Prospective longitudinal associations between household smoke exposure in early childhood and antisocial behavior at age 12.

Young children exert little control over household tobacco smoke exposure, which is considered a developmental neurotoxicant. Using the Quebec Longitudinal Study birth cohort, we examine prospective associations between early childhood smoke exposure and later antisocial behavior. Parents of 1035 children reported on the presence of household smokers at seven follow-ups from ages 1.5 to 7.5. At age 12, children self-reported on five aspects of early antisocial dispositions. After adjusting for confounders, every standard deviation increase in household smoke exposure was prospectively associated with a 19% standard deviation unit increase in conduct problems (ß=0.07; 95% confidence interval [CI] from 0.04 to 0.09), a 11% standard deviation unit increase in proactive aggression (ß=0.04; 95% CI from 0.01 to 0.07), a 13% standard deviation unit increase in reactive aggression (ß=0.07; 95% CI from 0.03 to 0.12), a 14% standard deviation unit increase in school indiscipline (ß=0.13; 95% CI from 0.05 to 0.20), and a 10% standard deviation unit increase in dropout risk (ß=0.07; 95% CI from 0.01 to 0.12). These long-term findings warrant fostering parental awareness of developmental risks by policy-makers/health practitioners. School curricula can equally integrate these ideas into their curriculum.

Prospective associations between televiewing at toddlerhood and later self-reported social impairment at middle school in a Canadian longitudinal cohort born in 1997/1998.

BACKGROUND: Using a large Canadian population-based sample, this study aimed to verify whether televiewing in toddlerhood is prospectively associated with self-reported social impairment in middle school. METHOD: Participants are from a prospective-longitudinal birth cohort of 991 girls and 1006 boys from the Quebec Longitudinal Study of Child Development. Child self-reported ratings of relational difficulties at age 13 years were linearly regressed on parent-reported televiewing at age 2 years while adjusting for potential confounders. RESULTS: Every additional 1 h of early childhood television exposure corresponded to an 11% s.d. unit increase in self-reported peer victimization [unstandardized ß = 0.03, 95% confidence interval (CI) 0.02-0.04], a 10% s.d. unit increase in self-reported social isolation (unstandardized ß = 0.04, 95% CI 0.03-0.05), a 9% s.d. unit increase in self-reported proactive aggression (unstandardized ß = 0.02, 95% CI 0.01-0.03) and a 6% s.d. unit increase in self-reported antisocial behavior (unstandardized ß = 0.01, 95% CI 0.01-0.01) at age 13 years. These results are above and beyond pre-existing individual and family factors. CONCLUSIONS: Televiewing in toddlerhood was prospectively associated with experiencing victimization and social withdrawal from fellow students and engaging in antisocial behavior and proactive aggression toward fellow students at age 13 years. Adolescents who experience relational difficulties are at risk of long-term health problems (like depression and cardiometabolic disease) and socio-economic problems (like underachievement and unemployment). These relationships, observed more than a decade later, and independent of key potential confounders, suggest a need for better parental awareness of how young children invest their limited waking hours.

Randomized non-inferiority trial to compare trimethoprim/sulfamethoxazole plus rifampicin versus linezolid for the treatment of MRSA infection.

