Horizontal transfer of penicillin-binding protein genes in penicillin-resistant clinical isolates of Streptococcus pneumoniae.

Abstract

Resistance to penicillin in clinical isolates of Streptococcus pneumoniae has occurred by the development of altered penicillin-binding proteins (PBPs) that have greatly decreased affinity for the antibiotic. We have investigated the origins of penicillin-resistant strains by comparing the sequences of the transpeptidase domain of PBP2B from 6 penicillin-sensitive and 14 penicillin-resistant strains. In addition we have sequenced part of the amylomaltase gene from 2 of the sensitive and 6 of the resistant strains. The sequences of the amylomaltase gene of all of the strains and of the PBP2B gene of the penicillin-sensitive strains show that S. pneumoniae is genetically very uniform. In contrast the PBP2B genes of the penicillin-resistant strains show -14% sequence divergence from those of the penicillin-sensitive strains and the

Multidrug Resistant Streptococcus Pneumoniae in a Case of Splenectomy

“…Newer macrolidcs such as azithromycin, c1arithromycin are also ineffective in these isolates. Since it results from alteration of penicillin binding proteins, it is not surprising that cephalosporins are much less effective against penicillin resistant isolates [6]. The present isolatc was moderatcly resistant to penicillin (MIC Img/L) and resistant to fluoroqinolone norfloxacin besides resistant to other drugs e.g.…”

“…Overall this repre-" scnted a 12.6 fold increased incidence as compared to general population [5]. However in another study the incidence of pncumococcal bacteremia or meningitis is increased hundred fold in children who have sickle cell disease with splenic dysfunction [6]. The infection also spreads rapidly inside the body because spleen is the principal site of clearance of non-opsonised pneumococci from the blood stream due to the prolonged contact with reticuloendothelial cells while passing through the cords of Billroth and splenic sinuses [7].…”

“…But lately intermediate (MIC 0.1-2 mg/L) to high (MIC > 4mg/L) level resistance to penicillin by this organism has been reported [6]. Cates et al [8] had reported high level resistance to penicillin in Strep pneumoniae in a case of post-splencctomy meningitis.…”

“…In vitro studies have shown that pneumococci grown in the presence of sub-inhibitory concentration of penicillin acquire resistance to this drug. Acquisition of high grade resistance to penicillin and to other antibiotics like erythromycin, chloramphenicol and clindamycin has probably originated from horizontal transfer of genetic material by means of plasm ids from other bacteria [6]. The rate of resistance to other commonly used antibiotics such as erythromycin (MIC > 4mglL), tctracycline (MIC > 2mglL) and trimethoprim/sulphamcthoxazole (MIC > 0.510.95 mg/L) is much greater in penicillin resistant strains than in penicillin susceptible strains [2].…”

DNA sequence variability at the rplX locus of Bacillus subtilis

“…Multilocus enzyme electrophoresis (MLEE) has been applied to a number of bacteria, with the results generally suggesting that prokaryotes have clonal population structures (Selander et al, 1985(Selander et al, , 1987Piffaretti et al, 1989). Studies of the extent and pattern of DNA sequence diversity have been fewer in number, but have suggested that genetic exchange is more prevalent than the MLEE results might indicate (DuBose et al, 1988;Dowson et al, 1989). Thus, the most fundamental question concerns the extent of recombination among prokaryotes (Maynard Smith et al, 1991), which raises the question as to whether it is meaningful to discuss bacterial 'species'.…”