Erythromycin-resistant Streptococcus pyogenes in Argentina

Erythromycin (ERY) resistance in Streptococcus pyogenes has recently emerged as a problem of growing concern all through the world. We are presenting the comparison of results of the continuous surveillance of erythromycin resistance in S. pyogenes performed since 1989 in the Hospital de Pediatría J.P.Garrahan of Buenos Aires City, with independently observed rates in other five centers of Buenos Aires and seven centers of six other Argentinian cities, obtained between 1999 and 2001. A significant increase of erythromycin resistance was observed among S. pyogenes isolated in the Hospital Garrahan (6.6% in 1998-1999 to 9.9% in 2000). Similar trends were also detected in other centers of other Argentinian cities when recent data were compared to results of a multicenter study performed in 1995. However, lower rates of resistance were recorded in Mendoza, Cipolletti and Neuquén in comparison with data of 1995, 1998 and 1998 respectively. The reason of such decreasing resistance rates deserves to be investigated. The average of ERY-resistance rates obtained in the surveyed centers was 6.7% (range 0.5-14.1%). Control of antimicrobial use should be performed to warrant the future effectiveness of macrolide antibiotics regarding the positive association between use and resistance. These results also suggest that susceptibility tests for macrolides should be performed whenever S. pyogenes is isolated in Argentina.

La resistencia a la eritromicina en Streptococcus pyogenes ha emergido en los últimos tiempos como un problema creciente en todo el mundo. En este trabajo se presenta la comparación de los resultados de la vigilancia continua de la resistencia a la eritromicina que se viene realizando en el Hospital de Pediatría J.P.Garrahan de Buenos Aires desde 1989, con resultados independientes de otros cinco centros de la ciudad de Buenos Aires y siete de otras seis ciudades argentinas, obtenidos entre 1999 y 2001. Se observó un aumento significativo en el Hospital Garrahan (6.6% en1998-1999 a 9.9% en el año 2000) y una tendencia similar en otros centros de diversas ciudades argentinas si secomparan estos datos con los de un estudio multicéntrico realizado en 1995. No obstante, se registraron menoresporcentajes de resistencia en Mendoza, Neuquén y Cipolletti, en relación a lo hallado en 1995, 1998 y 1998respectivamente. La razón de esta disminución merece ser investigada. El porcentaje promedio de resistencia aeritromicina obtenido en los distintos centros participantes de este estudio fue de 6.7% (rango 0.5-14.1%). Debeefectuarse un control en el uso de estos antibióticos para garantizar la efectividad futura de los macrólidos, teniendo en cuenta la asociación estrecha entre uso y resistencia. Estos resultados sugieren que deberían realizarse pruebas de sensibilidad a los macrólidos para todos los aislamientos de S. pyogenes en la Argentina.

Análisis de 942 episodios de bacteriemia en una institución cardiológica: experiencia con el sistema Bact-Alert / Analysis of 942 episodes of bacteremia in a cardiology hospital

