Best options for the exposure of traditional and innovative moss bags: A systematic evaluation in three European countries.

To develop an internationally standardized protocol for the moss bag technique application, the research team participating in the FP7 European project "MOSSclone" focused on the optimization of the moss bags exposure in terms of bag characteristics (shape of the bags, mesh size, weight/surface ratio), duration and height of exposure by comparing traditional moss bags to a new concept bag, "Mossphere". In particular, the effects of each variable on the metal uptake from the air were evaluated by a systematic experimental design carried out in urban, industrial, agricultural and background areas of three European countries with oceanic, Mediterranean and continental climate. The results evidenced that the shape, the mesh size of the bags and the exposure height (in the tested ranges), did not significantly influence the uptake capacity of the transplanted moss. The aspects more affecting the element uptake were represented by the density of the moss inside the bags and the relative ratio between its weight and the surface area of the bag. We found that, the lower the density, the higher the uptake recorded. Moreover, three weeks of exposure were not enough to have a consistent uptake signal in all the environments tested, thus we suggest an exposure period not shorter than 6 weeks, which is appropriate in most situations. The above results were confirmed in all the countries and scenarios tested. The adoption of a shared exposure protocol by the research community is strongly recommended since it is a key aspect to make biomonitoring surveys directly comparable, also in view of its recognition as a monitoring method by the EU legislation.

Is it possible to estimate atmospheric deposition of heavy metals by analysis of terrestrial mosses?

Here we present a critical review of diverse research studies involving estimation of atmospheric deposition of heavy metals from the concentrations of the contaminants in terrestrial moss. The findings can be summarized as follows: i) significant correlations between the concentrations of contaminants in moss and bulk deposition were observed in only 40.1% of the cases in which the relationship was studied and in only 14.1% of the cases, the coefficient of correlation was >0.7; ii) some method-related problems were identified (i.e. small sample sizes, elimination of some data from the regression analyses, large distances between the moss sampling sites and the bulk precipitation collectors, differences in times of exposure of the moss samples and collection times for the bulk precipitation), so that the results of the studies may not be completely valid, and iii) evidence was found in the relevant literature that moss does not actually integrate the atmospheric deposition received. We also discuss the reason why, in accordance with the published data, bulk deposition cannot be correctly estimated by determination of the final concentrations of contaminants in the organism, such as the existence of different sources of contamination, the physicochemical characteristics of the sources of deposition, physicochemical processes to which the organism is subjected and the biological processes that take place in the moss. Taking into account the above findings, it was concluded that, except for certain elements and specific cases (i.e. Pb and Cd), atmospheric deposition of elements cannot be accurately estimated from the concentrations of metals and metalloids in moss tissues. However, the analysis of moss does provide information about the presence of contaminants in the atmosphere, their spatial and temporal patterns of distribution and how they are taken up by live organisms. Use of mosses is therefore recommended as a complementary (rather than an alternative) technique in the conventional analysis of bulk deposition of contaminants.

Detection of new mutations conferring resistance to linezolid in glycopeptide-intermediate susceptibility Staphylococcus hominis subspecies hominis circulating in an intensive care unit.

Glycopeptides and linezolid are the most widely used antibiotics to treat infections by methicillin-resistant Staphylococcus spp. We report the presence of various isolates of methicillin-resistant S. hominis subsp. hominis with resistance to linezolid and reduced susceptibility to glycopeptides. We studied ten blood culture isolates of S. hominis subsp. hominis from nine patients admitted to our hospital. Etest was used to study susceptibility to antibiotics commonly prescribed against staphylococci. Domain V region of the 23S rRNA gene was amplified and sequenced to detect possible mutations that confer resistance to linezolid. Pulsed-field gel electrophoresis (PFGE) was used for the clonality study of isolates. All isolates were resistant to oxacillin, gentamicin, levofloxacin, cotrimoxazole, and linezolid, and susceptible to tigecycline and daptomycin. Nine of the isolates were resistant to erythromycin and clindamycin, and showed heterogeneous resistance to glycopeptides. C2190T, G2603T, and G2474T mutations were detected in domain V of the 23S rRNA gene. PFGE showed the presence of two different clones. This report alerts to the possible appearance of clinical strains of methicillin-resistant staphylococci with intermediate resistance to glycopeptides, resistance to linezolid, and multiple resistance to other second-line antibiotics.

Prevalence and evolution of methicillin-resistant Staphylococcus aureus in Spanish hospitals between 1996 and 2002.

Pulsed-field gel electrophoretic analysis of 2,144 methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from patients in Spanish hospitals over a 7-year period revealed 17 predominant profiles. Typing showed the replacement of Iberian clone E1 (ST247-MRSA-I) by two prevalent clones, E7 and E8, that are closely related to each other and have the same genetic background as ST125-MRSA-IV.

Interpretation of band differences to distinguish strains of Serratia marcescens by pulsed-field gel electrophoresis of XbaI DNA digests.

