Microbiome analysis in Lascaux Cave in relation to black stain alterations of rock surfaces and collembola

Anthropization of Palaeolithic caves open for tourism may favour collembola invasion and result in the formation of black stains attributed to pigmented fungi. However, ecological processes underpinning black stain formation are not fully understood. Here, we tested the hypotheses that black stains from the Apse room of Lascaux Cave display a specific microbiota enriched in pigmented fungi, and that collembola thriving on the stains have the potential to consume and disseminate these black fungi. Metabarcoding showed that the microbiota of black stains and neighbouring unstained parts strongly differed, with in black stains a higher prevalence of Ochroconis and other pigmented fungi and the strong regression of Pseudomonas bacteria (whose isolates inhibited in vitro the growth of pigmented fungi). Isotopic analyses indicated that Folsomia candida collembola thriving on stains could feed on black stain in situ and assimilate the pigmented fungi they were fed with in vitro. They could carry these fungi and disseminate them when tested with complex black stains from Lascaux. This shows that black stain formation is linked to the development of pigmented fungi, which coincides with the elimination of antagonistic pseudomonads, and points towards a key role of F. candida collembola in the dynamics of pigmented fungi.

Microbiome Analysis of New, Insidious Cave Wall Alterations in the Apse of Lascaux Cave

Lascaux Cave is a UNESCO site that was closed to the public following wall surface alterations. Most black stains that had formed on wall surface are stable or receding, but a new type of alteration visually quite different (termed dark zones) developed in Lascaux's Apse room in the last 15 years. Here, we tested the hypothesis that dark zones displayed a different microbial community than black stains previously documented in the same room, using metabarcoding (MiSeq sequencing). Indeed, dark zones, black stains and neighboring unstained parts displayed distinct microbial communities. However, similarly to what was observed in black stains, pigmented fungi such as Ochroconis (now Scolecobasidium) were more abundant and the bacteria Pseudomonas less abundant in dark zones than in unstained parts. The collembola Folsomia candida, which can disseminate microorganisms involved in black stain development, was also present on dark zones. Illumina sequencing evidenced Ochroconis (Scolecobasidium) in all collembola samples from dark zones, as in collembola from black stains. This study shows that the microbial properties of dark zones are peculiar, yet dark zones display a number of microbial resemblances with black stains, which suggests a possible role of collembola in promoting these two types of microbial alterations on wall surfaces.

Complex plant quality-microbiota-population interactions modulate the response of a specialist herbivore to the defence of its host plant

Many specialist herbivores have evolved strategies to cope with plant defences, with gut microbiota potentially participating to such adaptations.In this study, we assessed whether the history of plant use (population origin) and microbiota may interact with plant defence adaptation.We tested whether microbiota enhance the performance of Melitaea cinxia larvae on their host plant, Plantago lanceolata and increase their ability to cope the defensive compounds, iridoid glycosides (IGs).The gut microbiota were significantly affected by both larval population origin and host plant IG level. Contrary to our prediction, impoverishing the microbiota with antibiotic treatment did not reduce larval performance.As expected for this specialized insect herbivore, sequestration of one of IGs was higher in larvae fed with plants producing higher concentration of IGs. These larvae also showed metabolic signature of intoxication (i.e. decrease in Lysine levels). However, intoxication on highly defended plants was only observed when larvae with a history of poorly defended plants were simultaneously treated with antibiotics.Our results suggest that both adaptation and microbiota contribute to the metabolic response of herbivores to plant defence though complex interactions. Read the free Plain Language Summary for this article on the Journal blog.

Alternative developmental and transcriptomic responses to host plant water limitation in a butterfly metapopulation

Predicting how climate change affects biotic interactions poses a challenge. Plant-insect herbivore interactions are particularly sensitive to climate change, as climate-induced changes in plant quality cascade into the performance of insect herbivores. Whereas the immediate survival of herbivore individuals depends on plastic responses to climate change-induced nutritional stress, long-term population persistence via evolutionary adaptation requires genetic variation for these responses. To assess the prospects for population persistence under climate change, it is therefore crucial to characterize response mechanisms to climate change-induced stressors, and quantify their variability in natural populations. Here, we test developmental and transcriptomic responses to water limitation-induced host plant quality change in a Glanville fritillary butterfly (Melitaea cinxia) metapopulation. We combine nuclear magnetic resonance spectroscopy on the plant metabolome, larval developmental assays and an RNA sequencing analysis of the larval transcriptome. We observed that responses to feeding on water-limited plants, in which amino acids and aromatic compounds are enriched, showed marked variation within the metapopulation, with individuals of some families performing better on control and others on water-limited plants. The transcriptomic responses were concordant with the developmental responses: families exhibiting opposite developmental responses also produced opposite transcriptomic responses (e.g. in growth-associated transcripts). The divergent responses in both larval development and transcriptome are associated with differences between families in amino acid catabolism and storage protein production. The results reveal intrapopulation variability in plasticity, suggesting that the Finnish M. cinxia metapopulation harbours potential for buffering against drought-induced changes in host plant quality.

