[Matematical modeling of antibiotic resistance: perspectives from a meta-analysys]. / Modelos matemáticos en el estudio de la resistencia a los antimicrobianos. Perspectivas a partir de un metaanálisis.

The antibiotic resistance is one of the greatest challenges of the international health community. The study of antibiotic resistance must be a multidisciplinary task and, in this sense, the main goal of this work is to analyze the role that Mathematical Modeling can play in this scenario. A qualitative and cuantitative analysis of the works published in the scientific literature is done by means of a search in the most important databases: MEDLINE, SCOPUS and ISI Web of Science. Consequently, there are few papers related to our topic but the existing works have been published in high-quality and impact international journals. Moreover, we can state that mathematical models are a very important and useful tool to analyze and study both the treatments protocols for resistance prevention and the assesment of control strategies in hospital environtment, or the prediction of the evolution of diseases due to resistant strains.

[Epidemiological study and effect on antimicrobial use in the genus Acinetobacter in a university hospital]. / Estudio epidemiológico y efecto sobre la utilización de antimicrobianos en el genero Acinetobacter en un hospital universitario.

In recent years, bacteria of the genus Acinetobacter have gradually been gaining epidemiological importance. This is due to the fact that they have been emerging as opportunistic pathogens causing a great number of nosocomial infections, and due to their multiresistance to antimicrobial agents, which limits treatment options. This study aimed to determine the epidemiological importance of isolates of the genus Acinetobacter at the Clinical University Hospital of Salamanca, Spain. The identification and susceptibility of Acinetobacter was determined using the Pasco automated system for Gram-negative bacteria MIC/ID 6J. Clinical and epidemiological data were obtained from the clinical history. During the study period it was found that A. anitratus was the most frequently isolated species (56%). The origin of the bacteria was mainly nosocomial (70%), and it was most prevalent in the ICU.

Dynamics of nasopharyngeal colonization by potential respiratory pathogens.

Studies have shown that colonization of the nasopharynx by potential respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis is established early in childhood, although rates vary greatly according to locality, sampling frequency, individual and social factors. Factors influencing colonization and elimination are not as yet fully understood, but adhesion to mucosal receptors and immune responses are implicated in addition to bacterial properties and colonization resistance dynamics. Colonization in children and adults has been intensively studied in various localities. Potential pathogens are more likely to colonize the nasopharynx of children prone to recurrent otitis media, where impaired local immunity and repeated exposure to respiratory pathogens are additional risk factors. Adults with chronic respiratory tract disease also have higher carriage rates. The factors contributing to increased risk of carriage of potential respiratory pathogens, as well as to clinical infection and antimicrobial resistance, are summarized in this review.

Human aqueous humor levels of oral ciprofloxacin, levofloxacin, and moxifloxacin.

PURPOSE: To evaluate the penetration of ciprofloxacin, levofloxacin, and moxifloxacin into the aqueous humor after oral administration. SETTING: Alcorcon Hospital, Madrid, Spain. METHODS: Forty-two patients having cataract surgery were randomly divided into 3 groups the day before surgery. The first group received 2 oral 500 mg doses of ciprofloxacin at 12-hour intervals. The second group received a single oral 500 mg dose of levofloxacin. The third group received a single oral 400 mg dose of moxifloxacin. At the time of surgery, 0.1 mL aqueous fluid was aspirated from the anterior chamber just before the operation and immediately stored at -80 degrees C. Drug concentrations were measured using a biological assay. RESULTS: The mean aqueous level of ciprofloxacin was 0.50 microg/mL +/- 0.25 (SD); of levofloxacin, 1.50 +/- 0.50 microg/mL; and of moxifloxacin, 2.33 +/- 0.85 microg/mL. The mean aqueous levels of levofloxacin and moxifloxacin were above the 90% minimum inhibitory concentration for most of the common microorganisms that cause endophthalmitis. CONCLUSIONS: Therapeutic concentrations of fluoroquinolones, mainly levofloxacin and moxifloxacin, were reached with oral administration. These antibiotics may be effective for prophylaxis and adjuvant therapy of bacterial endophthalmitis.

Nuevos antibióticos activos frente a grampositivos / Novel antibiotics active against Gram-positive bacteria

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In vitro adhesion of Staphylococcus epidermidis to intraocular lenses.

