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Biomedical subjects

L Aguilar

Publications and source records attributed to L Aguilar.

At least 91 records · Page 5Linked to original sources
PubMed1999

In vitro bactericidal activity of peak serum concentrations of co-amoxiclav, amoxicillin and vancomycin against methicillin-resistant Staphylococcus aureus.

In order to explore the bactericidal activity of concentrations similar to the peak serum concentrations obtained after a single i.v. dose of 2,000/200 mg co-amoxiclav and 500 mg vancomycin, killing curves with co-amoxiclav (69/10 microg/ml), amoxicillin (69 microg/ml), clavulanic acid (10 microg/ml), and vancomycin (15 microg/ml) were performed against two isogenic (ss-lactamase positive and negative) methicillin-resistant Staphylococcus aureus strains in cation-supplemented Mueller-Hinton broth with 2% NaCl incubated at 35 degrees C. Colony counts were performed at 0, 1, 2, 3 and 4 hours in Mueller- Hinton plates supplemented with 4% NaCl and 25 microg/ml oxacillin to measure the resistant population. Similar initial inocula reductions were obtained for amoxicillin-clavulanic acid and vancomycin for both strains, and significant differences were found in comparison to the control. Clavulanic acid decreased the growth rate of the ss-lactamase negative strain when compared to control curves. The penicillin-binding protein 2a affinity of old ss-lactams in conjunction with clavulanic acid overcoming ss-lactamase resistance may explain these results.

Amoxicillin↗
PubMed1998

Effect of polymorphonuclear neutrophils on serum bactericidal activity against Streptococcus pneumoniae after amoxicillin administration.

The effect of phagocytic killing on serum bactericidal activity against Streptococcus pneumoniae was investigated 0, 1.5, 8 and 12 h after a single 875 mg oral dose of amoxicillin in healthy adults. Killing curves were determined with polymorphonuclear neutrophils (PMN), serum or PMN plus serum. Global killing (i. e. intracellular and extracellular killing) over 3 h of incubation was expressed as the area under the killing curve (AUKC; log cfu x h/ml). Amoxicillin did not affect the activity of PMN alone. For serum alone, the AUKC of post-administration samples (with supra-inhibitory amoxicillin concentrations) was significantly lower than in baseline samples. For serum plus PMN, significant bactericidal activity of serum was still found in samples after antibiotic concentrations had reached sub-inhibitory levels.

Adult↗
PubMed1998

In vivo efficacies of amoxicillin and cefuroxime against penicillin-resistant Streptococcus pneumoniae in a gerbil model of acute otitis media.

The comparative efficacies of amoxicillin and cefuroxime against acute otitis media caused by a penicillin-resistant (MIC, 2 micrograms/ml) Streptococcus pneumoniae strain were assessed in a gerbil model by challenging each ear with 10(7) bacteria through transbullar instillation. Each antibiotic was tested at two doses (5 and 20 mg/kg of body weight) administered at 2, 10, and 18 h postinoculation. Samples were obtained from the middle ear (ME) on days 3 and 7 postinoculation for determination of bacterial counts. Only amoxicillin, at both doses, was able to significantly halt the weight loss in animals, reducing both the number of culture-positive animals and the bacterial concentration in ME samples versus the values for untreated animals. Comparison of the efficacies between the antibiotics, determined by their ability to achieve culture-negative ME specimens, showed that amoxicillin at 5 mg/kg was significantly more active than cefuroxime at the same dose. The use of higher doses of either amoxicillin or cefuroxime did not produce significantly better results than those obtained with the lower dose but caused a greater inflammatory response. The more favorable results obtained with amoxicillin compared with those obtained with cefuroxime could be related to the antimicrobial susceptibility of the pneumococcal strain (MICs and minimum bactericidal concentrations of 1 and 1 microgram/ml and 4 and 4 micrograms/ml for amoxicillin and cefuroxime, respectively) as well as to the better pharmacokinetic parameters obtained with amoxicillin.

Acute Disease↗
PubMed1998

In vitro activities of co-amoxiclav at concentrations achieved in human serum against the resistant subpopulation of heteroresistant Staphylococcus aureus: a controlled study with vancomycin.

