[Evaluation of an advisory program in antibiotic therapy]. / Evaluación de un programa de asesoría en terapia antibiótica.

BACKGROUND: Increases in microbial resistance and pharmaceutical costs have prompted an interest in antibiotic control programs (ACP). Nevertheless, there is controversy on the optimal ACP design and implementation. An ACP based on the infectious diseases' specialist recommendations was evaluated. METHODS: Interventional study of two hospital departments (medical and surgical). Antibiotic costs, mortality rate, readmissions following an infectious disease, and incidence of MRSA and Clostridium difficile between the intervention period and the same period in the previous year were compared. An anonymous survey among health care workers in both departments was conducted. RESULTS: One-hundred and one antimicrobial therapy courses administered to 80 patients were evaluated. A total of 77 recommendations were issued, which consisted of therapy discontinuation (39%), switch to oral antibiotics (31%), decrease in the antimicrobial spectrum (24%) or enhancing the antimicrobial spectrum (6%). Eighty-five percent of the recommendations were accepted. The antimicrobial use remained stabilized, but the oral administration increased from 12.5 to 18.6 DDD/100 patient-days and parenteral use decreased from 25.9 to 22.3 DDD/100 patient-days. Antimicrobial costs decreased by 19.4% (901,794 pesetas). No changes, either in the mortality rate or in readmission rate due to infectious diseases was observed. In contrast, a decrease in the incidence of both MRSA (3.7% to 0.8%; p < 0.05) and Clostridium difficile (1.2% to 0%; p = 0.05) was observed. All health care workers that responded to the survey thought that ACP should be extended to the rest of the hospital. CONCLUSIONS: Our ACP, based on the advice of an infectious diseases specialist, was very well accepted and allows for a decrease in antibiotic costs by simplified therapy. The ACP did not cause a negative impact on patients' outcomes and would probably help reducing the incidence of some nosocomial pathogens.

Evaluación de un programa de asesoría en terapia antibiótica / Evaluation of an advisory program in antibiotic therapy

Objetivo. Los incrementos de la resistencia microbiana y de los costes farmacéuticos están suscitando interés por programas de control del empleo de antibióticos (PCEA).Sin embargo, existe controversia sobre el diseño y la puesta en práctica de los mismos. Evaluamos un PCEA de tipo educativo basado en la elaboración de recomendaciones por un infectólogo. Métodos. Estudio de intervención sobre dos servicios (médico y quirúrgico) del hospital. Comparamos el consumo de antibióticos, la mortalidad, los reingresos por patología infecciosa y la incidencia de Staphylococcus aureus resistente a metilcilina (SARM) y Clostridium difficile entre el período de intervención y el período equivalente del año anterior. Realizamos una encuesta anónima a los trabajadores sanitarios de ambos servicios. Resultados. Evaluamos 101 tratamientos (80 pacientes). Efectuamos 77 recomendaciones que consistieron en suspender los antibióticos (39 por ciento), cambiarlos a la vía oral (31 por ciento), reducir el espectro antimicrobiano (24 por ciento) y ampliar el espectro antimicrobiano (6 por ciento). El 85 por ciento de las recomendaciones fueron aceptadas. El consumo en dosis diarias definidas (DDD)/100 estancias se mantuvo estable, pero el empleo por vía oral pasó de 12,5 a 18,6 DDD/ 100 estancias y el uso por vía parenteral descendió de 25,9 a 22,3 DDD/100 estancias. El gasto en antibióticos disminuyó un 19,4 por ciento (901.794 ptas). No hubo cambios en la mortalidad ni en los reingresos por patología infecciosa. Sin embargo, apreciamos un descenso en la incidencia de casos de SARM (3,7 por ciento a 0,8 por ciento; p < 0,05) y diarrea por C. difficile (1,2 por ciento a 0 por ciento; p = 0,05). El 100 por ciento de los trabajadores sanitarios se mostró partidario de extender el PCEA al resto del hospital. Conclusiones. Nuestro PCEA, basado en la asesoría por infectólogos, es muy bien aceptado y permite reducir el gasto de antibióticos mediante la simplificación del tratamiento. No afecta negativamente a la evolución clínica de los pacientes y podría contribuir, quizá, a disminuir la incidencia de ciertos patógenos nosocomiales (AU)

Short-course therapy for right-side endocarditis due to Staphylococcus aureus in drug abusers: cloxacillin versus glycopeptides in combination with gentamicin.

