Molecular characterization of adult-colonizing Streptococcus agalactiae from an area-based surveillance study in Romania.

One hundred and forty-eight colonizing isolates from adult Romanian women were conventionally serotyped and screened for antibiotic resistance. Capsular type assignment by multiplex polymerase chain reaction (PCR) was performed for nonserotypeable isolates. Tetracycline and macrolide resistance genes (tetM, tetO, tetL, ermA, ermB, and mefA) including tetM gene association with conjugative elements of the Tn916 family were searched. Molecular typing included PCR screening for major surface protein antigen genes (bac, bca, alp1, alp2/3, alp4, and rib), mobile genetic elements (GBSi1 and IS1548), and rapid detection of hypervirulent clone ST-17. Genetic diversity was assessed by pulsed field gel electrophoresis (PFGE) analysis of SmaI macrorestriction patterns. Among the colonizing isolates studied, serotypes V and III predominated and high rates of tetracycline and macrolide resistance were observed. The tetM gene occurred in 140 tetracycline-resistant isolates and was associated with the int-Tn916 gene in 94 of them. Most of the isolates displayed a constitutive MLS(B) phenotype (38/46 isolates) and harbored the ermB gene. rib, alp2/3, and alp1 were the most common surface protein genes detected. Either IS1548 or GBSi1 intron were detected in almost half of the isolates and nine serotype III isolates belonged to clone ST-17. PFGE analysis of SmaI macrorestriction patterns, obtained from 118 isolates, revealed an apparent genetic diversity.

Molecular subtyping of group A streptococcal strains based on virulence regulon polymorphism.

A total of 64 Streptococcus pyogenes isolates included in a previous study (Shundi et al., 2000) were further analyzed by Vir typing. Vir typing is based on restriction fragment length polymorphism (RFLP) analysis of a 4- to 8-kb pathogenicity island (vir regulon) encoding emm and other virulence genes. As all our isolates contained a single vir regulon, the stoichiometric yield of restriction fragments avoided ambiguities in interpretation of results. By using both HaeIII and HinfI restriction endonucleases to generate RFLP profiles, the 64 GAS isolates were distributed among 22 Hae- and 26 Hinf-Vir types respectively.

Correlation between two DNA-based typing methods applied to Streptococcus pneumoniae strains: BOX-PCR assay as an alternative to ribotyping.

Seventy-nine Streptococcus pneumoniae isolates were characterized by ribotyping and BOX-PCR typing. The isolates comprised 14 most frequently identified serogroups and serotypes, 54 ribotypes (defined as each different combination of two DNA restriction fragment length polymorphism patterns obtained with HindIII and PvuII, respectively) and 51 BoxA-PCR patterns. There was close but not absolute correlation between molecular techniques. However, the discrimination indice of ribotyping--calculated on the basis of combination of the data obtained with both enzymes--equals that of BOX-PCR typing: D = 0.985 and the deduced genetic clustering of the pneumococcal strains was comparable.

Molecular typing of Enterococcus faecalis strains resistant to high levels of gentamicin and isolated in Romania.

Sixteen Enterococcus faecalis strains resistant to high levels of gentamicin, 15 of which were isolated in the same year in a Romanian hospital, harboured conjugative gentamicin resistance (Gm(r)) plasmids ranging from 55 to 85 kilobases. On the basis of restriction enzyme and DNA-DNA hybridization profiles of these plasmids, as well as of chromosomal SmaI macrorestriction and Tn916 hybridization patterns, clonal relationship was established for seven strains whereas the other strains were considered to be independent. Nine and seven of the Gm(r) plasmids carried Tn4001-like and Tn4001-truncated structures, respectively; the latter structures were truncated in the right-hand flanking extremity of the element.

Plasmid-borne high-level resistance to gentamicin in Enterococcus hirae, Enterococcus avium, and Enterococcus raffinosus.

Enterococcus hirae, E. avium, and E. raffinosus isolated in Romania, Tunisia, and Portugal harbored plasmids pICC8, pIP1700, and pIP1701, respectively, encoding resistance to high levels of gentamicin (Gmr). The Gmr marker was carried on pIP1700 by a Tn4001-like element and on pICC8 and pIP1701 by Tn4001-truncated structures. pICC8 carried, in addition to Gmr, chloramphenicol, erythromycin, and tetracycline-minocycline (TetM) resistance determinants. The gene tetM of pICC8 was carried on a Tn916-like element.

Antibiotics and bacterial resistance. A few elements of genetic basis for this relationship.

In the preantibiotic era, many people died of bacterial infections caused by such pathogens as Staphylococcus aureus and Streptococcus pyogenes, Streptococcus pneumoniae and Mycobacterium tuberculosis. Antibiotics have reduced the mortality from infectious diseases but not the prevalence of these diseases. It was not long after the clinical introduction of the first antibiotics in the 1950s that the first reports of bacterial resistance began to appear. Use, and often abuse or misuse, of antimicrobial agents has encouraged the evolution of bacteria toward resistance, resulting often in therapeutic failure. In the beginning, new antibiotics have always appeared in plenty of time to provide new cures for diseases caused by resistant bacterial pathogens. Also, some clinically important groups of bacteria showed no signs of major increases in resistance. For example, S. pneumoniae strains remained susceptible to penicillin long after other bacteria had become resistant to it. Recent developments of bacteria resistance to antibiotics are indeed disquieting.