A beta-lactam-resistant serotype 23F Streptococcus pneumoniae clinical isolate from the cerebrospinal fluid of a pediatric patient from California is unusual in that the MICs of cefotaxime and ceftriaxone (2.5 Sig/ml each) are higher than that of benzylpenicillin (0.3 p.g/ml); the isolate also has patterns of penicillin-binding proteins and of cell wall peptides which are atypical compared with those of previously examined penicillinresistant pneumococci.
Extracts from different parts of Cassia sieberiana, Chamaechrista nigricans, Guiera senegalensis, Lippia chevalieri, Pavetta oblongifolia, Piliostigma thonningii, Senna podocarpa and Terminalia macroptera were examined for in vitro antibacterial activity. These species were collected in the Contuboel region (Guinea-Bissau) which were used by the traditional healer's of the Fulani ethny to treat several disorders including venereal diseases (Diniz, 1996). Fifteen plant extracts were tested against nine strains ofNeisseria gonorrhoeae, including penicillin and tetracycline resistant strains. All the extracts exhibited antibacterial activity against all the tested strains. Two of the most active extracts (from Guiera senegalensis leaves and Terminalia macroptera root) were partitioned with different solvents and tested for antiNeisseria gonorrhoeae activity.
A total of 1,104 strains of Streptococcus pneumoniae were isolated from hospitalized patients (75.5%) and from colonization sites at the Public Health Institute (24.5%) during the last 4 years (1989-1993). Penicillin resistance (defined as MIC > or = 0.1 microgram/liter) was found to increase in time: 4.6% in 1989, 4.9% in 1990, 6.4% in 1991, 11.3% in 1992, and 17% in 1993. In 1992, 0.8% of the strains had penicillin MIC = 2 mg/liter. Increase in penicillin resistance was also evident among invasive strains [blood, cerebrospinal fluid (CSF), pleura]: 2/92 isolates from 1989-1992 (2.3%) were penicillin resistant as compared to 7/101 isolates from 1992 (6.9%). Multiresistance (resistance to three or more antibiotics) was 4.4% with penicillin, tetracycline, chloramphenicol being the predominant resistant phenotype at the end of 1992. In 1993, strains with resistance to penicillin plus chloramphenicol plus tetracycline increased further. Erythromycin resistance was usually associated with clindamycin resistance, but the majority of such strains remained susceptible to penicillin. Drift in the direction of increasing MIC values was also noted during this 3-year period among "susceptible" isolates: bacteria with MIC of 6-10 ng/ml representing the majority of isolates in 1990-1991 decreased and were replaced by cells with MIC of 20 ng/ml. The most frequent pneumococcal serotypes were 23, 19, 3, 6, 14, 9, and 8, with the frequency of type 9 increasing from 2.9% (in 1989) through 3.2% (1990) to 6.4% (1992). Among all antibiotic resistant strains, the prevalent serotypes were 23, 9, 14, and 6. The chromosomal backgrounds of resistant isolates tested by pulsed-field gel electrophoresis showed close resemblance to the background of the serotype 23F multiresistant clone first identified in Spain. The data suggest that the recent large increase in the frequency of penicillin-resistant pneumococci represents the import of this clone into Portugal during the early 1990s. The increased frequency of drug-resistant pneumococci highlights the importance of continued surveillance of these dangerous pathogens.
The penicillin MIC of 2 Streptococcus pneumoniae clinical isolates was increased 100-fold (from 0.02 to 2.0 micromilligrams) and 20-fold (from 0.5 to 10.0 micromilligrams) through gradual exposure of the bacteria to increasing concentrations of penicillin in the laboratory. In both mutants the affinity of all four high molecular mass penicillin binding proteins (PBPs) for penicillin was drastically reduced accompanied by major changes in the composition of peptidoglycan as resolved by HPLC. The ratio of crosslinked to monomeric peptides became virtually inverted in the resistant cell walls with monomers representing two-thirds of the muropeptide species. The proportion of the crosslinked tri-tetra dimer, a major component of the cell wall of the original isolates, decreased to one-third or one-sixth of its normal representation, while the amounts of tripeptide monomers with an alanyl-serine substitution on the lysine epsilon amino group increased by close to a factor of two. The growth rates of both mutants decreased by a factor of approximately two, as compared to the original bacteria.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.