OBJECTIVES: The therapeutic arsenal for MRSA infections is limited. The aim of this study was to assess the non-inferiority of a combination of trimethoprim/sulfamethoxazole plus rifampicin versus linezolid alone for the treatment of MRSA infection. METHODS: We conducted a randomized, open-label, single-centre, non-inferiority trial comparing trimethoprim/sulfamethoxazole (160 mg/800 mg three times daily) plus rifampicin (600 mg once a day) versus linezolid (600 mg twice a day) alone in adult patients with various types of MRSA infection. Patients were allocated 1:1 to either regimen. The primary outcome was clinical cure at 6 weeks after the end of treatment (non-inferiority margin 20%) assessed by both ITT and PP analyses. Secondary outcomes included the microbiologically documented persistence of MRSA in clinical cultures, mortality and adverse events. The study protocol has been registered with ClinicalTrials.gov (NCT00711854). RESULTS: Overall, 150 patients were randomized to one of the two treatment arms between January 2009 and December 2013 and were included in the ITT analysis. Of these 56/75 (74.7%) in the linezolid group and 59/75 (78.7%) in the trimethoprim/sulfamethoxazole and rifampicin group experienced clinical success (risk difference 4%, 95% CI -9.7% to 17.6%). The results were confirmed by the PP analysis, with 54/66 (81.8%) cured patients in the linezolid group versus 52/59 (88.1%) in the trimethoprim/sulfamethoxazole and rifampicin group (risk difference 6.3%, 95% CI -6.8% to 19.2%). There were no statistically significant differences between the two groups in any of the secondary outcomes, including microbiologically documented failure. Four adverse drug reactions attributed to the study medication occurred in the linezolid group versus nine in the trimethoprim/sulfamethoxazole and rifampicin group. CONCLUSIONS: Compared with linezolid, trimethoprim/sulfamethoxazole and rifampicin seems to be non-inferior in the treatment of MRSA infection.

Predicting academic and cognitive outcomes from weight status trajectories during childhood.

OBJECTIVE: To identify childhood body mass index (BMI) trajectories and to describe their association with subsequent academic and cognitive outcomes. STUDY DESIGN: Prospective cohort: Height and weight measured annually from 4 to 7 years. A mixture of regressions approach grouped children into BMI trajectories (n=1959 children; n=5754 BMI measures). Academic outcomes included teacher-rated progress and achievement. Cognitive outcomes measured by Kaufman's Assessment Battery for Children. Academic and cognitive outcomes were regressed according to BMI trajectories, controlling for family and individual covariates. Subjects drawn from Quebec Longitudinal Study of Child Development (Canada), a 1998 birth cohort (n=2120). RESULTS: Four clusters of BMI trajectories emerged: two healthy weight groups, one overweight group and one low weight group. Relative to healthy weight, belonging to the overweight or low weight clusters was negatively associated with cognitive and academic outcomes. With the exception of the low weight cluster, this relationship was insignificant in the adjusted model. CONCLUSIONS: Results suggest that during childhood being overweight does not increase risk for poor educational outcomes. Instead, being underweight may the increase risk for poorer cognitive outcomes. Further group-based trajectory modeling (GBTM) for BMI development over time is needed to confirm results.

Epidemic diffusion of KPC carbapenemase-producing Klebsiella pneumoniae in Italy: results of the first countrywide survey, 15 May to 30 June 2011.

Carbapenem-resistant Enterobacteriaceae (CRE) are emerging as a public health problem in various settings. In Italy, a rapid and remarkable increase of carbapenem-non-susceptible Klebsiella pneumoniae has been reported since 2010. Here we report on the results of a countrywide cross-sectional survey, carried out from 15 May to 30 June 2011 to investigate the diffusion of CRE in Italy and to characterise the most prevalent resistance mechanisms and their dissemination patterns. CRE were reported from most (23 of 25) participating laboratories, with an overall proportion of 3.5% and 0.3% among consecutive non-duplicate clinical isolates of Enterobacteriaceae from inpatients (n=7,154) and outpatients (n=6,595), respectively. K. pneumoniae was the most frequent species (proportion of carbapenem-non-susceptible isolates: 11.9%), while a minority of CRE of other species were detected. Carbapenemase production was detected in the majority (85%) of CRE. KPC-type enzymes were by far the most common (89.5% of carbapenemase producers), followed by VIM-1 (9.2%) and OXA-48 (1.3%). KPC-producing K. pneumoniae (KPC-KP) were detected in most centres and contributed majorly to the epidemic dissemination of CRE recently observed in our country. Dissemination of KPC-KP was mostly sustained by strains of clonal complex 258 (ST-258 producing KPC-2 or KPC-3, and ST-512 producing KPC-3), while a minority belonged to ST-101.

[Where are we in the treatment of chronic osteomyelitis?]. / Où en est-on dans le traitement médical des ostéomyélites chroniques?