PURPOSE: To compare the in vitro adherence of slime-producing and non-slime-producing Staphylococcus epidermidis to different intraocular lenses (IOLs) to study the organism's contribution to postoperative endophthalmitis. METHODS: Strains of slime-positive (ATCC 35984) and slime-negative (ATCC 12228) S epidermidis were used. The IOLs were made of poly(methyl methacrylate) (PMMA), PMMA with polypropylene haptics, silicone, hydrogel, acrylic, heparin-surface-modified (HSM) PMMA, and fluorine-surface-modified PMMA. The lenses were incubated overnight with bacteria, then sonicated and vortexed to separate the adhered bacteria. Quantitative cultures were performed and the results statistically analyzed. RESULTS: Slime-negative strains of S epidermidis adhered to all IOLs but at a lower level than slime-positive strains. The most adherent lenses were acrylic with the positive strain and PMMA with the negative strain. The least adherent IOLs were PMMA with the positive strain and hydrogel with the negative strain. There were no significant differences between rigid and foldable lenses. Polypropylene was significantly more adherent than PMMA to the slime-positive strain. The acrylic and the HSM PMMA IOLs were significantly more adherent to the positive strain. CONCLUSIONS: In vitro, there were significant differences in bacterial adhesion among IOL materials. Slime-positive strains of S epidermidis were more adherent than slime-negative ones.

Terapia antimicrobiana y medicina basada en la evidencia / Antimicrobial therapy and evidence-based medicine

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[Meropenem: microbiologic perspective]. / Meropenem: perspectiva microbiológica.

Meropenem is a beta-lactamic carbapenem derived from thienamycin and is structurally characterized by the presence of a beta-methyl group in position C1 which confers stability to the molecule versus renal dehydropeptidase 1 (DHP-1), thereby making the coadministration of an enzyme inhibitor unnecessary. Its esterochemical configuration of the lateral chain in C2 (dimethyl carbomoilpyrrolidenethium) increases the activity versus gram negative bacteria (enterobacteria and pseudomonas) and moreover, may explain the reduction in the proconvulsive effect observed in imipenem/cilastatin. Meropenem has great bactericide power and has a very wide spectrum of activity depending on it low molecular weight and zwiterionic structure, stability versus almost all the clinically important beta-lactamases and high affinity for the PBPs. It covers gram positive aerobes (Staphylococcus aureus, coagulase negative staphylococci, streptococci including Streptococcus pneumoniae resistant to penicillin, Enterococcus faecalis, Rhodococcus equi, Listeria monocytogenes) and gram negative bacteria (enterobacteria, P. aeruginosa, Acinetobacter, Aeromonas, Plesiomonas, Vibrio, Haemophilus influenzae, Neisseria, Moraxella) and anaerobes (Bacteroides, Prevotella, Porphyromonas, Fusobacterium, Clostridium, Peptostreptococcus, and Propionibacterium acnes), being more active than imipenem versus gram negatives: P. aeruginosa (2-4-fold), enterobacteria (2-32-fold) and H. influenzae (4-8-fold) and less active versus the gram positives (enterococci, streptococci and staphylococci). Meropenem has no activity on Enterococcus faecium, S. aureus resistant to methycillin, Stenotrophomonas maltophilia and other genera producers of chromosomic methalo-beta-lactamases (carbapenemases). Resistance may be due to impermeability given the loss of the OprD porin (OprD2 in enterobacteria and P. aeruginosa) loss of different membrane proteins (Proteus mirabilis, Proteus rettgeri, Enterobacter cloacae, Enterobacter aerogenes), modifications of the PBPs (gram positive) and the production of carbapenemases (chromosomic methalo-beta-lactamases).

Comparative evaluation of selective and nonselective media for primary isolation of Helicobacter pylori from gastric biopsies.