Reciprocal interactions between anthropogenic stressors and insect microbiota

Insects play many important roles in nature due to their diversity, ecological role, and impact on agriculture or human health. They are directly influenced by environmental changes and in particular anthropic activities that constitute an important driver of change in the environmental characteristics. Insects face numerous anthropogenic stressors and have evolved various detoxication mechanisms to survive and/or resist to these compounds. Recent studies highligted the pressure exerted by xenobiotics on insect life-cycle and the important role of insect-associated bacterial microbiota in the insect responses to environmental changes. Stressor exposure can have various impacts on the composition and structure of insect microbiota that in turn may influence insect biology. Moreover, bacterial communities associated with insects can be directly or indirectly involved in detoxification processes with the selection of certain microorganisms capable of degrading xenobiotics. Further studies are needed to assess the role of insect-associated microbiota as key contributor to the xenobiotic metabolism and thus as a driver for insect adaptation to polluted habitats.

Larval habitat determines the bacterial and fungal microbiota of the mosquito vector Aedes aegypti

Mosquito larvae are naturally exposed to microbial communities present in a variety of larval development sites. Several earlier studies have highlighted that the larval habitat influences the composition of the larval bacterial microbiota. However, little information is available on their fungal microbiota, i.e. the mycobiota. In this study, we provide the first simultaneous characterization of the bacterial and fungal microbiota in field-collected Aedes aegypti larvae and their respective aquatic habitats. We evaluated whether the microbial communities associated with the breeding site may affect the composition of both the bacterial and fungal communities in Ae. aegypti larvae. Our results show a higher similarity in microbial community structure for both bacteria and fungi between larvae and the water in which larvae develop than between larvae from different breeding sites. This supports the hypothesis that larval habitat is a major factor driving microbial composition in mosquito larvae. Since the microbiota plays an important role in mosquito biology, unravelling the network of interactions that operate between bacteria and fungi is essential to better understand the functioning of the mosquito holobiont.

Microorganisms Associated with Mosquito Oviposition Sites: Implications for Habitat Selection and Insect Life Histories

Mosquitoes are considered one of the most important threats worldwide due to their ability to vector pathogens. They are responsible for the transmission of major pathogens such as malaria, dengue, zika, or chikungunya. Due to the lack of treatments or prophylaxis against many of the transmitted pathogens and an increasing prevalence of mosquito resistance to insecticides and drugs available, alternative strategies are now being explored. Some of these involve the use of microorganisms as promising agent to limit the fitness of mosquitoes, attract or repel them, and decrease the replication and transmission of pathogenic agents. In recent years, the importance of microorganisms colonizing the habitat of mosquitoes has particularly been investigated since they appeared to play major roles in their development and diseases transmission. In this issue, we will synthesize researches investigating how microorganisms present within water habitats may influence breeding site selection and oviposition strategies of gravid mosquito females. We will also highlight the impact of such microbes on the fate of females' progeny during their immature stages with a specific focus on egg hatching, development rate, and larvae or pupae survival.

Diversity and Functions of Yeast Communities Associated with Insects

Following the concept of the holobiont, insect-microbiota interactions play an important role in insect biology. Many examples of host-associated microorganisms have been reported to drastically influence insect biological processes such as development, physiology, nutrition, survival, immunity, or even vector competence. While a huge number of studies on insect-associated microbiota have focused on bacteria, other microbial partners including fungi have been comparatively neglected. Yeasts, which establish mostly commensal or symbiotic relationships with their host, can dominate the mycobiota of certain insects. This review presents key advances and progress in the research field highlighting the diversity of yeast communities associated with insects, as well as their impact on insect life-history traits, immunity, and behavior.

Considerations for mosquito microbiome research from the Mosquito Microbiome Consortium

In the past decade, there has been increasing interest in mosquito microbiome research, leading to large amounts of data on different mosquito species, with various underlying physiological characteristics, and from diverse geographical locations. However, guidelines and standardized methods for conducting mosquito microbiome research are lacking. To streamline methods in mosquito microbiome research and optimize data quality, reproducibility, and comparability, as well as facilitate data curation in a centralized location, we are establishing the Mosquito Microbiome Consortium, a collaborative initiative for the advancement of mosquito microbiome research. Our overall goal is to collectively work on unraveling the role of the mosquito microbiome in mosquito biology, while critically evaluating its potential for mosquito-borne disease control. This perspective serves to introduce the consortium and invite broader participation. It highlights the issues we view as most pressing to the community and proposes guidelines for conducting mosquito microbiome research. We focus on four broad areas in this piece: (1) sampling/experimental design for field, semi-field, or laboratory studies; (2) metadata collection; (3) sample processing, sequencing, and use of appropriate controls; and (4) data handling and analysis. We finally summarize current challenges and highlight future directions in mosquito microbiome research. We hope that this piece will spark discussions around this area of disease vector biology, as well as encourage careful considerations in the design and implementation of mosquito microbiome research. Video Abstract.

