[Phenotypic and genotypic characterization of imipenem-resistant Pseudomonas aeruginosa isolated in a Buenos Aires hospital]

From 129 P. aeruginosa isolated at a health care centre located in Buenos Aires (Hospital "Eva Perón"), 14% produced IMP-13. Although 18 isolates were metallo-beta-lactamases (MBL) producers, only those isolates that displayed altered outer membrane protein profiles correlated with the resistant category according to CLSI or even Subcomisión de Antimicrobianos, SADEBAC, AAM. Phenotypic screening of metallo-beta-lactamases proved to be appropriate for detecting MBL producing isolates. IMP-13 producing isolates corresponded to at least five different clonal types, which not only suggests the dissemination of the resistant strain but also of the resistant marker.

[Comparison of different methods in order to identify Proteus spp]

Comparison of different methods in order to identify Proteus spp. The objectives were: (a) to identify Proteus strains to species level, following Farmer's and O'Hara's conventional biochemical reactions; b) to evaluate the sensitivity and specificity of both the API 20E method and a schema of reduced reactions (TSI and MIO agar: motility, indole and ornithine) comparing them with conventional methodology, and c) to evaluate the utility of SDS-PAGE (total proteins) in order to identify Proteus strains to species level. Two hundred and five Proteus spp. clinical isolates, were collected between January 1998 and September 2004, from inpatients and outpatients at Hospital de Clinicas. Strains were identified by means of conventional methodology, the API 20E method, and a schema of reduced reactions. SDS-PAGE (total proteins) was used in 48 out of the 205 strains. The API 20E method identified 79 out of 87 (90.8%) strains of P. mirabilis, 103 out of 103 P. vulgaris complex, and 15 out of 15 P. penneri. Eight strains of P. mirabilis were identified as Proteus spp., the acid production from maltose being necessary to identify them to species level. The schema of reduced reactions identified 205 out of 205 (100%) strains, that is, this schema of reduced reactions identified all the strains to species level without any additional tests, in marked contrast to the API 20E method. The SDS-PAGE (total proteins) identified the three species of the genus, even if the strains of P. mirabilis showed different biochemical reactions.

[Genetic environment of CTX-M-2 in Klebsiella pneumoniae isolates from hospitalized patients in Uruguay]

We studied two CTX-M-2-producing Klebsiella pneumoniae clinical strains, K96005 and K13, isolated from hospitalized patients in Uruguay, during 1996 and 2003, respectively. The genomic surroundings of bla(CTX-M-2) were characterized by PCR-mapping and DNA sequencing. Our results show that blaCTX-M-2 is included in a complex class-1 integron (InK13), associated with an orf513 in both isolates. The genetic array of the integron, aac(6')-lb, bla(OxA,2), orfD (gene cassette region), associated with an orf513-bla(CTX-M-2), seems to be widely disseminated over the Rio de la Plata region.

[Prevalence of metallo-beta-lactamase in carbapenem resistant Pseudomonas aeruginosa at a university hospital of Buenos Aires City]

The present study was conducted to estimate the prevalence of metallo-beta-lactamases in 91 consecutive carbapenem resistant Pseudomonas aeruginosa isolates, recovered from inpatients at Hospital de Clínicas in Buenos Aires. Both, phenotypic and genotypic methods detected the presence of carbapenemases in 10 (11%) isolates, corresponding to VIM-11 in 7/10 and VIM-2 in the others. Codifying genes were all included in class 1 integrons, upstream genes coding for aminoglycoside modifying enzymes. One hundred percent sensitivity and specificity was achieved by the metallo-beta-lactamases phenotypic screening method using EDTA (1 micromol) disks in the Pseudomonas aeruginosa isolates included in this study. Sensitivity to aztreonam in carbapenem resistant isolates was suspicious of the presence of these enzymes.

[Phenotypic and genotypic characterization of resistance to third-generation cephalosporins in Enterobacter spp]

Enterobacter spp. are becoming increasingly frequent nosocomial pathogens with multiple resistance mechanism to beta-lactam antibiotics. We carried out the phenotypic and genotypic characterization of beta-lactamases in 27 Enterobacter spp. (25 Enterobacter cloacae y 2 Enterobacter aerogenes), as well as the ability of different extended spectrum-lactamase (ESBL) screening methods. Resistance to third generation cephalosporins was observed in 15/27 (63%) isolates. Twelve resistant isolates produced high level chromosomal encoded AmpC beta-lactamase; 6 of them were also producers of PER-2. Resistance to third generation cephalosporins in the remaining 3 isolates was due to the presence of ESBLs, PER-2 in 2 cases, and CTX-M-2 in the other. Only CTX-M-2 production was detected with all tested cephalosporins using difusion synergy tests, while cefepime improved ESBLs detection in 7/8 PER-2 producers, 4/8 in the inhibitor approximation test and 7/8 with double disk test using cefepime containing disk with and without clavulanic acid. Dilution method, including cephalosporins with and without the inhibitor detected 1/9 ESBLs producers.

