Long-term trends of black carbon and particle number concentrations and their vehicle emission factors in Stockholm.

Black carbon (BC) and particle number (PN) concentrations are usually high in cities due to traffic emissions. European mitigation policies, including Euro emission standards, have been implemented to curb these emissions. We analyzed BC and PN (particle diameter Dp > 4 nm) concentrations in Stockholm spanning the years 2013-2019 (BC) and 2009-2019 (PN) measured at street canyon and rooftop sites to assess the effectiveness of the implemented policies. Combining these data with inverse dispersion modeling, we estimated BC and PN emission factors (EFBC and EFPN) for the mixed fleet, reflecting real-world driving conditions. The pollutants showed decreasing trends at both sites, but PN concentrations remained high at the canyon site considering the World Health Organization (WHO) recommendations. BC concentrations declined more rapidly than PN concentrations, showing a -9.4% and -4.9% annual decrease at the canyon and -7.2% and -0.5% at the rooftop site in the years 2013-2019. The EFBC and EFPN trends showed that the mitigation strategies for reducing particulate emissions for on-road vehicles were successful over the study period. However, the introduction of biofuels in the vehicle fleet -ethanol and later rapeseed methyl ester (RME)- increased the concentrations of particles with Dp < 10 nm before the adoption of particulate filters in the exhausts. Stricter Euro emission regulations, especially with diesel particulate filters (DPF) in Euro 5, 6, and VI vehicles, led to 66% decrease in EFBC and 55% in EFPN. Real-world EFBC surpassed HBEFA (Handbook Emission Factors for Road Transport) database values by 2.4-4.8 times; however, direct comparisons between real-world and HBEFA EFPN are difficult due to differences in lower cut-off sizes and measurement techniques. Our results underscore the necessity for revising the HBEFA database, updating laboratory testing methods and portable emission measuring systems (PEMS) measurements to account for liquid condensate contributions to PN measurements.

Increased sporulation rate of epidemic Clostridium difficile Type 027/NAP1.

Clostridium difficile PCR ribotype 027 comprised 0.2% of a collection of Swedish isolates in 1997-2001 (3 of 1,325 isolates). These isolates had lower moxifloxacin MICs than the epidemic type 027 isolates, but they had the same tcdC sequence and toxin yield. Type 027 produced 3- to 13-fold more toxin than did major Swedish types. One epidemic strain (027/NAP1a) sporulated more than did other type 027 isolates, a feature that should contribute to its survival and spread.

Norovirus strains belonging to the GII.4 genotype dominate as a cause of nosocomial outbreaks of viral gastroenteritis in Sweden 1997--2005. Arrival of new variants is associated with large nation-wide epidemics.

BACKGROUND: In recent years an increase of the incidence of nosocomial outbreaks caused by noroviruses has been observed throughout Sweden, with high peaks noted in the winter seasons 2002/2003 and 2004/2005, respectively. OBJECTIVES: To phylogenetically characterize norovirus strains causing nosocomial outbreaks from 1997 to 2005 and estimate the impact of norovirus-like disease on the Swedish health care system during the peak season 2002/2003 when a new variant of norovirus occurred. STUDY DESIGN: Stool samples from 115 randomly selected nosocomial outbreaks occurring during 1997--2005 throughout Sweden were studied by RT-PCR and sequencing. In addition, to investigate the impact on the health-care system, a questionnaire was distributed to infection control units (n=90) serving all Swedish hospitals, nursing homes and other health-care institutions during the largest epidemic of nosocomial outbreaks. RESULTS: Sequencing of 279 nucleotides of the norovirus RNA polymerase gene in stools containing norovirus RNA showed that strains belonging to the GII.4 genotype dominated. Each of the two large epidemics was due to a new variant within this cluster. The questionnaire revealed that 30,000-35,000 episodes of nosocomial norovirus-like infections occurred in 80 of 82 major Swedish hospitals affected in 2002/2003. CONCLUSION: New norovirus variants within the cluster GGII.4 may have a major impact on the health-care system.

Alcohol-based hand-disinfection reduced children's absence from Swedish day care centers.

AIM: To determine if the use of alcohol-based hand-disinfection as a complement to regular hand washing at daycare centers (DCCs) can reduce the childhood rate of absenteeism. METHODS: Children aged 0-6 years attending DCC were studied in a cluster randomized controlled trial during 30 weeks. Thirty matched pairs of DCCs were included in the study, where one of the DCCs was randomized to intervention and the other to control within each pair. The intervention consisted in children and staff using alcohol-based oily disinfectant gel containing 70% ethanol after regular hand washing. The main outcome was the rate of episodes of absence from DCC due to infection. A regression model was fitted at the individual level and controlling several possible confounders for illness. Absences were reported by the parents. RESULTS: Differences in missing absence reports between the two groups led to only evaluating those 29 DCCs (1431 children) that were able to provide complete reports. In the multivariate regression, the intervention significantly reduced the rate of absenteeism of a child by 12% compared to a child in a control DCC (IRR 95% CI: 0.799-0.965). CONCLUSION: Hand-disinfection used by children and staff significantly decreased childrens absences due to infections in Swedish DCCs.