The gut bacterial community affects immunity but not metabolism in a specialist herbivorous butterfly

Plant tissues often lack essential nutritive elements and may contain a range of secondary toxic compounds. As nutritional imbalance in food intake may affect the performances of herbivores, the latter have evolved a variety of physiological mechanisms to cope with the challenges of digesting their plant-based diet. Some of these strategies involve living in association with symbiotic microbes that promote the digestion and detoxification of plant compounds or supply their host with essential nutrients missing from the plant diet. In Lepidoptera, a growing body of evidence has, however, recently challenged the idea that herbivores are nutritionally dependent on their gut microbial community. It is suggested that many of the herbivorous Lepidopteran species may not host a resident microbial community, but rather a transient one, acquired from their environment and diet. Studies directly testing these hypotheses are however scarce and come from an even more limited number of species.By coupling comparative metabarcoding, immune gene expression, and metabolomics analyses with experimental manipulation of the gut microbial community of prediapause larvae of the Glanville fritillary butterfly (Melitaea cinxia, L.), we tested whether the gut microbial community supports early larval growth and survival, or modulates metabolism or immunity during early stages of development.We successfully altered this microbiota through antibiotic treatments and consecutively restored it through fecal transplants from conspecifics. Our study suggests that although the microbiota is involved in the up-regulation of an antimicrobial peptide, it did not affect the life history traits or the metabolism of early instars larvae.This study confirms the poor impact of the microbiota on diverse life history traits of yet another Lepidoptera species. However, it also suggests that potential eco-evolutionary host-symbiont strategies that take place in the gut of herbivorous butterfly hosts might have been disregarded, particularly how the microbiota may affect the host immune system homeostasis.

Who is eating fructose within the Aedes albopictus gut microbiota?

The Asian tiger mosquito Aedes albopictus is a major public health concern because of its invasive success and its ability to transmit pathogens. Given the low availability of treatments against mosquito-borne diseases, vector control remains the most suitable strategy. The methods used thus far are becoming less effective, but recent strategies have emerged from the study of mosquito-associated microorganisms. Although the role of the microbiota in insect biology does not require further proof, much remains to be deciphered in mosquitoes, especially the contribution of the microbiota to host nutrient metabolism. Mosquitoes feed on plant nectar, composed of mostly fructose. We used stable isotope probing to identify bacteria and fungi assimilating fructose within the gut of Ae. albopictus. Mosquitoes were fed a ¹³ C-labelled fructose solution for 24 h. Differences in the active microbial community according to the sex of mosquitoes were highlighted. The bacterium Lelliottia and the fungi Cladosporium and Aspergillus dominated the active microbiota in males, whereas the bacterium Ampullimonas and the yeast Cyberlindnera were the most active in females. This study is the first to investigate trophic interactions between Ae. albopictus and its microbiota, thus underscoring the importance of the microbial component in nectar feeding in mosquitoes.

The microbiome of the Melitaea cinxia butterfly shows marked variation but is only little explained by the traits of the butterfly or its host plant

Understanding of the ecological factors that shape intraspecific variation of insect microbiota in natural populations is relatively poor. In Lepidopteran caterpillars, microbiota is assumed to be mainly composed of transient bacterial symbionts acquired from the host plant. We sampled Glanville fritillary (Melitaea cinxia) caterpillars from natural populations to describe their gut microbiome and to identify potential ecological factors that determine its structure. Our results demonstrate high variability of microbiota composition even among caterpillars that shared the same host plant individual and most likely the same genetic background. We observed that the caterpillars harboured microbial classes that varied among individuals and alternated between two distinct communities (one composed of mainly Enterobacteriaceae and another with more variable microbiota community). Even though the general structure of the microbiota was not attributed to the measured ecological factors, we found that phylogenetically similar microbiota showed corresponding responses to the sex and the parasitoid infection of the caterpillar and to those of the host plant's microbial and chemical composition. Our results indicate high among-individual variability in the microbiota of the M. cinxia caterpillar and contradict previous findings that the host plant is the major driver of the microbiota communities of insect herbivores.

Identification of human skin bacteria attractive to the Asian Tiger mosquito

Aedes albopictus is a vector of arboviruses and filarial nematodes. Originating from Asia, this mosquito has rapidly expanded its geographical distribution and colonized areas across both temperate and tropical regions. Due to the increase in insecticide resistance, the use of environmentally friendly vector control methods is encouraged worldwide. Using methods based on semiochemicals in baited traps are promising for management of mosquito populations. Interestingly, human skin microbiota was shown to generate volatile compounds that attract the mosquito species Anopheles gambiae and Aedes aegypti. Here, we investigated the composition of skin bacteria from different volunteers and the attractive potential of individual isolates to nulliparous Ae. albopictus females. We showed that three out of 16 tested isolates were more attractive and two were more repulsive. We identified dodecenol as being preferentially produced by attractive isolates and 2-methyl-1-butanol (and to a lesser extent 3-methyl-1-butanol) as being overproduced by these isolates compared with the other ones. Those bacterial volatile organic compounds represent promising candidates but further studies are needed to evaluate their potential application for baited traps improvement.

Short-term impacts of anthropogenic stressors on Aedes albopictus mosquito vector microbiota

Recent studies have highlighted the potential role of microbiota in the biology of the Aedes albopictus mosquito vector. This species is highly anthropogenic and exhibits marked ecological plasticity, with a resulting high potential to colonize a wide range of habitats-including anthropized areas-under various climatic conditions. We put forward the hypothesis that climate and anthropogenic activities, such as the use of antibiotics in agriculture and human medicine, might affect the mosquito-associated bacterial community. We thus studied the additive impact of a temperature decrease and antibiotic ingestion on the temporal dynamics of Ae. albopictus survival and its associated bacterial communities. The results showed no effects of disturbances on mosquito survival. However, short-term temperature impacts on bacterial diversity were observed, while both the community structure and bacterial diversity were affected by early antibiotic ingestion. The genera Elizabethkingia, Chryseobacterium and Wolbachia, as well as an unclassified member of the Bacteroidales order were particularly affected. Antibiotics negatively impacted Elizabethkingia abundance, while Chryseobacterium was completely eliminated following both disturbances, to the benefit of Wolbachia and the unclassified Bacteroidales species. These results generated fresh insight into the effects of climate and anthropogenic activities such as the use of antibiotics on mosquito microbiota.