[Consensus for antimicrobial susceptibility testing for Enterobacteriaceae. Subcommittee on Antimicrobials, SADEBAC (Argentinian Society of Clinical Bacteriology), Argentinian Association of Microbiology]

Taking into account previous recommendations from the National Committee for Clinical Laboratory Standards (NCCLS), the Antimicrobial Committee, Sociedad Argentina de Bacteriología Clínica (SADEBAC), Asociación Argentina de Microbiología (AAM), and the experience from its members and some invited microbiologists, a consensus was obtained for antimicrobial susceptibility testing and interpretation in most frequent enterobacterial species isolated from clinical samples in our region. This document describes the natural antimicrobial resistance of some Enterobacteriaceae family members, including the resistance profiles due to their own chromosomal encoded beta-lactamases. A list of the antimicrobial agents that should be tested, their position on the agar plates, in order to detect the most frequent antimicrobial resistance mechanisms, and considerations on which antimicrobial agents should be reported regarding to the infection site and patient characteristics are included. Also, a description on appropriate phenotypic screening and confirmatory test for detection of prevalent extended spectrum beta-lactamases in our region are presented. Finally, a summary on frequent antimicrobial susceptibility profiles and their probably associated resistance mechanisms, and some infrequent antimicrobial resistance profiles that deserve confirmation are outlined.

Extended-spectrum beta-lactamases in enterobacteriaceae in Buenos Aires, Argentina, public hospitals

Resistance to extended-spectrum cephalosporins is often associated with plasmid encoded extended spectrum beta-lactamases (ESBL). In order to evaluate the prevalence and diversity of ESBLs in enterobacteria in our city, a 1-month-period survey was carried out from April to May 2000. Extended-spectrum-cephalosporin-resistant strains, isolated from inpatient clinical specimens other than stools, were collected among 17 participating hospitals. From a total of 427 enterobacterial strains that were collected during this period, 39 were extended-spectrum cephalosporin resistant. The National Committee for Clinical Laboratory Standards' Screening and Confirmatory Tests for ESBL production were performed using cefotaxime and ceftazidime; cefepime and cefepime-clavulanic acid-containing disks were included. beta-Lactamases were characterized by isoelectric focusing and PCR amplification using specific primers. Three different ESBLs were detected: SHV-related (4 isolates), PER-2-type (9 isolates), and CTX-M-2-related (26 isolates). Sequencing of the corresponding genes confirmed CTX-M-2 in 19 of 21 and CTX-M-31 (an allelic variant) in the remaining 2 of 21. CTX-M-2 (or its variant) was detected in all Escherichia coli, Enterobacter aerogenes, Serratia marcescens, Proteus mirabilis, and Providencia stuartii strains, while PER-2 was detected in Enterobacter cloacae, E. aerogenes, and Klebsiella pneumoniae; SHV-related ESBL were found only in K. pneumoniae. These results clearly show that CTX-M-2 is the most prevalent ESBL produced by enterobacterial species isolated from public hospitals in Buenos Aires.

[Consensus on antimicrobial sensitivity tests in gram-positive cocci. Subcommittee on Antimicrobials, SADEBAC (Argentinian Society of Clinical Bacteriology), Argentinian Association of Microbiology]

Antimicrobial susceptibility testing is mainly performed in Argentina by disk diffusion method, following National Committee for Clinical Laboratory Standards (NCCLS) recommendations. We worked out new recommendations for the reporting and interpretation of this test when dealing with gram-positive cocci, in accordance to local trends and epidemiology. General considerations for performing the diffusion assay, quality control, and an update on susceptibility testing for gram-positive cocci are reported in this first document. The present update should be considered as a group of recommendations summarized by Argentinean experts and as the result of a consensus meeting coordinated by the Subcomisión de Antimicrobianos of the Sociedad Argentina de Bacteriología Clínica (Asociación Argentina de Microbiología). Experts in antimicrobial agents were convened in order to prepare this final document. These recommendations take into account local needs, affordability and availability to be used in current practice, tending to contribute to the correct antimicrobial treatment election, according to the particular microorganism and the infection sites.

Third-generation cephalosporin resistance in Shigella sonnei, Argentina

Shigella sonnei resistant to cefotaxime (but not to ceftazidime) was isolated for the first time in stool samples from a pediatric patient with vomiting and bloody diarrhea in northern Argentina. Microbiologic and biochemical tests confirmed the presence of an extended spectrum beta-lactamase displaying an apparent isoelectric point value of 8.2.

In vitro reconstructed dermis implanted in human wounds: degradation studies of the HA-based supporting scaffold

The objective of the present study was to demonstrate the safety and efficacy of a dermal replacement for cutaneous wounds of diverse origin. Autologous fibroblasts were cultured in fleece scaffolds made from benzyl esters of hyaluronic acid and applied onto cutaneous lesions. The cases presented are (1) skin removal for multiple epithelioma and (2) chronic deep decubitus ulcer. Dermal-like tissue applied by the surgeon elicited no adverse reactions, and was fully integrated and well-vascularized by 1-3 weeks. In Case 1, the material was fully integrated after 1 week, and after 3 weeks an epidermal autograft was overlaid which showed good take with excellent integration observed after 4 weeks. At 12 months, skin demonstrated visual normo-elastic properties and no signs of excessive scarring. In Case 2, 2-3 weeks after the dermal implant was applied, the wound was invaded with granulation tissue and healing occurred by secondary intention. The ulcer was healed by 8 weeks, with the biomaterial completely resorbed and a complete re-epithelialization over the dermal-like tissue. These results suggest that autologous fibroblast culture in hyaluronan-derived scaffolds may be successfully grafted in diverse cutaneous pathologies and constitute a suitable bed for further epidermal implantation.

Use of dermal-like tissue in the management of chronic and acute full-thickness cutaneous wounds

This paper presents a dermal replacement technique for cutaneous wounds of diverse origin. An autologous tissue-engineered dermal-like structure was implanted in one patient with an acute surgical excision of a nevus and in another patient with a chronic post-traumatic ulcer. The dermal constructs were well integrated with the wound area, and, at 3 weeks, an epidermal covering was implanted. In both cases, 3 to 8 weeks after autografting, good integration of the transplanted epidermis with the surrounding native skin and a good take over the dermal-like tissue occurred. The use of this technology, despite its high cost, is increasing. Clinicians choose it because it helps heal critical wounds for which current therapies have failed.