Comparison of enterococcal populations in animals, humans, and the environment--a European study.

The objectives of the present study were to generate knowledge of enterococcal populations in the food chain, by studying the population structure (in measures of abundance and diversity) among enterococci in different geographical regions and in different parts of the food chain, as well as the similarities between different enterococcal populations. Altogether, 2868 samples were collected from humans (healthy and hospitalised individuals and clinical isolates), animals (slaughterhouse carcasses and farm animals), and the environment (pig farms, sewage, and surface water) in four European countries-Sweden, Denmark, UK, and Spain. The samples were characterised with regard to presence and numbers of enterococci, and eight (for faecal samples) or 24 (for environmental samples) isolates per sample were phenotyped and preliminarily identified with the PhP-RF system. In total, more than 20,000 isolates were typed. A majority of the samples (77%) showed the presence of presumed enterococci. The diversities of enterococci in environmental samples were generally high, and also faecal samples normally showed presence of more than one enterococcal strain. The most common species found were Enterococcus faecium (33%), E. faecalis (29%), and E. hirae (24%), but different enterococcal populations differed in their species distribution. Clinical isolates, hospitalised patients, and hospital sewage in Sweden showed a clear dominance of E. faecalis (80%, 57%, and 54%, respectively) whereas healthy individuals and urban sewage contained less E. faecalis (39% and 40%, respectively). The species distribution among isolates from slaughterhouses varied between animal species and also between countries, but E. faecalis seemed to be mainly associated with broiler, and E. hirae with cattle and pigs. The results from the study have indicated a simplified method to study the diversity of bacterial populations. Instead of collecting many samples and analysing one or a few isolates per sample, it is possible to collect fewer samples and analyse several isolates per sample. Both approaches yielded similar information on the diversity of the populations. Another useful information was that since samples from hospital sewage, urban sewage, and manure contained enterococcal populations that reflected those in faecal samples of hospitalised patients, healthy humans, and animals, respectively, such samples may be used as pooled faecal samples and may replace cumbersome samplings from many individuals.

Predisposing chronic diseases and hypophosphatemia in patients with influenza.

Almost half of the hospitalized influenza patients have a chronic disease, which increases the risk for secondary bacterial infections and for adults >65 years influenza is related to high mortality risk. The impact of diabetes mellitus (DM), asthma bronchiale, cardiovascular disease (CVD) and chronic obstructive pulmonary disease (COPD) on the risk of having a low serum phosphatemia (S-P) in addition to influenza is important to investigate as this increases both morbidity and mortality and can be prevented. Hypophosphatemia could be the explanation for reduced chemo-taxis and phagocytosis, which in addition to respiratory function may increase the risk of pneumonia and sepsis. Data for this study was collected from the medical journals retrospectively for 100 patients admitted to the Department of Infectious Diseases during the study period, 1992-94, with the clinical diagnosis influenza out of which seventy-two cases were used in the calculation. Forty-seven percent of the hospitalized influenza patients had a 2.7-fold risk of suffering from DM than of any other chronic disease and an almost significantly doubled risk of having a low S-P level with a chronic disease. The prevalence of hypophosphatemia (S-P<0.70 mmol/l) was high; 13.0% of the women and 15.0% of the men; 34.0% of all patients had S-P<0.82 mmol/l. Men, in contrast to women, showed clinical signs of a secondary bacterial infection more frequently (12/41 and 6/35, respectively). Our study gives indications for an involvement of low S-P with chronic disease.

Induction of toxins in Clostridium difficile is associated with dramatic changes of its metabolism.

Certain amino acids, and cysteine in particular, promptly blocked toxin expression in Clostridium difficile strain VPI 10463 when added to late-exponential-phase peptone-yeast cultures, i.e. prior to normal induction of toxins A and B. Glucose reduced toxin yields by 80-fold, but only when supplemented at inoculation. Forty upregulated C. difficile proteins were identified during maximum toxin expression, and most of these were enzymes involved in energy exchange, e.g. succinate, CO/folate and butyrate metabolism. Transcription of tcdA (toxin operon) and folD (CO/folate operon) was induced by 20- and 10-fold, respectively, and with strikingly similar kinetics between OD 0.8 and 1.2. The sigma factors tcdR and sigH were upregulated simultaneously with tcdA and folD (3.5-fold increase of mRNA level), whereas transcription of tcdC, codY, sigB and sigL showed little or no correlation with that of tcdA and folD. The results suggest a connection between toxin expression, alternative energy metabolism and initial sporulation events in C. difficile.

