Macrolide resistance phenotypes of commensal viridans group streptococci and Gemella spp. and PCR detection of resistance genes.

One hundred and sixty viridans group streptococci (VGS) and 26 Gemella spp. resistant to erythromycin were studied to detect macrolide lincosamide and streptogramin B (MLS(B)) phenotypes and to investigate resistance rates to other antibiotics. The M phenotype was most prevalent in both bacterial groups (59.6% in VGS, 69.2% in gemellae) and the iMLS(B) phenotype was found least often (9.3 and 13.9%, respectively). All isolates with M phenotype had the mef(A/E) gene, being prevalent the mef(E) subclass. cMLS(B) and iMLS(B) strains contained the erm(B) gene, alone or in combination with the mef(A/E) gene. Thirteen isolates were intermediately resistant to quinupristin/dalfopristin and 11 strains showed low susceptibility to telithromycin. Linezolid was active against all the isolates tested and tetracycline resistance was the major one in VGS (41.6%) and Gemella spp. (46.2%).

[In vitro activity of fluconazole, voriconazole and posaconazole against Candida spp]. / Actividad in vitro de fluconazol, voriconazol y posaconazol frente a Candida spp.

Voriconazole and posaconazole are two new triazoles with broad-spectrum antifungal activity. The in vitro activity of these agents was compared with that of fluconazole against 113 clinical isolates of Candida spp. exhibiting a wide range of MICs for fluconazole (< or =0.125 to >64 mg/l). They included 22 C. albicans isolates, 22 C. glabrata, 20 C. tropicalis, 15 C. dubliniensis, 13 C. parapsilosis, 13 C. krusei, 4 C. lusitaniae, 3 C. guilliermondii and 1 C. famata. MICs were determined by broth microdilution test performed according to the National Committee for Clinical Laboratory Standards' M27-A document. Voriconazole and posaconazole were quite active against all Candida spp. isolates, with MIC(90) of 0.25 and 0.5 mg/l, respectively. Fluconazole MIC(50) and MIC(90) were 1 and 32 mg/l. Voriconazole and posaconazole showed in vitro activity against fluconazole-susceptible and -resistant Candida isolates. Higher voriconazole and posaconazole MICs were observed in isolates exhibiting higher fluconazole MICs (>/=16 mg/l) than in those of fluconazole-susceptible isolates (MIC(90) for voriconazole and posaconazole in the fluconazole-resistant isolates were 0.5 mg/l versus 0.06 mg/l for voriconazole and 0.25 mg/l for posaconazole in the fluconazole-susceptible strains). C. dubliniensis was the most susceptible species, and voriconazole the most active antifungal agent against all Candida spp. tested.

Actividad in vitro de fluconazol, voriconazol y posaconazol frente a Candida spp / In vitro activity of fluconazole, voriconazole and posaconazole against Candida spp

Voriconazol y posaconazol son dos nuevos triazoles con un amplio espectro de actividad antifúngica. La actividad in vitro de estos antifúngicos se compara con la de fluconazol frente a 113 aislamientos clínicos de Candida spp. con un amplio rango de CMI de fluconazol (0,125 a >64 mg/l). Se estudiaron 22 C. albicans, 22 C. glabrata, 20 C. tropicalis, 15 C. dubliniensis, 13 C. parapsilosis, 13 C. krusei, 4 C. lusitaniae, 3 C. guilliermondii y 1 C. famata. La determinación de las CMI se realizó siguiendo las especificaciones del National Committee for Clinical Laboratory Standards, documento M27-A. Voriconazol y posaconazol mostraron buena actividad frente a todas las cepas de Candida spp., con una CMI90 de 0,25 y 0,5 mg/l, respectivamente. Las CMI50 y CMI90 de fluconazol fueron de 1 y 32 mg/l. Voriconazol y posaconazol poseen buena actividad tanto sobre las cepas de Candida spp. sensibles como resistentes al fluconazol. Las cepas con CMI de fluconazol más altas (16 mg/l) presentaban CMI de voriconazol y posaconazol ligeramente más elevadas que las sensibles al fluconazol. En las cepas resistentes al fluconazol las CMI90 de voriconazol y posaconazol fueron de 0,5 mg/l, mientras que las sensibles al fluconazol tuvieron una CMI90 de 0,06 mg/l para voriconazol y 0,25 mg/l para posaconazol. C. dubliniensis fue la especie más sensible y voriconazol el antifúngico con mejor actividad frente a estas cepas (AU)

Distribution of resistance genes tet(M), aph3'-III, catpC194 and the integrase gene of Tn1545 in clinical Streptococcus pneumoniae harbouring erm(B) and mef(A) genes in Spain.