Entre enero de 1996 y octubre de 1999, se estudiaron en el Instituto Cardiovascular, Fundación Favaloro, 10.793 hemocultivos y 942 episodios de bacteriemia. Utilizando el Sistema Bact-Alert (Organon Teknika) estos cultivos fueron positivos en 1.883 casos. 94 por ciento de los episodios fueron monomicrobianos. Del total de espisodios se aislaron 45 por ciento de bacterias gram positivas, 52 por ciento de gram negativas y 3 por ciento de hongos. Los focos de infección asociados fueron: 36,5 por ciento infecciones asociadas a catéteres, 9 por ciento mediastinitis, 9 por ciento infecciones urinarias, 6 por ciento neumonías, 6 por ciento endocarditis, 6 por ciento infecciones intraabdominales, 2,6 por ciento infecciones de prótesis, 2,5 por ciento infecciones de piel y partes blandas, 0,3 por ciento pericarditis, 0,2 por ciento meningitis, 2 por ciento empiemas, 0,2 por ciento aneurismas de aorta, 0,2 por ciento infecciones por líquido de infusión contaminado, 0,1 por ciento artritis, 0,1 por ciento endarteritis, 0,1 por ciento diarreas, y foco desconocido en 21 por ciento de los casos. La mediana en horas para positivización de los hemocultivos acorde a los distinto focos fue: 16,4 para infecciones asociadas a catéteres, 19,2 mediastinitis, 14,2 neumonías, 14,5 endocarditis, 11,8 infecciones intraabdominales, 13 infecciones urinarias y 19 para bacteremias de origen desconocido. El valor fue de 30,5 h para las contaminaciones. El 72 por ciento de los hemocultivos positivos con un microorganismo considerado como clínicamente significativo se detectó a las 24 h, 87 por ciento dentro de las 48 h y sólo 1 por ciento entre el 5§ y 7§ día. No hubo diferencias importantes en el tiempo de detección de hemocultivos positivos acorde a distintos focos. Tampoco resultó de utilidad la incubación de las botellas más allá del 5§ día, excepto para circunstancias especiales, puesto que no mejoró la recuperación de microorganismos clínicamente significativos.

Cultivos cuantitativos de catéteres por la técnica de Brun Buisson / Quantitative cultures from catheters, using the Brun Buisson technique

The objective of this collaborative work carried out in the Fundación Favaloro and the Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia, was to determine optimal conditions for incubation (time and atmosphere) of quantitative cultures of catheters processed according to the technique of vortex agitation (Brun Buisson method). From 689 processed catheters, 551 yielded negative cultures. From the 138 positive cultures, 125 yielded monomicrobial cultures and 13 polimicrobial cultures (total number of microorganisms was 151). In the last situation each micoorganism was considered on an individual basis. A total of 58 episodes of catheter related bacteremias occurred, being 52 monomicrobial and 6 polimicrobial (total number of microorganisms was 64). When colony counts were compared in aerobic and in 5-10 CO2 atmospheres, a very good correlation was obtained (p = 0.27; r2 = 0.9268). No advantage was observed by incubating plates for more than 48 hours. Colony counts performed at the second versus the third day, and at the second day versus the seventh, gave very good correlation (p = 0.10 and r2 = 0.9996; p = 0.31 and r2 = 0.9995, respectively).

Utilidad de la incubación prolongada y de los subcultivos terminales de hemocultivos de pacientes inmunocomprometidos / Utility of prolonged incubation and terminal subcultures of blood cultures from immunocompromised patients

The value of blind terminal subcultures (7 and 30 days) and prolonged incubation (30 days) of blood cultures from immunosuppressed patients was analyzed in the Fundación Favaloro, the Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia and the Hospital de Niños Ricardo GutiÚrrez. A total of 2707 blood cultures and 369 patients were included (transplantation of solid organs 154, oncohematologic disorders 106 and solid tumors 109). Bact-Alert bottles were incubated at 35 degrees C for 30 days in the Bact-Alert System. Bottles with positive signals were routinely removed, and aliquots of the broth were Gram stained and subcultured aerobically in chocolate agar and Sabouraud agar. A total of 136 bacteremic episodes were obtained. The positivization time of blood cultures was 81.6 at 24 h, 93.3 at 48 h, 94.5 at 72 h and 97.7 within 7 days. Only 3 (2.2) episodes were positive by blind terminal subcultures and 1 (0.75) by prolonged incubation (14 days). The median time and range of positivization in hours were 13.8 and 2.2-168, respectively. The microorganisms isolated were coagulase negative staphylococci (n = 24), Klebsiella pneumoniae (n = 22), Staphylococcus aureus (n = 21), Escherichia coli (n = 18), Acinetobacter spp (n = 9), Candida spp (n = 8), Pseudomonas aeruginosa (n = 6), Enterobacter cloacae (n = 5), Stenotrophomonas maltophilia (n = 5), Enterococcus faecalis, Salmonella spp and Capnocytophaga sputigena (n = 2), Enterobacter aerogenes, Enterococcus faecium, Citrobacter diversus, Candida albicans, Klebsiella oxytoca, Chryseomonas luteola, Serratia marcescens, Abiotrophia spp, Campylobacter jejuni, Moraxella catarrhalis, Moraxella urethralis, Neisseria sicca, beta hemolytic group G streptococci, Rhodococcus equi, Micrococcus spp, Cryptococcus neoformans and Streptococcus mitis (n = 1). In our experience, blind terminal subcultures and prolonged incubation of blood cultures from immunosuppressed patients are unnecessary and cost expensive.

