RESUMO
The resistance to divalent metal ions, antibiotics and H2O2 was investigated in Yersinia kristensenii strains 13, 15, 18 by performing subcultivations with CdSO4 (20 and 100 mg/L) in nutrient agar (NA) and M9 medium with thiamine. Metal resistance of all three strains in NA was the same and decreased in the following sequence: Ni > Zn = Co > Cd. The chloramphenicol (Cmp) resistance ranged between 32 and 256 mg/L and the H2O2 sensitivity was very low or even zero. In the presence of thiamine the metal resistance sequence changed to Zn = Cd > Ni, Co, Ni and Co tolerance being 10-20 mg/L. Cmp resistance of all strains increased to 256 mg/L and H2O2 sensitivity also rose. In Cd-treated cultures, the ratio of glucose to thiamine in culture medium affected Cd resistance. At normal content of glucose and thiamine (5 g/L and 5 mg/L), Cd resistance markedly decreased coincident with thiamine exhaustion in these slowly-growing cultures. The Cmp resistance decreased to 16 mg/L, Ni and Co intolerance and H2O2 hypersensitivity appeared. At lowered glucose or thiamine levels (5 g/L and 2.5 mg/L or 2.5 g/L and 5 mg/L) a marginal decrease of Cd resistance took place in response to limited glucose uptake. Low thiamine or low-glucose cultures were resistant to H2O2, and exhibited a small decrease in Cmp resistance and a low Ni, Co tolerance. The adaptation of strain 15 to Cd induced only a small decrease of Cd resistance. Lowered glucose-to-thiamine ratio in culture medium probably induced in Cd-treated cultures a response triggering Cd resistance.
Assuntos
Resistência Microbiana a Medicamentos/fisiologia , Peróxido de Hidrogênio/farmacologia , Metais Pesados/farmacologia , Tiamina/fisiologia , Yersinia/efeitos dos fármacos , Cádmio/farmacologia , Cátions Bivalentes/farmacologia , Resistência ao Cloranfenicol/fisiologia , Estresse Oxidativo , Yersinia/metabolismoRESUMO
Repeated cultivations (4 passages) of salmonellae (18 strains) resistant to cadmium, streptomycin and beta-lactam antibiotics in Müller-Hinton Broth (MHB) and Mac-Conkey Broth (MCB) without and with CdSO4 (2, 20 and 100 mg/L) showed a higher toxic effect of cadmium in MCB. The strains survived at CdSO4 100 mg/L in MHB for four transfers, in MCB only a single transfer. In dependence on the medium used and amount of metal added, the increase of resistance to antibiotics was different. In MHB, the same levels of resistance to carbenicillin and streptomycin were induced by CdSO4 (20 and 100 mg/L), in MCB it was by 2 and 20 mg/L. Simultaneous stop of the growth of a control culture S. typhimurium with chromosomal resistance to streptomycin, isolates with and without plasmid in MCB which contained CdSO4 100 mg/L, and the results of conjugal transfer of resistance suggest that changes of resistance to antibiotics were not mediated by determinants of resistance to antibiotics. The binding of cadmium to outer membrane protein can cause a decreased permeability to these antibiotics as a resistance mechanism.
Assuntos
Cádmio/farmacologia , Resistência Microbiana a Medicamentos , Salmonella/efeitos dos fármacos , Animais , Antibacterianos/farmacologia , Conjugação Genética , Resistência Microbiana a Medicamentos/genética , Resistência a Múltiplos Medicamentos/genética , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , Técnicas In Vitro , Lactamas , Fatores R/genética , Salmonella/genética , Salmonella/isolamento & purificação , Estreptomicina/farmacologia , SuínosRESUMO
Of 50 Salmonella species isolated from pigs, 30 were resistant to cadmium and 18 of these also to azlocillin. The azlocillin-resistant isolates were resistant to cadmium at 80-500 mg/L CdSO4. A broader spectrum of resistance to azlocillin, ampicillin and cephazolin was found in strains resistant to < 200 mg/L CdSO4. Resistance to silver, mercury, chloramphenicol and streptomycin was independent of the resistance to beta-lactam antibiotics and Cd2+. Production and levels of beta-lactamase do not correlate with the spectrum of resistance.