Moderate plant water stress improves larval development, and impacts immunity and gut microbiota of a specialist herbivore

While host plant drought is generally viewed as a negative phenomenon, its impact on insect herbivores can vary largely depending on the species involved and on the intensity of the drought. Extreme drought killing host plants can clearly reduce herbivore fitness, but the impact of moderate host plant water stress on insect herbivores can vary, and may even be beneficial. The populations of the Finnish Glanville fritillary butterfly (Melitaea cinxia) have faced reduced precipitation in recent years, with impacts even on population dynamics. Whether the negative effects of low precipitation are solely due to extreme desiccation killing the host plant or whether moderate drought reduces plant quality for the larvae remains unknown. We assessed the performance of larvae fed on moderately water-stressed Plantago lanceolata in terms of growth, survival, and immune response, and additionally were interested to assess whether the gut microbial composition of the larvae changed due to modification of the host plant. We found that larvae fed on water-stressed plants had increased growth, with no impact on survival, up-regulated the expression of one candidate immune gene (pelle), and had a more heterogeneous bacterial community and a shifted fungal community in the gut. Most of the measured traits showed considerable variation due to family structure. Our data suggest that in temperate regions moderate host plant water stress can positively shape resource acquisition of this specialized insect herbivore, potentially by increasing nutrient accessibility or concentration. Potentially, the better larval performance may be mediated by a shift of the microbiota on water-stressed plants, calling for further research especially on the understudied gut fungal community.

Silk properties and overwinter survival in gregarious butterfly larvae

All organisms are challenged by encounters with parasites, which strongly select for efficient escape strategies in the host. The threat is especially high for gregarious species entering immobile periods, such as diapause. Larvae of the Glanville fritillary butterfly, Melitaea cinxia, spend the winter in diapause in groups of conspecifics each sheltered in a silk nest. Despite intensive monitoring of the population, we have little understanding of the ecological factors influencing larval survival over the winter in the field. We tested whether qualitative and quantitative properties of the silk nest contribute to larval survival over diapause. We used comparative proteomics, metabarcoding analyses, microscopic imaging, and in vitro experiments to compare protein composition of the silk, community composition of the silk-associated microbiota, and silk density from both wild-collected and laboratory-reared families, which survived or died in the field. Although most traits assessed varied across families, only silk density was correlated with overwinter survival in the field. The silk nest spun by gregarious larvae before the winter acts as an efficient breathable physical shield that positively affects larval survival during diapause. Such benefit may explain how this costly trait is conserved across populations of this butterfly species and potentially across other silk-spinning insect species.

Shared larval rearing environment, sex, female size and genetic diversity shape Ae. albopictus bacterial microbiota

The Asian tiger mosquito Aedes albopictus became of public health concern as it can replicate and transmit viral and filarial pathogens with a strong invasive success over the world. Various strategies have been proposed to reduce mosquito population's vectorial capacity. Among them, symbiotic control of mosquito borne disease offers promising perspectives. Such method is likely to be affected by the dynamics of mosquito-associated symbiotic communities, which might in turn be affected by host genotype and environment. Our previous study suggested a correlation between mosquitoes’ origin, genetic diversity and midgut bacterial diversity. To distinguish the impact of those factors, we have been studying the midgut bacterial microbiota of two Ae. albopictus populations from tropical (La Réunion) and temperate (Montpellier) origins under controlled laboratory conditions. the two populations experienced random mating or genetic bottleneck. Microbiota composition did not highlight any variation of the α and β-diversities in bacterial communities related to host’s populations. However, sizes of the mosquitoes were negatively correlated with the bacterial α-diversity of females. Variations in mosquito sex were associated with a shift in the composition of bacterial microbiota. The females’ mosquitoes also exhibited changes in the microbiota composition according to their size and after experiencing a reduction of their genetic diversity. These results provide a framework to investigate the impact of population dynamics on the symbiotic communities associated with the tiger mosquito.

The mosquito holobiont: fresh insight into mosquito-microbiota interactions

The holobiont concept was first developed for coral ecosystems but has been extended to multiple organisms, including plants and other animals. Studies on insect-associated microbial communities have produced strong evidence that symbiotic bacteria play a major role in host biology. However, the understanding of these symbiotic relationships has mainly been limited to phytophagous insects, while the role of host-associated microbiota in haematophagous insect vectors remains largely unexplored. Mosquitoes are a major global public health concern, with a concomitant increase in people at risk of infection. The global emergence and re-emergence of mosquito-borne diseases has led many researchers to study both the mosquito host and its associated microbiota. Although most of these studies have been descriptive, they have led to a broad description of the bacterial communities hosted by mosquito populations. This review describes key advances and progress in the field of the mosquito microbiota research while also encompassing other microbes and the environmental factors driving their composition and diversity. The discussion includes recent findings on the microbiota functional roles and underlines their interactions with the host biology and pathogen transmission. Insight into the ecology of multipartite interactions, we consider that conferring the term holobiont to the mosquito and its microbiota is useful to get a comprehensive understanding of the vector pathosystem functioning so as to be able to develop innovative and efficient novel vector control strategies.

