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S Mella

Publications and source records attributed to S Mella.

At least 19 recordsLinked to original sources
PubMed2003

Prevalence and types of class 1 integrons in aminoglycoside-resistant Enterobacteriaceae from several Chilean hospitals.

Members of the family Enterobacteriaceae are responsible for a variety of nosocomial infections, treatment of which is limited due to their increasing resistance to antibiotics. Some bacterial genes encoding antibiotic resistance comprise the major part of gene cassettes, most of which are associated with integrons. In this work, the carriage of class 1, 2 and 3 integrons was investigated in 191 Enterobacteriaceae isolates from clinical specimens of hospitalized patients. Class 1 integrons were found to be the most common, whereas no class 3 integrons were detected. The variable regions of 13 class 1 integrons were characterized and four types were found. Type 1 harbours only ant(3")I, type 2 harbours ant(2")I and ant(3")I, type 3 harbours aac(6')Ib and ant(3")I and type 4 lacks inserted gene cassettes.

Aminoglycosides↗
PubMed2000

[Presence of integrons and their relationships with the resistance to third generation cephalosporins among nosocomial isolates of Acinetobacter baumannii].

BACKGROUND: Acinetobacter baumannii is an important etiological agent causing nosocomial infections. High level of resistance for different kind of antimicrobials has been observed, including beta-lactam antibiotics. This feature, chromosomal or plasmid encoded, has been associated to integrons harbouring antibiotic resistance gene cassettes. AIMS: To investigate the presence of integrons among clinical isolates resistant to third generation cephalosporins (3GC). MATERIAL AND METHODS: One hundred A. baumannii strains isolated from several Chilean hospitals were included in this study. Minimal inhibitory concentrations (MIC) of 3GC by an agar dilution method were carried out. Integrons class 1, 2 and 3 were investigated by colony blot hybridisation and confirmed by PCR. RESULTS: High level of resistance to all assayed 3GC was observed. On the other hand, integrón class 2 was the most prevalent (77% of isolates) followed by integron class 1 (52%). Forty six percent of isolates hybridised with probes for both of them. However, no positive hybridisation was detected for integron class 3. CONCLUSIONS: Nevertheless, most isolates harboured one or both class of integron; there was no direct relationship between the presence of these genetic structures and the resistance to this kind of beta-lactam antibiotics.

Acinetobacter↗
PubMed2000

[Activity of imipenem and meropenem against strains of Acinetobacter baumannii isolated from various Chilean hospitals].

The activity of two carbapenem compounds, imipenem and meropenem, against 447 strains of Acinetobacter baumannii isolated between 1990 and 1998 in different Chilean hospitals was determined. MIC ranges, MIC(50) and MIC(90), were determined by an agar dilution method. Similar antibacterial activities were observed for both antibacterials; however, a slight increase in the MIC(50) of imipenem and meropenem, and in the MIC(90) of meropenem was found among strains isolated from 1997-1998. Although A. baumannii remains susceptible to these antibiotics, the MIC(50) and MIC(90) have increased in recent years.

Acinetobacter↗
PubMed1998

Presence of integrons in isolates of different biotypes of Acinetobacter baumannii from Chilean hospitals.

Class 1 and class 2 integrons were investigated by hybridisation in 100 isolates of multiresistant biotypes of Acinetobacter baumannii from Chilean hospitals. Most isolates of A. baumannii biotype 9, the prevalent biotype, harboured integrons of class 2 (Tn7-like) whereas no integrons were detected in infrequent biotypes. Integron-carrying isolates exhibited broader antibiotic resistance patterns as well as higher resistance levels to various antimicrobials.

Acinetobacter↗
PubMed1998

[Adherence of Acinetobacter baumannii to rat tracheal tissue].

BACKGROUND: Acinetobacter baumannii is an important nosocomial pathogen whose virulence factors have not been fully elucidated. AIM: To study the adherence and hemagglutinating capacity of several biotypes of Acinetobacter baumannii. MATERIAL AND METHODS: Thirty nine strains of Acinetobacter baumannii isolated from hospitalized patients were studied. The adherence of these strains to small pieces of rat tracheal tissue was studied. Additionally, their ability to hemagglutinate human erythrocytes and the effect of D-mannose and D-galactose on the adherence and hemagglutinating capacity was assessed. Transmission electron microscopy of strains was performed looking for the presence of fimbriae. RESULTS: All strains exhibited adherence to tissues. All strains had also D-mannose and D-galactose resistant hemagglutinating ability. Fimbriae were found in Acinetobacter baumannii and E coil cells. CONCLUSIONS: Adherence of Acinetobacter baumannii to rat tracheal tissue, apparently not related to the presence of fimbriae, may be a virulence mechanism of this bacterium.

Acinetobacter↗
PubMed1998

Adherence of Acinetobacter baumannii to rat bladder tissue.

Acinetobacter baumannii, an important nosocomial pathogen, causes severe infections in patients of intensive care units, but its pathogenic attributes are unknown. Previously, the adherence of A. baumannii to cell lines has been negative in the authors' laboratory. In this work, the adherence of strains of A. baumannii of various biotypes to small pieces of rat bladder tissue was investigated. Tissue pieces were submerged into cultures of A. baumannii and sessile cells were counted after removing planktonic bacteria. Fimbriae and sessile cells were examined by transmission and scanning electron microscopy, respectively. In contrast to a uropathogenic strain of Escherichia coli, all cultures exhibited a mannose- and galactose-resistant agglutination of human group O red blood cells as well as mannose- and galactose-resistant adherence to the bladder tissue. Inhibition of exopolysaccharide synthesis did not modify adherence. Indeed, adherence, apparently unrelated to these fimbriae or to the exopolysaccharide, may be a factor contributing to the pathogenicity of A. baumannii in the urinary tract or in other tissues.