Use of a hyaluronan-based biomembrane in the treatment of chronic cholesteatomatous otitis media

OBJECTIVE

To test the efficacy and safety of a hyaluronan-based biomembrane in stimulating the healing process in patients undergoing tympanomastoid surgery.

STUDY DESIGN

The trial was an open, two-arm, controlled, randomized, prospective, multicenter study conducted at two different hospitals.

PATIENTS

Sixty subjects (18-65 years of age, both sexes) with chronic cholesteatomatous otitis media were enrolled and treated by the "one-stage open technique." Efficacy and safety parameters were assessed at 3, 5, 7, 9, 11, 13, 17, 21, and 25 weeks after surgery. Three sets of composite criteria were considered: patient's assessment of quality of healing, otomicroscopy, and audiometry.

RESULTS

Of the 60 patients, 50 completed the study. Subjects treated with the biomembrane had statistically significant better scores than controls (no treatment) for all variables considered, excluding audiometry (no significant differences). No adverse events occurred in treated patients.

CONCLUSION

Data demonstrate that the application of a hyaluronan-based biomembrane improves the healing of the mastoid cavity following "open" tympanoplasty. In particular, re-epithelialization was significantly faster after the application of the biomembrane. Moreover, the device neither caused any adverse events nor showed signs of ototoxicity. Re-epithelialization of open cavities and tympanic grafts still represents for surgeons an unpredictable step in the healing process. Hyaluronian-derivates may effectively contribute to the reduction of such variability.

Hyaluronan-based biopolymers as delivery vehicles for bone-marrow-derived mesenchymal progenitors

The tolerability and safety of hyaluronan-based three-dimensional scaffolds as a culture vehicle for mesenchymal progenitor cells was investigated in this pilot study. The proliferation patterns and extracellular matrix production of rabbit and human mesenchymal, bone-marrow-derived progenitors first were characterized in vitro. Subsequently rabbit autologous cells were cultured in this hyaluronan-based scaffold and implanted in a full-thickness osteochondral lesion. In vitro histologic findings showed that mesenchymal progenitor cells adhered and proliferated onto the hyaluronan-derived scaffold. Human stem cells were shown to produce the main extracellular matrix molecules, accompanied by an occasional synthesis of mature type II collagen. In vivo data demonstrated that the biomaterial, with or without mesenchymal progenitors, did not elicit any inflammatory response and was completely degraded within 4 months after implantation. With regard to the efficacy of this cell therapy, even among the small number of animals tested there was histologic evidence that lesions filled with the biomaterial, either seeded or unseeded with cells, achieved a faster and better healing compared to empty controls. The present data suggest that the hyaluronan-based scaffolds are well tolerated and safe and may be a valuable delivery vehicle for tissue engineering in the repair of articular cartilage defects.

Cefotaxime-hydrolysing beta lactamases in Morganella morganii

The frequency of enterobacterial isolates with high resistance to expanded-spectrum beta-lactam antibiotics (mainly cefotaxime or ceftriaxone) has increased notoriously in Argentina, mainly because of the spread of extended-spectrum beta-lactamases. The aim of this work was the study of extended-spectrum beta-lactamases in several Morganella morganii isolates with unusually high resistance to ceftriaxone. These strains produced at least two beta-lactamases, of apparent pIs of 5.4 and 8.2, molecular weight 23 000, well inhibited by clavulanate, compatible with a broad-spectrum beta-lactamase - perhaps TEM-1 - and an extended-spectrum beta-lactamase, respectively. The extended-spectrum beta-lactamase was identified as a CTX-M-type beta-lactamase - probably CTX-M-2 - by polymerase chain reaction, restriction profile analysis and DNA-DNA hybridisation. The remaining isolates studied produced either the broad-spectrum beta-lactamase plus the ubiquitous AmpC beta-lactamase (13 strains), or the AmpC beta-lactamase only (10 strains).

Chondrocyte aggregation and reorganization into three-dimensional scaffolds

Articular cartilage has a very limited self-repairing capacity; thus, chondral lesions normally result in chronic degeneration and, eventually, osteoarthritis development. Currently, tissue engineering offers a new tool for the clinical treatment of osteochondral defects. The present investigation aimed to develop an in vitro engineered cartilage using a new class of semisynthetic scaffolds. Two nonwoven meshes of hyaluronan esters (Hyaff(R) derivatives) were seeded with sternal chick embryo chondrocytes cultured for up to 21 days, after which time they were assessed for both the cellular growth profile and histological features. Avian chondrocytes easily adhered and proliferated onto hyaluronan-based scaffolds, demonstrating a significant preference for the fully esterified benzylic form. Histochemical staining revealed the presence of a neosynthesized glycosaminoglycan-rich extracellular matrix, and immunohistochemistry confirmed the deposition of collagen type II. Moreover, ultrastructural observations supported evidence that chondrocytes grown onto a hyaluronan-derived three-dimensional scaffold maintained their unique phenotype and organization in a cartilage-like extracellular matrix. These findings support the further pursuit of a transplantable engineered cartilage using human chondrocytes for the regeneration of chondral lesions.

