F. Javier Castillo

In vitro activity of cefditoren and other antimicrobial agents against 288 Streptococcus pneumoniae and 220 Haemophilus influenzae clinical strains isolated in Zaragoza, Spain

In vitro cefditoren antimicrobial activity was tested against 288 Streptococcus pneumoniae and 220 Haemophilus influenzae clinical strains isolated in our hospital from January 2005 to May 2006 by agar dilution and broth microdilution method, respectively. MICs were also determined for 13 and 10 comparison drugs, respectively. The pneumococci tested comprised 113 (39.2%) penicillin susceptible, 91 (31.6%) penicillin intermediate, and 84 (29.2%) penicillin resistant. Cefditoren was the most active drug on the basis of the MICs (MIC(90)=0.5 microg/mL), followed by ceftriaxone and levofloxacin (MIC(90)=1 microg/mL). Cefditoren MICs ranged from 0.25 to 1 microg/mL for ceftriaxone-resistant isolates, with a modal MIC of 0.5 microg/mL and an MIC(90) of 1.0 microg/mL. No S. pneumoniae isolates evaluated in this study showed MICs to cefditoren higher than 1 microg/mL (MIC range, <or=0.015 to 1 microg/mL). Against penicillin-resistant pneumococci, the rank order of intrinsic activity (MIC(90), microg/mL) was cefditoren (0.5)<ceftriaxone (2.0)=cefotaxime (2.0)<amoxicillin/clavulanate (8.0)=amoxicillin (8.0)=cefuroxime (8.0). Among the 220 strains of H. influenzae, 42 (19.09%) produced a beta-lactamase (Hi beta+) and 3 (1.1%) were beta-lactamase (Hi beta-) negative but have reduced susceptibility to ampicillin (BLNAR). The most active drugs on the basis of MICs were cefditoren and levofloxacin, showing MIC(50) and MIC(90) values of 0.015/0.06 microg/mL. Cefditoren at concentration of 0.06 microg/mL inhibited all 3 BLNAR (ampicillin MICs >4 microg/mL). Against H. influenzae (Hi beta+), the rank order of intrinsic activity (MIC(90), microg/mL) was cefditoren (0.03) < cefixime (0.06)<ceftriaxone (0.12)=cefotaxime (0.12)<cefuroxime (1.0)<amoxicillin/clavulanate (2.0)<ampicillin (>8.0).

Molecular epidemiology, resistance profiles and clinical features in clinical plasmid-mediated AmpC-producing Enterobacteriaceae

During the 30 months of surveillance period, 85 pAmpC-producing isolates were detected (prevalence 0.56% overall): blaCMY-2 gene in 70 E. coli, 2 K. pneumoniae and 6 P. mirabilis isolates; and the blaDHA-1 gene in 4 E. coli and 3 K. pneumoniae. In 8.23% of them, other β-lactamases (predominantly OXA-1) were identified. All pAmpC-producing isolates were susceptible to carbapenems, whereas high resistance to nalidixic acid, ciprofloxacin and trimethoprim-sulfamethoxazole was observed among pAmpC-producing isolates (80%, 60%, and 44.7%, respectively). In hospital patients, predisposing factors such as prior antibiotic use, previous hospitalization, presence of an indwelling device, invasive urinary tract procedures and mechanical ventilation were observed. In the community setting, urinary tract infection was the most common type of infection related to pAmpC-producing isolates. A wide heterogeneity of clones was found among our E. coli isolates by PFGE, suggesting that this mechanism of resistance is not due to the dissemination of a clonal strain. Surveillance of these resistance mechanisms in the community is thus needed. Awareness of pAmpC dynamic is required to prevent introduction into hospitals and to control the spread of this emerging resistance within the community.

Resistencia a antibióticos y factores de virulencia en aislados clínicos de Salmonella enterica

INTRODUCTION The increase of Salmonella enterica isolates multi-resistant to different antibiotics, including β-lactams and fluoroquinolones, is a problem of clinical importance. The dissemination of Salmonella Typhimurium resistant to ampicillin (AMP)-chloramphenicol (CHL)-streptomycin (STR)-sulphonamides and (SUL)-tetracycline (TET), that harbour the Salmonella Genomic Island type 1 (SGI1), and the acquisition of transferable genetic material have favoured the multi-resistance in this genus. METHODS A total of 114 clinical S.enterica isolates were studied (period 2009-2010). The susceptibility to 20 antibiotics was determined by disc diffusion and microdilution. The antimicrobial resistance mechanisms and the integrons were analysed by PCR, and sequencing in the AMP(R) isolates. In all the blaPSE-1-positive isolates, the clonal relationship was determined by PFGE, as well as the presence of SGI1 and 29 virulence genes by PCR. RESULTS Eighteen different serotypes were found among the 114 isolates studied, Typhimurium (61%) and Enteritidis (16%) being the most prevalent. High percentages of resistance to SUL (68%), TET (58%), AMP (55%) and STR (46%) were observed. The great majority (92%) of 63 AMP(R) isolates were multi-resistant, with the AMP-STR-TET-SUL phenotype (19 isolates) being the most frequent one and associated with the blaTEM-1b+strA-strB+tet(B)+sul2 genotype. Class 1 integrons (7 different structures) were observed in 48% AMP(R) isolates, highlighting the blaOXA-1+aadA1 structure (8 isolates), one empty integron and non-classical integrons (5 isolates). The blaPSE-1 gene was detected inside the classical SGI1 structure in 13 clonally-related isolates that showed the same virulence profile. CONCLUSIONS The high percentage of multi-resistant S.enterica isolates, especially associated to S.Typhimurium, to the AMP, STR, TET and SUL phenotype, and to the blaTEM-1b+strA-strB+tet(B)+sul2 genotype, shows an important risk of possible failures in the treatment of serious infections caused by this serotype.

