72 PP
SUSCEPTIBILITY OF VEILLONELLA SP. TO TEN DIFFERENT ANTIBIOTICS.
Litterio, M.*(1), Matteo, M.(2), Fiorilli, G.(1), Rubeglio, E.(1).
(1) Hospital Nacional de Pediatrí J.P.Garrahan. (2) Residencia de Microbiologí Hospital F.J.Muñz. Buenos Aires. Argentina.
The aim of the present study was to assess the antibiotic susceptibility of Veillonella sp. strains recovered from clinical samples of patients treated in a pediatric hospital. We studied thirty three (33) strains, identified using Gram stain and conventional biochemical test. Susceptibility tests were performed according National Committee for Clinical Laboratory Standars (NCCLS) criteria, by Agar dilution method, to the following antibiotics (ATB): Penicillin (PEN), Ampicillin (AMP), Piperacillin (PIP), Cefoxitin (CXT), Ceftriaxone (CRO), Imipenem (IMP), Tetracycline (TET), Clindamycin (CLI), Chloramphenicol (CMP) and Metronidazole (MTZ). The production of beta lactamase was studied by nitrocefin test, reaching negative results for the 33 strains.
Results :
|
Range (µg/ml) |
MIC 50 (µg/ml) |
MIC 90 (µg/ml) |
% S (n° strains) |
% 1 (n° strains) |
% R (n° strains) |
||||||
|
PEN |
0.125-4 |
2 |
4 |
15 (5) |
21 (7) |
63 (21) |
|||||
|
AMP |
<0.5-2 |
<0.5 |
2 |
100 (33) |
0 (0) |
0 (0) |
|||||
|
PIP |
2-128 |
16 |
128 |
70 (23) |
6 (2) |
24 (8) |
|||||
|
CXT |
<0.125-8 |
2 |
4 |
100 (33) |
0 (0) |
0 (0) |
|||||
|
CRO |
0.25-8 |
2 |
8 |
100 (33) |
0 (0) |
0 (0) |
|||||
|
IMP |
<0.03-0.25 |
0.06 |
0.125 |
100 (33) |
0 (0) |
0 (0) |
|||||
|
TET |
0.25-32 |
0.5 |
1 |
94 (31) |
0 (0) |
6 (2) |
|||||
|
CLI |
<0.125 |
<0.125 |
<0.125 |
100 (33) |
0 (0) |
0 (0) |
|||||
|
CMP |
0.25-2 |
1 |
2 |
100 (33) |
0 (0) |
0 (0) |
|||||
|
MTZ |
<0.125-2 |
1 |
2 |
100 (33) |
0 (0) |
0 (0) |
|||||
Note: % S: % of strains within susceptible categorie- % I: % of strains within intermidiate categorie-% R: % of strains within resistant categorie.
Conclusions:
'In vitro' resistance to AMP was not found even for PEN resistant strains. Although the breakpoints are different, the PEN MIC values were nearly always higher than those of AMP. However, in 50% of PEN resistant strains, the AMP MIC values rose over MIC 50 (at least from 2 to 3 dilutions). The same effect was observed in 24 and 48 % of PEN resistant strains when testing CXT and CRO respectively (with a minimum increase from 1 to 2 dilutions). On the other hand one third of PEN resistant strains were also resistant to PIP.