Group B Streptococcus highly resistant to gentamicin.

Sir, Antibiotic resistance in the group B Streptococcus (GBS) is not widely appreciated and many clinical laboratories do not undertake full antibiotic susceptibility tests of clinical isolates. However, antibiotic combinations such as a penicillin plus gentamicin are often used to manage severe GBS infection , exposing patients to enhanced risk of antibiotic-related toxicity whilst attempting to improve clinical response. We report the isolation of a strain of GBS that was highly resistant to gentamicin (MIC > 500 mg/L). Appropriate surveillance is required to control the spread of antibiotic resistance in GBS that now threatens effective therapy. Streptococcus agalactiae, the GBS, is the most frequent cause of severe neonatal sepsis. Significant infection is also seen in adult women as a complication of pregnancy and among immunocompromised patients. 1 Surveillance has shown that GBS remains universally susceptible to penicil-lins and glycopeptides such as vancomycin. 2 However, in vitro studies indicate that the rate of killing of GBS by these antibiotics is relatively slow compared with other streptococ-cal pathogens and have led some authors to recommend dual therapy using a penicillin plus gentamicin for severe GBS-associated infection. 1,3 This approach attempts to achieve synergic antibiotic activity against the GBS and requires the pathogen to be susceptible to both penicillins and amino-glycoside antibiotics. We report the isolation of a strain of GBS showing high-level resistance to gentamicin. A 49-year-old woman with no significant past medical history presented to her general practitioner complaining of dysuria. A clinical diagnosis of urinary tract infection was formed and the patient made an uneventful recovery following empirical ampicillin therapy. Microscopy of a mid-stream urine sample found leucocytes (90/µL) but no red blood cells. Culture showed GBS (10 7 –10 8 /L) that was sensitive to ampi-cillin and nitrofurantoin but resistant to trimethoprim and gentamicin (disc testing/BSAC methodology). In view of these findings, detailed investigations were carried out. The identity of the isolate was confirmed as S. agalactiae (GBS) by biochemical and 16S ribosomal RNA gene sequence analysis, but was found to be non-typeable by the UK national reference laboratory at Colindale, North London. Results of MIC estimation by microdilution methodology carried out in our laboratory are shown in Table 1. Notably, the isolate was highly resistant to gentamicin. We were able to find only one previous report of highly gentamicin-resistant GBS by interrogation of the MEDLINE database. Strain B128 of GBS was isolated from the infected leg wound of …