The most prevalent macrolide resistance phenotype and genotype among pneumococcal isolates was the cMLSB phenotype [erm(B) or erm(B)/mef(A)] (91.3%). We studied the distribution of other resistance genes, tet(M), catpC194, aph3'-III, in these strains, seeing evolution at work in that some strains carried different combinations of resistance determinants. The most prevalent patterns associated with resistance to erythromycin [erm(B)] were resistance to tetracycline [tet(M)] and chloramphenicol (catpC194) (48.2%) or resistance to tetracycline [tet(M)] alone (42.2%). In our isolates of Streptococcus pneumoniae there was a strong association of the erm(B) and tet(M) genes with Tn1545-related elements.

[Association between MLS antibiotic and tetracycline resistance genes in Streptococcus pneumoniae]. / Asociación de los genes de resistencia a antibióticos MLS y a tetraciclina en Streptococcus pneumoniae.

In Streptococcus pneumoniae, resistance to macrolide, lincosamide and streptogramin type B (MLS(B)) antibiotics is mediated by erm(B) and mef(A) determinants. Tetracycline resistance is always associated with resistance to minocycline and is due to the presence of the tet(M) gene. The erm(B) determinant is predominant. We demonstrated that the erm(B) gene could be present with mef(A), which is of streptococcal origin, and msr(A), which is of staphylococcal origin, this being an example of genetic promiscuity. The tet(M) determinant was associated with pneumococci harboring the erm(B) gene, while it was not associated with the strains harboring the mef(A) gene. This association is due to the fact that, in most of the cases, erm(B) and tet(M) reside in the same chromosomal conjugative transposon.

Asociación de los genes de resistencia a antibióticos MLS y a tetraciclina en Streptococcus pneumoniae / Association between MLS antibiotic and tetracycline resistance genes in Streptococcus pneumoniae

La resistencia a los macrólidos, lincosamidas y estreptograminas tipo B (MLSB) en Streptococcus pneumoniae es el resultado de la adquisición de alguno de los determinantes de resistencia: erm(B), mef(A) o ambos. El gen erm(B) es el gen de resistencia a MLSB predominante y puede coexistir con genes de origen estreptocócico, como mef(A), gen de flujo externo, y con genes de origen estafilocócico, como msr(A), gen de flujo externo; todo un ejemplo de promiscuidad genética. El gen tet(M), que codifica resistencia a la tetraciclina y la minociclina, está relacionado con la resistencia a la eritromicina en las cepas de neumococos que contienen el gen erm(B), mientras que no se relaciona con la resistencia a la eritromicina en los estreptococos que contienen el gen mef(A). Esta asociación es consecuencia de que los genes tet(M) y erm(B) están presentes, generalmente, en los mismos transposones conjugativos cromosómicos (AU)

[Presence of conjugative transposon Tn1545 in strains of Streptococcus pneumoniae with mef(A), erm(B), tet(M), catpC194 and aph3'-III genes]. / Presencia del transposón conjugativo Tn1545 en cepas de Streptococcus pneumoniae con los genes mef(A), erm(B), tet(M), catpC194 y aph3'-III.

We studied the association of MLS resistance genes (erm(B) and mef(A) with others non-MLS resistance genes: tet(M) (tetracycline and minocycline), catpC194 (chloramphenicol) and aph3'-III (kanamycin) in order to know how is selected the multiresistant in Streptococcus pneumoniae. The tet(M) and catpC194 genes were present very often in the pneumococci with the erm(B) gene but the aph3'-III was found only in four strains. Tn1545 was nearly always the responsible for the dissemination of these genes. In contrast, mef(A) was not associated with tet(M) and and catpC194 and is disseminated in a different conjugative transposon. The linkage of multiple antibiotic resistance genes on the same mobile element is of importance for public health, because the use of one antibiotic selects for the transposon which carries multidrug resistance genes.

Stability of dactimicin to aminoglycoside-modifying enzymes produced by 341 bacterial clinical isolates.

The stability of dactimycin to aminoglycoside-modifying enzymes produced by 341 bacterial clinical isolates has been studied. Enzymatic activities were measured by the phosphocellulose binding assay. The results demonstrated that dactimicin was stable to the following enzymes: (i) AAC(3)-II,-III,-IV and -V. (ii) AAC(2'); (iii)AAC(6')-I and -II;(iv) ANT(2"); (v)ANT(4'); (vi) APH(3')-I,-II,-III and -IV. In contrast, dactimicin was only inactivated by two enzymes, AAC(3)-I and the bifunctional AAC(6')/APH(2"). This staphylococcal enzyme modified and inactivated dactimicin by acetylation but not by phosphorylation, suggesting the possibility of a second target amino group, such as 6'-NH2, in addition to the C4 amino group, which is the target for AAC(3)-I.

Third type of plasmid conferring gentamicin resistance in Pseudomonas aeruginosa.

R1033 is a plasmid of compatibility group P (= P1) transferred from a wild strain of Pseudomonas aeruginosa. It confers resistance to gentamicin by gentamicin acetyl-transferase 1 and to kanamycin and neomycin by neomycin phosphotransferase 1.