A prospective, randomized clinical trial among drug abusers was conducted to assess the efficacy and safety of a short course of a combination of a glycopeptide (vancomycin or teicoplanin) and gentamicin compared with a combination of cloxacillin and gentamicin for treatment of right-side endocarditis caused by Staphylococcus aureus. Therapeutic success was significantly more frequent with cloxacillin than with a glycopeptide. No adverse effects were noted among patients in the cloxacillin group. A 14-day course of vancomycin or teicoplanin plus gentamicin is ineffective in this instance because it is associated with a high rate of clinical and microbiological failure.

Characterization of a nosocomial outbreak caused by a multiresistant Acinetobacter baumannii strain with a carbapenem-hydrolyzing enzyme: high-level carbapenem resistance in A. baumannii is not due solely to the presence of beta-lactamases.

From February to November 1997, 29 inpatients at Ramón y Cajal Hospital, Madrid, Spain, were determined to be either colonized or infected with imipenem- and meropenem-resistant Acinetobacter baumannii (IMRAB) strains (MICs, 128 to 256 microg/ml). A wide antibiotic multiresistance profile was observed with IMRAB strains. For typing IMRAB isolates, pulsed-field gel electrophoresis was used. For comparative purposes, 30 imipenem- and meropenem-susceptible A. baumannii (IMSAB) strains isolated before, during, and after the outbreak were included in this study. The molecular-typing results showed that the outbreak was caused by a single IMRAB strain (genotype A). By cloning experiments we identified a class D beta-lactamase (OXA-24) encoded in the chromosomal DNA of this IMRAB strain which showed carbapenem hydrolysis. Moreover, the outer membrane profile of the IMRAB strain showed a reduction in the expression of two porins at 22 and 33 kDa when compared with genetically related IMSAB isolates. In addition no efflux mechanisms were identified in the IMRAB strains. In summary, we report here the molecular characterization of a nosocomial outbreak caused by one multiresistant A. baumannii epidemic strain that harbors a carbapenem-hydrolyzing enzyme. Although alterations in the penicillin-binding proteins cannot be ruled out, the reduction in the expression of two porins and the presence of this OXA-derived beta-lactamase are involved in the carbapenem resistance of the epidemic nosocomial IMRAB strain.

Molecular characterization of FOX-4, a new AmpC-type plasmid-mediated beta-lactamase from an Escherichia coli strain isolated in Spain.

A clinical strain of Escherichia coli (Ec GCE) displayed resistance to cefoxitin, cefotetan, cefotaxime, and ceftazidime. Susceptibility was not restored by the addition of clavulanic acid. Two beta-lactamases with apparent pIs of 5.4 and 6.4 were identified; the beta-lactamase with a pI of 6.4 was transferred by conjugation and associated with a 40-kb plasmid. Analysis of the nucleotide sequence showed a new ampC beta-lactamase gene that is closely related to those encoding the FOX-3, FOX-2, and FOX-1 beta-lactamases but whose product has four novel amino acid mutations, at positions 11 (M-->T), 43 (A-->E), 233 (V-->A), and 280 (Y-->H). This first cephamycinase from Spain was named FOX-4.

OXA-24, a novel class D beta-lactamase with carbapenemase activity in an Acinetobacter baumannii clinical strain.