Chronic osteomyelitis is a multifaceted bacterial infection with common features, which requires surgery for remission. The duration and modality of concomitant administration of antibiotic agents for adult patients is still based on expert opinions. The traditional recommendation of 6 to 12 weeks of antibiotic therapy with intravenous administration for at least the first 2 weeks is more and more challenged in favor of an oral antibiotic treatment with selected agents from the start. There is no evidence that the total duration of antibiotic therapy for more than 6-12 weeks improves outcome, when compared with shorter regimens. External advice from an expert team with combined surgeons and infectious disease physicians may help to reduce antibiotic consumption in a cost-effective way.

Ortho-para H2 conversion by proton exchange at low temperature: an accurate quantum mechanical study.

We report extensive, accurate fully quantum, time-independent calculations of cross sections at low collision energies, and rate coefficients at low temperatures for the H⁺ + H2(v = 0, j) → H⁺ + H2(v = 0, j') reaction. Different transitions are considered, especially the ortho-para conversion (j = 1 → j' = 0) which is of key importance in astrophysics. This conversion process appears to be very efficient and dominant at low temperature, with a rate coefficient of 4.15 × 10⁻¹° cm³ molecule⁻¹ s⁻¹ at 10 K. The quantum mechanical results are also compared with statistical quantum predictions and the reaction is found to be statistical in the low temperature regime (T < 100 K).

Healthcare-acquired infections in rehabilitation units of the Lombardy Region, Italy.

BACKGROUND: Little data are available on the frequency and risk factors for infection in patients in rehabilitation units. METHODS: This was a 2-year retrospective cohort study conducted in 131 rehabilitation units (RUs) of the Lombardy Region, including those for patients requiring musculoskeletal, cardiac, respiratory, neurological and general geriatric rehabilitation. RUs were stratified into three groups by infection rate calculated from administrative data, and a random sample of RUs in each group was selected for analysis. Discharges from these RUs were randomly selected for chart review, and healthcare-acquired infection was confirmed using CDC/NHSN definitions. A logistic regression analysis explored the association among demographic variables of age, sex, type of rehabilitation unit, Charlson comorbidity score, and location prior to RU admission for selected infections. RESULTS: For the 3,028 discharges from 28 RUs, hospital administrative data had a sensitivity of 0.45 and a positive predictive value of 0.89 to identify infections in the chart review. At least one infection occurred in 14.9% of patient discharges, with 71% of infections being urinary, 8.0% respiratory, and 5% skin and soft tissue. Urinary infection was associated with female sex [odds ratio (OR) 1.48, 95% confidence interval (CI) 1.13-1.93], age 75-85 years (OR 2.21, 95% CI 1.12-4.34), Charlson comorbidity score of ≥3 (OR 1.54, 95% CI 1.10-2.17), and the transfer from acute care (OR 1.45, 95% CI 1.04-2.02). For respiratory infection, male sex (OR 3.06, 95% CI 1.51-6.18), comorbidity score of 1 or 2 (OR 2.16, 95% CI 1.08-4.36), and transfer from a healthcare setting other than an acute care hospital were independent risks (OR 3.14, 95% CI 1.15-8.53). CONCLUSION: Infections are common in residents of these rehabilitation units, and risk factors may differ with type of infection. The proportion of infections which may be prevented and effective prevention strategies need to be determined.

Quantum mechanical study of the proton exchange in the ortho-para H2 conversion reaction at low temperature.