Prescription of antibiotic agents in Swedish intensive care units is empiric and precise.

Since the prescription of antibiotics in the hospital setting is often empiric, particularly in the critically ill, and therefore fraught with potential error, we analysed the use of antibiotic agents in Swedish intensive care units (ICUs). We examined indications for antibiotic treatment, agents and dosage prescribed among 393 patients admitted to 23 ICUs at 7 tertiary care centres, 11 secondary hospitals and 5 primary hospitals over a 2-week period in November 2000. Antibiotic consumption was higher among ICU patients in tertiary care centres with a median of 84% (range 58-87%) of patients on antibiotics compared to patients in secondary hospitals (67%, range 35-93%) and in primary hospitals (38%, range 24-80%). Altogether 68% of the patients received antibiotics during the ICU stay compared to 65% on admission. Cefuroxime was the most commonly prescribed antibiotic before and during admission (28% and 24% of prescriptions, respectively). A date for decision to continue or discontinue antibiotic therapy was set in 21% (6/29) of patients receiving prophylaxis, in 8% (16/205) receiving empirical treatment and in 3% (3/88) when culture-based therapy was given. No correlation between antibiotic prescription and laboratory parameters such as CRP levels, leukocyte and thrombocyte counts, was found. The treatment was empirical in 64% and prophylactic in 9% of cases. Microbiological data guided prescription more often in severe sepsis (median 50%, range 40-60% of prescriptions) than in other specified forms of infection (median 32%, range 21-50%). The empirically chosen antibiotic was found to be active in vitro against the pathogens found in 55 of 58 patients (95%) with a positive blood culture. This study showed that a high proportion of ICU patients receive antimicrobial agents and, as expected, empirical-based therapy is more common than culture-based therapy. Antibiotics given were usually active in vitro against the pathogen found in blood cultures. We ascribe this to a relatively modest antibiotic resistance problem in Swedish hospitals.

Correlation of disease severity with fecal toxin levels in patients with Clostridium difficile-associated diarrhea and distribution of PCR ribotypes and toxin yields in vitro of corresponding isolates.

We investigated in vivo and in vitro yields of toxins A and B from and PCR ribotypes of Clostridium difficile isolates from 164 patients with differing severities of C. difficile-associated diarrhea (CDAD) (patients were grouped as follows: <3 loose stools per day, n = 45; 3 to 10 per day, n = 97; >10 per day, n = 22). The median fecal toxin levels in each group were 0.5, 6.8, and 149 U/g feces (P < 0.001), respectively. Patients with severe diarrhea also had more-frequent occurrence of blood in stool and vomiting, but there was no association with fecal toxin levels per se. There was no correlation between fecal toxin level and toxin yield in vitro for the corresponding C. difficile isolate or between its PCR ribotype and disease severity. A broad range of toxin yields among isolates belonging to major PCR ribotypes indicated a presence of many subtypes. We hypothesize that bacterial and host factors that affect C. difficile toxin levels in feces are important determinants of symptoms in CDAD patients. An inverse correlation between toxin yield and spore count (r = 0.66) in stationary-phase cultures supported the notion that toxin production and sporulation represent opposite alternative survival strategies for C. difficile cells facing nutrient shortage.

Antimicrobial susceptibility pattern of Clostridium difficile and its relation to PCR ribotypes in a Swedish university hospital.

All 238 Clostridium difficile isolates were susceptible to metronidazole and vancomycin, whereas 84% and 1% were resistant to clindamycin and fusidic acid. Etest MICs for metronidazole were lower than agar dilution MICs (P < 0.01) but without difference in susceptible-intermediate-resistant categorization. No particular PCR ribotype was associated with clindamycin or fusidic acid resistance.

Rectal colonization and frequency of enterococcal cross-transmission among prolonged-stay patients in two Swedish intensive care units.

The aims of this study were to gain insight into the dynamics of the rectal flora during prolonged ICU stay, with a particular focus on colonization and cross-transmission with resistant pathogens, and to evaluate methods for the rapid isolation of relevant bacteria from rectal swabs. Patients admitted to a general intensive care unit (GICU) or a cardiothoracic ICU (TICU) at the University Hospital of Linköping, Sweden, between 1 November 2001 and January 2002 with a length of stay > 5 d were included (n = 20). Chromogenic UTI agar medium was used for discrimination of different species, and appropriate antibiotics were added to detect resistance. Direct plating was compared to enrichment broth for a subset of specimens. The study showed an early alteration in rectal flora, with a dramatic decrease in Gram-negative rods in favour of Gram-positive bacteria. An ampicillin- and high-level gentamicin resistant clone of Enterococcus faecium was found in 6 of 10 patients in the GICU and 2 of 11 patients in the TICU. Enrichment broth did not enhance the detection of Gram-negative bacteria compared to direct plating on Chromogenic UTI medium, but enrichment broths were needed for optimal detection of resistant Gram-positive bacteria.

