Superiority of D-zone Testing Method over Standard Method to detect
Abstract
Objective: In this prospective study, we determined phenotypic resistance to
erythromycin among gram positive bacteria.
Methods: Bacterial isolates were identified by conventional methods and by the
MicroScan: D-test zone was performed according to the Clinical and Laboratory
Standards institutes (CLSI) recommendations to determine inducible resistance to
clindamycin on gram positive bacteria isolated from different clinical specimens
.Bacterial isolates included : group A streptococci (GAS), group B streptococci (GBS),
viridans streptococci, S.pneumoniae, Staphylococcus aureus (S.aureus) ( both methicillin
susceptible (MSSA) and methicillin resistant (MRSA) .
Results: A total of 1072 gram positive bacterial isolates were tested .The majority was
from swabs collected from outpatient clinics. Erythromycin resistance was 8/23 (35%)
for S. pneumoniae, 12/91(13%) for GAS and 17/300(5.7%) for GBS. All GAS and
viridans streptococci possessed the efflux phenotype only, 8(8.8% and 1(20%),
respectively. For GBS, cMLSB was 11(3.7%), 3 (1%) iMLSB and 2(0.33%) were of
efflux phenotype. All S.pneumoniae strains possessed cMLSB phenotype. Seventy five
isolates (16.3%) of MSSA were resistant to erythromycin compared to 160(83%) of
MRSA. The majority of MSSA, 31/460 (6.7%) had an efflux phenotype while
26/460(5.6%) were of cMLSB and 19/460(4%) iMLSB phenotypes. Constitutive MLSB
was the most predominant resistant phenotype, 152/193(78.8%) among MRSA.
Conclusion: D-test zone should be considered for routine testing to detect inducible
clindamycin resistance among significant gram positive bacteria.
Keywords: Inducible resistance, constitutive resistance, efflux, erythromycin,
clindamycin.
erythromycin among gram positive bacteria.
Methods: Bacterial isolates were identified by conventional methods and by the
MicroScan: D-test zone was performed according to the Clinical and Laboratory
Standards institutes (CLSI) recommendations to determine inducible resistance to
clindamycin on gram positive bacteria isolated from different clinical specimens
.Bacterial isolates included : group A streptococci (GAS), group B streptococci (GBS),
viridans streptococci, S.pneumoniae, Staphylococcus aureus (S.aureus) ( both methicillin
susceptible (MSSA) and methicillin resistant (MRSA) .
Results: A total of 1072 gram positive bacterial isolates were tested .The majority was
from swabs collected from outpatient clinics. Erythromycin resistance was 8/23 (35%)
for S. pneumoniae, 12/91(13%) for GAS and 17/300(5.7%) for GBS. All GAS and
viridans streptococci possessed the efflux phenotype only, 8(8.8% and 1(20%),
respectively. For GBS, cMLSB was 11(3.7%), 3 (1%) iMLSB and 2(0.33%) were of
efflux phenotype. All S.pneumoniae strains possessed cMLSB phenotype. Seventy five
isolates (16.3%) of MSSA were resistant to erythromycin compared to 160(83%) of
MRSA. The majority of MSSA, 31/460 (6.7%) had an efflux phenotype while
26/460(5.6%) were of cMLSB and 19/460(4%) iMLSB phenotypes. Constitutive MLSB
was the most predominant resistant phenotype, 152/193(78.8%) among MRSA.
Conclusion: D-test zone should be considered for routine testing to detect inducible
clindamycin resistance among significant gram positive bacteria.
Keywords: Inducible resistance, constitutive resistance, efflux, erythromycin,
clindamycin.
Somily, A. M., & Babay, H. A. H. (2008). Superiority of D-zone Testing Method over Standard Method to detect. International Journal of Health Sciences, 2(2). Retrieved from https://pub.qu.edu.sa/index.php/journal/article/view/46
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