Modelo experimental de infeccion por Helicobacter pylori en el raton. Estudio del dano gastrico producido por indometacina / Experimental model of infection of Helicobacter pylori in the mouse. A study of gastric damage caused by indomethacin

INTRODUCTION: The action of non-steroidal anti-inflammatory drugs (NSAIDs) on the Helicobacter Pylori (Hp) infected mucosa is a matter of debate. Some authors consider them to cause additive iatrogeny whilst others attribute a purportedly protective action to them. The development of on experimental animal model could help clarify this phenomenon. OBJECTIVES: 1--To develop an animal model of Hp gastric infection. 2--To evaluate the aggressiveness of NSAIDs in this model. MATERIALS AND METHODS: Male 6 month old BALC/C mice weighing 38 g were studied. Pylori Hp infection was ruled out. On three occasions, in the same week, 18 mice were inoculated intra-gastrically with 0.6 ml of Hp culture broth (brain-heart infusion) containing 1 x 10 8-1 x 10 9 CFU/ml. Another group of mice were inoculated with sterile saline. After two months the mice were killed and their stomachs studied. They were divided into groups: a) 6 Hp negative control mice. b) 8 Hp negative mice with prior intra-peritoneal injection of 25 mg/Kg indomethacin (24 hs.) c) 8 mice inoculated with Hp with indomethacin. d) 8 mice inoculated with Hp, without indomethacin. The stomachs were opened along the greater curvature and photographed macroscopically in order to map the necrotic area. The antrums were biopsied to test for urease and separate antrum and body specimens were send for staining with Warthin-Starry H & B and histopathology. RESULTS: All the mice inoculated with Hp acquired the infection. The necrotic area was larger in Group B: 55.5 +/- 7.87 mm than in Group C: 15 +/- 1.82 mm P < 0.00019. HISTOLOGY: Group A: normal mucosa. Group B: extensive coagulation necrosis and focal erosions. Group C: ulcers with inflammatory infiltrate and smaller necrotic area, presence of Hp on the surface epithelium. Group D: no ulcers, Hp present. CONCLUSION: An animal model of Hp infection was successfully developed Hp infection could play a potentially protective role against indomethacin aggression in the mouse.

Sistema bact-alert de hemocultivos: evaluación de los subcultivos terminales / Bact-Alert system for hemocultures: evaluation of terminal subcultures

Few laboratory microbiological procedures are as important as the isolation of microorganisms from blood. To evaluate the usefulness of the terminal subcultures, 5669 blood cultures giving negative results after 7 days of incubation in the Bact/Alert System (Organon Teknika) were studied. Bottles were distributed as follows: 1562 adult aerobic bottles, 119 adult anaerobic bottles, 3960 pediatric bottles and 28 FAN bottles. From 5669 blood cultures, 10 subcultures that yielded growth had not been detected by the system. These included 5 adult aerobic bottles and 5 pediatric bottles, 7 of these microorganisms were considered contaminants according to clinical data (2 Micrococcus spp, 1 staphylococci coagulase negative, 1 Burkholderia cepacia, 1 Peptoestreptococcus spp, 1 Corynebacterium spp, 1 Scedosporium spp) while the other 3 were considered true bacteremia (1 Pseudomonas aeruginosa, 1 Proteus mirabilis, 1 Streptococcus sanguis), although no one made any change in treatment on the basis of the previous isolation. Based on these results the routinary utilization of terminal subcultures is not advisable and should be used only for special cases or a second system of blood culture should be added according to clinical or epidemiological data.

