Manuel López-Brea

Differences in Genotypes of Helicobacter pylori from Different Human Populations

DNA motifs at several informative loci in more than 500 strains of Helicobacter pylori from five continents were studied by PCR and sequencing to gain insights into the evolution of this gastric pathogen. Five types of deletion, insertion, and substitution motifs were found at the right end of the H. pylori cag pathogenicity island. Of the three most common motifs, type I predominated in Spaniards, native Peruvians, and Guatemalan Ladinos (mixed Amerindian-European ancestry) and also in native Africans and U.S. residents; type II predominated among Japanese and Chinese; and type III predominated in Indians from Calcutta. Sequences in the cagA gene and in vacAm1 type alleles of the vacuolating cytotoxin gene (vacA) of strains from native Peruvians were also more like those from Spaniards than those from Asians. These indications of relatedness of Latin American and Spanish strains, despite the closer genetic relatedness of Amerindian and Asian people themselves, lead us to suggest that H. pylori may have been brought to the New World by European conquerors and colonists about 500 years ago. This thinking, in turn, suggests that H. pylori infection might have become widespread in people quite recently in human evolution.

Antibiotic resistance problems with Helicobacter pylori

Helicobacter pylori is very susceptible in vitro to most antibiotics, but when they are used in the clinical setting, eradication of the bacteria from the gastric mucosa is not obtained. Dual or triple therapy including two of the following antibiotics: amoxicillin, tetracycline, metronidazole or clarithromycin, plus a proton pump inhibitor, bismuth salt or ranitidine bismuth citrate is the most frequently used. Various in vitro susceptibility methods have been used: disk diffusion, agar dilution and Epsilometer test (E-test). Metronidazole resistance among H. pylori strains is now found worldwide, and resistance rates vary according to the population studied. It is higher in developing than in developed countries and it could reach 80-90% in Africa. The prevalence on clarithromycin resistance is much lower, usually below 10%, although very high values are reported in Peru. Infection with metronidazole- or clarithromycin-resistant H. pylori strains is correlated with treatment failure when using regimens including these antibiotics.

High Prevalence of Clarithromycin-Resistant Helicobacter pylori Strains and Risk Factors Associated with Resistance in Madrid, Spain

ABSTRACT Clarithromycin is one of the antibiotics used for the treatment of Helicobacter pylori infections, and clarithromycin resistance is the most important factor when it comes to predicting eradication failure. The present study analyzed H. pylori isolates for the presence of 23S rRNA gene mutations and determined the risk factors associated with resistance among H. pylori isolates collected in Madrid, Spain, in 2008. We studied 118 H. pylori strains isolated from the same number of patients. A total of 76.3% of the patients were born in Spain, 52.7% were children, 20.3% had previously been treated, and 66.1% were female. Clarithromycin resistance was determined by Etest. H. pylori strains were considered resistant if the MIC was ≥1 mg/liter. DNA extraction was carried out by use of the NucliSens easyMAG platform with NucliSens magnetic extraction reagents (bioMérieux). The DNA sequences of the 23S rRNA genes of clarithromycin-resistant and -sensitive strains were determined to identify specific point mutations. The vacA genotype and cagA status were determined by PCR. We found that 42 (35.6%) strains were resistant to clarithromycin by Etest. Etest results were confirmed by detection of the presence of point mutations in 34 (88.1%) of these strains. Eight H. pylori strains were resistant to clarithromycin by Etest but did not have a point mutation in the 23S rRNA gene. Mutation at A2143G was found in 85.3% of the strains, mutation at A2142G in 8.8%, and mutation at T2182C in 5.9%. Dual mutations were found in 8.8% of the strains. H. pylori clarithromycin-resistant strains were strongly associated with pediatric patients, with patients born in Spain, and with patients who had previously been treated (P ≤ 0.02). In addition, H. pylori strains resistant to clarithromycin more frequently presented the vacA s2/m2 genotype and were more likely to be cagA negative than susceptible strains (39.1% and 11.2%, respectively; P value < 0.001). We concluded that, in the present study, H. pylori clarithromycin-resistant strains are more frequently found in children, in patients mostly born in Spain, and in individuals who were previously treated for H. pylori infection and that these individuals are more likely colonized with a less virulent H. pylori strain.

Activities of Polymyxin B and Cecropin A-Melittin Peptide CA(1-8)M(1-18) against a Multiresistant Strain of Acinetobacter baumannii

ABSTRACT Polymyxin B (PXB) and the cecropin A-melittin hybrid CA(1-8)M(1-18) (KWKLFKKIGIGAVLKVLTTGLPALIS-NH2) were compared for antibiotic activity on reference and multiresistant Acinetobacter baumannii strains. Significant differences for both peptides were observed on their inner membrane interaction and inhibition by environmental factors, supporting the use of CA(1-8)M(1-18) as a potential alternative to PXB against Acinetobacter.

Five-year analysis of antimicrobial Susceptibility of the Streptococcus milleri group

Abstract Susceptibility to 17 antibiotics was studied in 180 strains of the Streptococcus milleri group (88 Streptococcus anginosus, 63 Streptococcus constellatus, and 29 Streptococcus intermedius) isolated over a 5-year period. Minimum inhibitory concentrations of penicillin were in the intermediate range for 5.6% of the strains. Resistance to erythromycin and clindamycin was found in 17.1% and 16.6% of the isolates, respectively. A steady increase in the susceptibility to ciprofloxacin was observed over the study period. Imipenem was the most active beta-lactam agent tested. Glycopeptide antibiotics showed excellent activity. Only slight differences between the three species were found in terms of antibiotic susceptibility. Intermediate resistance to penicillin is appearing among the Streptococcus milleri group in our area; consequently, care must be taken when choosing a macrolide for the management of infections caused by these microorganisms.

