Cefuroxime non-susceptibility in multidrug-resistant Klebsiella pneumoniae overexpressing ramA and acrA and expressing ompK35 at reduced levels.
OBJECTIVE
The aims were to study if efflux and down-regulation of porins contribute to cefuroxime resistance in Klebsiella pneumoniae and to co-resistance to unrelated antibiotics.


METHODS
Ten cefuroxime-non-susceptible but cefotaxime-susceptible blood culture isolates of K. pneumoniae and one multiply antibiotic-resistant (MAR) laboratory strain (selected by chloramphenicol) were examined. Transcription of the genes acrA, ompK35, ramA, marA and soxS was determined with quantitative RT-PCR.


RESULTS
All clinical isolates and the MAR laboratory strain had similar antibiograms with non-susceptibility to cefuroxime, tigecycline, chloramphenicol and nalidixic acid. Phenylalanine arginine beta-naphthylamide (PAbetaN) increased susceptibility to tigecycline, chloramphenicol and nalidixic acid, but not to cefuroxime. Increased acrA transcription and decreased ompK35 transcription was seen in all strains. Increased ramA transcription was seen in all strains except one clinical isolate.


CONCLUSIONS
This multidrug-resistant phenotype of K. pneumoniae is associated with increased acrA and ramA transcription and decreased ompK35 transcription. Since the cefuroxime resistance was not reversed by PAbetaN, it was probably attributable to decreased levels of OmpK35, rather than to efflux.
Källman
Owe
O
Clinical Microbiology, MTC, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm, Sweden. owe.kallman@karolinska.se
Motakefi
Alma
A
Wretlind
Bengt
B
Kalin
Mats
M
Olsson-Liljequist
Barbro
B
Giske
Christian G
CG
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D001769:Blood / Q000382:microbiology; D002444:Cefuroxime / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D020869:Gene Expression Profiling; D005798:Genes, Bacterial; D006801:Humans; D007710:Klebsiella Infections / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D018272:Porins / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014158:Transcription, Genetic
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C119261:OmpK35 porin, Klebsiella pneumoniae; D018272:Porins; C095947:RamA protein, Klebsiella; D002444:Cefuroxime