BACKGROUND: In this study, we compared and evaluated the efficacy of five culture media for the primary isolation of Helicobacter pylori from gastric biopsies. MATERIALS AND METHODS: A total of 1,174 biopsies (antrum and corpus) taken from 587 patients were plated in parallel on two selective media--Skirrow's medium and brain-heart infusion (BHI) agar supplemented with 10% sheep blood, polymyxin B, vancomycin, trimethoprim, and amphotericin B (HPA medium), and on three nonselective media--chocolate agar with Isovitalex, Columbia blood agar, and BHI-10% sheep blood agar. RESULTS: An isolation rate of 57.9% (680 of 1,174) was obtained with a combination of all media. HPA medium gave the highest isolation rate, 99.4% (676 of 680). Chocolate agar, Columbia blood agar, brain-heart blood agar, and Skirrow's medium showed very poor performance (23.5%, 28.5%, 65.9%, and 71% of all isolates, respectively). The number of cultures in HPA medium discarded due to contamination was only 2 (0.32%). There was no difference in the positive rate of culture in HPA medium between the antrum and the corpus of the stomach. CONCLUSIONS: The HPA medium is superior to Skirrow's medium and nonselective media in promoting growth of H. pylori and, on the basis of these results, we recommended the use of HPA medium for primary isolation of H. pylori from gastric biopsies.

[Requests for microbiological diagnosis by primary care physicians in the Salamanca area]. / Demanda de diagnóstico microbiológico por los médicos de atención primaria del área de Salamanca.

OBJECTIVES: To assess requests for microbiological analysis made by Primary Care doctors and to evaluate the quality of the procedure by the indicator: proportion of contaminated urine samples. DESIGN: A retrospective crossover study of requests to the Microbiology Laboratory in the University Hospital of Salamanca during 1995. SETTING: The study covered the Salamanca Health Area, which consists of 35 Health Centres and a catchment population of 358,408. PATIENTS AND OTHER PARTICIPANTS: The requests for microbiological diagnosis and results of the 43,317 samples processed were analysed. INTERVENTIONS: The data was distributed according to care level and the Area's Health Centres. MEASUREMENTS AND RESULTS: 9,574 (22%) of the total number of samples received turned out positive, 27.4% of the requests originated in Primary Care (PC). The overall request rate from PC was 33 per 1,000 inhabitants. CONCLUSIONS: The microbiological analysis most frequently requested from PC is urine culture. Relationship between request and positives is 4 to 1.

In vitro activity of BAY y 3118, and nine other antimicrobial agents against anaerobic bacteria.

The antibacterial activity of BAY y 3118, a new chlorofluoroquinolone, was determined against 257 strains of anaerobic bacteria and compared with the activities of ofloxacin, ciprofloxacin, sparfloxacin, imipenem, cefoxitin, clindamycin, chloramphenicol, metronidazole, and ornidazole. Overall, BAY y 3118 was the most active agent tested against the Bacteroides fragilis group. Its activity (MIC90, 0.5 mg/L) was 16-fold lower than that of sparfloxacin (MIC90, 8 mg/L), and more than 100-fold lower than that of ofloxacin (MIC90, 64 mg/L) and ciprofloxacin (MIC90, 128 mg/L) against the group. No strains belonging to this group were resistant to metronidazole (MICs range, 0.12-2 mg/L) and ornidazole (MICs range, 0.12-4 mg/L). BAY y 3118 was more active than those quinolones against Prevotella and Porphyromonas spp., Fusobacterium spp., Clostridium perfringens and C. difficile (MIC90, 0.12, 0.06, 0.12 and 0.25 mg/L, respectively). The activity of BAY y 3118 against Peptostreptococcus spp. (MIC90, 1 mg/L) was slightly lower than that of the other Gram-positive bacteria tested. In general, BAY y 3118 was more active than cefoxitin, and it was superior to antianaerobic chemical agents like metronidazole, ornidazole and clindamycin. Pharmacokinetic and clinical trials are required to define the role of BAY y 3118 in the treatment of anaerobic infections.

[An experimental model of bacterial translocation]. / Modelo experimental sobre translocación bacteriana.

The authors submit an experimental model for bacterial translocation (administering OF-1 mice Zymosan intra-peritoneally at a dose of 1 mg/kg weight). The existence is confirmed of this new mechanism of infection (0% of translocation in control groups, as against 80% in the trial group -p < 0.001). The bacteria in the translocated organs coincide with those present in the fecal flora of the experimental animal. This study is the point of departure for subsequent research to study the physiopathological mechanisms of the phenomenon, which will enable us subsequently to reach better preventive and/or therapeutic decisions.