Discrimination between hypervirulent and non-hypervirulent ribotypes of Clostridioides difficile by MALDI-TOF mass spectrometry and machine learning.

Hypervirulent ribotypes (HVRTs) of Clostridioides difficile such as ribotype (RT) 027 are epidemiologically important. This study evaluated whether MALDI-TOF can distinguish between strains of HVRTs and non-HVRTs commonly found in Europe. Obtained spectra of clinical C. difficile isolates (training set, 157 isolates) covering epidemiologically relevant HVRTs and non-HVRTs found in Europe were used as an input for different machine learning (ML) models. Another 83 isolates were used as a validation set. Direct comparison of MALDI-TOF spectra obtained from HVRTs and non-HVRTs did not allow to discriminate between these two groups, while using these spectra with certain ML models could differentiate HVRTs from non-HVRTs with an accuracy >95% and allowed for a sub-clustering of three HVRT subgroups (RT027/RT176, RT023, RT045/078/126/127). MALDI-TOF combined with ML represents a reliable tool for rapid identification of major European HVRTs.

Spectroscopic Signatures of Internal Hydrogen Bonds of Brønsted-Acid Sites in the Zeolite H-MFI.

The location of Brønsted-acid sites (bridging OH groups, b-OH) at different crystallographic positions of zeolite catalysts influences their reactivity due to varying confinement. Selecting the most stable b-OH conformers at each of the 12 T-sites (T=Si/Al) of H-MFI, a representative set of 26 conformers is obtained which includes free b-OH groups pointing into the empty pore space and b-OH groups forming H-bonds across five- or six-membered rings of TO4 tetrahedra. Chemically accurate coupled-cluster-quality calculations for periodic models show that the strength of internal H-bonds and, hence, the OH bond length vary substantially with the framework position. For 11 of the 19 H-bonded b-OH groups examined, our predictions fall into the full width at half maximum range of the experimental signals at 3250±175 cm-1 and 7.0±1.4 ppm which supports previously debated assignments of these signals to H-bonded b-OH sites.

Relation of corona-specific health literacy to use of and trust in information sources during the COVID-19 pandemic.

BACKGROUND: COVID-19 has developed into a worldwide pandemic which was accompanied by an «infodemic¼ consisting of much false and misleading information. To cope with these new challenges, health literacy plays an essential role. The aim of this paper is to present the findings of a trend study in Switzerland on corona-specific health literacy, the use of and trust in information sources during the COVID-19 pandemic, and their relationships. METHODS: Three online surveys each with approximately 1'020 individuals living in the German-speaking part of Switzerland (age ≥ 18 years) were conducted at different timepoints during the COVID-19 pandemic, namely spring, fall and winter 2020. For the assessment of corona-specific health literacy, a specifically developed instrument (HLS-COVID-Q22) was used. Descriptive, bivariate, and multivariate data analyses have been conducted. RESULTS: In general, a majority of the Swiss-German population reported sufficient corona-specific health literacy levels which increased during the pandemic: 54.6% participants in spring, 62.4% in fall and 63.3% in winter 2020 had sufficient corona-specific health literacy. Greatest difficulties concerned the appraisal of health information on the coronavirus. The most used information sources were television (used by 73.3% in spring, 70% in fall and 72.3% in winter) and the internet (used by 64.1, 64.8 and 66.5%). Although health professionals, health authorities and the info-hotline were rarely mentioned as sources for information on the coronavirus, respondents had greatest trust in them. On the other hand, social media were considered as the least trustworthy information sources. Respondents generally reporting more trust in the various information sources, tended to have higher corona-specific health literacy levels. CONCLUSIONS: Sufficient health literacy is an essential prerequisite for finding, understanding, appraising, and applying health recommendations, particularly in a situation where there is a rapid spread of a huge amount of information. The population should be supported in their capability in appraising the received information and in assessing the trustworthiness of different information sources.

Implementation of a Clostridioides difficile sentinel surveillance system in Germany: First insights for 2019-2021.