Molestias abdominales y heces blandas en consumidor habitual de carne de vacuno poco cocinada

S. hominis (S. bovihominis) y S. suihominis son coccidios heteroxenos1 . En la sarcocistosis intestinal el hombre actua como hospedador definitivo y los hospedadores intermediarios son el ganado vacuno y el cerdo, respectivamente. El hospedador definitivo elimina en sus heces esporocistos, que infectan al hospedador intermediario cuando este los ingiere. Los esporocistos contienen cuatro esporozoitos que son liberados en el intestino delgado. Los parasitos sufren despues dos divisiones multiples (esquizogonias), una en las celulas endoteliales de arterias y otra en las de capilares. Pueden encontrarse merozoitos libres en sangre y dentro de celulas mononucleares sanguineas. Los merozoitos liberados de la segunda generacion de esquizontes inician la formacion de quistes en los tejidos (musculo esqueletico o cardiaco). Los quistes maduros estan llenos de bradizoitos, estadio infectante para el hombre. El hombre, hospedador definitivo, adquiere la infeccion por consumo de carne de vacuno o de cerdo cruda o poco cocinada que contiene quistes maduros. Los bradizoitos son liberados de los quistes por la accion de enzimas digestivas, alcanzando la lamina propia de las vellosidades del intestino delgado y transformandose en micro y macrogametocitos. El microgameto fertiliza al macrogameto dando lugar al cigoto, que al rodearse de una pared se convierte en ooquiste. Los ooquistes esporulan en la lamina propia intestinal dando lugar en su interior a dos esporocistos, cada uno con cuatro esporozoitos alargados y un cuerpo residual disperso o compacto. Debido a que la pared del ooquiste es fina y se rompe con facilidad, observamos con frecuencia en las heces tanto esporocistos aislados como ooquistes enteros1-3. Los esporocistos son muy Correspondencia: Dr. A. Clavel. Servicio de Microbiologia. Hospital Clinico Universitario Lozano Blesa. Avda. San Juan Bosco 15. 50009 Zaragoza.

Detection of carbapenemase-producing Enterobacteriaceae in various scenarios and health settings.

Detection of carbapenemase-producing Enterobacteriaceae (CPE) is an important task at microbiology laboratories in hospitals. As the prevalence of CPE is increasing worldwide, the implementation of phenotypically based screening as well as confirmatory procedures to detect CPE are important for microbiologists. In addition to detection of carbapenem hydrolysis, the inhibition of activity against a carbapenem in the presence of several inhibitor compounds specific to class A, B, or class C beta-lactamases is a useful method to confirm the presence of carbapenemases in bacterial isolates. There is also a proteomic approach that compares the MALDI-TOF spectrum generated by the intact carbapenem (non-hydrolyzed) with that obtained after hydrolysis of the beta-lactam ring by beta-lactamase to reveal the presence of carbapenemases in bacterial isolates. Proteomic methods will probably be more frequently implemented in laboratories in the near future. Finally, molecular methods to directly or indirectly detect the presence of a carbapenemase genes are increasingly being used in microbiology laboratories. One of the main advantages of these methods is their speed, and also that they can be used directly with the clinical sample without the need for an isolated bacterial colony. Multiplex PCR, real-time PCR, DNA microarrays and pyrosequencing are some examples of molecular-based tests. Their main disadvantage is their cost, although prices are going down as the range of services increases. Surveillance of carriers is also an important task for infection control purposes. In this case, commercially available chromogenic medium supplemented with low carbapenem concentrations has shown an excellent ability to detect CPE. Moreover, molecular methods to detect specific carbapenemase genes directly from rectal swabs, stools, or other colonization sources have had excellent results.

Usefulness of PCR-RFLP coa gene for clonal classification of methicillin-resistant Staphylococcus aureus isolates in tertiary hospitals

Abstract One hundred and one methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates were classified into 10 genotypes based on their polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) coa pattern. PCR-RFLP coa patterns correlated with the clonal complex (CC) with the exception of CC5, which was related to 2 patterns (B and E). The PCR-RFLP coa gene technique provides a useful preliminary method to monitor variations in MRSA populations.

Pseudomonas aeruginosa Isolates from Spanish Children: Occurrence in Faecal Samples, Antimicrobial Resistance, Virulence, and Molecular Typing

Pseudomonas aeruginosa is a major opportunistic human pathogen, responsible for nosocomial infections and infections in patients with impaired immune systems. Little data exist about the faecal colonisation by P. aeruginosa isolates in healthy humans. The occurrence, antimicrobial resistance phenotype, virulence genotype, and genetic lineages of P. aeruginosa from faecal samples of children from two different Spanish regions were characterised. Seventy-two P. aeruginosa were isolated from 1,443 faecal samples. Low antimicrobial resistance levels were detected: ceftazidime (8%), cefepime (7%), aztreonam (7%), gentamicin (3%), ciprofloxacin (1%), and imipenem (1%); susceptibility to meropenem, amikacin, tobramycin, levofloxacin, and colistin. Four multidrug-resistant strains were found. Important differences were detected between both geographical regions. Forty-one sequence types were detected among the 48 tested strains. Virulence and quorum sensing genes were analysed and 13 virulotypes were detected, being 26 exoU-positive strains. Alteration in protein OprD showed eight different patterns. The unique imipenem-resistant strain showed a premature stop codon in OprD. Intestinal colonisation by P. aeruginosa, mainly by international clones (as ST244, ST253, and ST274), is an important factor for the systemic infections development and the environmental dissemination. Periodic active surveillance is useful to identify these community human reservoirs and to control the evolution of antibiotic resistance and virulence activity.