The effects of concentrations that simulated those in human serum after a single intravenous dose of amoxicillin (2 g), amoxicillin-clavulanic acid (2,000 and 200 mg, respectively), or vancomycin (500 mg), on the viability and beta-lactamase activity of two isogenic (beta-lactamase and non-beta-lactamase producer) heteroresistant Staphylococcus aureus strains were studied in an in vitro pharmacodynamic model. A reduction of > or = 97% of the initial inoculum was obtained with vancomycin and amoxicillin-clavulanic acid against both strains, with respect to the total bacterial population and the oxacillin-resistant subpopulation. The same pattern was observed with amoxicillin and the beta-lactamase-negative strain. beta-Lactamase activity in the beta-lactamase-positive strain changed over time parallel to viability, decreasing with amoxicillin-clavulanic acid or vancomycin and increasing in the amoxicillin and control groups. Clavulanic acid concentrations achievable in serum that changed over time allowed amoxicillin to act against the beta-lactamase-producing methicillin-resistant S. aureus to a similar extent as vancomycin.

Amoxicillin↗
PubMed1998

Taenia solium: description of the intestinal implantation sites in experimental hamster infections.

Experimental infections in golden hamsters with viable Taenia solium metacestodes were used to study by light and electron microscopy the implantation site of the adult tapeworm in the intestinal wall. Implantation sites from 3-, 4-, 10-, and 40-day infections were located in the upper third of the duodenum, excised and fixed in Zenker's or Karnovsky's solution, embedded in Polybed resin, and sectioned longitudinally to observe the position of the worm on the intestinal wall. The scolex of the tapeworm was situated between host villi, with the rostellum penetrating the intestinal wall and the suckers entrapping adjacent villi. Serial sections through several whole implantation sites revealed that the worm was anchored to the host by all 4 suckers simultaneously, each of which was located at a different level and had entrapped intestinal villi in its cavity. Host tissue within the suckers was damaged, exhibiting various degrees of cell lysis and necrosis of epithelial and submucosal cells. The tegumentary surface and microtriches of the scolex were well preserved, with occasional coalescence of tegumentary microvesicles in 10- and 40-day-old infections; microtriches were in direct contact with the damaged host tissue. This study is the first morphological and ultrastructural description of the attachment of T. solium to the intestinal wall employing an experimental model, the results of which may contribute to a better understanding of the biology of human tapeworm infections.

Animals↗
PubMed1998

Comparative development of Taenia solium in experimental models.

Various mammals were evaluated as experimental models of adult Taenia solium. Suppressed and nonsuppressed hosts were used as experimental models. Infections were performed per os with cysticerci obtained from pigs; immunosuppression was induced with methyl prednisolone acetate at intervals of 10-14 days after infection. Tapeworms developed in hamsters, gerbils, and chinchillas but failed to develop in rabbits, cats, pigs, and rhesus monkeys. In infectable animals, treatment with the steroid facilitated maintenance and development of the parasite, and more tapeworms were obtained. Mature and some pregravid proglottids were recovered from hamsters and gerbils, whereas a gravid T. solium was obtained from a chinchilla at 12 wk postinfection. Eggs recovered from the chinchilla transformed into cysticerci in a pig 12 wk after oral infection. The T. solium-chinchilla experimental system seems to be an alternative definitive host for this parasite and thus the basis for a great diversity of studies.

Animals↗
PubMed1997

Spinal intraosseous arteriovenous malformation as a cause of juvenile scoliosis. A case report.

STUDY DESIGN: A case report. OBJECTIVES: To report and discuss an unusual case of scoliosis resulting from an arterial malformation of the spine. SUMMARY OF BACKGROUND DATA: This is a report of clinical manifestation, physical findings, computed tomography scan, magnetic resonance imaging, bone scan, and results after surgery in an 8-year-old boy with a painful scoliosis resulting from an intraosseous arteriovenous malformation of the spine. METHODS: Radiographs, computed tomography scan, magnetic resonance imaging, and bone scans were studied and oriented us to the diagnosis of scoliotic attitude secondary to a benign-appearing tumor in the right lamina of L4. Surgery was performed through a posterior midline approach to remove the lesion en bloc. Postoperative treatment was performed with a Boston orthosis. RESULTS: Final pathology reports diagnosed an intraosseous arteriovenous malformation. After 32 months, the boy had no pain, and scoliotic attitude diminished despite radiographs still showing a single 10 degrees right lumbar curve. CONCLUSIONS: Primary intraosseous arteriovenous malformations are rare. This case shows the scarce specificity of clinical findings, radiology, and bone scan in the diagnosis of these lesions when they are localized in vertebral territory. Surgical excision of the lesion relieves pain but does not completely correct the scoliotic attitude.