Bacterial microbiota associated with Rhipicephalus sanguineus (s.l.) ticks from France, Senegal and Arizona

Background

Ticks of the group Rhipicephalus sanguineus (sensu lato) are distributed worldwide and are major pathogen vectors of both dogs and humans. Previous phylogenetic reconstructions have suggested the existence of two main lineages within this group, “Tropical” and “Temperate”. Symbiotic interactions contribute to vector development, survival, reproduction and competence. The diversity of microbial communities associated with different populations of R. sanguineus (s.l.) remains poorly characterized, however, this knowledge will aid in future studies of hosts-microbiota-pathogen interactions. To gain insight into the bacterial communities associated with R. sanguineus (s.l.) ticks, 40 specimens from France, Senegal and Arizona were analyzed by high-throughput 16S amplicon sequencing. All tick specimens were taxonomically classified using the mitochondrial 12S rDNA gene, which provides sufficient phylogenetic resolution to discriminate different lineages of R. sanguineus.

Results

Rhipicephalus sanguineus (s.l.) samples from Senegal belonged to the “Tropical” lineage, samples from France belonged to the “Temperate” lineage, whereas both lineages were identified in samples from Arizona. Regardless of origin, each bacterial microbiota was dominated by three genera: Coxiella, Rickettsia and Bacillus. Rickettsia and Coxiella were the two main genera found in females whereas males had a higher proportion of Bacillus. Significant differences of relative abundances were evidenced between specimens from different geographical origins.

Conclusions

This study highlights differences in the microbiota composition within R. sanguineus (s.l.) specimens from different genotypes, genders and geographical origins. This knowledge will help in future studies of the symbiotic interactions, biology and vector competence of the R. sanguineus (s.l.) complex.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2352-9) contains supplementary material, which is available to authorized users.

Carryover effects of larval exposure to different environmental bacteria drive adult trait variation in a mosquito vector

Conditions experienced during larval development of holometabolous insects can affect adult traits, but whether differences in the bacterial communities of larval development sites contribute to variation in the ability of insect vectors to transmit human pathogens is unknown. We addressed this question in the mosquito Aedes aegypti, a major arbovirus vector breeding in both sylvatic and domestic habitats in Sub-Saharan Africa. Targeted metagenomics revealed differing bacterial communities in the water of natural breeding sites in Gabon. Experimental exposure to different native bacterial isolates during larval development resulted in significant differences in pupation rate and adult body size but not life span. Larval exposure to an Enterobacteriaceae isolate resulted in decreased antibacterial activity in adult hemolymph and reduced dengue virus dissemination titer. Together, these data provide the proof of concept that larval exposure to different bacteria can drive variation in adult traits underlying vectorial capacity. Our study establishes a functional link between larval ecology, environmental microbes, and adult phenotypic variation in a holometabolous insect vector.

Identification of sympatric cryptic species of Aedes albopictus subgroup in Vietnam: new perspectives in phylosymbiosis of insect vector

Background

The Aedes (Stegomyia) albopictus subgroup includes 11 cryptic species of which Ae. albopictus is the most widely distributed. Its global expansion associated with a documented vector competence for several emerging arboviruses raise obvious concerns in the recently colonized regions. While several studies have provided important insights regarding medical importance of Ae. albopicus, the investigations of the other sibling species are scarce. In Asia, indigenous populations within the Ae. albopictus subgroup can be found in sympatry. In the present study, we aimed to describe and compare molecular, morphological and bacterial symbionts composition among sympatric individuals from the Ae. albopictus subgroup inhabiting a Vietnamese protected area.

Results

Based on morphological structure of the cibarial armarture, we identified a cryptic species in the forest park at Bù Gia Mập in the south-eastern region of Vietnam. Analysis of nuclear (ITS1-5.8S-ITS2) and mitochondrial (cox1, nad5) markers confirmed the divergence between the cryptic species and Ae. albopictus. Analysis of midgut bacterial microbiota revealed a strong similarity among the two species with a notable difference; contrary to Ae. albopictus, the cryptic species did not harbour any Wolbachia infection.

Conclusions

These results could reflect either a recent invasion of Wolbachia in Ae. albopictus or alternatively a loss of this symbiont in the cryptic species. We argue that neglected species of the Ae. albopictus subgroup are of main importance in order to estimate variation of host-symbionts interactions across evolution.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2202-9) contains supplementary material, which is available to authorized users.

French invasive Asian tiger mosquito populations harbor reduced bacterial microbiota and genetic diversity compared to Vietnamese autochthonous relatives

The Asian tiger mosquito Aedes albopictus is one of the most significant pathogen vectors of the twenty-first century. Originating from Asia, it has invaded a wide range of eco-climatic regions worldwide. The insect-associated microbiota is now recognized to play a significant role in host biology. While genetic diversity bottlenecks are known to result from biological invasions, the resulting shifts in host-associated microbiota diversity has not been thoroughly investigated. To address this subject, we compared four autochthonous Ae. albopictus populations in Vietnam, the native area of Ae. albopictus, and three populations recently introduced to Metropolitan France, with the aim of documenting whether these populations display differences in host genotype and bacterial microbiota. Population-level genetic diversity (microsatellite markers and COI haplotype) and bacterial diversity (16S rDNA metabarcoding) were compared between field-caught mosquitoes. Bacterial microbiota from the whole insect bodies were largely dominated by Wolbachia pipientis. Targeted analysis of the gut microbiota revealed a greater bacterial diversity in which a fraction was common between French and Vietnamese populations. The genus Dysgonomonas was the most prevalent and abundant across all studied populations. Overall genetic diversities of both hosts and bacterial microbiota were significantly reduced in recently established populations of France compared to the autochthonous populations of Vietnam. These results open up many important avenues of investigation in order to link the process of geographical invasion to shifts in commensal and symbiotic microbiome communities, as such shifts may have dramatic impacts on the biology and/or vector competence of invading hematophagous insects.

