Klebsiella pneumoniae: development of a mixed population of carbapenem and tigecycline resistance during antimicrobial therapy in a kidney transplant patient.

Nine isolates of Klebsiella pneumoniae were isolated from a renal transplant patient suffering from recurrent urosepsis over a period of 4 months. Imipenem resistance was detected after imipenem-ertapenem therapy. When treatment was switched to tigecycline the K. pneumoniae developed resistance to tigecycline (MIC = 8 mg/L). The nine isolates were tested by determination of agar dilution MICs, phenotypic carbapenemase, extended-spectrum beta-lactamases and metallo-beta-lactamase (MBL) testing and pulsed-field gel electrophoresis. Polymerase chain reaction and sequencing analysis were employed for identification of bla genes and mapping of the integron carrying the MBL gene. The nine isolates were clonally related and all produced the SHV-12 enzyme. Five MBL-producing isolates showed imipenem MICs ranging from 2 to 64 mg/L and all were detected by testing with imipenem and EDTA. The five isolates harboured the bla(VIM-1) gene. Three isolates showed increased tigecycline MICs (4-8 mg/L). Serial blood cultures obtained on the same day resulted in a VIM-positive/tigecycline-susceptible and a VIM-negative/tigecycline-resistant K. pneumoniae isolate. No isolate developed concurrent imipenem and tigecycline resistance. The patient had a persistent urinary tract infection and recurrent bacteraemia caused by a mixed population of Klebesiella pneumoniae isolates adapting to the selective pressure of antimicrobial therapy at the time. The present study is a worrisome example of what could happen when an immunocompromised host is subjected to the pressures of antimicrobial therapy. In addition, we report the first treatment-emergent MIC increase of tigecycline from 0.5 to 8 mg/L in K. pneumoniae.

[Incidence and risk factors for hepatitis A in the province of Guadalajara (Spain)]. / Incidencia y factores de riesgo de hepatitis A en la provincia de Guadalajara.

BACKGROUND: The decrease in the prevalence of hepatitis A in Spain may modify the characteristics of this infection because of the rise in the susceptible adult population. The aim of this study was to determine the incidence of this disease, as well as the epidemiological characteristics and the complications of patients diagnosed in the province of Guadalajara between 1991 and 1999. PATIENTS AND METHODS: The inclusion criterion was the presence of specific IgM together with an increase in alanine aminotransferase concentrations and/or symptoms compatible with acute hepatitis. RESULTS: The mean incidence was 7.13 cases/105 inhabitants. Considerable differences were found between years due to the presence of an outbreak. Most cases occurred in children and young adults. The most frequent risk factor found overall was contact with an infected individual but the distribution of risk factors differed between children and adults. CONCLUSIONS: The decrease in the prevalence of hepatitis A in Spain entails an increase in the susceptible adult population. Consequently, hepatitis A may cease to be a typically pediatric disease and may become one that also affects young adults in whom it may have different characteristics. This consideration should be borne in mind when designing a vaccination strategy.

[Susceptibility to penicillin and 13 antimicrobial agents in erythromycin-resistant viridans group streptococci isolated from blood cultures]. / Sensibilidad a penicilina y otros 13 antimicrobianos de estreptococos del grupo viridans resistentes a eritromicina aislados de hemocultivos.

From March 1998 to June 1999, we studied 63 sequential blood culture isolates of viridans group streptococci which showed a 49% resistance to erythromycin. A high level of resistance to penicillin (46%) was also found. A statistically significant correlation was detected between the two types of resistance. The erythromycin-resistant strains were phenotypically and genotypically characterized, and no differences were found between the resistance to penicillin and the M or MLS(B) phenotypes. The penicillin-erythromycin-resistant strains included: 16 S. mitis, five S. sanguis and one S. salivarius. The rank order of activity (% of susceptibility) for all 14 agents against 31 erythromycin- resistant isolates was the following: vancomycin = rifampicin (100) > chloramphenicol (98) > meropenem (65) > cefotaxime (61) > amoxicillin- clavulanic acid (42) > cefepime = ciprofloxacin (39) > tetracycline = trimethoprim-sulfamethoxazole (36) > cefuroxime (32) > penicillin = ampicillin = cefaclor (29). The species S. milleri and S. bovis were the most susceptible. The most resistant strains were two S. mitis and one S. sanguis and showed multiresistance to six different groups of antimicrobial agents. The frequent association between macrolide resistance and resistance to other antimicrobial agents suggests that the susceptibility of all clinically significant isolates needs to be evaluated and alternative agents for the prevention and treatment of viridans group streptococci infections should be identified.