Acinetobacter baumannii RYC 52763/97, a clinical isolate involved in a prolonged nosocomial outbreak at our hospital, was resistant to all beta-lactams tested, including imipenem and meropenem, which had MICs of 128 and 256 microg/ml, respectively. This strain synthesized three beta-lactamases: a plasmid-mediated TEM-1 beta-lactamase (pI 5.4), an AmpC-type chromosomal cephalosporinase (pI 9.4), and a novel, presumptively chromosomally mediated OXA-related enzyme (pI 9.0) named OXA-24. After cloning and sequencing, the deduced amino acid sequence of the OXA-24 beta-lactamase showed 40% homology with the OXA-10 (PSE-2) and OXA-7 beta-lactamases, 39% homology with the OXA-11 and OXA-5 enzymes, and 33% homology with the LCR-1 beta-lactamase. The amino acid sequence of the OXA-24 beta-lactamase contained the STFK motif found in serine beta-lactamases, but the typical class D triad KTG was replaced by KSG and the motif YGN was replaced by FGN. The OXA-24 beta-lactamase hydrolyzed benzylpenicillin and cephaloridine but lacked activity against oxacillin, cloxacillin, and methicillin. The enzymatic activity was inhibited by chloride ions and by tazobactam (50% inhibitory concentration [IC(50)], 0.5 microM), sulbactam (IC(50), 40 microM), and clavulanic acid (IC(50), 50 microM). Carbapenem MICs for an Escherichia coli transformant (pBMB-1) expressing the cloned OXA-24 enzyme had a fourfold increase. Relative V(max)/K(m) values of 13 and 6 were obtained with imipenem and meropenem, respectively, and a positive microbiological assay result with imipenem was obtained with a purified enzymatic extract of this transformant strain. Therefore, we consider this new beta-lactamase to be involved in the carbapenem resistance of A. baumannii RYC 52763/97.

Cloning, nucleotide sequencing, and analysis of the gene encoding an AmpC beta-lactamase in Acinetobacter baumannii.

A clinical strain of Acinetobacter baumannii (strain Ab RYC 52763/97) that was isolated during an outbreak in our hospital and that was resistant to all beta-lactam antibiotics tested produced three beta-lactamases: a TEM-1-type (pI, 5.4) plasmid-mediated beta-lactamase, a chromosomally mediated OXA-derived (pI, 9.0) beta-lactamase, and a presumptive chromosomal cephalosporinase (pI, 9.4). The nucleotide sequence of the chromosomal cephalosporinase gene shows for the first time the gene encoding an AmpC beta-lactamase in A. baumannii. In addition, we report here the biochemical properties of this A. baumannii AmpC beta-lactamase.

PCR-based DNA fingerprinting (REP-PCR, AP-PCR) and pulsed-field gel electrophoresis characterization of a nosocomial outbreak caused by imipenem- and meropenem-resistant Acinetobacter baumannii.

OBJECTIVE: To demonstrate the usefulness of REP-PCR and AP-PCR on molecular typing of A. baumannii isolates. METHOD: From February to November 1997, 29 inpatients at Ramón y Cajal Hospital, Madrid-23 in five intensive care units (ICUs) and six at two different medical departments-were either colonized or infected with imipenem- and meropenem-resistant Acinetobacter baumannii (IMRAB) strains (MICs of 64-256 mg/L). A wide antibiotic multiresistance profile was observed with IMRAB strains, and only tobramycin, sulbactam and colistin displayed valuable activity. For typing IMRAB isolates, repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR) and arbitrary primer sequence-based polymerase chain reaction (AP-PCR) methods were used and compared with pulsed-field gel electrophoresis (PFGE) as reference technique. For comparative purposes, 30 imipenem- and meropenem-susceptible A. baumannii (IMSAB) strains isolated before, during and after the outbreak were included in this study. RESULTS: The molecular typing results showed that the outbreak was caused by a single IMRAB strain (genotype 1). On the other hand, seven different genotypes were observed in the pre-, at- and post-outbreak strains tested by REP-PCR. Regarding AP-PCR, three of four at-outbreak IMSAB strains were indistinguishable from the IMRAB profile. Thus, with AP-PCR, only six genotypes were obtained, apart from the IMRAB genotype. CONCLUSION: Under our experimental conditions, REP-PCR had a higher discriminatory power than AP-PCR, with PFGE as reference technique. The REP-PCR technique is a useful and expeditious method for the epidemiologic characterization of A. baumannii nosocomial outbreaks, the results being comparable to those obtained with the PFGE technique.

Biochemical and genetic characteristics of TEM-29B, a novel extended spectrum beta-lactamase.