French invasive Asian tiger mosquito populations harbor reduced bacterial microbiota and genetic diversity compared to Vietnamese autochthonous relatives

The Asian tiger mosquito Aedes albopictus is one of the most significant pathogen vectors of the twenty-first century. Originating from Asia, it has invaded a wide range of eco-climatic regions worldwide. The insect-associated microbiota is now recognized to play a significant role in host biology. While genetic diversity bottlenecks are known to result from biological invasions, the resulting shifts in host-associated microbiota diversity has not been thoroughly investigated. To address this subject, we compared four autochthonous Ae. albopictus populations in Vietnam, the native area of Ae. albopictus, and three populations recently introduced to Metropolitan France, with the aim of documenting whether these populations display differences in host genotype and bacterial microbiota. Population-level genetic diversity (microsatellite markers and COI haplotype) and bacterial diversity (16S rDNA metabarcoding) were compared between field-caught mosquitoes. Bacterial microbiota from the whole insect bodies were largely dominated by Wolbachia pipientis. Targeted analysis of the gut microbiota revealed a greater bacterial diversity in which a fraction was common between French and Vietnamese populations. The genus Dysgonomonas was the most prevalent and abundant across all studied populations. Overall genetic diversities of both hosts and bacterial microbiota were significantly reduced in recently established populations of France compared to the autochthonous populations of Vietnam. These results open up many important avenues of investigation in order to link the process of geographical invasion to shifts in commensal and symbiotic microbiome communities, as such shifts may have dramatic impacts on the biology and/or vector competence of invading hematophagous insects.

Pyrosequencing 16S rRNA genes of bacteria associated with wild tiger mosquito Aedes albopictus: a pilot study

The Asian tiger mosquito Aedes (Stegomya) albopictus is an invasive species that has spread across the world in the last two decades, showing a great capacity to adapt to contrasting climates and environments. While demonstrated in many insects, the contribution of bacterial symbionts in Aedes ecology is a challenging aspect that needs to be investigated. Also some bacterial species have already been identified in Ae. albopictus using classical methods, but a more accurate survey of mosquito-associated bacterial diversity is needed to decipher the potential biological functions of bacterial symbionts in mediating or constraining insect adaptation. We surveyed the bacteria associated with field populations of Ae. albopictus from Madagascar by pyrosequencing 16S rRNA gene amplicons. Different aspects of amplicon preparation and sequencing depth were tested to optimize the breadth of bacterial diversity identified. The results revealed that all mosquitoes collected from different sites have a bacterial microbiota dominated by a single taxon, Wolbachia pipientis, which accounted for about 99% of all 92,615 sequences obtained. As Ae. albopictus is known to harbor two Wolbachia strains (wAlbA and wAlbB), a quantitative PCR was used to estimate the relative densities, (i.e., the bacteria-to-host gene ratios) of each strains in individual mosquitoes. Relative densities were between 6.25 × 10(0.01) and 5.47 × 10(0.1) for wAlbA and between 2.03 × 10(0.1) and 1.4 × 10(1) for wAlbB. Apart from Wolbachia, a total of 31 bacterial taxa were identified at the genus level using different method variations. Diversity index values were low and probably underestimated the true diversity due to the high abundance of Wolbachia sequences vastly outnumbering sequences from other taxa. Further studies should implement alternative strategies to specifically discard from analysis any sequences from Wolbachia, the dominant endosymbiotic bacterium in Ae. albopictus from this area.

Diversity and function of bacterial microbiota in the mosquito holobiont

Mosquitoes (Diptera: Culicidae) have been shown to host diverse bacterial communities that vary depending on the sex of the mosquito, the developmental stage, and ecological factors. Some studies have suggested a potential role of microbiota in the nutritional, developmental and reproductive biology of mosquitoes. Here, we present a review of the diversity and functions of mosquito-associated bacteria across multiple variation factors, emphasizing recent findings. Mosquito microbiota is considered in the context of possible extended phenotypes conferred on the insect hosts that allow niche diversification and rapid adaptive evolution in other insects. These kinds of observations have prompted the recent development of new mosquito control methods based on the use of symbiotically-modified mosquitoes to interfere with pathogen transmission or reduce the host life span and reproduction. New opportunities for exploiting bacterial function for vector control are highlighted.