Actividad in vitro de seis fluoroquinolonas y penicilina frente a 101 estreptococos del grupo viridans caracterizados en su resistencia a la eritromicina / In vitro activity of six fluoroquinolones and penicillin against 101 viridans group streptococci characterized by their susceptibility to erythromycin

El aumento del uso de fluoroquinolonas, que incluye en la actualidad el tratamiento de las infecciones de vías respiratorias bajas, parece asociarse con un incremento paralelo de la resistencia bacteriana. Hemos estudiado la actividad de la penicilina y seis fluoroquinolonas frente a un total de 101 aislamientos consecutivos de estreptococos del grupo viridans (58 sensibles y 43 resistentes a la eritromicina) procedentes de hemocultivos. El porcentaje de resistencia a la penicilina fue de un 35 por ciento y se asoció significativamente con la resistencia a la eritromicina. Las fluoroquinolonas estudiadas muestran buena actividad frente a los estreptococos del grupo viridans independientemente de su sensibilidad a la eritromicina. La CMI50 y la CMI90 del norfloxacino fueron 8 y 16 mg/l, respectivamente. Ofloxacino y ciprofloxacino muestran la misma actividad (CMI50 1 mg/l y CMI90 2 mg/l); levofloxacino fue similar, con ambos valores de 1 mg/l. Las más activas fueron trovafloxacino y moxifloxacino (CMI50 0,12 mg/l y CMI90 0,25 mg/l). Sin embargo, hemos encontrado dos cepas resistentes al trovafloxacino (CMI 4 mg/l), que muestran sensibilidad reducida a todas las fluoroquinolonas ensayadas, incluido moxifloxacino (CMI 2 mg/l). Es necesario un seguimiento de la actividad de las fluoroquinolonas sobre este grupo de cepas y consideramos que el estudio de los genes de resistencia implicados sería de gran interés (AU)

[The prevalence of hepatitis A in the Guadalajara province. Is Spain a country with low endemia?]. / Prevalencia de hepatitis A en la provincia de Guadalajara. Es España un país de baja endemia?

BACKGROUND: Spain, together with the other southern European countries, was considered to be an area with a moderate degree of endemia. This fact has consequences for tourists that visit these areas and for vaccination strategies. A prevalence study was proposed in order to get to know the situation of this infection in the Guadalajara province. METHODS: 284 specimens of serum were taken from patients who were classified according to their age, sex and place of residence (with more or less than 10.000 inhabitants). In these specimens the presence of hepatitis A antibodies were studied, using a Microparticule Enzyme Immunoassay (MEIA) (Abbott). RESULTS: An increase in the prevalence was observed in older people, there is a low prevalence population (80%) in adults aged between 30 and 74 years. No differences were observed related to sex. In the stratified analysis according to age, differences were observed between the groups from rural and urban origins. CONCLUSIONS: The low prevalence of hepatitis A was found among the younger population, as seen in other studies carried out on a national level, and this together with a decrease in the frequency, means that Spain is included among the countries with low endemia. This fact has consequences for tourists who visit our country and for vaccination strategies, due to the increase in the number of adults who are susceptible to the infection.

Sensibilidad a penicilina y otros 13 antimicrobianos de estreptococos del grupo viridans resistentes a eritromicina aislados de hemocultivos / Susceptibility to penicillin and 13 antimicrobial agents in erythromycin-resistant viridans group streptococci isolated from blood

Entre marzo de 1998 y junio de 1999 aislamos 63 estreptococos del grupo viridans procedentes de hemocultivos, de los cuales el 49 por ciento fueron resistentes a eritromicina, y encontramos una resistencia a penicilina del 46 por ciento, con una relación estadísticamente significativa entre ambas resistencias. Las cepas resistentes a eritromicina están caracterizadas fenotípica y genotípicamente, y no se ha encontrado diferencia significativa entre resistencia a penicilina y los fenotipos M y MLSB. Las cepas resistentes a ambos antibióticos fueron: 16 S. mitis, 5 S. sanguis y 1 S. salivarius. Frente a los 31 aislamientos resistentes a eritromicina ensayamos los 14 antibióticos que referimos por orden de actividad ( por ciento de cepas sensibles): vancomicina = rifampicina (100) > cloranfenicol (98) > meropenem (65) > cefotaxima (61) > amoxicilina-ácido clavulánico (42) > cefepima = ciprofloxacino (39) > tetraciclina = trimetoprima-sulfametoxazol (36) > cefuroxima (32) > penicilina = ampicilina = cefaclor (29). Para el conjunto de los antibióticos, las especies más sensibles fueron S. milleri y S. bovis. Las cepas más resistentes fueron dos S. mitis y un S. sanguis en las que se asocia resistencia a seis grupos diferentes de antimicrobianos. Los bajos porcentajes de sensibilidad encontrados, junto a la frecuencia de asociación de resistencias, sugieren la necesidad de determinar la sensibilidad de todos los aislamientos clínicamente significativos y de evaluar nuevos antimicrobianos que nos permitan disponer de agentes alternativos para la prevención y el tratamiento de las infecciones por estreptococos del grupo viridans resistentes a los fármacos de elección (AU)