Clostridial collagenase releases bioactive fragments from extracellular matrix molecules

The current study was designed to investigate the biological role of small extracellular matrix fragments in wound healing. Human burn eschar tissue was digested with bacterial collagenase, and small aminoacidic fragments were inoculated in both human dermal fibroblast cultures and polyvinyl alcohol sponges implanted subcutaneously in the rat. Proliferation assays on cell cultures and biochemical and histologic analyses of the animal model were then performed. Results showed that fibroblasts treated with low concentrations of eschar fragments duplicated significantly faster than controls. Biochemical and histologic data from sponge implants showed that the inflammatory response was augmented by eschar-derived fragments at postoperative day 2, whereas protein and hydroxyproline synthesis were decreased at day 14. In conclusion, these data substantiate that the application of bacterial collagenase to débride necrotic tissue may have an indirect healing effect resulting from the local release of bioactive matrix-derived fragments.

Histamine effects on conjunctival fibroblasts from patients with vernal conjunctivitis

Histamine, an important mast cell mediator in allergic disorders, may affect extracellular matrix production and cell growth in vernal keratoconjunctivitis (VKC). In the present study, the histamine reactivity of conjunctival fibroblasts derived from VKC patients was investigated in vitro. Conjunctival fibroblast cultures were derived from biopses of 8 tarsal VKC patients and 5 normal subjects. These cells were maintained in vitro and stimulated with different concentrations of histamine with and without H1 (clorpheniramine) and H2 (cimetidine) receptor antagonists. Comparisons were made to fibroblasts grown in the same media without histamine and to fibroblasts stimulated with just antihistamine. The effects of histamine were evaluated by: (1) the MTT test to assess cell proliferation; (2) an in vitro wound model for cell migration and (3) the measurement of procollagen I (PIP) and procollagen III (PIIIP) in supernatants for collagen production. Results showed: (1) While VKC-derived fibroblasts proliferated at a faster rate than normal cells in unstimulated media, after histamine stimulation, VKC and normal cells grew at a similar rate. Both H1 and H2 antagonists significantly inhibited (P<0.05) histamine-induced cell proliferation. (2) Histamine enhanced cell migration after wounding; this effect was inhibited only by H2 antagonism. (3) When stimulated with histamine, VKC fibroblasts produced significantly more PIP than those in control media. Furthermore, VKC-derived fibroblasts were more sensitive to histamine challenge, producing significantly more PIP than normal fibroblasts. H1 and H2 antagonists did not modify histamine-stimulated PIP production. The enhanced proliferative and productive capacity of VKC fibroblasts may be the result of a selective overgrowth of one or more fibroblast subpopulations in a chronically inflamed tissue. Histamine increased proliferation, migration and collagen production in both normal and VKC fibroblasts. Since H2 antagonism modulated both cell growth and migration, but not histamine-induced collagen production, the latter may be mediated by a different receptor. These results showed that histamine is at least partially responsible for fibroblast stimulation.

Semisynthetic resorbable materials from hyaluronan esterification

In recent years, research on new, biocompatible, degradable materials has seen the development of a series of modified natural polymers. Among these, a new class of materials consisting of different hyaluronan derivatives promises to be useful in a whole range of clinical applications thanks to their varied biological properties. These new materials are obtained by chemical modification of purified hyaluronan consisting of the partial or total esterification of the carboxyl groups of this natural polymer. This review on the properties of the new materials reports some of their biocompatibility and characterization aspects based on findings from studies conducted on the ethyl and benzyl hyaluronan esters, two representative members of this new class of compounds, and is intended to arouse interest in the potential of other, as yet unexplored derivatives. From the results of a number of investigations, the various derivatives appear to possess different physico-chemical properties, especially as far as the degree of hydration and polymer stability are concerned. In addition, the type of esterification and extent of chemical esterification of hyaluronan considerably affects the biological properties of these materials, offering a range of polymers either favouring or, conversely, inhibiting the adhesion of certain types of cell.

In vitro engineering of human skin-like tissue

Coverage of large, full-thickness burns presents a challenge for the surgeon due to the lack of availability of the patient's own skin. Currently, tissue engineering offers the possibility of performing a suitable therapeutic wound coverage after early burn excision by using cultured keratinocyte sheets supported by a dermal layer. The aim of this study was to develop and characterize a skin substitute composed of both epidermal and dermal elements. For this purpose we grew keratinocytes and fibroblasts separately for 15 days within two different types of biomaterials. Cells then were co-cultured for an additional period of 15 days, after which samples were taken and processed with either classic or immunohistochemical stainings. Results showed that (1) human fibroblasts and keratinocytes can be cultured on hyaluronic acid-derived biomaterials and that (2) the pattern of expression of particular dermal-epidermal molecules is similar to that found in normal skin. The data from this study suggest that our skin equivalent might be useful in the treatment of both burns and chronic wounds.

In vitro engineering of human skin-like tissue

Coverage of large, full-thickness burns presents a challenge for the surgeon due to the lack of availability of the patient's own skin. Currently, tissue engineering offers the possibility of performing a suitable therapeutic wound coverage after early burn excision by using cultured keratinocyte sheets supported by a dermal layer. The aim of this study was to develop and characterize a skin substitute composed of both epidermal and dermal elements. For this purpose we grew keratinocytes and fibroblasts separately for 15 days within two different types of biomaterials. Cells then were co-cultured for an additional period of 15 days, after which samples were taken and processed with either classic or immunohistochemical stainings. Results showed that (1) human fibroblasts and keratinocytes can be cultured on hyaluronic acid-derived biomaterials and that (2) the pattern of expression of particular dermal-epidermal molecules is similar to that found in normal skin. The data from this study suggest that our skin equivalent might be useful in the treatment of both burns and chronic wounds.