Scedosporium apiospermum pneumonia after autologous bone marrow transplantation

Although opportunistic infections after bone marrow transplantation (BMT) are very common, only five cases ofPseudallescheria boydii infection have been reported in the literature, two of which were autopsy findings. A case ofScedosporium apiospermum infection after BMT, treated initially with amphotericin B (total dose of 2.5 g) and then with itraconazole (for 25 days), is reported here. When the patient failed to improve,Scedosporium apiospermum pneumonia was diagnosed and therapy was changed. The patient was treated successfully with miconazole (600 mg/8h for 32 days) and ketoconazole (200 mg/8h for 7 days) plus surgery.

Carbapenem resistance mediated by beta-lactamases in clinical isolates of Acinetobacter baumannii in Spain.

Four patients colonized/infected with carbapenem-resistant strains ofAcinetobacter baumannii are described. The first patient had a decubitus ulcer infection and had been on intravenous imipenem for 50 days. Two other patients, from whomAcinetobacter baumannii was isolated from urine, were hospitalized in the same ward as the first patient. The fourth patient had been mechanically ventilated in the intensive care unit for 4 month and had nosocomial pneumonia. He had been on intravenous meropenem for 1 month. Minimum inhibitory concentrations (MICs) of imipenem (128 mg/l) and meropenem (>128 mg/l) were the same for the isolates from the first three patients, and all of these isolates had the same repetitive extragenic palindromic polymerase chain reaction (rep-PCR) pattern. The MICs of carbapenems were lower for patient 4s isolate, which also had a different rep-PCR pattern. Beta-lactamases that hydrolyzed imipenem were detected in all four isolates; isoelectric points were 8.6−7.7 in the first three isolates and 6.8−7 in the fourth isolate.

Comparison of three methods for identification of Streptococcus milleri group isolates to species level.

Abstract A collection of 180 clinical isolates of Streptococcus milleri group were identified to species level using two phenotypic methods (a commercial system and the reference method based on differential phenotypic reactions) and a genotypic method (hybridisation of the 16S rRNA gene with species-specific probes) in order to evaluate the performance of the respective methods. A high level of agreement (80%) was observed between the results of the reference method and the genotypic method. The highest level of agreement was found for the species Streptococcus anginosus (83%), a high level of agreement (76%) also being achieved for Streptococcus constellatus and Streptococcus intermedius. The sensitivity of the commercial system compared to the genotypic method was 76% overall, but it was low (57.5%) for Streptococcus intermedius. Twenty-five strains belonged to the recently described CI strains.

Factores microbiológicos que afectan a la erradicación de Helicobacter pylori en población adulta y pediátrica

Objetivos Estudiar factores microbiologicos como la sensibilidad a antimicrobianos y factores de virulencia de Helicobacter pylori relacionados con la erradicacion del microorganismo de la mucosa gastrica, tanto en poblacion pediatrica como adulta. Metodos Se obtuvieron 55 cepas aisladas a partir del cultivo de biopsias de 16 pacientes pediatricos y de 39 adultos. La sensibilidad antibiotica se realizo mediante el metodo de dilucion en agar y el estudio de los factores de virulencia, gen cagA y los alelos s1 y s2 del gen vacA mediante reaccion en cadena de la polimerasa (PCR). El seguimiento tras el tratamiento que se instauro con amoxicilina, claritromicina y omeprazol se realizo mediante la prueba del aliento con urea marcada. Se estudio la relacion entre la concentracion inhibitoria minima (CIM) a amoxicilina y claritromicina y la presencia de estos factores de virulencia con la erradicacion del microorganismo. Resultados La erradicacion fue del 69% (38/55), 71,7% en adultos y 62,5% en ninos. La resistencia a claritromicina y amoxicilina fue 14,5 y 0%, respectivamente. Las tasas de erradicacion globales en relacion con las variables estudiadas fueron del 75 y 53% en cepas con CIM de amoxicilina ≤ 0,016 mg/l y CIM de amoxicilina ≥ 0,032 mg/l (intervalo ≤ 0,008-0,5) (p > 0,05), 79 y 12% en cepas con CIM de claritromicina 0,05) y 82 y 62% en cepas s1 y s2 (p > 0,05), respectivamente. Conclusiones La infeccion por cepas con CIM mas altas a amoxicilina y claritromicina y por aislamientos cagA– y vacA s2 se relacionaron con tasas mas bajas de erradicacion de H. pylori, tanto en poblacion adulta como infantil en la terapia con amoxicilina, claritromicina y omeprazol.

In vitro activity of ebrotidine, ranitidine, omeprazole, lansoprazole, and bismuth citrate against clinical isolates of Helicobacter pylori.

The aim of this study was to determine the in vitro activity of ranitidine, ebrotidine, bismuth citrate, omeprazole, and lansoprazole against 113 clinical isolates ofHelicobacter pylori cultured from gastric biopsies. An agar dilution method using Mueller-Hinton agar plus 7% horse blood, an inoculum of 106 cfu/spot, and incubation in a CO2 incubator for 2 to 5 days was used. The minimum inhibitory concentrations for 50 and 90% of the isolates tested, respectively, were as follows: ranitidine, 1024 and 1024 mg/l; ebrotidine, 64 and 256 mg/1; bismuth citrate, 1 and 4 mg/l; omeprazole, 16 and 16 mg/1; and lansoprazole, 1 and 1 mg/l. Ebrotidine was more active than ranitidine, and lansoprazole was the most active compound against theHelicobacter pylori isolates tested.