Hemocultivos: utilidad de los antibiogramas presuntivos / Blood cultures: use of presumptive antiobiograms

Mortality associated to bacteremia varies between 20 and 40 depending upon several factors, such as focus of infection, microorganism, host conditions, etc. It has also been documented that mortality may double when the patient does not receive antibiotic treatment to which the microorganism is susceptible. The objective of our work has been to determine the correlation between disk diffusion antibiogram according to NCCLS guidelines, from isolated colonies, and the one performed directly from the blood culture flask. During 1996, in the Institute of Cardiology and Cardiovascular Surgery (ICYCC) in Buenos Aires City, 81 episodes of bacteremia were studied. In every case, an antibiogram was carried out: 1) from the bottle: a- Directly (D), harvesting 20 microliters in Mueller Hinton agar, b- Diluted (d), previous centrifugation and Gram staining to adjust turbidity equivalent to 0.5 Mc Farland; 2) from isolated colonies, according to NCCLS guidelines. There were almost no major errors, except with two strains of Enterobacter cloacae versus cephalotin. The diluted method was not so convenient to read inhibition zones, especially with staphylococci. With gram-positive bacteria, the main problems appeared in the direct method with erythromycin, oxacillin and ciprofloxacin because of minor errors. With gram-negative bacteria, major errors were observed in the direct method, mainly with piperacillin (7) and to a lesser extent with piperacillin tazobactam (2). Except for imipenem, trimethoprim sulfamethoxazoie and cefotaxime, all antimicrobial agents presented minor errors with both methodologies. Based upon the high rate of minor errors, we consider it is important to confirm results obtained with the standard technique (NCCLS), considering as presumptive those results from the blood culture bottles (D and d).

Evaluación de la reincubación de hemocultivos positivos por el sistema BACT-ALERT para la detección de bacteriemias polimicrobianas / Evaluation of the reincubation of positive blood cultures for detection in the BACT-ALERT system for the detection of polymicrobial bacteremia

Between February and September 1997, 6588 blood cultures at the Instituto de CardiologÝa y CirugÝa Cardiovascular and Hospital de Niños Ricardo GutiÚrrez were studied by using the Bact-Alert system (Organon Teknika) 341 contaminants and 294 episodes of bacteremia (600 samples) were analyzed. From these samples, 280 (95.3) were monomicrobial episodes and 14 (4.7) polymicrobial episodes. Positive blood cultures detected by the Bact-Alert system were processed and then reincubated during 7 days, when they were Gram stained and subcultured in blood agar, chocolate agar (both in 5-10 CO2), laked blood agar supplemented with hemin and vitamin K in anaerobic atmosphere (only anaerobic bottles) and CLDE (aerobic conditions). Following reincubation, 3 out of 14 polymicrobial bacteremias were detected, rising the level of detection from 3.7 to 4.7. Taking into account the total number of bacteremias, only in 3 out of 294 (1), a second microorganism was detected. Otherwise, in blood cultures where a contaminating microorganism was initially isolated, no further isolates representing a true bacteremia were recovered. Reincubation and terminal subculture of initially positive blood cultures did not provide relevant data in order to change therapeutic measures in the studied population. Due to the increase in costs and labor we consider that this methodology is not routinely advised.

Actividad in vitro de trovafloxacina, otras fluoroquinolonas y de diferentes antimicrobianos frente a aislamientos clínicos. Grupo colaborativo WHONET-Argentina / [In vitro activity of trovafloxacin, of other fluoroquinolones and of related antimicrobials against clinical isolates. Grupo colaborativo WHONET-Argentina]