Antioxidant effects of hyaluronan and its alpha-methyl-prednisolone derivative in chondrocyte and cartilage cultures

OBJECTIVE

To compare hyaluronan and its alpha-methyl prednisolone derivative (HYC-141) with respect to their potential to directly cause tissue damage and to protect tissues from attack by reactive oxygen species.

METHODS

Cartilage samples and chondrocytes were isolated from 15-day chick embryos and were exposed to enzyme-based and activated inflammatory cell-free radical generating systems in the presence of varying concentrations of alpha-methyl prednisolone, hyaluronan, and HYC-141. Tissue and cell vitality was measured by determining the incorporation of radioactive sulphate into newly synthesized glycosaminoglycans.

RESULTS

Only alpha-methyl prednisolone caused a significant decrease in biosynthetic activity. All the tested substances were capable, to some extent, of protecting tissues and cells from damage by reactive oxygen species; HYC-141 demonstrated the greatest protective effect.

CONCLUSION

These data suggest that HYC-141 may possess certain advantages over the individual component molecules in the local treatment of arthropathies.

Antimicrobial activity of 5,6-dihydrobenzo-[a]-carbazoles. Part II

A new series of twenty-two 5,6-dihydrobenzo[a]carbazoles was synthesized, some showing good antibacterial activity. The presence and position of substituents seems to be critical for such activity.

Different effects of acute administration of aminophylline and nitroglycerin on exercise capacity in patients with syndrome X

To investigate the effects of the acute administration of aminophylline and nitroglycerin on effort ischemia, 20 patients with syndrome X underwent 3 bicycle exercise tests after sublingual nitroglycerin (0.3 mg) and after 90 minutes of oral administration of aminophylline (400 mg). Compared with the basal test, only aminophylline induced a significant increase in the time to ischemic threshold and to angina; these findings support the potential therapeutic role of this adenosine receptor blocking agents and suggest a possible role of "steal phenomenon" in the pathogenesis of effort angina in patients with syndrome X.

Abnormal response to exercise in middle-aged NIDDM patients with and without autonomic neuropathy

The cardiovascular response to exercise in middle-aged non-insulin-dependent diabetes mellitus (NIDDM) patients and the potential role of clinical characteristics and autonomic function were evaluated. One hundred and eight NIDDM patients, aged 40-65 years, were compared with a control group of 112 subjects, matched by age, sex, physical fitness, and presence of hypertension. All subjects performed a maximal exercise test. The diabetic patients completed cardiovascular autonomic neuropathy (CAN) tests: deep breathing, postural hypotension and lying to standing. There were no significant differences in total work capacity, heart rate, and blood pressure, either at rest or at peak exercise between the two groups. Diabetic patients showed significantly lower values of systolic and diastolic blood pressure during exercise, significantly slower recovery of heart rate (at 5th minute the average values were 102.7 +/- 14.1 beats min-1 vs 91.9 +/- 11.1, p < 0.001); and significantly higher proportion of blunted increase of heart rate (9.2% vs 0.9%, p < 0.001) and systolic blood pressure (9.2% vs 0.7%, p < 0.001) during exercise. No correlation between the exercise results and the main clinical characteristic (presence of hypertension, BMI, duration of diabetes, treatment, microalbuminuria, total score of CAN) was observed. These findings suggest that the cardiovascular response to exercise could be impaired also in the absence of signs of CAN. This impairment was higher in patients showing a dysfunction of orthosympathetic activity.

Non-typhoid Salmonella spp. resistant to cefotaxime

beta-Lactamases with pIs of 5.4 and 8.1 were detected by hydrolysis of ampicillin and ceftriaxone respectively among cefotaxime resistant serovars of Salmonella spp. suggesting TEM-1 and an unidentified extended spectrum beta-lactamase have spread throughout these strains in Argentina.

Antimicrobial activity of 5,6-dihydrobenzo-[a]-carbazoles

A new series of 5,6-dihydrobenzo[a]carbazoles was synthesized, some showing good antibacterial activity. The presence of a dialkylamino ethyl chain on the 2-, 3- or 4-O-substituent seems to be critical for such activity.

Usefulness of changes in exercise tolerance induced by nitroglycerin in identifying patients with syndrome X

Two exercise tests, one under basal conditions and one after sublingual nitroglycerin (NTG), were performed in 39 patients with stable angina pectoris--16 with critical coronary stenoses and 23 with normal coronary arteries (syndrome X). Under basal conditions, times at ischemic threshold, at peak exercise, and at complete ECG recovery were similar in the two groups. Peak ST depression was significantly higher in patients with coronary artery disease (CAD). In a similar proportion of patients, ST-segment depression developed earlier or at a low heart rate. Patterns of heart rate, blood pressure, and rate-pressure product during exercise and recovery were also similar. After NTG an increase in the ischemic threshold was observed in a significantly higher proportion of patients with CAD (93.8% vs 39.1%). Furthermore, a subgroup of patients with syndrome X showed a worsening of exercise performance. This suggests that NTG does not directly affect small coronary vessels. Our results confirm that no relevant differences exist in exercise responses between patients with CAD and those with syndrome X under basal conditions. NTG-induced changes in this response could be useful in identifying patients with normal coronary arteries. Moreover, this test could be used as a guide to therapeutic approaches.