OBJECTIVES: Clostridioides difficile is a major cause of nosocomial diarrhea. Several "hypervirulent" lineages such as ribotype 027 (RT027) and RT078 are of high epidemiological importance, leading to outbreaks and more severe courses of disease. An active surveillance system targeting molecular epidemiology and corresponding antimicrobial resistance has not been established in Germany. METHODS: Since October 2019, University Hospitals throughout Germany collected by two dates every year (1st April and October, respectively) their first ten unselected samples being tested positive for C. difficile. RESULTS: Out of 1026 samples received from 29 sites, 876 toxigenic C. difficile strains could be cultivated. PCR ribotyping of these strains revealed a large strain diversity with RT014 (17.5%) dominating, followed by isolates of the major nosocomial lineage RT001 (7.1%) and the "hypervirulent" lineage RT078 (5.9%). Notably, prevalence of RT027 was low with ∼3.5% at all time points analyzed, while the abundance of RT001 isolates significantly declined from 12.3% to 3.7% during the sampling period (P < 0.001). Antimicrobial resistance against clarithromycin, moxifloxacin, and rifampicin was detected in 18%, 15%, and 4% of the tested isolates, respectively. Highest resistance rates were found among RT027 isolates (83%, 87% and 63% for clarithromycin, moxifloxacin, and rifampicin, respectively). Vancomycin resistance was not detected, and metronidazole resistance was observed only for a single RT027 isolate. CONCLUSIONS: This Germany-wide continuing surveillance effort with a standardized mode of isolate acquisition indicates that isolates of RT027 were only sporadically detected under these strain acquisition conditions, and RT001 seems to become less important in the hospital setting, being replaced by other RTs.

Molecular epidemiology and antimicrobial resistance of Clostridioides difficile in Germany, 2014-2019.

Clostridioides difficile is a Gram positive spore-forming rod and mainly responsible for nosocomial diarrhea in developed nations. Molecular and antimicrobial surveillance is important for monitoring the strain composition including genotypes of high epidemiological importance such as ribotype 027 (RT027) and corresponding resistance patterns. 1535 isolates obtained from samples sent between 2014 and 2019 to the German National Reference Center (NRC) for diagnostic reasons (NRC strain set), and 1143 isolates from a Tertiary Care University Center in Saarland, Germany (non-NRC strain set), were evaluated using antibiotic susceptibility testing and ribotyping. In the NRC strain set, RT027 overtook RT001, the main RT found in the preceding studies, and dominated with 36.2%, followed by RT001 (13.3%), and RT014 (8.5%). Of note, since 2016 a constant decrease of RT027 could be noticed. In the non-NRC strain set a large strain diversity was present with RT014 (18%) and RT001 (8.9%) being most prevalent. In NRC samples, resistance towards metronidazole, vancomycin, moxifloxacin, clarithromycin and rifampicin was 2.7%, 0%, 57.1%, 53.2% and 19.2%, respectively. Metronidazole resistance was almost exclusively found in RT027 isolates. Rifampicin resistance was also observed predominantly in isolates of RT027, constituting an almost four-fold increase, when compared to preceeding studies in this region. In conclusion these data demonstrate that RT027 is a driver for rifampicin and metronidazole resistance, underlining the importance of continuous surveillance efforts.

Application and clinical impact of the RESIST-4 O.K.N.V. rapid diagnostic test for carbapenemase detection in blood cultures and clinical samples.

Invasive infections caused by carbapenemase-producing bacteria are associated with excess mortality. We applied a rapid diagnostic test (RDT) on clinical samples with an elevated likelihood of carbapenemase-producing bacteria and documented its impact on antibiotic treatment decisions. Among 38 patients, twelve tested positive for infections caused by carbapenemase-producing bacteria (31.6%), mainly in blood cultures. KPC (n = 10) was more frequent than OXA-48 (n = 2). RDT-based carbapenemase detection led to a treatment modification to ceftazidime/avibactam-containing regimens in all patients before detailed antibiotic testing results became available. Eleven patients (92%) survived the acute infection, whereas one patient with a ceftazidime/avibactam- and colistin-resistant OXA-48-positive isolate died.

Dimerization of Linear Butenes and Pentenes in an Acidic Zeolite (H-MFI).

