Group 1 beta-lactamases of Aeromonas caviae and their resistance to beta-lactam antibiotics.

The contribution of beta-lactamase production to beta-lactam antibiotic resistance was examined in an Aeromonas caviae mutant strain, selected in vitro by cefotaxime and derived from a wild-type strain isolated in our laboratory from crude sewage. Both strains produced beta-lactamase. The mutant strain (AC7m) produced beta-lactamase constitutively, in contrast to the parental strain (AC7), which was inducible by cefoxitin. AC7m was regarded as a mutant from AC7, which over-expressed beta-lactamase. The mutant strain showed a remarkable reduction in sensitivity to most of the beta-lactam antibiotics tested, such as (i) aminopenicillins and their combinations with clavulanic acid and sulbactam, (ii) carboxypenicillins, (iii) ureidopenicillins, and (iv) cephalosporins. This strain remained susceptible to ceftazidime, imipenem, and aztreonam. Isoelectric focusing of sonic extracts revealed that both strains AC7 and AC7m shared a common major beta-lactamase band at pI 6.5. The plasmid DNA assays showed that the beta-lactamases expressed by each A. caviae strain were chromosomally encoded. Based on substrate and inhibitor profiles determined in sonic extracts for AC7 and AC7m, the enzymes displayed on isoelectric focusing at pI 6.5 were assigned to chromosomal Group 1 beta-lactamases. Imipenem would therefore be the appropriate choice for therapy of infections caused by A. caviae beta-lactamase over-expressing mutants.

[Carriers of beta hemolytic streptococci from groups A, B, and C among schoolchildren in Las Palmas]. / Portadores de estreptococos betahemolíticos de los grupos A, B y C en escolares de Las Palmas.

BACKGROUND: Betahemolytic streptococci, particularly group A, are the most frequently isolated pathogen in the cases of acute pharyngotonsilitis in school-aged children. A study was carry out in school children of Las Palmas de Gran Canaria with the aim of knowing of the state of pharyngeral carriers of betahemolytic streptococci in Lancefield groups A, B and C. METHODS: A total of 1,002 healthy school children (520 boys and 482 girls) with ages ranging from 4 to 15 of aged were included in the study in which a pharyngeal exudate was obtained to detect the presence of betahemolytic streptococci. RESULTS: 69.5% of the healthy school children were not pharyngeal carriers of betahemolytic streptococci. The prevalence of streptococci group A in all the age groups studied was of 6%. The prevalence of beta streptococci groups B and C were of 11 and 13.5%, respectively. CONCLUSIONS: The results of this study are in agreement with the literature reviewed in which the rate of pharyngeal carriers of beta-hemolytic streptococci in school children of Las Palmas de Gran Canaria are more similar that studies reported from tropical and subtropical zones showed a high prevalence of groups B and C and a lower prevalence of a group A than others communities of our country and zones with temperature climate where showed a high prevalence of group A and lower prevalence of groups B and C.

Antibacterial susceptibility patterns of Pseudomonas strains isolated from chronic canine otitis externa.

Development of antibiotic resistance in bacteria is a problem of great concern. It is important to establish the convenience of antimicrobial susceptibility tests in animal infections. The aim of this study was to test the susceptibility to antibiotics of Pseudomonas strains isolated from chronic canine otitis externa. We tested 23 strains of Pseudomonas: 19 Ps. aeruginosa, three Ps. fluorescens and one Pseudomonas spp. The most effective antibiotics were tobramycin (100% susceptible), marbofloxacin (91.3%) and ceftazidime (91.3%). Ticarcillin and gentamicin, commonly used for the treatment of otitis externa also showed good results (susceptibility of strains was 86 and 65.2% respectively). Lower susceptibility was found using enrofloxacin (52.1%) probably due to its indiscriminate use. We emphasize the need for a rational policy of antibiotic prescribing in order to prevent the selection of resistant strains.

Aminoglycoside resistance mechanisms in clinical isolates of Pseudomonas aeruginosa from the Canary Islands.

Strains of Pseudomonas aeruginosa resistant to aminoglycoside antibiotics were selected from 152 clinical isolates. We identified two patterns of resistance correlating with the resistance mechanism characterized by changes in permeability, enzymatic modification due to the acetylating enzyme, AAC(6')-II, or a combination of both. We detected enzymatic activity of the phosphorylase enzyme, APH(3'), in all the isolates. We compared the mechanisms of resistance detected by three methods i.e., radioenzymatic assay, phenotype of resistance and DNA probes. The phenotype of resistance was tested using a kit developed by Schering-Plough Corp. Hybridization was made with 18 DNA probes for the most frequent genes encoding for aminoglycoside-modifying enzymes. All isolates with AAC(6') activity hybridized with the aac(6')-Ib probes and to a minor degree, with the aac(6')-IIb probe. None of the isolates showed hybridization with aph(3')-I, aph(3')-II, or aph(3')-III DNA probes. Serotyping of the strains showed that the O:11 serotype was the most frequent one in strains whose resistance was due to the AAC(6') enzyme. The O:6 serotype was associated with changes in permeability. Encoding of the resistance mechanism seemed to be chromosomal in all the strains.