Ortho-para H(2) conversion reactions mediated by the exchange of a H(+) proton have been investigated at very low energy for the first time by means of a time independent quantum mechanical (TIQM) approach. State-to-state probabilities and cross sections for H(+) + H(2) (v = 0, j = 0,1) processes have been calculated for a collision energy, E(c), ranging between 10(-6) eV and 0.1 eV. Differential cross sections (DCSs) for H(+) + H(2) (v = 0, j = 1) → H(+) + H(2) (v' = 0, j' = 0) for very low energies only start to develop a proper global minimum around the sideways scattering direction (θ≈ 90°) at E(c) = 10(-3) eV. Rate coefficients, a crucial information required for astrophysical models, are provided between 10 K and 100 K. The relaxation ortho-para process j = 1 → j' = 0 is found to be more efficient than the j = 0 → j' = 1 conversion at low temperatures, in line with the extremely small ratio between the ortho and para species of molecular hydrogen predicted at the temperature of interstellar cold molecular clouds. The results obtained by means of a statistical quantum mechanical (SQM) model, which has previously proved to provide an adequate description of the dynamics of the title reactions at a higher collision energy regime, have been compared with the TIQM results. A reasonable good agreement has been found with the only exception of the DCSs for the H(+) + H(2) (v = 0, j = 1) → H(+) + H(2) (v' = 0, j' = 0) process at very low energy. SQM cross sections are also slightly below the quantum results. Estimates for the rate coefficients, in good accord with the TIQM values, are a clear improvement with respect to pioneering statistical studies on the reaction.

Emergency surgery during the COVID-19 pandemic: what you need to know for practice.

INTRODUCTION: Several articles have been published about the reorganisation of surgical activity during the COVID-19 pandemic but few, if any, have focused on the impact that this has had on emergency and trauma surgery. Our aim was to review the most current data on COVID-19 to provide essential suggestions on how to manage the acute abdomen during the pandemic. METHODS: A systematic review was conducted of the most relevant English language articles on COVID-19 and surgery published between 15 December 2019 and 30 March 2020. FINDINGS: Access to the operating theatre is almost exclusively restricted to emergencies and oncological procedures. The use of laparoscopy in COVID-19 positive patients should be cautiously considered. The main risk lies in the presence of the virus in the pneumoperitoneum: the aerosol released in the operating theatre could contaminate both staff and the environment. CONCLUSIONS: During the COVID-19 pandemic, all efforts should be deployed in order to evaluate the feasibility of postponing surgery until the patient is no longer considered potentially infectious or at risk of perioperative complications. If surgery is deemed necessary, the emergency surgeon must minimise the risk of exposure to the virus by involving a minimal number of healthcare staff and shortening the occupation of the operating theatre. In case of a lack of security measures to enable safe laparoscopy, open surgery should be considered.

Population structure of modern-day Italians reveals patterns of ancient and archaic ancestries in Southern Europe.

European populations display low genetic differentiation as the result of long-term blending of their ancient founding ancestries. However, it is unclear how the combination of ancient ancestries related to early foragers, Neolithic farmers, and Bronze Age nomadic pastoralists can explain the distribution of genetic variation across Europe. Populations in natural crossroads like the Italian peninsula are expected to recapitulate the continental diversity, but have been systematically understudied. Here, we characterize the ancestry profiles of Italian populations using a genome-wide dataset representative of modern and ancient samples from across Italy, Europe, and the rest of the world. Italian genomes capture several ancient signatures, including a non-steppe contribution derived ultimately from the Caucasus. Differences in ancestry composition, as the result of migration and admixture, have generated in Italy the largest degree of population structure detected so far in the continent, as well as shaping the amount of Neanderthal DNA in modern-day populations.

Comparing the cost-effectiveness of linezolid to trimethoprim/sulfamethoxazole plus rifampicin for the treatment of methicillin-resistant Staphylococcus aureus infection: a healthcare system perspective.

