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M Del Grosso

Publications and source records attributed to M Del Grosso.

6 recordsLinked to original sources
PubMed2002

Prevalence, determinants, and molecular epidemiology of Streptococcus pneumoniae isolates colonizing the nasopharynx of healthy children in Rome.

The aim of this study was to determine the factors favouring Streptococcus pneumoniae nasopharyngeal colonization of healthy children attending daycare centres and to describe the circulation of penicillin-nonsusceptible strains using molecular techniques. A single nasopharyngeal swab was obtained from 610 children attending daycare centres in the southeast area of Rome. Streptococcus pneumoniae isolates were serotyped, and antibiotic susceptibility was assayed by the E test. The genetic determinants of erythromycin resistance were detected by a duplex polymerase chain reaction, and the penicillin-nonsusceptible isolates were typed by pulsed-field gel electrophoresis. The overall carriage rate of Streptococcus pneumoniae was 14.9%. Living with more than three persons in the same household was the only risk factor statistically associated with carriage. Sixteen of 85 (18.8%) strains were nonsusceptible to penicillin, and 44 (52%) were resistant to erythromycin. Of the erythromycin-resistant strains, the vast majority showed a high level of resistance and carried the erm(B) gene. The penicillin-nonsusceptible strains belonged to six different serotypes; molecular typing showed that in only one case (2 strains) was there a circulation of the same clone in the same daycare centre. In view of the high rate of resistant Streptococcus pneumoniae strains, risk factors for carriage of resistant strains were evaluated. Children who received macrolides in the previous month had a higher risk of being colonized by macrolide-resistant strains as well as by strains resistant to both penicillin and erythromycin. Limiting the use of antibiotics in children seems the most appropriate measure to control the spread of antibiotic-resistant strains.

Anti-Bacterial Agents↗
PubMed2002

Macrolide efflux genes mef(A) and mef(E) are carried by different genetic elements in Streptococcus pneumoniae.

Susceptibilities to macrolides were evaluated in 267 Streptococcus pneumoniae isolates, of which 182 were from patients with invasive diseases and 85 were from healthy carriers. Of the 98 resistant isolates, 20 strains showed an M phenotype and carried mef. Strains that carried both mef(A) and mef(E) were found: 17 strains carried mef(A) and 3 carried mef(E). The characteristics of the strains carrying the mef genes and the properties of the mef-containing elements were studied. Strains carrying mef(A) belonged to serotype 14, were susceptible to all the antibiotics tested except erythromycin, and appeared to be clonally related by pulsed-field gel electrophoresis (PFGE). The three mef(E) strains belonged to different serotypes, showed different susceptibility profiles, and did not appear to be related by PFGE. The sequences of a fragment of the mef-containing element, which encompassed mef and the msr(A) homolog, were identical among the three mef(E)-positive strains and among the three mef(A)-positive strains, although there were differences between the sequences for the two variants at 168 positions. In all mef(A)-positive strains, the mef element was inserted in celB, which led to impairment of the competence of the strains. In line with insertion of the mef(E) element at a different site, the competence of the mef(E)-positive strains was maintained. Transfer of erythromycin resistance by conjugation was obtained from two of three mef(A) strains but from none of three mef(E) strains. Due to the important different characteristics of the strains carrying mef(A) or mef(E), we suggest that the distinction between the two genes be maintained.

Bacterial Proteins↗
PubMed2001

Activity of quinupristin-dalfopristin in invasive isolates of Streptococcus pneumoniae from Italy.

Eighty-five recent isolates of Streptococcus pneumoniae from patients with invasive disease were examined for their susceptibility to erythromycin, clindamycin, penicillin and quinupristin-dalfopristin by E test. A novel duplex PCR assay was used to detect the presence of the erm(B) or mef(A) genes in all of the erythromycin-resistant isolates. All of the strains tested were susceptible to the combination quinupristin-dalfopristin, regardless of their susceptibility to penicillin or to erythromycin. By duplex PCR, two-thirds of the erythromycin-resistant strains harbored erm, and one-third harbored mef. The activity of quinupristin-dalfopristin was not influenced by the genetic determinant of erythromycin resistance. The in vitro susceptibility of S. pneumoniae to quinupristin-dalfopristin is promising for future use; however, it is important to monitor the possible emergence of resistance.

Anti-Bacterial Agents↗
PubMed2000

Detection and characterization of vancomycin-resistant enterococci in farm animals and raw meat products in Italy.

The emergence of vancomycin-resistant enterococci (VRE) in Europe has been ascribed to the long-time use of the glycopeptide antibiotic avoparcin as feed additive in food animals, until its ban in 1997 in EU. The pres- ence of VRE in food of animal origin is believed to represent a potential risk for the consumer. We studied the fecal carriage of VRE in broiler chickens and slaughter pigs in Italy before the avoparcin ban and eval- uated the impact of avoparcin withdrawal on the presence of VRE in raw meat products. Broilers and pigs were both found to be frequently colonized by VRE, as 36% and 24.6% of the flocks or the herds, respec- tively, were positive. Molecular typing of VRE strains by PFGE showed that animals housed in different pens within the same farm were colonized by clonally related strains. After the avoparcin ban, a decrease in the rate of VRE contamination in meat products was observed. Such a decrease was statistically significant in poultry (from 18.8% to 9.6%) but not in pork products (from 9.7% to 6.9%). The majority of VRE from all sources carried the vanA resistance gene and included Enterococcus faecium, E. faecalis, E. hirae, E. durans, and E. gallinarum. None of the strains carried the vanB gene, whereas constitutively resistant vanC-positive strains were frequently found. Our results show that avoparcin withdrawal has been successful in reducing VRE contamination in meat products. However, this measure needs to be complemented by a prudent use of glycopeptide antibiotics in human medicine.

Animals↗
PubMed2000

The alleles of the bft gene are distributed differently among enterotoxigenic Bacteroides fragilis strains from human sources and can be present in double copies.

Enterotoxigenic Bacteroides fragilis (ETBF) strains are associated with diarrheal disease in children. These strains produce a zinc metalloprotease enterotoxin, or fragilysin, that can be detected by a cytotoxicity assay with HT-29 cells. Recently, three different isoforms or variants of the enterotoxin gene, designated bft-1, bft-2, and bft-3, have been identified and sequenced. We used restriction fragment length polymorphism analysis of the PCR-amplified enterotoxin gene to detect the isoforms bft-1 and bft-2 or bft-3 borne by ETBF. By sequencing the portion of the bft gene corresponding to the mature toxin in some strains and applying allele-specific PCR for strains categorized as bft-2 or bft-3, we found in our collection two strains harboring bft-3, a variant that had been described for isolates from East Asia. Analysis of 66 ETBF strains from different sources showed that bft-1 is the most frequent allele, being present in 65% of isolates; it is largely predominant in isolates from feces of adults, while bft-2 is present in isolates from feces of children. This association is statistically significant (P, 0.0064). Sixteen strains were examined by Southern hybridization using, as probes, the bft and second metalloprotease genes, both included in a pathogenicity islet. Five strains were found to harbor double copies of both genes, suggesting that the whole islet was duplicated. Four of these strains, harboring bft-1 (three strains) or bft-2 (one strain), were found to produce a large amount of biologically active toxin, as determined by a cytotoxicity assay with HT-29 cells. The strains harboring bft-3, either in a single copy or in double copies, produced the smallest amount of toxin in our collection.

Adult↗