Antihypertensive efficacy and tolerability of different drug regimens in isolated systolic hypertension in the elderly

The pharmacological treatment, mainly based on diuretics, of isolated systolic hypertension (ISH) has recently been shown to reduce the risk of stroke and coronary heart disease in the elderly. The purpose of this study was to compare the antihypertensive effect and tolerability of different drug regimens in elderly subjects with ISH (systolic blood pressure--SBP-- > or = 160 mmHg and diastolic blood pressure--DBP-- < 90 mmHg). A multicentre, randomized, controlled open trial was planned in the general practice setting. Four widely used treatment schedules were tested: hydrochlorothiazide 25 mg plus amiloride 2.5 mg (H+Am), nifedipine slow release 20 mg (N), atenolol 50 mg (At) and atenolol 25 mg plus chlorthalidone 6.25 mg (At+C). After a baseline evaluation, 308 patients (76.3% female, mean age 75.3 +/- 7.1 years) were randomized and followed up for 6 months. After 3 months the drug dosage was doubled if the systolic blood pressure goal (SBP < 160 mmHg and SBP reduction of at least 20 mmHg) had not been reached. Ninety-four subjects (30.5%) presented contraindications to beta-blockers. At the 3rd- and 6th-month visits all treatment groups, except At, showed a significant reduction in SBP compared to the control group; DBP showed no significant reduction in any group at any time. At the end of the follow-up the percentage of hypertensives who had reached the BP goal was 14.6% in the control group, 52.9% in H+Am, 54.8% in N, 28.6% in At and 52.2% in At+C.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence and variability of orthostatic hypotension in the elderly. Results of the 'Italian study on blood pressure in the elderly (SPAA)'. The 'Gruppo di Studio Sulla Pressione Arteriosa nell'Anziano'

The prevalence of orthostatic hypotension (OH) in an elderly outpatient population was assessed according to the most common criteria given in the literature. Short-term OH variability and relationships between OH and its known risk factors were also analysed. A sample of 3858 elderly outpatients aged 65 years or more was randomly recruited by 444 Italian general practitioners. The patients' blood pressure (BP) and heart rate were recorded in both lying and standing positions at two visits 7 days apart. Three definitions were used for the identification of OH: (1) a decrease in systolic BP greater than 20 mmHg (SOH); (2) a decrease in both systolic (greater than 20 mmHg) and diastolic (greater than 10 mmHg) BP (SDOH); (3) any decrease in systolic BP associated with symptoms (SyOH). Prevalence figures for SOH were 13.8% at the first and 12.6% at the second visit, and respectively 5.3 and 4.8% for SDOH, 14.1 and 11.8% for SyOH. All the criteria were met by less than 2% of subjects at each visit. The diagnosis of OH was confirmed at both visits in 36.3% of cases for SOH, in 25.7% for SDOH, and in 43.9% for SyOH. Each different OH definition identifies a population subgroup characterized by different sets of risk-factors. The presence and prevalence of OH is difficult to define because different people may be identified by the currently accepted criteria or by the same criterion over a short time.

Paradoxical effect of long-term treatment of nifedipine on total ischemic load in patients with stable angina pectoris

In 50 patients with stable effort angina the effect of three drugs, metoprolol, nifedipine, and diltiazem was assessed by analyzing exercise stress test response and ambulatory ECG recordings. Both metoprolol and diltiazem caused a significant increase in time to ischemic threshold during exercise and a significant decrease of maximum ST-segment depression (during exercise and ambulatory ECG monitoring) and in the average number of daily ischemic episodes. Only metoprolol significantly reduced heart rate and rate-pressure product at the ischemic threshold during exercise. In the group of patients treated with nifedipine no significant improvement was observed in exercise tolerance or in number of ischemic episodes/24 h. Moreover, the subset of nonresponders in the two methods was larger than in the other two groups. In some of these patients a clearcut worsening of total ischemic load was observed, despite the control of symptoms. This adverse effect might be attributed to the different consequences of the vasodilatory effect of nifedipine on blood flow through stenosed vessels.

Effects of long-term treatment with prazosin on left ventricular diastolic function in mild to moderate hypertension

It is not well established if blood pressure control is associated with an improvement in diastolic function, whose impairment represents an early marker of cardiac involvement in systemic hypertension. The purpose of this study was to evaluate whether a prolonged treatment with an alpha 1-blocking agent can lead to a reversal of the abnormalities of left ventricular filling. Eleven never-treated patients with mild to moderate essential hypertension were examined before and after at least six months of treatment with prazosin. Cardiac function and left ventricular mass were measured by means of radionuclide ventriculography and echocardiography. Average blood pressure values significantly decreased during the treatment period: from 163.54 +/- 17.80 mm Hg to 146.81 +/- 13.14 mm Hg for systolic blood pressure and from 106.09 +/- 6.96 mm Hg to 92.90 +/- 8.93 mm Hg for diastolic blood pressure. All the indices of left ventricular mass showed a trend toward reduction, but the differences with respect to the baseline values did not reach statistical significance. Average value of ejection fraction was normal before treatment and did not change significantly after treatment. All indices of diastolic function were significantly lower than normal controls' values at the beginning of the study and tended to worsen at the end of the study. Our findings suggest that diastolic function is not consistently affected by the therapy with alpha 1-adrenoreceptor antagonists despite good blood pressure control.

