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Biomedical subjects

G Orefici

Publications and source records attributed to G Orefici.

At least 91 records · Page 5Linked to original sources
PubMed1989

Beta-lactamase production and biological characteristics in nitrosoguanidine induced Mycobacterium fortuitum mutants.

In order to elucidate the role of beta-lactamase in the resistance of M. fortuitum to beta-lactams, M. fortuitum ATCC 19542 and three mutants, strains D 316, D 319 and D 170 obtained from it by nitrosoguanidine treatment, were studied. Furthermore the kinetics of the beta-lactamase production during the bacterial growth and many biochemical and enzymatic characteristics of parent and mutant strains were investigated. Amoxicillin MICs well correlated with the beta-lactamase production in the high producer strains D 316 and D 319; on the contrary in strain D 170 a high MIC was joined with a moderate production of the enzyme showing that not only beta-lactamase but also other mechanisms can be effective in the resistance of M. fortuitum to beta-lactams. Clavulanic acid, an inhibitor of beta-lactamase, reduced MICs to amoxicillin in high and in low producer strains. The production of extracellular beta-lactamase occurred in a M. fortuitum mutant strain mainly during the stationary phase, indicating that a cell wall damage or initial autolysis could be responsible for the release of enzyme. Enzymatic and biochemical characteristics were not affected by nitrosoguanidine treatment except for nitrate test which showed only a weak positivity in high producer strains.

Anti-Bacterial Agents↗
PubMed1988

Preservation of capsular material of streptococcal cells by specific lectins determined by immunoelectron microscopy.

We describe the use of lectins as specific stabilizing agents for the polysaccharide capsular components of two Gram-positive bacteria, Streptococcus agalactiae and Streptococcus bovis. Treatment of bacterial suspensions with wheatgerm agglutinin and concanavalin A allowed better morphological preservation as well as immunoelectron microscopic localization of a capsular component (lipoteichoic acid) by employing specific antibodies and the protein A-gold technique. Data obtained indicate that lectins are useful agents in preserving highly water-soluble capsular components during the electron microscopy procedures for both unembedded and embedded samples.

Animals↗
PubMed1988

Possible virulence marker for Streptococcus agalactiae (Lancefield Group B).

Mouse passage of a stock strain of each of the serotypes Ia, Ib, Ia/c, II and III of Streptococcus agalactiae was followed by increased virulence. The change was associated with an increased content of sialic acid and also with the appearance of an antigen common to all passaged strains. This antigen was subsequently detected in all but one of 12 strains isolated from infected babies or diabetic adults, but in none of 12 organisms recovered from carriers.

Animals↗
PubMed1988

In vitro effect of cefoxitin and amikacin combination on M. fortuitum.

The possible in vitro synergistic effect between amikacin and cefoxitin against 29 clinical isolates of M.fortuitum was studied either by the agar dilution checkerboard technique and by the killing curve on Mueller Hinton agar plus OADC enrichment and on 7H11. As evaluated by FIC index on MHA a synergistic effect was noted on 20 (68.96%) strains tested, an additive effect on 8 (27.60%) isolates, and a possible antagonistic effect only on 1 (3.44%) isolate. On 7H11 a synergistic effect was shown on 10 (38.50%) isolates, an additive effect on 12 (46.10%) and an antagonistic effect on 4 (15.40%) isolates. The killing curve observed on three strains (562, 565 and 505), specially selected as representative of synergistic (562), additive (565) and antagonistic effect (505) on the basis of their checkerboard results, showed synergistic effect on strains 562 and 565 as well as on strain 505 where complete killing was obtained in 24 h by a combination of two antibiotics used at 1/2 Mic. By the killing curve technique both antibiotics were found to be bactericidal but the effect was earlier for amikacin than for cefoxitin.

Amikacin↗
PubMed1987

Adherence of group B streptococci to adult and neonatal epithelial cells mediated by lipoteichoic acid.

We have investigated the role of lipoteichoic acid in mediating the adherence of different serotypes of group B streptococci to human adult and neonatal epithelial cells. Pretreatment of neonatal buccal and vaginal epithelial cells with lipoteichoic acid, but not with deacylated lipoteichoic acid, induced a marked inhibition in the adherence of all strains tested. Pretreatment of bacteria with substances known to bind lipoteichoic acid, such as monoclonal and polyclonal antipolyglycerophosphate antibodies and albumin, also resulted in adherence inhibition. Group B streptococci adhered in 6- to 10-fold-higher numbers to buccal epithelial cells from neonates older than 3 days than to those from neonates less than 1 day old. This increase in receptiveness for group B streptococci was paralleled by an increased ability of epithelial cells from older neonates to bind group B streptococcal lipoteichoic acid. These data suggest a role for the lipid portion of lipoteichoic acid in the adherence of different serotypes of group B streptococci to vaginal and neonatal epithelial cells.

Age Factors↗
PubMed1987

Adherence of S. bovis to adult buccal epithelial cells.

