Background
Carbapenem-resistance is frequently detected in
Enterobacteriaceae
isolated from patients in Tunisia. The study was performed to identify frequent carbapenemases in Tunisian isolates.
Methods
Between May 2014 and January 2018, 197 ertapenem-resistant
Enterobacteriaceae
were isolated at the microbiological department of the Military Hospital of Tunis. The strains were phenotypically characterized and then subjected to in-house polymerase chain reaction (PCR) targeting the carbapenemase genes
bla
IMP
, bla
VIM
, bla
NDM
, bla
SPM
, bla
AIM
, bla
DIM
,bla
GIM
, bla
SIM
, bla
KPC
, bla
BIC
, and
bla
OXA-48
.
Results
The assessed 197 ertapenem-resistant
Enterobacteriaceae
from Tunis comprised 170
Klebsiella pneumoniae
,
19 Enterobacter cloacae
, 6
Escherichia coli
,
1 Citrobacter sedlakii
, and 1
Enterobacter asburiae.
Thereby, 55 out of 197 isolates (27.9%) were from blood cultures, suggesting a systemic disease. The carbapenemase gene
bla
OXA-48
quantitatively dominated by far with 153 detections, followed by
bla
NDM
with 14 detections, which were distributed about the whole study interval. In contrast,
bla
BIC
and
bla
VIM
were only infrequently identified in 5 and 3 cases, respectively, while the other carbapenamases were not observed.
Conclusions
The carbapenemase gene
bla
OXA-48
was identified in the vast majority of ertapenem-resistant Tunisian
Enterobacteriaceae
while all other assessed carbapenemases were much less abundant. In a quantitatively relevant minority of isolates, the applied PCR-based screening approach did not identify any carbapenemases.
Two multidrug-resistant Salmonella enterica serovar Wien strains (SW468 and SW1107) were isolated in 2001 in Tunis. Both strains produced the β-lactamases TEM-1, SHV-2a, and CMY-4, whereas strain SW1107 also produced the β-lactamase CTX-M-3. The imipenem-resistant strain (SW468) was totally devoid of the OmpF-immunorelated porin. Imipenem resistance was shown as being related to porin loss and CMY-4 β-lactamase production.
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