[Transient hyperglycemia in acute myocardial infarct: the short- and long-term risk factor for mortality]

To evaluate the prevalence and prognostic significance of hyperglycemia in acute myocardial infarction, we studied 700 patients (mean age 63.3 +/- 10.97) subsequently admitted to the UCIC of Tradate Hospital during the period January 1976 to December 1987. Patients were followed up for a median period of four years. On the basis of fasting blood glycaemia values in the first five days of hospitalization, excluding the admission day, patients were divided into groups: 401 patients (57.0%) with constantly normal glycaemia; 84 patients (12.0%) with glycaemia equal or superior to 120 mg/100 ml, and with subsequent normalization; and 215 patients (31.0%) with diabetes mellitus diagnosed before hospitalization and/or with persistent hyperglycaemia. The overall mortality was 284 (40.5%) and cardiovascular deaths were 90.8%. Within the first month of myocardial infarction 98 patients died. The mortality rate was 9.4% in normoglycaemic patients and 20.2% in transient hyperglycaemic patients, similar to the value observed in diabetic patients (20.0%). During the follow-up 186 patients died. Late mortality after the first month is higher in diabetic patients (40%) and patients with transient hyperglycaemia (37%) compared to normoglycaemic patients (25.3%). Multivariate analysis shows that independent predictive variables are: for mortality in the first month, Killip class only; and after the first month, Killip class, metabolic classification, sex and supraventricular arrhythmias. The present study shows that transient hyperglycaemia has a low prevalence in the first days of acute myocardial infarction. Transient hyperglycaemia could be attributed not only to increased sympathetic tone elicited by acute myocardial infarction, but is probably a pathologic condition with an adverse outcome to which multiple factors contribute.

Left ventricular diastolic function in normotensive adolescents with different genetic risk of hypertension

Abnormalities of the diastolic function of the left ventricle are the first sign of cardiac involvement in arterial hypertension. We have studied the diastolic function in a group of normotensive adolescents with confirmed family history of hypertension. M-mode echocardiography was performed in 86 normotensive males aged 14-19 years: 41 sons of at least one hypertensive parent (SHT) and 45 sons of normotensive parents (SNT). Cross-sectional area of the left ventricle and left ventricular (LV) mass index were significantly greater in the SHT than in the SNT group (10.05 +/- 1.84 vs. 8.9 +/- 1.56 cm/m2, p less than 0.01 and 129.3 +/- 296.3 vs. 109.23 +/- 25.7 g/m2, p less than 0.002, respectively). No significant difference between the two groups was observed in the indices of left ventricular diastolic function, except for mitral valve opening rate (463.51 +/- 90.45 in SHT vs. 416.71 +/- 78.84 mm/s in SNT; p less than 0.02). From the analysis of the subgroup of adolescents having left ventricular mass greater than the upper normal value, we observed that they showed mean time of rapid filling significantly longer than SNT: this could represent an early marker of the pathological character of such hypertrophy. Our results suggest that the higher LV mass observed in the SHT is not associated with chamber and myocardial stiffness abnormalities.

Antihypertensive treatment of the elderly in general practice

In order to assess the antihypertensive care received by the elderly, where clear therapeutic guidelines are lacking, a population of 3,858 aged over 64 years was studied. Data were derived from a large Italian 'Study on Blood Pressure in the Elderly', carried out in general practice. Over 90% of the 2,059 known hypertensive patients were receiving drug treatment, with no age or sex-related differences. A single drug was prescribed to 50.2% of treated patients; only 5.5% were receiving three or more drugs. Diuretics and older sympatholytic agents were by far the most frequently prescribed categories, with four drugs (hydrochlorothiazide, amiloride, methyldopa and chlorthalidone) accounting for over 50% of all prescriptions. Low-dosage treatment schedules were frequently used, often associated with less-often-than-daily drug administration. Our study shows that physicians' attitudes to the treatment of arterial hypertension in the elderly are fairly uniform, with treatment of all subjects but with low drug dosages.

[Relations between pressure overload and early signs of cardiac involvement in arterial hypertension]

In arterial hypertension the indexes of left ventricular hypertrophy are not related to resting blood pressure, whereas a positive association with exercise blood pressure has been observed. It has not been investigated a possible relationship between response to stress and left ventricular diastolic function, the latter being early involved in arterial hypertension even before the development of ventricular hypertrophy. The present study was aimed at assessing a possible relationship between blood pressure response to dynamic exercise and index of left ventricular mass, systolic and diastolic function in a group of untreated hypertensives. fourty hypertensives aged 16-56 years were studied, 27 with mild hypertension and 13 with moderate or severe hypertension. The control group consisted of 23 normotensive healthy subjects, aged 14-40 years. All the subjects underwent a maximum-graded bicycle exercise in the supine position and a M-mode echocardiogram under the B-mode drive. Average values of the indexes of ventricular hypertrophy and of systolic function were overlapping in the 3 groups. Significant differences were observed in the indexes of diastolic function; with regard to normatensive controls, hypertensive subjects showed an increase in isovolumic relaxation time and rapid filling time, a decrease of isovolumic and rapid filling rates and a reduction of mitral valve closing and opening velocities.(ABSTRACT TRUNCATED AT 250 WORDS)

[Potentiating effect of a supine position on ischemia induced by exercise]

Though sitting bicycle and treadmill are the commonest devices used in exercise stress testing, supine ergometric test shows some advantages, especially in research investigations. The latter allows better ECG and blood pressure recordings during exercise. Recently, a greater frequency of ST-segment depression has been reported with supine vs upright exercise, but some doubt as to the ischemic significance of this result has been raised. Thus, we compare the ECG and hemodynamic pattern during upright and supine bicycle exercise in 50 subjects with chest pain, without prior myocardial infarction: 31 had documented coronary artery disease (CAD) and 19 had normal coronary vessels. In a subgroup (22 CAD patients and all subjects without CAD) a measurement of myocardial perfusion was performed during exercise using thallium-201 radionuclide ventriculography. Initial work-load and the further graded increases were identical for both postures. The frequency of ST-segment depression was higher during supine exercise (84% vs 74%). The increase in sensitivity (+7% vs CAD) was wider if a more direct measurement of myocardial ischemia was adopted as gold standard (+13% vs TI-201 responses) and was not associated with a decreased specificity (Tab. II). In the supine position the threshold of exercise-induced ST-segment depression was significantly lower. Chest pain appeared more frequently and at a lower work-load. Accentuation and precocity of exercise-induced ischemia in the supine-position could be attributed to an increased imbalance between supply and demand of MVO2 at equivalent work-load, heart rate changes, systolic blood pressure and double product were significantly higher.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence of symptoms generally attributed to hypertension or its treatment: study on blood pressure in elderly outpatients (SPAA)