The in vitro activity of trovafloxacin (TRV) has been evaluated in comparison with that of other antimicrobial agents against 5671 clinical isolates recovered by representative institutions of different provinces in our country. The resistance percentage to gentamicin and third generation cephalosporins among enterobacteriaceae was high: 17

respectively, with a considerable variation according to the analyzed species. The resistance to ciprofloxacin (CIP) and TRV affected approximately 9

of the isolates, without significant differences between both drugs. Fluoroquinolones (FQ) presented excellent activity on 166 isolates of Salmonella spp., 208 of Shigella flexneri and 76 of Shigella sonnei, where only one S.sonnei isolate was resistant to CIP, but susceptible to TRV. About half the isolates of Salmonella spp. and S.sonnei and almost all S.flexneri isolates were resistant to ampicillin, and more than 60

of Shigella spp. isolates were resistant to trimethoprim-sulfamethoxazole. A 41

of Staphylococcus aureus and 55

of coagulase-negative staphylococci isolates were resistant to oxacillin, presenting a highly associated multi-resistance. The resistance to FQ was also strongly related to oxacillin resistance, but the resistance to TRV was significantly lower than the CIP resistance: 9

for S.aureus and 4

for coagulase-negative staphylococci. A similar behavior was observed with Enterococcus spp., where 54

of the isolates were resistant to norfloxacin and only 13

were resistant to TRV. Neither Streptococcus pneumoniae (n = 193) nor Haemophilus influenzae (n = 139) isolates presented resistant to TRV.

Hemocultivos: variables metodológicas / Blood cultures: methodologyc variables

El rendimiento de los hemocultivos depende de un gran número de variables entre las que se encuentran: técnica aséptica para la obtención de los mismos, volumen de la muestra, dilución con el medio, tiempo de incubación, subcultivos, medios de cultivo empleados y/o sistema utilizado y presencia de sustancias inhibitorias en la sangre, entre otros. También hay que considerar situaciones especiales como ser búsqueda de anaerobios, micobacterias, hongos y gérmenes fastidiosos. La realización de hemocultivos cuantitativos, en la práctica diaria, se reserva para el diagnóstico de sepsis relacionada a catéteres de larga permanencia. Para su interpretación hay que tener en cuenta el germen aislado, el tiempo en que se positivizó la muestra y número de ellas en que se recuperó el germen, pero fundamentalmente la clínica del paciente y factores de riesgo como ser: catéteres, válvulas cardíacas protésicas, prótesis osteoarticulares, sistemas de derivación ventrículo-peritoneal, neutropenia, extremos de la vida, enfermedad de base (ej. SIDA), etc. Por todo esto es esencial la comunicación e intercambio de información entre bacteriólogo y médico

Rendimiento de las técnicas cuantitativas y semicuantitativas en bacteriemias asociadas a catéteres / Catheter related bacteremia: efficiency of cuantitative and semicuantitative techniques

La sepsis relacionada a catéteres (SRC) constituye una complicación nosocomial ampliamente documentada. La detección de infección en los dispositivos intravasculares, su relación con bacteriemia y la diferenciación con contaminación o colonización por gérmenes de los mismos es un problema importante, ya que los microorganismos pueden colonizar la punta del catéter por distintas vías. Diversos autores han desarrollado técnicas semicuantitativas y cuantitativas para el cultivo de los mismos. En el Instituto de Cardiología y Cirugía Cardiovascular (ICYCC) y el Hospital de Niños "R. Gutiérrez" (HNRG), en el período comprendido entre julio de 1992 y marzo de 1994, se estudiaron un total de 806 catéteres (centrales y periféricos) y su relación con bacteriemia; se sembraron por la técnica semicuantitativa de Maki y la cuantitativa de Brun-Buisson. Se calcularon los valores de sensibilidad (S), especificidad (E), valor predictivo positivo (VP+) y negativo (VP-). Según el punto de corte de 15 UFC para la técnica de Maki, los resultados fueron: S=83,6 por ciento, E=91,3 por ciento, VP+=48,8 por ciento y VP-=98,2 por ciento; considerando el punto de corte de 1.000 UFC/ml para la técnica de Brun-Buisson, correspondieron a 76,8 por ciento, 93,6 por ciento, 54,4 por ciento y 97,7 por ciento respectivamente. La combinación de las dos técnicas, permitió incrementar el diagnóstico de bacteriemia relacionada a catéteres en un 8,2 por ciento