OBJECTIVE: Few industry-independent studies have been conducted to compare the relative costs and benefits of drugs to treat methicillin-resistant Staphylococcus aureus (MRSA) infection. We performed a stochastic cost-effectiveness analysis comparing two treatment strategies-linezolid versus trimethoprim-sulfamethoxazole plus rifampicin-for the treatment of MRSA infection. METHODS: We used cost and effectiveness data from a previously conducted clinical trial, complementing with other data from published literature, to compare the two regimens from a healthcare system perspective. Effectiveness was expressed in terms of quality-adjusted life-years (QALYs). Several sensitivity analyses were performed using Monte Carlo simulation, to measure the effect of potential parameter changes on the base-case model results, including potential differences related to type of infection and drug toxicity. RESULTS: Treatment of MRSA infection with trimethoprim-sulfamethoxazole plus rifampicin and linezolid were found to cost on average €146 and €2536, and lead to a gain of 0.916 and 0.881 QALYs, respectively. Treatment with trimethoprim-sulfamethoxazole plus rifampicin was found to be more cost-effective than linezolid in the base case and remained dominant over linezolid in most alternative scenarios, including different types of MRSA infection and potential disadvantages in terms of toxicity. With a willingness-to-pay threshold of €0, €50 000 and €200 000 per QALY gained, trimethoprim-sulfamethoxazole plus rifampicin was dominant in 100%, 96% and 85% of model iterations. A 95% discount on the current purchasing price of linezolid would be needed when it goes off-patent for it to represent better value for money compared with trimethoprim-sulfamethoxazole plus rifampicin. CONCLUSIONS: Combined treatment of trimethoprim-sulfamethoxazole plus rifampicin is more cost-effective than linezolid in the treatment of MRSA infection.

Analysis of the Herschel/HEXOS Spectral Survey Towards Orion South: A massive protostellar envelope with strong external irradiation.

We present results from a comprehensive submillimeter spectral survey toward the source Orion South, based on data obtained with the HIFI instrument aboard the Herschel Space Observatory, covering the frequency range 480 to 1900 GHz. We detect 685 spectral lines with S/N > 3σ, originating from 52 different molecular and atomic species. We model each of the detected species assuming conditions of Local Thermodynamic Equilibrium. This analysis provides an estimate of the physical conditions of Orion South (column density, temperature, source size, & V LSR ). We find evidence for three different cloud components: a cool (T ex ~ 20 - 40 K), spatially extended (> 60″), and quiescent (ΔVFWHM ~ 4 km s -1) component; a warmer (T ex ~ 80 - 100 K), less spatially extended (~ 30″), and dynamic (ΔVFWHM ~ 8 km s -1) component, which is likely affected by embedded outflows; and a kinematically distinct region (T ex > 100 K; V LSR ~ 8 km s -1), dominated by emission from species which trace ultraviolet irradiation, likely at the surface of the cloud. We find little evidence for the existence of a chemically distinct "hot core" component, likely due to the small filling factor of the hot core or hot cores within the Herschel beam. We find that the chemical composition of the gas in the cooler, quiescent component of Orion South more closely resembles that of the quiescent ridge in Orion-KL. The gas in the warmer, dynamic component, however, more closely resembles that of the Compact Ridge and Plateau regions of Orion-KL, suggesting that higher temperatures and shocks also have an influence on the overall chemistry of Orion South.

Boys' behavioral inhibition and the risk of later delinquency.

BACKGROUND: In some studies, shyness and anxiety have protected at-risk boys from developing delinquency. In others, shyness and withdrawal have increased risk. We argue that this is because behavioral inhibition, which is the protective factor, has been confounded with social withdrawal and other constructs. Our study addresses 3 major questions: (1) is behavioral inhibition, as distinguished from social withdrawal, a protective factor in the development of delinquency; (2) does the protective effect depend on whether disruptiveness is also present; and (3) does inhibition increase the risk of later depressive symptoms even if it protects against delinquency? METHODS: The subjects were boys from low socioeconomic status areas of Montreal, Quebec. Age 10- to 12-year predictors were peer-rated inhibition, withdrawal, and disruptiveness; age 13- to 15-year outcomes were self-rated depressive symptoms and delinquency. Eight age 10- to 12-year behavioral profiles were compared with 4 age 13- to 15-year outcome profiles. RESULTS: Inhibition seemed to protect disruptive and nondisruptive boys against delinquency. Disruptive boys who were noninhibited were more likely than chance to become delinquent; disruptive boys who were inhibited were not. Inhibition did not increase the risk for depression among disruptive boys. Among nondisruptive boys, only nondisruptive-inhibited boys were significantly less likely than chance to become delinquent. However, withdrawal was not protective. Disruptive-withdrawn boys were at the greatest risk for delinquency or delinquency with depressive symptoms. CONCLUSION: Inhibition and social withdrawal, although behaviorally similar, present different risks for later outcomes and, therefore, should be differentiated conceptually and empirically.