[In vitro activity of six fluoroquinolones and penicillin against 101 viridans group streptococci characterized by their susceptibility to erythromycin]. / Actividad in vitro de seis fluoroquinolonas y penicilina frente a 101 estreptococos del grupo viridans caracterizados en su resistencia a la eritromicina.

The increase in the use of the fluoroquinolones, including for the treatment of lower respiratory tract infections, seems to be associated with a parallel increase in bacterial resistance. We studied the activity of penicillin and six fluoroquinolones against 101 viridans group streptococci isolated from blood (58 erythromycin-susceptible and 43 erythromycin-resistant). The percentage of strains not susceptible to penicillin was 35% and there were statistically significant differences in the percentages of penicillin resistance between erythromycin-susceptible and -resistant strains. The fluoroquinolones studied showed good activity against our viridans group streptococci independent of their susceptibility to erythromycin. The norfloxacin MIC(50) and MIC(90) were 8 and 16 mg/l, respectively. Ofloxacin and ciprofloxacin showed the same activity (MIC(50) 1 mg/l and MIC(90) 2 mg/l); levofloxacin was similar with MIC(50) and MIC(90) of 1 mg/l. The fluoroquinolones with enhanced activity were moxifloxacin and trovafloxacin (MIC(50) 0.12 mg/l and MIC(90) 0.25 mg/l). However, we found two strains resistant to trovafloxacin (MIC = 4 mg/l) that showed reduced susceptibility to all the fluoroquinolones tested, including moxifloxacin (MIC = 2 mg/l). Mutations in the topoisomerase genes parC and gyrA have been shown to occur in strains with reduced susceptibility; therefore, ongoing surveillance for the development of fluoroquinolone resistance in viridans streptococci is necessary.

[Different phenotypes of erythromycin-resistant blood isolates in viridans group streptococci] / Fenotipos de resistencia a macrólidos, lincosamidas y estreptograminas en Streptococcus del grupo viridans aislados de hemocultivos.

Macrolide resistance has been widely studied in Streptococcus pyogenes and Streptococcus pneumoniae although not in viridans group streptococci (VGS). We studied 30 blood culture isolates of viridans group streptococci (25 resistant to erythromycin: 10 S. mitis, 8 S. milleri, 6 S. sanguis and 1 S. salivarius; and 5 susceptible: 2 S. mitis, 2 S. milleri and 1 S. sanguis). We carried out a double-disk test and determined MICs. The susceptibility testing was carried out by agar dilution for 14-, 15- and 16-member lactone ring macrolides, as well as for clindamycin and quinupristin-dalfopristin. Fifty-six percent of the erithromycin-resistant strains (6 S. mitis, 6 S. milleri and 2 S. sanguis) showed an MLS(B) phenotype, with a high level of intrinsic resistance to all the macrolides studied and clindomycin; 28% were of the M phenotype (4 S. sanguis, 2 S. mitis and 1 S. salivarius). We found a third resistance phenotype, which was present in 4 strains with MICs of 2-8 µg/ml, with resistance to macrolides and different degrees of resistance to clindamycin. All isolates were fully susceptible to quinupristin-dalfopristin. The MLS(B) and M phenotypes initially described in S. pyogenes and S. pneumoniae are also observed in VGS.

[Phenotypes of macrolide, lincosamide, and streptogramin resistant Streptococcus viridans isolated from blood]. / Fenotipos de resistencia a macrólidos, lincosamidas y estreptograminas en Streptococcus del grupo viridans aislados de hemocultivos.

