Estudio de susceptibilidad a cefalosporinas de primera generación en enterobacterias aisladas de urocultivo, según criterios CLSI y EUCAST / Susceptibility to first-generation Cephalosporins in Enterobacteriaceae isolated from urine culture according to CLSI and EUCAST breakpoints

Resumen Actualmente se recomienda el uso de cefazolina para determinar la susceptibilidad a cefalosporinas orales de primera generación en cepas de enterobacterias en ITU no complicada. Nuestro objetivo fue establecer la susceptibilidad a cefalosporinas orales en cepas urinarias según puntos de corte para cefalotina o cefazolina y la correlación de susceptibilidad entre cefazolina y cefadroxilo. Se estudió la concordancia entre cefalotina y cefazolina en 52 cepas por método de Kirby-Bauer y Vitek XL. En Escherichia coli fue de 0% para VitekXL y 50% para Kirby-Bauer. La concordancia entre cefazolina y cefadroxilo fue 95,6%. En el laboratorio debiera usarse cefazolina para determinar susceptibilidad a cefalosporinas orales de primera generación. La concordancia entre cefazolina y cefadroxilo sugiere que cefazolina podría predecir susceptibilidad para cefadroxilo.

Currently, the use of cefazolin is recommended to determine the susceptibility to first-generation oral cephalosporins in strains of enterobacteria in uncomplicated UTI. We determined susceptibility differences to oral cephalosporins in urinary strains according to cefazolin or cefalotin breakpoints and the correlation of susceptibility between cefazolin and cefadroxil. We studied 52 strains with cefalotin and cefazolin by disk-diffusion and MIC (Kirby-Bauer and Vitek XL) and a subgroup by disk-diffusion for cefadroxil. Agreement among different methods was 100% for K. pneumoniae and Proteus spp. In Escherichia coli, agreement for Vitek and disk-diffusion were 0 and 50% respectively. Susceptibility to first generation cephalosporins in E. coli should be determined with cefazolin. Agreement between cefazolin and cefadroxil suggests that cefazolin could also predict the susceptibility of cefadroxil.

Resistance pattern of clinical isolates involved in surgical site infections

Wound infections due to the incursion of microbes need to be averted or to heal the wounds by antibiotics. Antibiotics are not only aid in cure of infections but also help to prevent the flourishing and production of one or more species of microorganism, resultant in purulent discharge. This current study was carried out to evaluate the resistance pattern of clinical isolates from surgical site infections by the Kirby Bauer disc diffusion method. A total of 257 clinical isolates were collected from different hospitals in Karachi and evaluated by using fifteen antibiotics belonging to different groups. Staphylococcus aureus [n=87], Escherichia coli [n=76], Pseudomonas aeruginosa [n=56], Proteus [n=21] and Klebsiella [n=17] species are the most common clinical isolates of surgical site infections. Among the semi-synthetic penicillins, ampicillin was found to be resistant to nearly all clinical isolates but amoxicillin was moderately sensitive to S. aureus. Combinations of semi-synthetic penicillins are more sensitive than the penicillin alone. Co-amoxiclave exhibits superior sensitivity to all the surgical infection isolates except Pseudomonas aeruginosa which showed 68.75% resistance. Pseudomonas aeruginosa was highly resistant to cephalosporin except ceftraixone which showed 21.88% resistance. S. aureus was slightly responsive to cefazolin, cephradine, cefaclor, ceftizoxime, cefuroxime and ceftriaxone. E. coli, Gram-negative clinical isolate was showed 25% and 31.25% resistance to ceftriaxone and cefuroxime. In the Klebsiella species, 71.42% and 64.29% resistance to cefazolin and cefuroxime respectively, was observed. Aminoglycosides such as gentamycin and tobramycin were found to be more susceptible to all the clinical isolates. Quinolones like ofloxacin and enoxacin were showed good sensitivity to nearly all the clinical isolates. On the basis of the present study, it is recommended to adopt a rational use of antibiotics in prophylaxis and the utilization of a coordinated scheme of surgical wound inspections.