Molecular profile of Epstein-Barr virus infection in HHV-8-positive primary effusion lymphoma.

Primary effusion lymphoma (PEL) selectively involves the serous body cavities, occurs predominantly in immunodeficient patients and is infected consistently by human herpesvirus type-8. PEL is also frequently infected by Epstein-Barr virus (EBV). The precise pathogenetic role of EBV coinfection in PEL is not fully understood. The lymphoma fails to express the EBV transforming proteins EBNA-2 and LMP-1, whereas it expresses EBNA-1 (latency I phenotype). Some studies have hypothesized that other EBV-positive lymphomas expressing the latency I phenotype may associate with specific molecular variants of EBNA-1, although this issue has not been addressed in PEL. On this basis, this study is aimed at a detailed molecular characterization of EBV in PEL. Fifteen EBV positive PEL (12 AIDS-related, one post-transplant, two arising in immunocompetent hosts) were subjected to molecular characterization of the viral genes EBNA-1 and LMP-1, as well as definition of EBV type-1/type-2. The EBNA-1 gene displayed a high degree of heterogeneity in different cases of PEL, with seven distinct recognizable variants and subvariants. A wild-type LMP-1 gene was detected in 10/15 cases, whereas in 5/15 cases the LMP-1 gene harbored a deletion spanning codons 346-355. EBV type-1 occurred in 11/15 PEL whereas EBV type-2 occurred in 4/15 cases. Despite a high degree of genetic variability of the virus in different PEL cases, each single PEL harbored only one EBV variant, consistent with monoclonality of infection and suggesting that infection preceded clonal expansion. Overall, our results indicate that: (1) individual PEL cases consistently harbor a single EBV strain; (2) EBNA-1 displays a high degree of heterogeneity in different PEL cases; (3) no specific EBV genotype preferentially associates with PEL.

Strategies and challenges of antimicrobial stewardship in long-term care facilities.

As people are living longer the demand for long-term care facilities (LTCFs) continues to rise. For many reasons, antimicrobials are used intensively in LTCFs, with up to a half of this use considered inappropriate or unnecessary. Over-use of antimicrobials can have direct adverse consequences for LTCF residents and promotes the development and spread of resistant bacteria. It is therefore critical that LTCFs are able to engage in antimicrobial stewardship programmes, which have the potential to minimize the antibiotic selective pressure, while improving the quality of care received by LTCF residents. To date, no antimicrobial stewardship guidelines specific to LTCF settings have been published. Here we outline the scale of antimicrobial use in LTCFs and the underlying drivers for antibiotic over-use. We further describe the particular challenges of antimicrobial stewardship in LTCFs, and review the interventional studies that have aimed to improve antibiotic use in these settings. Practical recommendations are then drawn from this research to help guide the development and implementation of antimicrobial stewardship programmes.

General issues on microbial translocation in HIV-infected patients.

The lumen of the gastrointestinal tract is home to an enormous quantity of different bacterial species that thrive in an often symbiotic relationship with the host. It is the principal source of microbial products because of its massive bacterial load. Injury to the immune component of the gastrointestinal mucosal surface, along with damage to the intestinal epithelial microenvironment with its antimicrobial functions, may affect systemic immune activation during the chronic phase of HIV infection through the increased translocation of luminal microbial products. Moreover, microbial translocation, which is defined as "the passage of both viable and nonviable microbes and microbial products such as endotoxin across anatomically intact intestinal barrier", may be a fundamental mechanism through which HIV accelerates progression of chronic viral hepatitis. Improvements in the tools available to microbiota research, and especially advancement of our knowledge in this area may help us in controlling the evolution of HIV disease, although population complexity and diversity between individuals make this challenging.

Clinical stability in human immunodeficiency virus-infected patients with community-acquired pneumonia.