Prevalence, genomic and metabolic profiles of Acinetobacter and Asaia associated with field-caught Aedes albopictus from Madagascar

The presence of cultivable bacteria Acinetobacter and Asaia was recently demonstrated in the mosquito vector Aedes albopictus. However, it is not known how prevalent these bacteria are in field populations. Here, the presence of these bacteria in Ae. albopictus populations from Madagascar was diagnosed by amplification of 16S rRNA gene fragments. Both genera were detected at relatively high frequencies, 46% for Asaia and 74% for Acinetobacter. The prevalence of Acinetobacter correlated significantly with mosquito gender, and the prevalence of Asaia with the interaction between mosquito gender and the sampling site. For each bacterial genus, more male than female mosquitoes were infected. Using pulse field gel electrophoresis, no significant difference in genome size was found between Acinetobacter isolates from mosquitoes compared with free-living Acinetobacter. However, a great diversity was observed in plasmid numbers (from 1 to 12) and sizes (from < 8 to 690 kb). Mosquito isolates utilized fewer substrates than free-living isolates, but some substrates known as blood or plant components were specifically utilized by mosquito isolates. Therefore it is likely that a specific subpopulation of Acinetobacter is selected by Ae. albopictus. Overall, this study emphasizes the need to gain a global view on the bacterial partners in mosquito vectors.

Stress ulceration requiring definitive surgery after severe trauma

Despite antiulcer prophylaxis 19 severely injured patients at our institution developed stress ulceration (SU) between 1989 and 1999 requiring surgery for perforation (n = 4) or bleeding (n = 15). A herald bleed (HB) 10.7 +/- 1.2 days after admission, 7.2 +/- 1.2 days before definitive operative therapy, and requiring 7.1 +/- 0.9 units of blood occurred in 93 per cent of patients operated on for bleeding. Bleeding preceded perforation in one patient. Central nervous system damage was part of the injury pattern in 68 per cent of the patients including spinal cord (42%), severe head injury (16%), or both (10%). Forty-two per cent had acalculous cholecystitis found at surgery. Eight patients had vagotomy and antrectomy (VA), and 11 patients had vagotomy and pyloroplasty (VP). VA required more time than VP (255 +/- 41 vs 158 +/- 13 minutes; P = 0.02). One patient (12.5%) rebled after VA versus two (18%) after VP; one patient in each group required reoperation. There was no difference in mortality, length of stay, or intensive care unit stay. A herald bleed preceded recurrent hemorrhage of SU by one week. Spinal cord or head injury increase the risk of SU. More than 40 per cent of patients with SU had acalculous cholecystitis found at operation. VA provides no benefit on rebleeding or reoperation over VP, so anatomical considerations and not rebleed rates should determine the surgical procedure.

Penetrating esophageal injuries: multicenter study of the American Association for the Surgery of Trauma

OBJECTIVE

The purpose of this study was to define the period of time after which delays in management incurred by investigations cause increased morbidity and mortality. The outcome study is intended to correlate time with death from esophageal causes, overall complications, esophageal related complications, and surgical intensive care unit length of stay.

METHODS

This was a retrospective multicenter study involving 34 trauma centers in the United States, under the auspices of the American Association for the Surgery of Trauma Multi-institutional Trials Committee over a span of 10.5 years. Patients surviving to reach the operating room (OR) were divided into two groups: those that underwent diagnostic studies to identify their injuries (preoperative evaluation group) and those that went immediately to the OR (no preoperative evaluation group). Statistical methods included Fisher's exact test, Student's T test, and logistic regression analysis.

RESULTS

The study involved 405 patients: 355 male patients (86.5%) and 50 female patients (13.5%). The mean Revised Trauma Score was 6.3, the mean Injury Severity Score was 28, and the mean time interval to the OR was 6.5 hours. There were associated injuries in 356 patients (88%), and an overall complication rate of 53.5%. Overall mortality was 78 of 405 (19%). Three hundred forty-six patients survived to reach the OR: 171 in the preoperative evaluation group and 175 in the no preoperative evaluation group. No statistically significant differences were noted in the two groups in the following parameters: number of patients, age, Injury Severity Score, admission blood pressure, anatomic location of injury (cervical or thoracic), surgical management (primary repair, resection and anastomosis, resection and diversion, flaps), number of associated injuries, and mortality. Average length of time to the OR was 13 hours in the preoperative evaluation group versus 1 hour in the no preoperative evaluation group (p < 0.001). Overall complications occurred in 134 in the preoperative evaluation group versus 87 in the no preoperative evaluation group (p < 0.001), and 74 (41%) esophageal related complications occurred in the preoperative evaluation group versus 32 (19%) in the no preoperative evaluation group (p = 0.003). Mean surgical intensive care unit length of stay was 11 days in the preoperative evaluation group versus 7 days in the no preoperative evaluation group (p = 0.012). Logistic regression analysis identified as independent risk factors for the development of esophageal related complications included time delays in preoperative evaluation (odds ratio, 3.13), American Association for the Surgery of Trauma Organ Injury Scale grade >2 (odds ratio, 2.62), and resection and diversion (odds ratio, 4.47).

CONCLUSION

Esophageal injuries carry a high morbidity and mortality. Increased esophageal related morbidity occurs with the diagnostic workup and its inherent delay in operative repair of these injuries. For centers practicing selective management of penetrating neck injuries and transmediastinal gunshot wounds, rapid diagnosis and definitive repair should be made a high priority.

Blunt hepatic injury: a paradigm shift from operative to nonoperative management in the 1990s

OBJECTIVE

To analyze the outcome of hemodynamically stable patients with blunt hepatic injury managed nonoperatively, and to examine the impact of this approach on the outcome of all patients with blunt hepatic injury.

SUMMARY BACKGROUND DATA

Until recently, operative management has been the standard for liver injury. A prospective trial from the authors' institution had shown that nonoperative management could safely be applied to hemodynamically stable patients with blunt hepatic injury. The present study reviewed the authors' institutional experience with blunt hepatic trauma since that trial and compared the results with prior institutional experience.