Caracterización clínica y molecular de bacteriemias causadas por enterobacterias productoras de β -lactamasas de espectro extendido: 2004-2007 / Clinical and molecular characterization of ESBL-producing enterobacteria isolated from bacteremia in a university hospital

Introduction: Extended-spectrum-β-lactamases (ESBL) are plasmid-encoded enzymes that confer resistance to multiple antimicrobials. ESBL-producing enterobacteria that cause bacteremia limit therapeutic options and increase mortality. Objective: To perform a clinical and molecular description of bacteremia caused by ESBL-producing enterobacteria. Method: We retrospectively studied the cases of bacteremia due to ESBL-producing Escherichia coli, Klebsiella pneumoniae and Proteus spp in adults admitted to a university hospital during the years 2004-2007. We reviewed the clinical records and antimicrobial susceptibility patterns. Molecular typing was performed by polymerase chain reaction and study of clonality by pulsed-field electrophoresis. Results: We found a prevalence of 9.8 percent ESBL in enterobacteria causing bacteremia. Decreased susceptibility to quinolones and aminoglycosides was observed, without resistance to carbapenems. The predominant ESBL types were CTX-M (96 percent), TEM (62 percent) and GES (28 percent). 79 percent of the strains presented more than one type of ESBL. Clinical analysis revealed high prevalence of risk factors, previous use of antimicrobials and of invasive devices. There was no significant clonality. Conclusion: The presence of ESBLs in bloodstream infections is a clinical problem that must be considered when choosing empiric therapy.

Introducción: β-lactamasas de espectro extendido (BLEE) son enzimas plasmidiales que confieren resistencia a múltiples antimicrobianos. Las bacteriemias por enterobacterias productoras de BLEE restringen las opciones terapéuticas y aumentan la mortalidad. Objetivo: Realizar una descripción clínica y molecular de las bacteriemias causadas por enterobacterias productoras de BLEE. Método: Se estudiaron retrospectivamente los casos de bacteriemia por Escherichia coli, Klebsiella pneumoniae y Proteus spp. confirmadas para BLEE, en adultos ingresados en un hospital universitario durante los años 2004-2007. Se revisaron los registros clínicos y de susceptibilidad. Se realizó tipificación molecular por reacción de polimerasa en cadena y estudio de clonalidad por electroforesis de campo pulsado. Resultados: Se identificó una prevalencia de BLEE de 9,8 por ciento en enterobacterias causantes de bacteriemias. Se observó susceptibilidad disminuida a quinolonas y aminoglucósidos, sin resistencia a carbapenémicos. Los tipos de BLEE predominantes fueron CTX-M (96 por ciento), TEM (62 por ciento) y GES (28 por ciento). El 79 por ciento de las cepas presentó más de un tipo de BLEE. El análisis clínico reveló alta frecuencia de patologías de riesgo, uso previo de antimicrobianos y uso de dispositivos invasores. No se encontró clonalidad significativa. Conclusión: La presencia de BLEE en bacteriemias constituye un problema clínico que debe ser considerado al elegir la terapia empírica.

Antimicrobial activity of erythromycin and clarithromycin against clinical isolates of Escherichia coli, Staphylococcus aureus, klebsiella and proteus by disc diffusion method

Fifty clinical isolates comprising of Escherichia coli, Staphylococcus aureus, Klebsiella and Proteus were collected from different local pathological laboratories and their resistant pattern against two well known macrolides; erythromycin and clarithromycin were studied using disc diffusion method. Klebsiella [41.67% against erythromycin and 58.34% against clarithromycin] and Proteus [66.67% against erythromycin and clarithromycin] species were found to be more resistant against the studied macrolides as compared to the rest of organisms. In case of Staphylococcus aureus and Escherichia.coli, resistant found were 27.78% and 23.54% against erythromycin and 22.23% and 35.30% against clarithromycin respectively. It is concluded from these figures that microbial resistance against these macrolides are increasing in our population which is alarming and therefore it is recommended to physicians to prescribe these antibiotics unless no other substitute is available in clinical practices

Risk factors for Hospital-Acquired Pneumonia in nonventilated adults

Although most recent publications focus on Ventilator-associated Pneumonia, Non-Ventilator-associated Hospital-acquired pneumonia (NVHAP) is still worrisome. We studied risk factors for NVHAP among patients admitted to a small teaching hospital. Sixty-six NVHAP case patients and 66 controls admitted to the hospital from November 2005 through November 2006 were enrolled in a case-control study. Variables under investigation included: demographic characteristics, comorbidities, procedures, invasive devices and use of medications (Sedatives, Antacids, Steroids and Antimicrobials). Univariate and multivariable analysis (hierarchical models of logistic regression) were performed. The incidence of NVHAP in our hospital was 0.68 percent (1.02 per 1,000 patients-day). Results from multivariable analysis identified risk factors for NVHAP: age (Odds Ratio[OR]=1.03, 95 percent Confidence Interval[CI]=1.01-1.05, p=0.002), use of Antacids (OR=5.29, 95 percentCI=1.89-4.79, p=0.001) and Central Nervous System disease (OR=3.13, 95 percentCI=1.24-7.93, p=0.02). Although our findings are coherent with previous reports, the association of Antacids with NVHAP recalls a controversial issue in the physiopathology of Hospital-Acquired Pneumonia, with possible implications for preventive strategies.