A clinical strain of Escherichia coli (strain Ec 41553) that was resistant to ceftazidime produced a TEM-type beta-lactamase with a pI of 5.4. Clavulanic acid restored the ceftazidime activity, thus suggesting an extended spectrum beta-lactamase (ESBL). The gene encoding ESBL was located in a plasmid of 57 kb. After cloning and sequencing, the ESBL (TEM-29B) showed one amino acid replacement with respect to the TEM-1 sequence, Arg-164 to His. This change increased mainly the rate of hydrolysis of ceftazidime but not of cefotaxime and aztreonam. The relevance of this substitution in the increase of ceftazidime MIC is thus stressed.

Zidovudine therapy protects against Salmonella bacteremia recurrence in human immunodeficiency virus-infected patients.

Fifty-five human immunodeficiency virus-infected patients with Salmonella bacteremia were studied to assess the rate of and causes for recurrence and to determine the influence on relapse of zidovudine, cotrimoxazole, and antimicrobial suppressive therapy according to the susceptibility of the isolates. Overall, 22% of patients relapsed in a median time of 87 days, independent of CD4 cell count, Salmonella serotype, or duration of antibiotic therapy. The use of zidovudine was associated with the lowest rate of recurrences compared with cotrimoxazole or amoxicillin as suppressive therapy. In the microbiologic assay, zidovudine showed bactericidal effect on Salmonella species at current dosages, and resistance to zidovudine was uncommon (2 cases, 4%). Due to its direct effect on Salmonella species, a zidovudine-containing regimen may protect against the recurrence of the disease.

Spread of amikacin resistance in Acinetobacter baumannii strains isolated in Spain due to an epidemic strain.

Sixteen amikacin-resistant clinical Acinetobacter baumannii isolates from nine different hospitals in Spain were investigated to determine whether the high incidence of amikacin-resistant A. baumannii was due to the dissemination of an amikacin-resistant strain or to the spread of an amikacin resistance gene. The epidemiological relationship studied by repetitive extragenic palindromic PCR and low-frequency restriction analysis of chromosomal DNA showed that the same clone was isolated in eight of nine hospitals, although other clones were also found. The strains were studied for the presence of the aph(3')-VIa and aac(6')-I genes, which encode enzymes which inactivate amikacin, by PCR. All 16 clinical isolates had positive PCRs with primers specific for the amplification of the aph(3')-VIa gene, whereas none had a positive reaction for the amplification of the aac(6')-I gene. Therefore, the high incidence of amikacin resistance among clinical A. baumannii isolates in Spain was mainly due to an epidemic strain, although the spread of the aph(3')-VI gene cannot be ruled out.

[in vitro activity of carbapenems against Enterobacteriaceae and Pseudomonas aeruginosa hyperproducers of group 1 chromosomal beta-lactamases]. / Actividad in vitro de los carbapenémicos frente a Enterobacteriaceae y Pseudomonas aeruginosa hiperproductoras de betalactamasas cromosómicas del grupo 1.

Resistance to imipenem and meropenem, reported sporadically in Enterobacteriaceae and more frequently in Pseudomonas aeruginosa, can be caused, among other mechanisms, by the combination of changes in permeability and hyperproduction of inducible chromosomal beta-lactamases. In this study, the in vitro activity of imipenem and meropenem was analysed by the agar dilution method against cefotaxime, ceftazidime, and aztreonam resistant clinical strains of Enterobacteriaceae (n = 202) and P. aeruginosa (n = 90). This phenotype is consistent with the hyperproduction of group 1 chromosomal beta-lactamases and was previously determined in stably derepressed mutants in the same species, obtained from strains with inducible beta-lactamase expression by selection with cefotaxime and ceftazidime. Likewise, the activity of imipenem and meropenem against the same number of clinical isolates susceptible to cefotaxime, ceftazidime, and aztreonam was evaluated. In general, imipenem and meropenem showed an excellent activity, which was intrinsically greater for meropenem against Enterobacteriaceae and P. aeruginosa organisms. Nevertheless, imipenem and meropenem activity was slightly affected on cefotaxime, ceftazidime, and aztreonam resistant isolates of E. cloacae (MIC90, 1 and 0.2 microgram/ml, respectively), E. aerogenes (1 and 0.2 microgram/ml), C. freundii (1 and 0.1 microgram/ml), M. morganii (1 and 0.5 microgram/ml), and S. marcescens (4 and 0.5 micrograms/ml). On the other hand, the activity of imipenem and meropenem against ceftazidime and aztreonam resistant isolates of P. aeruginosa was more significantly affected, with MIC90 values of 64 and 16 micrograms/ml, respectively.