The ability of S. bovis 83/5364, glucan-positive (biotype I) and S. bovis R 81/536 glucan-negative (biotype II) to adhere to buccal epithelial cells (BEC) by lipoteichoic acid (LTA) was examined. LTA from both biotypes was prepared by cold phenol extraction from supernatants of penicillin supplemented cultures and partially purified by Sepharose CL-6B chromatography. Both glucan-positive and glucan-negative S. bovis strains adhered to BEC, but biotype I seemed to be more adhesive. For both biotypes the adhesion was not significantly inhibited by treatment of the bacteria with anti-LTA serum, while the preincubation of BEC with LTA, extracted from S. agalactiae, or cardiolipin strongly decreased the S. bovis binding.

Bacterial Adhesion↗
PubMed1986

Expression and some properties of beta-lactamase from Mycobacterium fortuitum.

Several species of mycobacteria have been reported to produce beta-lactamases, but only those of M. smegmatis have been purified and partially characterized. This study is a preliminary report of the presence of beta-lactamase activity in M. fortuitum, strain Cow 18. A partial purification of the beta-lactamase has also been achieved. M. fortuitum was grown in either Sauton or glucose-yeast extract medium (GYM) and sonicated cells or culture filtrates were assessed for the presence of beta-lactamase activity using a chromogenic compound (PADAC) as substrate. Cells growing in GYM medium released a detectable amount of enzyme, whereas microorganisms showed only intracellular beta-lactamase activity. The enzyme present in the culture filtrate of M. fortuitum Cow 18 was concentrated by Amicon ultrafiltration and partially purified through Sephadex G-75 and QAE-Sephadex A-50 ion exchanger columns. The spectrum of activity of this enzyme included some cephalosporins (cephaloridine, cephalothin) and some penicillins, the hydrolysis of the former being generally more pronounced. Furthermore, cefoxitin, ceftazidime and cefotaxime were not hydrolysed.

Culture Media↗
PubMed1985

Colonization and infection of mothers and neonates with group B streptococci in three Italian hospitals.

In the absence of previous published studies from Italy on the epidemiology of group B streptococci we investigated 1516 mothers at delivery and 1294 neonates in three hospitals. Of mothers in labour, 7.5% were colonized with group B streptococci and 4.9% of their babies. Of the neonates born to a positive mother 45.1% were colonized, whilst only 2.2% of babies born to a negative mother were colonized. For the mothers, the vagina was colonized more often (7.3% of all women) than the cervix (6.0%), the urethral meatus (3.9%) or the rectum (2.9%). For the neonates, the rates of colonization of the throat, external auditory canal, and the umbilicus were 3.2%, 3.0% and 2.6%, respectively. The distributions of the serotypes were similar to that reported from other parts of Europe and the USA and vertical transmission of group B streptococci was demonstrated in most of the mothers and their neonates. Of 30 mother-neonate pairs, 25% of mothers carried group B streptococci intermittently and 58% had persistent carriage until the 90th day postpartum, the rectum being the commonest positive site. Of 20 infants that were positive at birth, only six were still positive on the 15th day and none by the 90th day of life. Of 1294 infants, four (0.3%) developed early-onset sepsis with group B streptococci and one died. The overall incidence of clinical infection amongst colonized infants was 6.2%.

Female↗
PubMed1985

Influence of sialic contents on the chemiluminescent response of human leucocytes to group B streptococci.

The sialic acid content in reference strains of various Group B streptococci serotypes was studied before and after serial passages in mouse to enhance the virulence. The passages in mouse strongly increased the sialic acid content but the neuraminidase treatment reduced the to comparable values in reference and in virulent strains. The chemiluminescent response of human polymorphonuclear leucocytes to different GBS strains was higher for reference strains and lower for virulent strains. Sialic acid removal by neuraminidase increased the chemiluminescent response in virulent and in reference strains. Negative correlation between sialic acid content and chemiluminescence was demonstrated in strains of the same serotype, before and after passages in mouse and neuraminidase treatment for types Ic, II and III but no correlation was found considering the sialic acid content in strains belonging to different serotypes.

Animals↗
PubMed1985

Water supply as a source of Pseudomonas aeruginosa in a hospital for hematological malignancies.

This report details of an investigation on a significant increase in nosocomial bacteremias due to multiply-resistant Pseudomonas aeruginosa strains which occurred in a hematological ward. Serotyping according to Habs method showed a high frequence of the serotype 12. Control cultures identified in the hospital building water reservoirs the presence of the organism. After disinfection of these water reservoirs, the frequence of nosocomial septicemias caused by serotype 12 Pseudomonas aeruginosa strains on the overall bacteremic episodes declined immediately and showed a declining trend in the following 13 months period. To conclude serotyping of Pseudomonas aeruginosa is a useful epidemiological marker and allows to discover from where the diffusion of the organism responsible of outbreaks starts.

Cancer Care Facilities↗
PubMed1984

National survey of hospital infection control organization in Italian public hospitals.

A questionnaire was mailed to 1073 Italian public hospitals in an attempt to find out if infection control programmes existed, the type of programme used and available resources. After two attempts a total of 54.9 per cent of the hospitals responded to the request and of these 16.1 per cent claimed to have an infection control programme. Sixty-six per cent of the hospitals who have a control programme also have a system of continuous surveillance whilst the remainder investigated epidemics only. Infection control programmes were encountered most frequently in paediatrics, obstetrics and surgical departments. The organisms most often surveyed were the salmonellas, other types of enterobacteria, staphylococci and streptococci.

Cross Infection↗