Choice of antibiotic for empirical therapy of acute cystitis in a setting of high antimicrobial resistance.

BACKGROUND: A high prevalence of antimicrobial resistance among urinary isolates in the Garhwal region of Uttaranchal. AIMS: To identify the most appropriate antibiotic for empirical treatment of community-acquired acute cystitis on the basis of local antimicrobial sensitivity profile. SETTINGS AND DESIGN: A prospective clinico-microbiological study including all clinically diagnosed patients with community acquired acute cystitis attending a tertiary care teaching hospital over a period of three years. METHODS AND MATERIAL: Clean-catch midstream urine specimens, from 524 non-pregnant women with community-acquired acute cystitis, were subjected to semi-quantitative culture and antibiotic susceptibility by the Kirby- Bauer disc diffusion method. A survey was also conducted on 30 randomly selected local practitioners, to know the prevalent prescribing habits in this condition. STATISTICAL ANALYSIS: The difference between the susceptibility rates of E. coli isolates to Nitrofurantoin and the other commonly prescribed antibiotics was analysed by applying the z test for proportion. RESULTS: 354 (67.5%) specimens yielded significant growth of E. coli.> 35% of the urinary E.coli isolates were resistant to the fluoroquinolones, which were found to be the most commonly used empirical antibiotics in acute cystitis. Resistance was minimum against Nitrofurantoin (9.3%, 33) and Amikacin (11.0%,39).> 80% of the fluoroquinolone-resistant strains were found to be sensitive to Nitrofurantoin. CONCLUSION: The best in vitro susceptibility profile in our study has been shown by Nitrofurantoin and a significantly high proportion of the urinary E. coli isolates have already developed resistance to the currently prescribed empirical antibiotics, viz. the fluoroquinolones. In view of these in vitro susceptibility patterns, a transition in empirical therapy appears imminent.

[Antibiotics for causative microorganisms of urinary tract infections]

Urinary tract infection is a common bacterial disease in children which may cause chronic renal failure and hypertention. Many reports suggest that the rate of antibiotic resistance to infectious organisms is increasing. Therefore periodic surveillance of resistance rates is needed to ensure that appropriate recommendations can be made for better management and preventing of late sequelae. In this cross sectional descriptive study we investigate the results of urinalysis, urine culture and antibiotic sensitivity of the isolated organisms in the urine of 1556 children aged under 10 years in Mashhad city between April 2001 and June 2002. Described parameters are age, sex, incidence of significant bacteriuria, leucocyturia, causative bacterial agents, and antibiotic sensitivity pattern. The most common age group in both sexes was infantile period. Median age was 20.3 months in boys and 47.5 months in girls. E.coli, klebsiella and proteus were the causative organisms in 87.3%. They were sensitive to cefotaxime, cefixime, cephalotin, amikacin, ciprofloxacin, nitrofurantoin and gentamicin in more than 96% while resistant to trimetoprim-sultamethoxazol in about 75%. We recommend, with regard to continuous changing in causative microorganisms isolated from patients with urinary tract infection and antibiotic sensitivity pattern, as a guideline for physicians, to determine bacterial sensitivity in populations yearly

Antibacterial activity of lactose-binding lectins from Bufo arenarum skin

Amphibians respond to microbial infection through cellular and humoral defense mechanisms such as antimicrobial protein secretion. Most humoral defense proteins are synthetized in the skin. In this study we isolated two beta-galactoside-binding lectins with molecular weights of 50 and 56 KDa from the skin of Bufo arenarum. These lectins have significant hemagglutination activity against trypsinized rabbit erythrocytes, which was inhibited by galactose-containing saccharides. They are water-soluble and independent of the presence of calcium. The antimicrobial analysis for each lectin was performed. At mumolar concentration lectins show strong bacteriostatic activity against Gram negative bacteria (Escherichia coli K12 4100 and wild strains of Escherichia coli and Proteus morganii) and Gram positive bacteria (Enterococcus faecalis). The antibacterial activity of these lectins may provide an effective defense against invading microbes in the amphibian Bufo arenarum.

Invitro comparative evaluation of aminoglycosides at a cancer centre.

A comparative study of in vitro activity of amikacin, gentamicin, netilmicin, tobramycin and isepamicin was done. A total of 200 clinical isolates of Gram negative organisms from various clinical sources were tested. E.Coli was the most frequently isolated organism followed by Pseudomonas spp., Klebsiella spp., Proteus spp., Acinetobacter spp. and Enterobacter spp. Of the 5 aminoglycosides tested, isepamicin showed the highest numbers of susceptible isolates followed by amikacin, netilmicin, gentamicin and tobramycin. MIC 90 value of isepamicin was lower as compared to amikacin.