Beta-lactam stability in frozen microdilution PASCO MIC panels using strains with known resistance mechanisms as biosensors.

The stability of amoxicillin/clavulanate, piperacillin/tazobactam, cefepime, imipenem, and meropenem in PASCO (PASCO System, DIFCO Laboratories, Detroit, MI, USA) frozen microdilution susceptibility panels stored for 16 weeks at -20 degrees C and -70 degrees C was evaluated. The increase in MIC values for the five American-Type Culture Collection (ATCC) quality control strains for susceptibility testing recommended by the National Committee for Clinical Laboratory Standards (NCCLS) and for 13 strains with different well-characterized resistance mechanisms was indicative of bioactivity deterioration. The overall agreement (+/- 1 twofold dilution) at purchase between the MIC values of PASCO frozen microdilution susceptibility panels and the standard agar dilution method was 97.7%. Minimum inhibitory concentration values for the associations of amoxicillin/clavulanate and piperacillin/tazobactam remained unchanged for the study period at -70 degrees C. In contrast, a carbapenem bioactivity decrease was detected only with strains having well-characterized resistance mechanisms from the 12th week onwards. At -20 degrees C, antibiotic deterioration with these latter strains was observed earlier than with ATCC strains: the activity of meropenem and imipenem remained unchanged only for the first 2 weeks, while a loss of activity was detected for amoxicillin/clavulanate and piperacillin/tazobactam at the 7th and 10th week, respectively. Cefepime was highly stable both at -20 degrees C and -70 degrees C. Strains with well-characterized resistance mechanisms should be used in routine quality control studies of antibiotic stability for susceptibility testing panels during the storage period.

Multicentre comparative study on the antibacterial activity of FK-037, a new parenteral cephalosporin.

The in vitro antibacterial activity of FK-037, a new parenteral cephalosporin structurally related to cefpirome and cefepime, was compared with that of cefotaxime, ceftazidime, aztreonam, cefpirome, cefepime, imipenem and meropenem against 1,837 clinical isolates obtained from three Spanish hospitals. FK-037 inhibited 90% of Enterobacteriaceae isolates at < or = 0.25 microgram/ml, with the exception of Enterobacter aerogenes (MIC90 1 microgram/ml), Enterobacter cloacae and Citrobacter freundii (MIC90 8 micrograms/ml). In cefotaxime- and ceftazidime-resistant Klebsiella pneumoniae strains producing SHV-2 and SHV-6 beta-lactamases, the activity of FK-037, cefpirome and cefepime was similar (MIC range 0.25-32 micrograms/ml). In Enterobacteriaceae strains hyper-producing chromosomally inducible beta-lactamases, FK-037 (MIC90 range, 0.25-8 micrograms/ml) was 8- to 16-fold more active than cefotaxime and ceftazidime but two- to eightfold less active than cefpirome and cefepime. FK-037 and cefpirome were twofold more active than ceftazidime and cefepime against Pseudomonas aeruginosa isolates, with MIC90 values of 16 micrograms/ml. The activity of FK-037, cefpirome and cefepime was two- to eightfold lower in ceftazidime-resistant derepressed Pseudomonas aeruginosa mutants. FK-037 (MIC range, 0.12-2 micrograms/ml) and the other beta-lactam agents tested were active against methicillin-susceptible staphylococci; however, only cefpirome and, particularly, FK-037 (MIC90 of 32 micrograms/ml) displayed some activity against methicillin-resistant strains. In penicillin-susceptible, -intermediate and -resistant Streptococcus pneumoniae isolates, the MIC90s of FK-037 were 0.03, 0.5 and 1 microgram/ml, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

New extended-spectrum TEM-type beta-lactamase from Salmonella enterica subsp. enterica isolated in a nosocomial outbreak.

