODS
Isolation from stool specimen and species identification of current enteric pathogen was carried out according to standard methods. Susceptibility to antibiotics was determined by the disc diffusion method on Mueller-Hinton agar. Minimal inhibitory concentrations (MICs) were measured with E-test strips. The production of extended spectrum beta-lactamase (ESBL) was studied by the double disc synergy method and E-test ESBL strips. Plasmid DNA isolation was performed by the rapid alkaline lysis method. Plasmid DNA was transferred by conjugation to a recipient strain of Escherichia coli.


RESULTS
The isolate of S. enterica serotype typhimurium was resistant to ceftriaxone (MIC >256 mg/l), cefotaxime and ceftazidime, and produced ESBL. Ceftriaxone and cefotaxime resistance were co-transferred on a 3.2-kb plasmid to the E. coli recipient strain. Loss of the 3.2-kb plasmid from the transconjugant resulted in the co-loss of ceftriaxone and cefotaxime resistance confirming the carriage of ceftriazone resistance on the 3.2-kb plasmid.


CONCLUSIONS
Plasmid-mediated high-level resistance to ceftriaxone and ESBL production in Salmonella serotype typhimurium is an emerging problem among Salmonella that requires closer monitoring of antimicrobial resistance among these bacterial species.
Microbiology Section, Department of Laboratory Medicine, Infectious Diseases Hospital, Kuwait. dimitrov_varn90@hotmail.com
T S
TS
Dimitrov
E E
EE
Udo
T
T
Verghese
M
M
Emara
Alla
A
Al-Saleh
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002443:Ceftriaxone / Q000494:pharmacology*; D018550:Cephalosporin Resistance; D005260:Female; D005759:Gastroenteritis / Q000188:drug therapy / Q000382:microbiology*; D006801:Humans; D007223:Infant; D007730:Kuwait; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D012480:Salmonella Infections / Q000188:drug therapy / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D002443:Ceftriaxone