Clinical stability (CS), defined as normalization of vital signs, is often used to manage inpatients with community-acquired pneumonia (CAP). The main objective of our study was to identify a reliable definition of CS for human immunodeficiency virus (HIV)-positive patients with CAP. During an 18-month period, 437 HIV-positive Italian inpatients with CAP were enrolled in the study. We used 3 definitions of CS (from a less conservative [definition 1] to a more conservative [definition 3] definition) based on combinations of different thresholds for vital signs. Assessments were performed at admission and daily during the hospital stay. For the 3 definitions, 14.9%, 8.0%, and 4.8% of patients were stable at baseline, with deterioration after reaching CS in 7.16%, 4.76%, and 2.05%, respectively. The 8 patients whose conditions deteriorated after reaching CS definition 3 (systolic blood pressure, >90 mm Hg; pulse, <90 beats/min; respiratory rate, <20 breaths/min; oxygen saturation, >90%; temperature, <37 degrees C; ability to eat; and normal mental status) survived and were discharged from the hospital. The more conservative definition of CS appears to be reliable for the management of HIV-infected patients with CAP.

Outbreak of extended-spectrum beta-lactamase producing Serratia marcescens in an intensive care unit.

Serratia marcescens has recently been identified as an important etiological agent in nosocomial infections, and is considered to be an opportunistic pathogen agent in immunosuppressed patients undergoing long periods of intensive care. Research carried out in 1991 and 1992 showed that it was of epidemiological relevance in only 1-2% of clinical isolates at the Ospedale di Circolo, Varese, Italy. However, between 7 February and 11 October 1993, the incidence of cases attributable to S. marcescens had increased to 5%; 157 strains of Serratia marcescens were isolated from clinical specimens of 43 patients admitted to an intensive care unit; these strains, characterized by epidemic spread, showed the same pattern of multiresistance to antibiotics including monobactams and oxyimino-cephalosporins. During the same period 23 isolates were also recovered from 18 patients admitted to wards other than the intensive care unit; these strains, characterized by a wide range of antibiotic susceptibility, were also sensitive to beta-lactam antibiotics with the exception of first generation cephalosporins. The production of extended-spectrum beta-lactamases (ES beta Ls) and their genetic determinism were studied. All the epidemic strains of S. marcescens resistant to ceftazidime, cefotaxime, ceftriaxone and aztreonam produced three different beta-lactamases with pI 5.4, 5.5 and 8.4 respectively. In contrast, non-epidemic strains produced only a beta-lactamase with pI 8.4. The beta-lactamase with pI 5.5 was plasmid-mediated, hydrolizing ceftazidime and aztreonam, showing it to be an ES beta L; while the beta-lactamase with pI 5.4, although plasmid-mediated, did not hydrolize monobactams or oxyimino-cephalosporins.(ABSTRACT TRUNCATED AT 250 WORDS)

Physico-chemical properties of amphoteric, isoelectric, macroreticulate buffers.

We report here the properties of a new family of resins possessing an amphoteric character and able to strongly buffer at their pI values. They have been adopted as carriers for growth of cells in tissue culture and for hydroponics (Righetti et al. 1991; J. Biotechnol. 17, 169-176) but it is to be expected that such resins could have interesting chromatographic applications. It has been found that such beads [made by incorporating a pK 6.2 weak acrylamido base and a pK 4.6 weak acrylamido acid in a 2:1 ratio (thus with a pI of 6.2) into a neutral polyacrylamide backbone], independently from their initial conditioning (acid- or base-washed), spontaneously seek their equilibrium position (pI value) upon washing off excess titrant. Thus, upon potentiometric titration, they are seen to buffer in both directions of the pH scale (contrary to the behaviour of a pure carboxyl or a pure amino surface, which will exhibit only unidirectional buffering power). From the behaviour of these amphoteric beads when polymerized in the absence or in the presence of salts (0.2 M NaCl), it is hypothesized that, for exerting buffering power, both the buffering ion and its counterion must be incorporated non-randomly in the chain, but as a couple or in close proximity. Upon random incorporation of the two ions, buffering power is lost.