The number of band differences in DNA macrorestriction profiles required to distinguish unrelated strains from an index strain varies in an outbreak with the species and restriction enzyme used. In order to define this difference for epidemiological studies of Serratia marcescens, we produced DNA fingerprints from 57 isolates of the organism using the restriction enzyme XbaI and pulsed-field gel electrophoresis (PFGE). The isolates were selected on the basis of their epidemiology, serotype and phage-typing patterns to include 28 unrelated strains and 29 representatives from 2 distinct outbreaks. One of the outbreaks was prolonged. lasting for several years. Electrophoretic profiles consisting of 20 or more clearly resolved bands were obtained for all isolates. Twenty-six of the unrelated strains had unique profiles with over 10 band differences from all other strains, while 27 of the outbreak representatives could be assigned to the appropriate outbreak with confidence. The majority of the outbreak isolates had none or 2 band differences from the index profile, although 3 isolates differed by 5-7 bands. The 2 exceptions among the unrelated strains differed by 4 bands, and 3 phage typing reactions, and were isolated from London and Berlin 3 years apart, while the 2 exceptions among the outbreak collection had clearly unique profiles with over 20 band differences from each other and the outbreak profiles. Cluster analysis using Dice coefficient and UPGMA gave cut-off values of 75-78% similarity overall for related isolates, while the closest similarity for unrelated strains was 70%. The results of this study together with those of the 6 previous reports of PFGE for S. marcescens (which used either enzymes XbaI or SpeI) confirm that this technique is of value for this species and that with XbaI at least, most epidemiologically related strains will only differ by 3-4 bands. However, on occasion up to 7 band differences can be found within an apparent outbreak, which may be suggestive of genetic drift.

[Epidemiology of Serratia marcescens between 1987 and 1995 at Vall d'Hebron Hospital]. / Epidemiología de Serratia marcescens entre 1987 y 1995 en el Hospital Vall d'Hebron.

BACKGROUND: Nosocomial infection have a relative high prevalence, which is necessary to reduce in order to improve the quality of patient care. The aims of this work is to study the behaviour of Serratia marcescens in our hospital as between 1987 and 1995. METHODS: Between February 1987 and March 1995 we detected 679 isolates of Serratia marcescens in 504 patients. We used serotype as first marker and phagotype as second, and evaluation of PGFE as a discriminator of doubtful strains was done. RESULTS: 35.8% of the strains were from the respiratory tract, 37.2% from urinary tract; and 11.7% were isolated in blood culture, among them 23.3% came form children younger than 7 years. We noticed a tendency to decrease the number of isolates along the studied period. The most frequent serotypes were O:6, O:3 and O:2; representing the 36.0% of the total. Serotypes O:6;14, O:4, O:5, O:11 and polyagglutinables accounted for 37% of the total. The frequency was variable from year to year, and the predominant serotypes were different in every one of the hospitals in which the center is divided. A 60% of the patients were hospitalized in the General Hospital Vall d'Hebron building, in ICU (20%) and in chirurgical services (25%). Ninety-six patients had more than one isolate, 91 of them (94.8%) can be classified by phenotypic test. The PFGE is discriminatory in three of the five unclassificable isolates. In more than 35% of the patients the strains isolated along the time are different. The 66.7% of the patients acquired Serratia strains in the same admission, and in some cases with few days of difference. We detected 17 cross infections, predominantly in ICUs. With PFGE we could discriminate isolates which produced cross infections between patient who are not in the same hospital. CONCLUSIONS: Although the prevalence of Serratia marcescens is diminishing, it is able to produce crossed infections that, in general, affected few patients. The serotype and phagotype discriminate 94.8% of isolates. The PFGE is high discriminatory and reproducible, only 6.8% of the 44 strains tested by this method can not be typed.

Epidemiological markers of Serratia marcescens isolates causing nosocomial infections in Spain (1981-1991).

The distribution of epidemiological markers (serotyping and phage-typing) of Serratia marcescens isolates from nosocomial episodes (63 nosocomial cutbreaks with 475 isolates, and 1208 sporadic cases) received in our laboratory during the period 1981-1991 was studied. The records for 1683 isolates from Spanish hospitals have been analyzed. In relation with the sporadic cases, the predominant types were serotype O6 (13.4%) and serotype O14 (11.4%); polyagglutinable strains accounted for 15.6%; in outbreaks, type O14 is clearly predominant (27.4%). Phage-typing was a good secondary marker, with a 87.9% of typability; the number of lytic patterns was very high, extended patterns (six or more phages) being the most frequent. We have studied the characteristics of S. marcescens isolates causing infections in the nosocomial environment in Spain.

An additional set of phages to characterize epidemic methicillin-resistant Staphylococcus aureus strains from Spain (1989-92).

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) isolates in Spain have increased dramatically; in 1986 there were only 1.2% MRSA amongst all nosocomial Staphylococcus aureus (SA) isolates, by 1989 this percentage had risen to 44% in some hospital causing a very serious epidemic situation in the country. We have characterized these isolates by direct, reverse and Fisk phage typing and we have also looked for an additional local set of phages to help us to differentiate these strains. We have been able to differentiate an epidemic strain from other MRSA strains which cause sporadic hospital outbreaks, and we have also distinguished between some variants of the epidemic strain.