Quantum chemical evidence is produced to show that dimerization of linear butenes and pentenes at zeolitic Brønsted sites in H-MFI yields alkanes featuring cyclohexane rings rather than branched alkenes. The absence of any C=C double bond in the formed cyclic alkane explains the observations that oligomerization stops at the dimer. The calculated reaction enthalpies for the dimerization of 2-pentene in the gas phase are -84 kJ mol-1 for branched alkenes, but -153 and -154 kJ mol-1 for alkyl-cyclopentane and -hexane, respectively. Together with calculated adsorption enthalpies of the dimers, -111 and -127 kJ mol-1 , respectively, this implies surface dimer formation enthalpies of -264 and -281 kJ mol-1 , respectively, in close agreement with the experimental value of -285 kJ mol-1 . In contrast, the predicted enthalpy for formation of branched alkoxides, -198 kJ mol-1 , deviates by 87 kJ mol-1 from experiment. Calculated IR spectra for the Brønsted OH group show the observed conversion of the band at approximately 3000 cm-1 (hydrogen bond with alkene) to a less intense band at approximately 3450-3500 cm-1 (interaction with alkane).

Donor-Acceptor Dihydropyrenes Switchable with Near-Infrared Light.

The use of low-intensity NIR light to operate molecular switches offers several potential advantages including enhanced penetration into bulk materials, in particular biological tissues, and reduced radiation damage due to the limited photon energies. The latter, however, pose a challenge for designing reasonably bistable systems. We have developed a general design strategy for direct one-photon NIR photoswitches based on negative photochromic dihydropyrenes carrying opposing strong donor-acceptor substituents either along the long axis of the molecule or across it. Thus, two series of 2,7- and 4,9-disubstituted dihydropyrenes were synthesized, and their photothermal properties investigated as a function of the type, strength, and position of the attached donor and acceptor substituents as well as the polarity of the environment. By shifting the excitation wavelength deep into the NIR, both NIR one-photon absorption cross-section and photoisomerization efficiency could be maximized while retaining a reasonable thermal stability of the metastable cyclophanediene isomer. Thus, the lowest optical transition was shifted beyond 900 nm, the NIR cross-section was enhanced by two orders of magnitude, and the thermal half-lives vary between milliseconds and hours. These unique features open up ample opportunities for noninvasive, optically addressable materials and material systems.

Participation of adults with cognitive, physical, or psychiatric impairments in family of origin and intimate relationships: a grounded theory study.

BACKGROUND: How adults with disabilities perceive participation has received little attention. Our purpose was to formulate a grounded theory on participation, based on the subjective experience of adults with cognitive, physical, or psychiatric impairment(s), and to identify barriers, facilitators, and support needs concerning participation in different areas of life. We aimed to explore whether the United Nations' Convention on the Rights of Persons with Disabilities (CRPD), ratified by Switzerland in 2014, and its principles are being met. Here we report on the main category and focus on the participation areas 'family of origin' and 'intimate relationships.' METHODS: In a qualitative, grounded theory study, we conducted problem-centered interviews with 23 adults with cognitive, physical, or psychiatric impairments (30-53 years; 11 men, 12 women), with different housing (on their own, assisted living, with parents) and work situations (primary vs. secondary labor market) in nine German-speaking Swiss cantons. RESULTS: Participation can be understood as a continuum that extends on a horizontal level (from participation is restricted to participation takes place) and a vertical level (separative setting vs. inclusive setting). In separative as well as in inclusive settings, diverse levels of participation are possible. Many participants were stuck in an 'in-between' area between separative and inclusion-oriented settings. In the family of origin, there was a thin line between fulfilling relations that enhance participation and conflictual relations and overprotective parenting that limit participation. In intimate relationships, opportunities for participation were limited overall. Many interviewees were single. Social environment and family of origin (e.g., parents) can enable and facilitate intimate relationships and sexual contacts but can also be an important barrier. CONCLUSIONS: Participation can be understood as a continuum. Participation restrictions exist in separative as well as in inclusive-oriented settings, also in the areas of family of origin and intimate relationships. Participation barriers must be torn down in separative as well as in inclusion-oriented settings. Trajectories to inclusive settings should be facilitated. Families with children with impairment(s) should be supported from early on to create the best possible participation possibilities for the (adult) person with impairment(s) and to support the family of origin itself.

The awareness, visibility and support for young carers across Europe: a Delphi study.

