264. Clindamycin and Erythromycin Resistance in Colonizing Group B Streptococcus (2007-2009).
Session: Poster Abstract Session: Antimicrobial Susceptibility and Resistance
Friday, October 21, 2011
Room: Poster Hall B1
Background: : Estimates of Group B Streptococcus (GBS) antibiotic resistance to clindamycin and erythromycin range between 12-15% and 25-32%, respectively. In a recent study, an even higher proportion of clindamycin (40.7%) and erythromycin (41.9%) antibiotic resistance in colonizing GBS derived from college students in Southeastern Michigan has been described. Our objective was to retrospectively characterize GBS antibiotic resistance patterns and trends among a collection of non-invasive isolates in three consecutive years (2007-2009) at a large teaching hospital in Southeastern Michigan.

Methods: GBS isolates were derived from anogenital sources recovered from women during routine prenatal screens. Each isolate was assayed for susceptibility to clindamycin, erythromycin, penicillin and vancomycin, employing standard microbiological methods. Group comparisons were calculated by Chi square for trends, where appropriate.

Results:In total, 3818 anogenital GBS were evaluated. The number of positive GBS cultures/total samples tested increased from 19.6% in 2007 (1199/6120), 22.7% in 2008 (1343/5930) to 23.4% in 2009 (1276/5443) longitudinally over the course of the study (p<0.0001).  Erythromycin resistance (E-R) remained prevalent with no statistically significant annual differences; 40% (484/1199) of all isolates in 2007, 41% (557/1343) in 2008 and 43% (545/1276) in 2009 (p=0.52).  Of E-R GBS, a high correlation with clindamycin resistance (C-R) was exhibited as well. Dual E-R/C-R profiles occurred in 35% (418/1199) of all isolates in 2007, 37% (494/1343) in 2008 and 37% (468/1276) in 2009 (p=0.564).  An additional small number of GBS each year had intermediate susceptibility to either clindamycin or erythromycin. Neither penicillin nor vancomycin resistant GBS was observed. 

Conclusion: This study demonstrated that carriage of clindamycin and erythromycin resistant GBS among women in Southeastern Michigan was common and stable during the three years period. This observed prevalence of GBS resistance is consistent with one prior report and is higher than documented in recent epidemiologic surveys of the U.S. population spanning the same time frame.

Subject Category: A. Antimicrobial agents and Resistance

Frank Martilotti1, Angela Diskin2, Padma Nandula1, Barbara Robinson-Dunn, PhD3, Bobby Boyanton3, Bishara Freij, MD1 and Graham Krasan1, (1)William Beaumont Hospital, Royal Oak, MI, (2)Microbiology, William Beaumont Hospital, Royal Oak, MI, (3)Clinical Pathology, Oakland University-William Beaumont School of Medicine, Royal Oak, MI


F. Martilotti, None

A. Diskin, None

P. Nandula, None

B. Robinson-Dunn, None

B. Boyanton, None

B. Freij, None

G. Krasan, None

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