A number of symptoms that appear to be associated with high blood pressure (headache, dizziness, epistaxis, tinnitus, weakness, drowsiness), and are usually regarded as secondary to hypertension or to antihypertensive drug therapy, were studied in 3858 elderly patients, 67.8% of whom were hypertensive. Of the hypertensive patients, 71.2% were under treatment. Headaches and dizziness were significantly more prevalent in the hypertensive than in the normotensive subjects (32.5 versus 27.4% and 41.5 versus 35.3%, respectively; P less than 0.05) and in treated compared with untreated hypertensives (33.3 versus 29.4% and 43.3 versus 37.1%; P less than 0.05). These differences disappeared after statistical correction for 'awareness of hypertension'. In multiple logistic analysis, female sex, age and awareness of hypertension were significantly associated with a higher prevalence of symptoms, whereas hypertension and antihypertensive treatment were not. We conclude that the presence of these symptoms does not constitute a reliable criterion for starting antihypertensive treatment or judging its efficacy.

Assessment of ventricular function in arterial hypertension with radionuclide ventriculography

Diastolic function of the left ventricle was assessed in 29 untreated patients with mild to moderate hypertension and in 21 normotensive control subjects using gated radionuclide ventriculography. In hypertensive patients, the time to peak filling rate was significantly longer (p less than 0.01) than that in control subjects, and first-third filling fraction and peak filling rate were significantly reduced (p less than 0.001). The ejection fraction and peak ejection rate were also significantly reduced in hypertensive patients (p less than 0.001). No relation was observed between diastolic functional impairment and age, cardiac hypertrophy, or severity of hypertension. Thus, early impairment of ventricular filling is present in hypertension, even in young patients without evidence of cardiac hypertrophy.

Arm position as a source of error in blood pressure measurement

The present study was designed to assess the value of correct positioning of a patient's arm when measuring blood pressure (BP). A total of 181 subjects were examined, 141 hypertensives on treatment, 25 untreated hypertensives, 15 normotensives. All the subjects underwent three BP measurements after a 5-min resting period in supine position. Then two BP readings were recorded in standing position with the arm either positioned by the patient's side or supported passively at patient's heart level. Average systolic BP (SBP) in standing position were 144.6 +/- 20.2 mmHg with the arm at the side and 136.4 +/- 21.1 mmHg with the arm at the heart level (p less than 0.001); average diastolic pressures were 99.0 +/- 12.0 mmHg and 90.2 +/- 12.3 mmHg (p less than 0.001), respectively. A fall in SBP greater than or equal to 20 mmHg from the supine to the upright position was detected in 18.2% of cases when measurement was performed at heart level; such a reduction was inapparent in two-thirds of cases when the arm was placed at the patient's body side. Incorrect positioning of a patient's arm during BP measurements in standing position leads to overestimation of BP values and masks the presence of postural hypotension.

Accuracy and reproducibility of the assessment of the global ejection fraction using 195mAu and a single-crystal digital gamma camera: influence of collimator design

A sequence of RAO first-pass studies (first with 99mTc and then twice with 195mAu) was performed in 18 normal volunteers and in 12 CAD patients using two different types of collimator for medium energy: a standard collimator (MEMS) and a special high-sensitivity collimator (MEHS). The following data were compared: the peak count rate, the net LV end-diastolic counts and the LVEF. Using MEMS the end-diastolic counts acquired were so low (12% of 99mTc average value) that EF standard deviation had a mean value of 0.061 (range 0.045-0.081). With MEHS the following results were obtained: 1. the peak count rate and LV net end-diastolic counts with 195mAu were 55% and 50% respectively, of 99mTc values; 2. a good correlation was shown between LVEF values either with 99mTc and 195mAu (r = .97), or with 195mAu sequential studies (r = .98).

[Usefulness of exertion tests in the evaluation of the effectiveness of antihypertensive therapy]

Aim of this study was to assess the reliability of blood pressure (BP) response to exercise compared with the occasional BP measurements in evaluating the efficacy of an antihypertensive therapy. We have studied 40 subjects (22 M, 18 F mean age 33.3 +/- 6.6) with essential hypertension (19 with mild hypertension, 8 with moderate hypertension, 13 with severe hypertension). Every patient underwent a maximum graded exercise test in the supine position on a bicycle ergometer before starting the antihypertensive treatment. An exercise test was repeated with the same procedure after resting BP had been normalized for at least six months. Both systolic and diastolic BP at peak exercise were significantly reduced (systolic BP from 212.13 +/- 25.79 mmHg to 194.38 +/- 21.58 mmHg; diastolic BP from 128.00 +/- 16.52 to 114.1 +/- 11.02 mmHg) during the second test. An excessive BP increase (above the 95% confidence limits of the BP response to exercise in a group of normotensives) was observed in 32 subjects during the first test. A "hypertensive" response to stress persisted in 13 subjects during the second test even if the resting BP values were normalized. Our data support the value of stress testing in both the evaluation of the hypertensive patient and the assessment of the individual response to treatment.