BACKGROUND: Across Europe, young carers (YCs) and their need for support receive limited attention in the media, policy and empirical research, even though, similar to adult carers, they also provide care to ill family members. The Delphi study, a qualitative research methodology, which provides the focus for this article, had the overall aim of exploring existing successful strategies to support YCs. Compared to YCs, even less is known about adolescent young carers (AYCs), a group that is in a critical life transition phase. The study forms part of an EU Horizon 2020 funded research project on AYCs aged 15-17 years old. METHODS: A two-round Delphi study was conducted with 66 experts on YCs from 10 European countries. Topics included: (i) visibility and awareness-raising of YCs at local, regional, and national levels, (ii) current interventions to support YCs, and (iii) future strategies to support YCs. RESULTS: Experts reported a lack of visibility and awareness about YCs in general, and AYCs in particular. Although awareness is slowly increasing in most countries, with the UK ranked highest, experts acknowledged that it remains challenging to identify YCs in many countries. Furthermore, the level and type of support available for YCs differs, with most countries mainly offering support on a local level. Diverse views were expressed regarding future strategies to support YCs. Experts highlighted the importance of specific legislation to formalise the rights of YCs, and the issue of whether young people should be safeguarded from caregiving or if this should be considered part of regular family life. They also emphasised the relevance of available integrated support services for YCs, including schools, family, health and social care. CONCLUSIONS: In most European countries, there is a lack of awareness and visibility on YCs. Identification of YCs is a crucial first step and there is need for a common definition of YCs, together with greater opportunities for young adults to identify themselves as YCs.

Quality assurance for genotyping and resistance testing of Clostridium (Clostridioides) difficile isolates - Experiences from the first inter-laboratory ring trial in four German speaking countries.

Clostridium (Clostridioides) difficile is a major cause of nosocomial diarrhoea. A first inter-laboratory ring trial was performed in four European countries to evaluate the genotyping and antibiotic susceptibility testing (AST) accuracy. Six C. difficile isolates representing the epidemiologic important ribotypes (RT), RT001, RT002, RT010, RT014, RT027, and RT078 were blinded and send to 21 participating laboratories. Participants tested the samples with their genotyping and AST methods in use for concordance with reference. A total of 21 genotyping- and 14 antimicrobial susceptibility data sets were obtained. Ribotyping (11 participants) correctly identified most RTs (median 91% concordance rate) except for RT002, which was misidentified in 4/11 reports. However, this isolate was correctly asserted to RT002 after an update of a publicly available ribotyping database. Multilocus sequence typing, surface layer sequence typing, DNA microarray based genotyping, and whole genome sequencing, which were used by 1-3 participants, identified all six isolates correctly. AST was done by epsilometry by the participants and compared to agar dilution data determined by the coordinating reference centre. Susceptibilities against metronidazole, moxifloxacin, and vancomycin were correctly identified in 235 of 237 cases and in accordance to agar dilution as the gold standard. Genotyping of the C. difficile test strains revealed a remarkable high concordance on the level of ribotypes with a wide variety of methods. Epsilometry appears to be a reliable method for AST of C. difficile isolates in routine clinical microbiology laboratories.

Factors affecting reported Clostridioides difficile infection rates; the more you look the more you find, but should you believe what you see?

Reported rates of C. difficile infection (CDI) have increased in many settings; however, these can be affected by factors including testing density (test-density) and diagnostic methods. We aimed to describe the impact of multiple factors on CDI rates. Hospitals (n = 182) across five countries (France, Germany, Italy, Spain, and UK) provided data on; size and type of institution, CDI testing methodology, number of tests/month and patient-bed-days (pbds)/month over one year. Incidence rates were compared between countries, different sized institutions, types of institutions and testing method. After univariate analyses, the highest CDI rates were observed in Italy (average 11.8/10,000pbds/hospital/month), acute/primary hospitals (12.3/10,000pbds/hospital/month), small hospitals (16.7/10,000pbds/hospital/month), and hospitals using methods that do not detect toxin (NO-TOXIN) (e.g. GDH/NAAT or standalone NAAT) (10.7/10,000pbds/hospital/month). After adjusting for test-density, highest incidence rates were still in Italy, acute/primary hospitals and those using NO-TOXIN. The relative rate in long-term healthcare facilities (LTHCFs) increased, but size of institution no longer influenced the CDI rate. Test-density appears to have the largest effect on reported CDI rates. NO-TOXIN testing still influences CDI rates, even after adjusting for test-density, which is consistent with tests that 'overcall' true CDI. Low test-density can mask the true burden of CDI, e.g. in LTHCFs, highlighting the importance of good quality surveillance.

Proton-Gated Ring-Closure of a Negative Photochromic Azulene-Based Diarylethene.

