64 PP
COMPARATIVE IN VITRO SUSCEPTIBILITYOF GRAM-NEGATIVE ANAEROBIC RODS (NON BACTEROIDES FRAGILIS GROUP) AGAINST FOUR MACROLIDES AT TWO pH.
Fernandez Canigia L.,* Di Martino A., Litterio M., Castello A., Fernanmdez M., Rollet R., Greco G., Predari S., Bianchini H.
Subcomisión Bacterias Anaerobias, SADEBAC-Asociación Argentina de Microbiología. Buenos Aires. Argentina
The susceptibility of 58 gram-negative rods to roxithrommycin (ROX), clarithromycin(CLA), erithromycin (ERI) and azithromycin (AZI) were determined by the agar-dilution method of the NCCLS. The strains studied were: P. intermedia/nigrescen 20, P. bivia 6, P. gingivalis 7, P. asaccharolytica 2, P. levii 1, Porphyromonas spp 6, F. nucleatum 6, Fusobacterium spp. 2, F. mortiferum 1, F. varium 1, B. urealyticus 3, B. capillosus 1, M. multiacida 1, Desulfovibrio sp. 1. Brucella agar medium adjusted to two different pH (7.00 and 8.00) before autoclaving, was used. Inoculated plates were incubated in an anaerobic chamber.
MIC50/MIC90 of four macrolides at pH 7 and pH8
|
STRAINS(Nš) |
pH |
ROX |
CLA |
ERI |
AZI |
|
PI/NIG (20) |
7 |
.03/.06 |
.03/.06 |
.03/.125 |
.03/.125 |
|
PI/NIG (20) |
8 |
.03/.06 |
.03/.03 |
.03/.03 |
.03/.03 |
|
PORPHY (16) |
7 |
.03/.125 |
.03/.5 |
.03/.125 |
.03/1 |
|
PORPHY (16) |
8 |
.03/.125 |
.03/.03 |
.03/.03 |
.03/.06 |
|
PBIV (6) |
7 |
.03/.5 |
.03/.06 |
.03/ 2 |
.125/ 2 |
|
PBIV (6) |
8 |
.03/.125 |
.03/.03 |
.03/.125 |
.03/.06 |
|
FUSO (10) |
7 |
>16/>16 |
1/>16 |
>16/>16 |
.05/ 4 |
|
FUSO (10) |
8 |
,125/ 8 |
1/4 |
1/8 |
.06/.125 |
|
OTHERS (6) |
8 |
.5/ 1 |
.25/.5 |
.5/1 |
.125/.25 |
PI/NIG: P.intermedia nigrescen PORPHY: Porphyromonas
PBIV: P. bivia FUSO: Fusobacteium
The overall MIC of Macrolides tested were grater at pH7 than pH8. Fusobacterium sp susceptibility showed to be the most influenced by the pH changes.