Macrolide resistance has been widely studied in Streptococcus pyogenes and Streptococcus pneumoniae although not in viridans group streptococci (VGS). We studied 30 blood culture isolates of viridans group streptococci (25 resistant to erythromycin: 10 S. mitis, 8 S. milleri, 6 S. sanguis and 1 S. salivarius; and 5 susceptible: 2 S. mitis, 2 S. milleri and 1 S. sanguis). We carried out a double-disk test and determined MICs. The susceptibility testing was carried out by agar dilution for 14-, 15- and 16-member lactone ring macrolides, as well as for clindamycin and quinupristin-dalfopristin. Fifty-six percent of the erithromycin-resistant strains (6 S. mitis, 6 S. milleri and 2 S. sanguis) showed an MLS(B) phenotype, with a high level of intrinsic resistance to all the macrolides studied and clindomycin; 28% were of the M phenotype (4 S. sanguis, 2 S. mitis and 1 S. salivarius). We found a third resistance phenotype, which was present in 4 strains with MICs of 2-8 microg/ml, with resistance to macrolides and different degrees of resistance to clindamycin. All isolates were fully susceptible to quinupristin-dalfopristin. The MLS(B) and M phenotypes initially described in S. pyogenes and S. pneumoniae are also observed in VGS.

[Microbial drug resistance and the presence of plasmids in Salmonella strains isolated from different sources]. / Resistencias a antimicrobianos y presencia de plásmidos en cepas de Salmonella aisladas de diferentes orígenes.

BACKGROUND: To establish the relationship between the presence of plasmid and their antimicrobial resistance of Salmonella strains. METHODS: We tested 171 strains of Salmonella isolated from different sources: natural waters (73 strains), food (23 strains), and from clinical samples (75 strains). The disk diffusion method was used to test the antimicrobial susceptibility of the strains to 13 drugs. Plasmid analysis were performed by agarose gel electrophoresis technique. RESULTS: Antimicrobial resistances of the strains significantly varies according to their primary isolation sources. Strains isolated from the water environment exhibited a full susceptibility to cephalothin and colistin, whilst all the strains isolated from food were sensitive to ampicillin, gentamicin, kanamycin, neomycin, tobramycin and trimethoprim-sulphamethoxazole. On the other hand, resistances to colistin, gentamicin and trimethoprim-sulphamethoxazole were not found in clinical isolates. From the 171 Salmonella strains tested, only 12.2% were sensitive to all the antimicrobials. The most frequently antibiotic resistances detected were to streptomycin (49.3%), tetracycline (33.1%) and nalidixic acid (30.7%). The percentage of strains that harboured plasmids was different depending on the source of isolation, ranging from 41.4% for water isolated, 76% for clinical isolates and 86.9% for food isolates. The relationship between antimicrobial resistance and plasmid presence is very close, since higher percentages of resistance to chloramphenicol, carbenicillin, cephalothin, kanamycin, neomycin, nalidixic acid and trimethoprim-sulphamethoxazole were obtained in strains containing plasmids. CONCLUSIONS: (a) The most frequently resistance detected in strains of Salmonella was to streptomycin (49.3% of the strains). On the other hand, only 0.6% of the strains were resistant to gentamicin. (b) Percentages of resistance to some antibiotics was higher in strains harbouring plasmids, that implies a relationship between the plasmid presence and the antibiotic resistance in Salmonella. (c) Curing of extrachromosomic elements by acridine orange showed a percentage of resistance lost greater than 70% for cephalothin, kanamycin, neomycin, and nalidixic acid. This indicates that the resistance to those antibiotics is mainly linked to plasmids. In the case of the unusual nalidixic acid-resistance, previously described in Shigella strains, suggests that are needed more studies to demonstrate the direct association between antimicrobial resistance and presence of plasmids.

Comparison of epidemiological markers of Salmonella strains isolated from different sources in Spain.

A comparative study of the phage types, antimicrobial susceptibility patterns, and plasmid profiles of 171 strains of Salmonella isolated from food, epidemic outbreaks, and water-contaminated environments as well as sporadic human isolates was carried out to determine the most adequate marker in epidemiological investigations. Typing based on the plasmid profiles appears to be the most effective method for grouping strains with the same serotype obtained from a single outbreak and from environmental sources. However, none of the three markers tested allow us total discrimination and identification of related strains from a common source for epidemiological tracing. Therefore, the combined use of the three methods is necessary for determining whether common source isolates are related.

Susceptibilities of species of the Bacteroides fragilis group to 10 antimicrobial agents.

A total of 94 clinical isolates of the Bacteroides fragilis group was tested for susceptibility to metronidazole, chloramphenicol, clindamycin, cefoxitin, cefotetan, cefmetazole, moxalactam, mezlocillin, amoxicillin-clavulanic acid, and imipenem. All the strains tested were susceptible to imipenem, metronidazole, amoxicillin-clavulanic acid, and chloramphenicol. The rate of resistance to clindamycin was 21%. The results of this study demonstrate a difference in resistance rates from one species of the B. fragilis group to another.