Proton-responsive photochromic molecules are attractive for their ability to react on non-invasive rapid optical stimuli and the importance of protonation/deprotonation processes in various fields. Conventionally, their acidic/basic sites are on hetero-atoms, which are orthogonal to the photo-active π-center. Here, we incorporate azulene, an acid-sensitive pure hydrocarbon, into the skeleton of a diarylethene-type photoswitch. The latter exhibits a novel proton-gated negative photochromic ring-closure and its optical response upon protonation in both open and closed forms is much more pronounced than those of diarylethene photoswitches with hetero-atom based acidic/basic moieties. The unique behavior of the new photoswitch can be attributed to direct protonation on its π-system, supported by 1H NMR and theoretical calculations. Our results demonstrate the great potential of integrating non-alternant hydrocarbons into photochromic systems for the development of multi-responsive molecular switches.

Hospital outbreak due to Clostridium difficile ribotype 018 (RT018) in Southern Germany.

Clostridium (Clostridioides) difficile is the main cause of nosocomial diarrhoea. Ribotype 018 (RT018) has been recognized as the predominant strain responsible for C. difficile infection (CDI) in Italy, whereas in most other European countries only sporadic RT018 cases occur. Between August and October 2015, a suspected C. difficile outbreak at two associated hospitals in Southern Germany was investigated by comprehensive molecular typing. Surprisingly, RT018 was detected in 9/82 CDI patients, which has never been described before in a German outbreak. Phenotypic analysis revealed fluoroquinolone and macrolide resistance. Genetic subtyping using multiple-locus variable-number tandem-repeat analysis (MLVA) and whole genome sequencing (WGS) was performed and outbreak isolates were directly compared to sporadic German RT018 isolates and to epidemic ones from Milan, Northern Italy. Molecular typing confirmed a hospital outbreak with closely related RT018 isolates. Both, MLVA and WGS revealed high similarity of outbreak strains with epidemic isolates from Italy, but low similarity to other German isolates. Comparison between both typing strategies showed that ribotyping in combination with MLVA was appropriate to identify related isolates and clonal complexes, whereas WGS provided a better discrimination with more detailed information about the phylogenetic relationship of isolates. This is the first hospital outbreak in Germany presumably caused by cross-national transmission of an Italian epidemic RT018 strain.

[Self-help support, self-help groups and self-help friendliness in Switzerland-between subsidiary structure and national development needs]. / Selbsthilfeunterstützung, Selbsthilfegruppen und Selbsthilfefreundlichkeit in der Schweiz ­ zwischen subsidiären Strukturen und nationalem Entwicklungsbedarf.

The Swiss welfare state is marked by strong federalism and subsidiarity, e. g. when it comes to social and health policies. This contribution presents findings of the first national study on self-help in Switzerland.This contribution is based on three sub-projects: 1. an oral and an online survey of the management personnel of the national organization Self-help Switzerland (Selbsthilfe Schweiz) and all regional self-help centers; 2. a quantitative-descriptive evaluation of the Self-help Switzerland's database with over 2500 self-help groups; and 3. twelve semi-structured interviews with experts from the social and health system.Little support is given at the national level to the self-help system. While Self-help Switzerland deals with topics of national importance, promotion of self-help has so far primarily been the domain of the regional self-help centers. This led to large regional differences in the dissemination and the development of self-help groups. There are also regional disparities in the cooperation between self-help groups and centers with the professionals and institutions from the social and health system.Self-help is discussed as characteristic for the federalist and subsidiary culture of the Swiss welfare state. The current self-help landscape is regionally based and locally financed. There is a substantial need for development on the national level: a legal base is required as well as stronger funding for self-help support and initiatives for self-help friendliness.

Isolation and toxin gene detection of Clostridium (Clostridioides) difficile from traditional and commercial quail farms and packed quail meat for market supply - Short communication.