[Sensitivity of groups A, B and C beta hemolytic streptococci to antibiotics]. / Sensibilidad a antibióticos en estreptococos beta hemolíticos de los grupos A, B y C.

We studied the susceptibility of 330 strains of beta hemolytic streptococci (60 group A, 125 group B, 145 group C) isolated from healthy school children in Las Palmas de Gran Canaria to 17 antibiotics. Only 2% of group A streptococci showed resistance to erythromycin, and 18% to 31% of the beta hemolytic streptococci strains were resistant to trimethoprim-sulfamethoxazole. All of these strains showed susceptibility to betalactam antibiotics, chloramphenicol, clindamycin and vancomycin. Most of them were resistant to tetracycline and aminoglycoside antibiotics.

Multicenter evaluation of Neo-Sensitabs, a standardized diffusion method for yeast susceptibility testing.

The agar diffusion method Neo-Sensitabs for sensitivity testing, was evaluated with 33 reference strains by fourteen laboratories. Tablets with 5-fluorocytosine, amphotericin B, nystatin, fluconazole, itraconazole, ketoconazole and tioconazole were used on Shadomy modified medium. These tests classify each strain as susceptible, intermediate or resistant to all tested antifungals by measuring the inhibition zone diameters. Intra and interlaboratory reproducibility was studied. Neo-Sensitabs sensitivity for fungi was easy to perform and reliable method with a reproducibility of 97.1% and superior to other commercialized methods, being specially interesting for antifungal susceptibility in vitro testing of triazole derivatives fluconazole and itraconazole.

Type I beta-lactamases of Enterobacter cloacae and resistance to beta-lactam antibiotics.

The interaction of type-I beta-lactamases from Enterobacter cloacae with diverse beta-lactam compounds was examined. The ability of penicillin and cefoxitin to induce beta-lactamase production in this strain was assessed. The effect of beta-lactamase inhibitors was measured on beta-lactamase extracts and on intact cells. E. cloacae 78 strain is a stably derepressed mutant showing limited susceptibility to a number of antibiotics except imipenem. Imipenem would therefore be the appropriate choice for therapy of infections caused by stably derepressed mutants of Enterobacter sp. producing type-I beta-lactamases.

Selection of subpopulations resistnat to amikacin and netilmicin of gentamicin-resistant clinical strains of Staphylococcus aureus and Staphylococcus epidermidis.

Recently we have found several strains of Staphylococcus aureus and Staphylococcus epidermidis, which in spite of containing aminoglycoside-modifying enzymes (AMEs) remained susceptible to antibiotics such as netilmicin (NET) and amikacin (AN). Assuming an interest in this agent from a clinical point of view, the aim of this study was to determine if these strains became resistant after prolonged contact with such antibiotics. We found that minimal inhibitory concentrations (MICs) of the bacterial strains not only increased when using these two agents, but also when using other aminoglycosides such as gentamicin (GM), tobramycin (TM), amikacin (AN) and isepamicin (ISE). In order to see the effect of prolonged use of NET on enzyme production, three strains containing AMEs were selected and we could observe an increase in the enzyme levels after successive passages through media containing NET.

Clinical presentation of acute Q fever in lanzarote (Canary Islands): a 2-year prospective study.

The clinical manifestations of acute Q fever may differ markedly from country to country. In this regard, fever and hepatitis seem to be the dominant clinical features of acute Coxiella burnetii infection in Lanzarote, Canary Islands. A possible interaction between environmental factors and some strains of C. burnetii could explain the different clinical presentations of acute Q fever.

[In vitro study of the stability of reduced intraerythrocyte glutathione against a group of drugs frequently used during the neonatal period]. / Estudio "in vitro" de la estabilidad del glutation reducido intraeritrocitario, frente a un grupo de fármacos de utilización frecuente en el período neonatal.

Authors have studied in 32 samples of cord blood (normal newborns and normal births) the stability of glutathione reduced form (GSH) in human erythrocytes opposite to ten drugs (gentamicin, cephazolin, amikacin, carbenicillin, amoxicillin, benzodiacepine, metil-prednisolone, phenilbarbituric acid, fosfomycin, trimethroprim-sulphamethoxazole) using it at similar concentration to the highest haemotic levels that are obtained in the newborn with therapeutic doses. They showed that these drugs have not an effect on stability of GSH. For this reason is very unprobable that these drugs are cause of haemolitic crisis in the newborn. In the another hand, they suggest the use co-trimoxazole in the newborn always, in correct doses.