Arteriovenous Malformations↗
PubMed1997

Effect of clavulanic acid and/or polymorphonuclear neutrophils on amoxicillin bactericidal activity against Streptococcus pneumoniae.

The effects of polymorphonuclear neutrophils (PMNs) and/or clavulanic acid on the bactericidal activity of amoxicillin (at human serum achievable concentrations) against a serotype 3 penicillin-susceptible Streptococcus pneumoniae strain [minimal inhibitory concentration/minimal bactericidal concentration (MIC/MBC) values of penicillin, amoxicillin, and amoxicillin/clavulanic acid (2:1) = 0.01/0.01 microgram/ml] and a serotype 9 penicillin-resistant strain [MIC/MBC of penicillin, amoxicillin, and amoxicillin/clavulanic acid (2:1) = 1/2 microgram/ml] were studied. Against the penicillin-resistant strain, subinhibitory concentrations of amoxicillin reduced the growth rate; this effect was increased by the addition of clavulanic acid. A reduction of the penicillin-resistant initial inocula (3 x 10(6) cfu/ml) at subinhibitory concentrations was obtained only with amoxicillin plus clavulanic acid and PMNs. At suprainhibitory concentrations, both clavulanic acid and PMNs increased the bactericidal activity of amoxicillin, as evidenced by an increased reduction in the penicillin-resistant initial inocula. The combined effect of these antibiotics and immune defenses may help explain the maintenance of their clinical efficacy in respiratory tract infections, despite the increase in the incidence of penicillin-resistant pneumococci.

Amoxicillin↗
PubMed1997

Detection of antibodies against hepatitis A in blood spots dried on filter paper. Is this a reliable method for epidemiological studies?

Diluted dried blood drops on filter paper were compared with serum samples as a specimen source for qualitative anti-HAV antibody determination by ELISA. A total of 298 serum samples and dried blood drops were collected from a population of healthy adolescents (15.3 +/- 1.2 years old). The prevalence of anti-HAV antibody obtained by testing serum samples was 7.7% (95% CI:4.8 10.1). Compared with serum sampling the sensitivity and specificity of diluted dried blood drops were 91.3 and 99.3%. The positive and negative predictive values were 91.3 and 99.3%, respectively, and the likelihood ratios of positive and negative results were 91 and 0.09. It is proposed that this test represents a reliable procedure for anti-HAV antibody testing.

Adolescent↗
PubMed1997

Suspicion of quinolone active metabolite following discrepancy between predicted and experimental urine bactericidal activities.

The prediction of urine antibacterial activity from pharmacological and microbiological parameters was assessed by using experimental urine levels and urine bactericidal titers determined up to 72 h after a 400-mg single dose of two quinolones in a phase I study. The area under the bactericidal curve (AUBC) was accurately predicted for norfloxacin but significantly (P < 0.001) underestimated for rufloxacin (actual value was four times higher than the predicted value against Escherichia coli and two times higher against Staphylococcus aureus). In vitro susceptibility differences between the two strains predicted the ex vivo AUBC differences for norfloxacin but not for rufloxacin, where ex vivo differences were greater than expected. Urine bactericidal titers for up to 72 h were accurately predicted for norfloxacin against E. coli and S. aureus and for rufloxacin against S. aureus, but experimental activity for up to 48 h was four times higher (P < 0.001) than the predicted activity for rufloxacin against E. coli. In the case of norfloxacin, the duration of adequate urine antibacterial activity against S. aureus was overestimated. Inaccurate estimations of ex vivo antibacterial activity of a suspected active metabolite (as with rufloxacin) when an adequate cutoff is not established may have dosing implications.

Anti-Infective Agents↗
PubMed1997

Pharmacodynamic effects of amoxicillin versus cefotaxime against penicillin-susceptible and penicillin-resistant pneumococcal strains: a phase I study.

Serum bactericidal activity against a penicillin-susceptible strain and a penicillin-resistant strain of Streptococcus pneumoniae (amoxicillin and cefotaxime MICs, 0.001 and 1 microg/ml, respectively, and MBCs, 0.01 and 2 microg/ml, respectively) was measured in 12 healthy volunteers who each received an oral 875-mg dose of amoxicillin and an intramuscular 1-g dose of cefotaxime in a crossover fashion. The areas under the bactericidal activity-time curves for the two strains were found to be similar for both antibiotics despite the significantly higher (P < 0.002) AUC/MIC and peak level/MIC values for cefotaxime.

Adult↗