Clostridium (Clostridioides) difficile is a Gram-positive anaerobic rod-shaped bacterium and the main cause of nosocomial diarrhoea in humans. In recent years, the transmission of C. difficile from environmental reservoirs (e.g. food) to humans has become a major focus of research. The aim of this study was to investigate the prevalence and corresponding toxin genes of C. difficile in faecal samples and meat of quails. Thirty samples of packed quail meat in Mashhad, Iran and 500 faecal samples (pooled to n = 5) were collected on quail farms in the Northeastern Khorasan region for further investigation. Of 100 pooled quail faecal samples 10% showed cultural growth of C. difficile. In meat samples two out of 30 specimens (7%) showed cultural growth. In six of ten isolates from faecal samples toxin genes (tcdB and tcdA) were present, while four isolates harboured no toxin genes. However, in meat isolates no toxin genes were present. Mutations in the tcdC gene were not detected, indicating that 'hypervirulent' strains such as RT027 and RT078 were not present. The data suggest that quail and quail products might hold a potential for the spread of C. difficile.

External Reversal of Chirality Transfer in Photoswitches.

The transfer of stereoinformation is at the heart of asymmetric reactions. By incorporating the natural monoterpene l-menthone into the backbone of a diarylethene, we achieved efficient chirality transfer upon photocyclization, resulting in the preferred formation of one major closed isomer in a diastereomeric ratio (d.r.) of 85:15. More significantly, we were able to completely reverse the diastereomeric outcome of the ring closure simply by altering the chemical environment or the irradiation conditions. As a result, we could selectively accumulate the less favored minor closed isomer, with remarkable d.r. values of >99:1 and 74:26, respectively. Computations revealed that a stability inversion after photocyclization is the basis for the observed unprecedented control over diastereoselectivity.

Molecular characterization, toxin detection and resistance testing of human clinical Clostridium difficile isolates from Lebanon.

Clostridium (Clostridioides) difficile is the main cause for nosocomial diarrhoea in industrialised nations. Epidemiologic data on the pathogen's occurrence in other world regions are still scarce. In this context we characterized with phenotypic and molecular genetic methods C. difficile isolates stemming from hospitalised patients with diarrhoea in Lebanon. From 129 stool samples of symptomatic patients at a tertiary care University hospital in Lebanon, a total of 107 C. difficile strains were cultivated and underwent ribotyping, toxin gene detection and antibiotic resistance testing. Ribotype 014 (RT014, 16.8%) predominated, followed by RT002 (9.3%), RT106 (8.4%) and RT070 (6.5%). Binary toxin gene-positive isolates (RT023, RT078 and RT126) were rarely detected and RT027 was absent. Interestingly, within one isolate only the toxin A gene (tcdA) was detected. Multiple-locus variable-number tandem repeat analysis (MLVA) revealed strong strain diversity in most RTs. The isolates were sensitive to metronidazole and vancomycin, and only a small proportion of strains displayed resistance against moxifloxacin, rifampicin, and clarithromycin (5.6%, 1.9%, and 2.8%), respectively. The data indicate that the genetic strain composition of Lebanese strains differs markedly from the situation seen in Europe and North America. Especially the epidemic RTs seen in the latter regions were almost absent in Lebanon. Interestingly, most strains showed almost no resistance to commonly used antibiotics that are suspected to play a major role in the development of C. difficile infection, despite frequent use of these antibiotics in Lebanon. Thus, the role of antimicrobial resistance as a major driving force for infection development remains uncertain in this area.

Outbreak of Burkholderia cepacia complex infections associated with contaminated octenidine mouthwash solution, Germany, August to September 2018.

Three German patients developed nosocomial pneumonia after cardiac surgery and had Burkholderia cepacia complex detected in respiratory specimens. Two patients died of septic multi-organ failure. Whole-genome sequencing detected genetically identical B. cepacia complex strains in patient samples, from a batch of octenidine mouthwash solution, which had been used for nursing care, as well as in samples obtained from the manufacturer during production. Contamination of medical products during manufacturing may lead to international outbreaks.

Gas-Phase Vibrational Spectroscopy of the Aluminum Oxide Anions (Al2 O3 )1-6 AlO2.

We use cryogenic ion trap vibrational spectroscopy in combination with density functional theory to probe how the structural variability of alumina manifests itself in the structures of the gas-phase clusters (Al2 O3 )n AlO2- with n=1-6. The infrared photodissociation spectra of the D2 -tagged complexes, measured in the fingerprint spectral range (400-1200 cm-1 ), are rich in spectral features and start approaching the vibrational spectrum of amorphous alumina particles for n>4. Aided by a genetic algorithm, we find a trend towards the formation of irregular structures for larger n, with the exception of n=4, which exhibits a C3v ground-state structure. Locating the global minima of the larger systems proves challenging.