Occurrence and relatedness of vancomycin-resistant enterococci in animals, humans, and the environment in different European regions.

Vancomycin-resistant enterococci (VRE) in Europe are thought to have emerged partly due to the use of the glycopeptide avoparcin in animal husbandry. We compared the occurrence of VRE in geographical regions of Europe in which until 1997 large amounts of avoparcin were used (Spain, United Kingdom, and Denmark) with the occurrence of VRE in Sweden, where avoparcin was banned in 1986. We also studied the relatedness between VRE strains from different regions and habitats. In total, 2,580 samples were collected from humans, animals, and the environment (soil, sewage, recipient water). VRE resistant to 20 microg/ml vancomycin were identified in 8.2% of the samples and were found most frequently in raw and treated urban sewage samples (means, 71% and 36% of the samples, respectively), pig manure (17%), and hospital sewage (16%). The proportions of VRE-positive sewage samples were similar in Sweden, Spain, and the United Kingdom, whereas pig feces and manure were more often positive in Spain than in Sweden (30% versus 1%). Most VRE were Enterococcus faecium carrying vanA, and computerized biochemical phenotyping of the isolates of different ecological origins showed a high degree of polyclonality. In conclusion, it seems that animal-associated VRE probably reflect the former use of avoparcin in animal production, whereas VRE in human-associated samples may be a result of antibiotic use in hospitals. Since there seems to be a reservoir of the resistance genes in all countries studied, precautions must be taken to limit the use of antibiotics and antibiotic-like feed additives.

Limited value of routine microbiological diagnostics in patients hospitalized for community-acquired pneumonia.

Current guidelines recommend microbiological diagnostic procedures as a part of the management of patients hospitalized for community-acquired pneumonia (CAP), but the value of such efforts has been questioned. Patients hospitalized for CAP were studied retrospectively, focusing on the use of aetiological diagnostic methods and their clinical impact. Adult patients, without known human immunodeficiency virus infection, admitted to hospital for CAP during 12 months, were evaluated with regard to the importance of aetiological diagnosis for tailoring antibiotic therapy, antibiotic-associated diarrhoea, Clostridium difficile disease, length of hospital stay and mortality. Of the 605 studied patients, 482 (80%) were subjected to Mycoplasma pneumoniae and/or respiratory virus serology and/or cultures of blood and/or sputum. They had a better prognosis than patients not subjected to microbiological diagnostics (mortality within 3 months was 9% vs 24%, p = 0.001), apparently reflecting differences in general health (e.g. less dementia diagnosis) but not the outcome of diagnostics. A presumptive aetiology was obtained only in 132 of the 482 patients, Streptococcus pneumoniae and M. pneumoniae being the most common agents (in 49 and 36 patients, respectively). Establishing an aetiological diagnosis had no impact on the number of in-hospital changes of therapy, on the proportion of new regimens having a narrower antimicrobial spectrum than the initial one or on the outcome. Therapy was changed to a drug directed specifically against the identified pathogen in only 16 out of these 132 patients and again without any overall improvement in the outcome variables. In a setting with a low frequency of antibiotic-resistant respiratory tract pathogens current routine microbiological diagnostics were found to be of limited value for the clinical management of patients hospitalized for CAP. Improved diagnostics in CAP are urgently needed, as establishing an aetiological diagnosis carries a potential for optimizing the antibiotic therapy.

Suppression of toxin production in Clostridium difficile VPI 10463 by amino acids.

The impact of various growth conditions on the expression of toxins and other proteins by Clostridium difficile VPI 10463 was studied. During non-starved conditions, the rate of toxin synthesis paralleled that of total protein during both exponential growth and stationary phase, and in both defined and complex media. Biotin limitation reduced growth rate and bulk protein synthesis, whereas toxin expression continued, leading to a 50- to 200-fold increase in intracellular toxin levels. Concomitantly, several 22 kDa proteins were up-regulated as revealed by two-dimensional PAGE analysis. The toxin yield was 30-fold higher in peptone yeast extract (PY) than in PY containing glucose (PYG). By contrast, glucose limitation reduced toxin yields by 20- to 100-fold in defined media. By elevating the buffering capacity and bicarbonate concentration, toxin yields were increased by 10-fold in PY and PYG. The high toxin production by C. difficile during growth in PY was lowered 100-fold by adding a blend of nine amino acids and several 60-100 kDa proteins were concomitantly down-regulated. It was concluded that toxin expression in C. difficile VPI 10463 was not affected by growth rate, growth phase, catabolite repression or the stringent response. Instead the co-expression of toxins and a few specific additional proteins appeared to be influenced by metabolic pathways involving CO2 assimilation, carboxylation reactions and metabolism of certain amino acids.