[Enzymatic resistance to beta lactam antibiotics within the genus Proteus and evaluation of Proteus mirabilis phenotypes and genotypes for resistance to third- and fourth-generation cephalosporins].
BACKGROUND
The aim of this study was to evaluate betalactam resistance within the genus Proteus and characterize the betalactamases responsible for this resistance.


METHODS
We analyzed 99 strains (87, P. mirabilis; 10 P. vulgaris, and 2, P. penneri) isolated from patients at one University Hospital. Antibiotic susceptibility tests were performed according to NCCLS recommendations. Presence of extended spectrum betalactamases (ESBL) was inferred by both double disk diffusion tests and minimum inhibitory concentration (MIC) of third and fourth generation cephalosporins alone and in the presence of clavulanic acid. Isoelectric points (pI) of the enzymes were estimated by isoelectrofocusing and the presence of the encoding genes was confirmed by polymerase chain reaction (PCR).


RESULTS
A broad spectrum betalactamase could be detected in those isolates (28%) resistant to penicillin and first generation cephalosporins while CTX-M-2 enzyme could be detected in P. mirabilis isolates resistant to third and fourth generation cephalosporins (18%). One of the P. vulgaris displayed reduced susceptibility to cefotaxime due to an enzyme of pI 7.4, while resistance to cefotaxime in one P. penneri was related to an enzyme of pI 6.8. Both enzymes were active on cefotaxime (1,000 mg/l) in the iodometric assay.


CONCLUSIONS
The broad extended spectrum betalactamase within genus Proteus was TEM-1, while CTX-M-2 was the ESBL responsible for the third and fourth generation cephalosporins in P. mirabilis. In P. vulgaris and P. penneri this resistance was associated with the hyperproduction of the chromosomal encoded betalactamase.
Rodríguez
Cynthia
C
Cátedra de Análisis Clínicos I, Laboratorio de Bacteriología, Hospital de Clínicas, Universidad de Buenos Aires, Argentina.
Radice
Marcela
M
Perazzi
Beatriz
B
Castro
Silvia
S
Juárez
Josefina
J
Santini
Pilar
P
Vay
Carlos
C
Famiglietti
Angela
A
Gutkind
Gabriel
G
D001118:Argentina / Q000453:epidemiology; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D002439:Cefotaxime / Q000378:metabolism / Q000494:pharmacology; D002511:Cephalosporins / Q000145:classification / Q000378:metabolism / Q000494:pharmacology*; D002876:Chromosomes, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D007526:Isoelectric Point; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D011511:Proteus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D011512:Proteus Infections / Q000453:epidemiology / Q000382:microbiology; D011513:Proteus mirabilis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D044095:Proteus penneri / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D011514:Proteus vulgaris / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D013045:Species Specificity; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
D001426:Bacterial Proteins; D002511:Cephalosporins; C071167:beta-lactamase CTX-2; D001618:beta-Lactamases; C034413:beta-lactamase TEM-1; C056342:beta-lactamase TEM-2; D002439:Cefotaxime