A new extended-spectrum beta-lactamase was detected in a lactose-positive Salmonella enterica subsp. enterica strain that caused a nosocomial outbreak involving eight patients in a pediatric cardiology unit. This strain showed high levels of resistance to ceftazidime and aztreonam and relatively low levels of resistance to cefotaxime and ceftriaxone. Resistance was associated with a conjugative plasmid of 59 kb, which encoded a new beta-lactamase with an isoelectric point of 5.9 that strongly hydrolyzed ceftazidime and to a much lesser extent hydrolyzed cefotaxime. The enzyme activity was inhibited by clavulanate. The corresponding bla gene was cloned and sequenced. The deduced amino acid sequence showed three significant amino acid replacements with respect to the TEM-1 sequence: Arg-164-->His, Glu-240-->Lys, and Thr-265-->Met. This combination is unique among extended-spectrum beta-lactamases and served to characterize the new enzyme, TEM-27.

Right-sided endocarditis caused by Staphylococcus aureus in drug abusers.

A prospective, open, and randomized study of right-sided endocarditis caused by Staphylococcus aureus in drug abuse patients is reported. The following parenteral treatments were compared. Group A patients were treated with 2 g of cloxacillin every 4 h and 1.5 mg of gentamicin per kg of body weight every 8 h for 2 weeks. Group B patients were treated with teicoplanin at 10 mg/kg/12 h on the 1st to 3rd days, 6 mg/kg/12 h on the 4th to 7th days, and 7 mg/kg/24 h on the 8th days. Drug abusers with bacteremia caused by S. aureus and suggestive signs of endocarditis were included. Clinical failures were observed in one patient in group A and in four of six patients in group B. Three patients in group B developed breakthrough bacteremia with teicoplanin-susceptible strains on days +6, +14, and +19. Serum teicoplanin levels and serum bactericidal titers showed a decrease in the 2nd week, when dosages received were 7 mg/kg/day. In conclusion, in treatment of right-sided endocarditis caused by S. aureus in drug abusers with teicoplanin, the use of dosages of 7 mg/kg/day is not recommended even if patients have received dosages of 12 mg/kg/day during the 1st week.

Gene sequence and biochemical characterization of FOX-1 from Klebsiella pneumoniae, a new AmpC-type plasmid-mediated beta-lactamase with two molecular variants.

Klebsiella pneumoniae BA32, a clinical isolate from Buenos Aires, Argentina, was found to produce a plasmid-encoded beta-lactamase (FOX-1) which conferred resistance to broad-spectrum cephalosporins and cephamycins. Resistance could be transferred by conjugation or transformation into Escherichia coli K-12 via a 48.5-kb plasmid (pGLK1) that produced two FOX-1 molecular variants with isoelectric points of 6.8 and 7.2 and apparent molecular sizes of 37 and 35 kDa, respectively. The kinetic study revealed that the two variants had very similar substrate and inhibition profiles. These values resemble those of chromosomally mediated class C (group 1) cephalosporinases. The structural gene of FOX-1 (blaFOX-1) was cloned into a 2,270-bp PstI-PstI fragment and was expressed in E. coli TG1. The deduced 382-amino-acid sequence of FOX-1 exhibited a high degree of similarity with chromosomally encoded AmpC beta-lactamases of Pseudomonas aeruginosa, Serratia marcescens, Enterobacter cloacae, E. coli, and Citrobacter freundii. These findings suggest that FOX-1 is a plasmid-mediated AmpC-type beta-lactamase that is encoded by a single gene and that has two molecular variants.

Development of an enzyme-linked immunosorbent assay method for typing and quantitation of Klebsiella pneumoniae lipopolysaccharide: application to serotype O1.

We describe a method for the typing and quantitation of Klebsiella pneumoniae serotype O1 lipopolysaccharide (LPS) based on inhibition in an enzyme-linked immunosorbent assay of a reaction of known O1 LPS antigen and anti-O1 antibody by unknown LPS extracts. Serotype O1 was found in 32% of the 124 K. pneumoniae clinical isolates tested, showing that this serotype is frequent among the eight O serotypes which have been described previously.