Antibiogram of aerobic pyogenic isolates from wounds and abscesses of patients at Rawalpindi

During the years 1996-1998 pus specimens from wounds and abscesses of patients were cultured on to MacConkey and blood agar plates in microbiology section, pathology laboratory of Rawalpindi Medical College. Organisms were isolated from 220 samples. Staphylococcus aureus was the most common Pathogen [49%] followed by E.coli [25.9%] Klebsiella [9.5%], Pseudomonas aeruginosa [8.6%], Proteus sp [4%] and acinetobactor sp [2.7%]. Quinolones, aminoglycosides and cephalosporins were found to be the most effective antimicrobial in vitro while amoxicillin, minocycline and trimethoprim-Sulphamethaxazole were least effective

In vitro activity of penicillins, cephalosporins, aminoglycosides and aztreonam against clinical isolates of fluoroquinolone - resistant [FQR] aerobic gram-negative bacilli

A retrospective analysis of antibiotic susceptibility pattern of 634 clinical isolates of aerobic gram-negative bacilli isolated from urine, sputum, ear discharge and wounds was performed. The bacteria consisted of 270 isolates of Escherichia coli, 265 Pseudomonas aeruginosa, 58 Klebsiella sp., and 41 isolates of Proteus sp. Out of these 634 isolates, 191 [30.1%] were found resistant to three commonly used fluoroquinolones that is ciprofloxacin, ofloxacin and enoxacin. Out of 270 isolates of Escherichia coli, 104 [38.5%] were fluoroquinolone-resistant [FQR] while 59/265 [22.3%] isolates of Pseudomonas aeruginosa, 20/58 [34.5%] isolates of Klebsiella sp., and 8/41 [19.5%] isolates of Proteus sp. were found FQR. Cummulative susceptibility of these 191 FQR isolates to other eleven antibiotics was; amoxycillin 9.4%, coamoxy-clav 23%; coampi-sulbac 30.4%; gentamicin 68.1%; tobramycin 70.2%; cephradine 16.7%; cefaclor 25.6%; ceftizoxime 49.2%; ceftazidime 48.7%; cefuroxime 36.7% and aztreonam 26.2%

Consumo de antimicrobianos y variación de resistencia de bacilos Gram negativos en un período de diez años: Hospital San Juan de Dios, Chile / Consumption of antimicrobials and variation of Gram negative bacilli resistance in a 10 years period: Hospital San Juan de Dios, Chile

El problema de la resistencia bacteriana a antimicrobianos presenta una elevada prevalencia, con serias implicancias desde el nivel de salud pública hasta los resultados de la terapia individual. Los objetivos del trabajo fueron estudiar niveles de resistencia y su relación con el consumo de antimicrobianos de uso libre (ampicilina, gentamicina) y restringido (amikacina, cefazolina, cefotaxima) en bacilos gram negativos (E. Coli, K. pneumoniae, proteus sp., P. aeruginosa, A. baumannii) en el período de 1987 a 1997 en el Hospital San Juan de Dios. E. coli incrementó su resistencia a ampicilina y cefazolina, relacionado a un aumento en su consumo. Presentó baja resistencia a aminoglicósidos y antibioticos de uso restringido y poca variación de ésta a pesar de variar su consumo. La resistencia de K. pneumoniae a gentamicina disminuyó significativamente la última década, asociada a disminución en su consumo. Para cefotaxima y amikacina hubo relación entre resistencia y consumo de antimicrobianos. La resistencia de proteus sp disminuyó para antibióticos de uso libre como ampicilina, y gentamicina, esta última en clara relación con el consumo. P. aeruginosa mostró baja resistencia a amikacina y alta a gentamicina, mientras que A. baumannii presentó alta resistencia a ambas. La existencia de factores no considerados en el estudio, tales como la velocidad variable de adquisición de resistencia, características de cada paciente, medidas epidemiológicas implementadas y ocurrencia de epidemias, nos impide descartar la existencia de una fuerte relación causal entre consumo y resistencia. Tal relación es avalada en diversos estudios mediante una asociación consistente, una variación concurrente, un patrón dosis - respuesta y la presencia de un modelo biológico que explica el fenómeno. Junto a las medidas de control de infecciones, la clave para combatir la resistencia bacteriana es el uso prudente de antimicrobianos. La monitorización del consumo de antibióticos en el nivel hospitalario (mediante el DDD) y de las variaciones en la resistencia a éstos, permite implementar estrategias eficientes de manejo del problema