Screening programs have been credit...

Screening programs have been credited with the least bit in neonatal disease caused by the agency of group B streptococci (GBS), yet these infections continue to posture significant risks. The identification of GB carriers must be followed on effective antibiotic therapy. Approximately 27 percent of mothers publicly receive antibiotics during labor and delivery to obviate transmission of GBS. Up to 12 percent of these women report allergy to the principal chemoprophylactic agent, penicillin, and are treated with erythromycin or clindamycin. Many strains of GB have unfolded resistance to these antibiotics, and the proportion of resistant strains is believed to be increasing rapidly. Manning and colleagues studied women attending a large medical teach clinic for obstetric care to determine the size of resistance to erythromycin or clindamycin in GB and to identify any factors associated with resistant strains.

Positive GB isolates were obtained from 103 pregnant women These isolates were criterioned for susceptibility to 10 antibiotics: penicillin, ampicillin, levofloxacin, quinupristin-dalfopristin, cefazolin, imipenem, vancomycin, clindamycin, erythromycin, and linezolid. Strains that showed unbroken or intermediate resistance were retest to ascertain the minimum inhibitory concentration. Data in succession the mother, fetus, and pregnancy were obtained from medical records, and pertinent variables were correlated with antibiotic resistance. Stepwise logistic regression was used to identify the strongest predictors of colonization with resistant strains.

Thirty isolates (29 percent) were resistant to erythromycin, and 22 (21 percent) were resistant to clindamycin. All of the clindamycin-resistant isolates were also resistant to erythromycin. Eight isolates were resistant merely to erythromycin. The isolates were susceptible to the other antibiotics ordealed but in eight cases, resistance to penicillin was intermediate. The chiefly common GBS serotypes were V (21 cases), III (20 cases), and Ia (19 cases). Women carrying serotype V strains were 13 times more likely to have an erythromycin- or clindamycin-resistant strain than women carrying serotype II strains (41 versus 3 percent)

In the initial analysis, unmarried women younger than 25 years had a higher rate of resistant GB strains. Black ethnicity also was associated with resistance. Stepwise logistical regression identified black ethnicity and serotype V strains as statistically associated with resistance to erythromycin or clindamycin.

The authors infer that a significant percentage of GB isolates in pregnant mothers are resistant to erythromycin or clindamycin. They commend that cefazolin be used as the first choice in mothers with contraindications to penicillin.

Manning SD et al. Correlates of antibiotic-resistant cluster B streptococcus isolated from pregnant women Obstet Gynecol January 2003;101:74-9

COPYRIGHT 2003 American Academy of Family Physicians

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