Acinetobacter↗
PubMed1997

Activity of selected beta-lactams, ciprofloxacin, and amikacin against different Acinetobacter baumannii biotypes from Chilean hospitals.

The activity of some third generation cephalosporins, aztreonam, imipenem, ciprofloxacin, and amikacin against isolates of Acinetobacter baumannii of various biotypes has been studied. The isolates, independently of the biotype, exhibited a broad multiresistance against cephalosporins. Ceftazidime was the most active and cefoperazone the least active compound. Aztreonam also showed low activity and no imipenem-resistant strains were found. Ciprofloxacin and amikacin were somewhat more active than cephalosporins, but resistant isolates were also frequent. Isolates of Biotypes 9 and 8 exhibited broader multiresistance than those of Biotype 6 and "other."

Acinetobacter↗
PubMed1995

Identification and biotyping of Acinetobacter spp. isolated in Chilean hospitals.

Two hundred and eighty-one isolates of Acinetobacter spp. obtained from clinical specimens in hospitals from five Chilean cities were identified to species level and biotyped. Respiratory tract and wound secretions were the main sources of the isolates. Acinetobacter baumannii was the most frequent species (96.8%), followed by Acinetobacter genospecies 3 (2.8%). Twelve different biotypes of A. baumannii strains were found of which biotypes 9, 8 and 6 were the most frequent. Isolates of other biotypes were rare. These results differ from most other Latin American and European countries.

Acinetobacter↗
PubMed1994

[Prevalence of endemic dental fluorosis and its relation with fluoride content of public drinking water].

The prevalence of dental fluorosis, a manifestation of chronic fluoride toxicity on ameloblasts, is increasing in communities with or without fluoride supplementation of drinking water. The aim of this work was to study the prevalence and severity of fluorosis in Chile and its relationship to socioeconomic level and fluoride content of drinking water. Six hundred ninety three children aged 7 to 12 years old, coming from four cities with drinking water fluoride levels of 0, 0.3, 1 and 2.2 ppm were subjected to a standardized odontological examination looking for clinical manifestations of fluorosis. The global prevalence of fluorosis was 32%, being 61.4% in the city with the highest drinking water fluoride concentration and 20% in the city without fluoride in the drinking water. Likewise, the prevalence of fluorosis was higher in children of high socioeconomic level. It is concluded that the high prevalence of fluorosis, although generating only mild lesions, should be object of epidemiological surveillance.

Child↗
PubMed1993

Activity of imipenem, third-generation cephalosporins, aztreonam and ciprofloxacin against multi-resistant gram-negative bacilli isolated from Chilean hospitals.

The activity of imipenem against nosocomial strains of Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter spp. and methicillin-resistant Staphylococcus aureus resistant to some third-generation cephalosporins, aztreonam, or ciprofloxacin was assessed. These strains represent the most prevalent multi-resistant nosocomial microorganisms in Chile since they were isolated from clinical specimens in 11 Chilean hospitals. A high proportion of the strains were resistant to several beta-lactams, yet all strains of K. pneumoniae and Acinetobacter spp. were susceptible to imipenem; resistance was exhibited by only one strain of P. aeruginosa and 16 strains of S. aureus. Synergy between cefotaxime and clavulanic acid was found in almost all strains of K. pneumoniae, suggesting the presence of plasmid-coded beta-lactamases, probably with extended-spectrum activity. Killing A. baumannii by imipenem was rapid, but slower for P. aeruginosa. Killing of K. pneumoniae was also somewhat slower despite the lower MIC of imipenem for this strain. Bactericidal activity was even slower against one strain of methicillin-resistant S. aureus. These results suggest that imipenem would be an adequate alternative to other broad-spectrum agents in the treatment of infections due to nosocomial multi-resistant Gram-negative bacilli.

Anti-Bacterial Agents↗
PubMed1992

[Prevalence of dental fluorosis in Chile: a pilot study].

The prevalence of enamel fluorosis and its severity was studied in 118 young men of 2 socio-economic levels. The subjects were born and resided for at least 6 years in Chilean communities with different natural levels of fluoride in drinking water. There was a high prevalence of enamel defect overall (54%) most of it of mild degree (36%). This was not related to the level of fluoride in drinking water, however further studies are needed since Chilean children are receiving fluoride from other sources. A national program to supplement drinking water with fluoride should take this information into account.

Adolescent↗
PubMedDate not supplied

Activity of cefepime, cefotaxime, ceftazidime, and aztreonam against extended-spectrum-producing isolates of Klebsiella pneumoniae and Escherichia coli from Chilean hospitals.

Resistance of Gram-negative bacilli to third-generation cephalosporins has been increasing due to the production of extended-spectrum beta-lactamases. In this work, the activities of cefepime, cefotaxime, ceftazidime, and aztreonam, alone and in association with clavulanic acid, against isolates of Klebsiella pneumoniae and Escherichia coli are compared. These isolates produce extended-spectrum beta-lactamases as shown by the synergy tests and by the decrease in the MICs of cephalosporins in the presence of clavulanic acid. Cefepime was the most active compound against these microorganisms. In addition, the microorganisms exhibited lower frequencies of resistance to this cephalosporin.

Anti-Bacterial Agents↗