METHODS

Six hundred sixty-one patients with blunt hepatic trauma during the 5-year period ending December 1998 were reviewed (NONOP2). The outcomes were compared with two previous studies from this institution: operative 1985 to 1990 (OP) and nonoperative 1993 to 1994 (NONOP1).

RESULTS

All 168 OP patients were managed operatively. Twenty-four (18%) of 136 NONOP1 patients and 101 (15%) of the 661 NONOP2 patients required immediate exploration for hemodynamic instability. Forty-two (7%) patients failed nonoperative management; 20 were liver-related. Liver-related failures of nonoperative management were associated with higher-grade injuries and with larger amounts of hemoperitoneum on computed tomography scanning. Twenty-four-hour transfusions, abdominal infections, and hospital length of stay were all significantly lower in the NONOP1 and NONOP2 groups versus the OP cohort. The liver-related death rate was constant at 4% in the three cohorts over the three time periods.

CONCLUSIONS

Although urgent surgery continues to be the standard for hemodynamically compromised patients with blunt hepatic trauma, there has been a paradigm shift in the management of hemodynamically stable patients. Approximately 85% of all patients with blunt hepatic trauma are stable. In this group, nonoperative management significantly improves outcomes over operative management in terms of decreased abdominal infections, decreased transfusions, and decreased lengths of hospital stay.

Early versus delayed feeding with an immune-enhancing diet in patients with severe head injuries

BACKGROUND

Although early enteral feeding clearly reduces septic morbidity after blunt and penetrating trauma, data for head-injured patients are conflicting. This study examines the effects of early vs delayed enteral feedings on outcome in patients with severe closed-head injuries with a Glasgow Coma Scale (GCS) score greater than 3 and less than 11.

METHODS

Thirty patients were prospectively randomized to receive an immune-enhancing diet (Impact with fiber) early (initiated < 72 hours after trauma) delivered via an endoscopically placed nasoenteric tube (Stay-Put) or late (administered after gastric ileus resolved). This formula was continued for 14 days or until the patient tolerated oral feeding. Goal rate of nutrition was 21 nonprotein cal/kg/d and 0.3 g N/kg/d.

RESULTS

Two patients in the early group were excluded due to inability to place the tube, and one patient in the late group died before 72 hours. Five of the remaining 27 died, 1 in the early group and 4 in the late group. There were no significant differences between the groups in length of stay, intensive care unit (ICU) days, significant infection, or GCS score. However, major infection correlated inversely with admission GCS score (R = -0.6, p < .003). Time to reach a GCS score of 14 was significantly longer in patients with significant infections compared with those without (p < .02).

CONCLUSIONS

No difference in length of stay or infectious complications is shown in patients with severe closed-head injury when they are given early vs delayed feeding using an immune-enhancing formula. Severity of the head injury is closely associated with significant infection.

Rectal trauma: management based on anatomic distinctions

Principles of rectal wound management, including routine diversion, injury repair, presacral drainage and distal washout, evolved from World War II and the Vietnam conflict and have been questioned in recent years. We believe significant confusion arises because of imprecise definition of injury location relative to retroperitoneal involvement. Our 5-year experience with penetrating rectal injuries at a Level I trauma center was analyzed. Injuries to the anterior and lateral surfaces of the upper two-thirds of the rectum were classified as intraperitoneal (IP, serosalized), and those of the posterior surface extraperitoneal (EP, no serosa); injuries to the lower one-third were EP. A total of 58 injuries were managed (92% gunshot wounds). Of these, 16 were IP, and 42 had some EP component. Ten patients underwent repair without diversion (6 IP, 4 EP); there were no leaks. Ten septic complications occurred in the remaining population: 2 necrotizing fasciitis, 5 abdominal abscess, and 3 presacral infections (PIs) (2 presacral abscesses and 1 wound tract infection). PI is the only complication that can be specifically associated with EP rectal injuries relative to management; as associated injury confounds interpretation of the other complications. The operative management in the 38 patients with diverted EP wounds with respect to presacral infection (PI) demonstrated the following: repair injury (n = 10), 0 PI versus no repair (n = 28), 3 PI (P = 0.55); washout (n = 33), 2 PI versus no washout (n = 5), 1 PI (P = 0.35); presacral drain (n = 30), 1 PI versus no drain (n = 8), 2 PI (P = 0.11). We conclude that most IP injuries can be managed with primary repair. EP wounds to the upper two-thirds of the rectum should usually be repaired. EP wounds to the lower one-third, which are explored and repaired, do not require drainage. EP wounds that are not explored should be managed with presacral drainage to minimize the incidence of presacral abscess.

Impact of stomach and colon injuries on intra-abdominal abscess and the synergistic effect of hemorrhage and associated injury

BACKGROUND

Colon wounds are recognized to be highly associated with intra-abdominal abscess (IAA) after penetrating trauma, whereas gastric wounds are thought to contribute minimally to abscess because of the bactericidal effect of low pH. This study evaluated the impact of stomach or colon wounds, the contribution of other risk factors, and associated abdominal injuries on IAA.

METHODS

Patients with penetrating colon or stomach wounds during a 10-year period were reviewed and stratified by age, Injury Severity Score, transfusions, and associated abdominal injuries. Early deaths (<48 hours) from hemorrhage were excluded. Outcomes analyzed were IAA and death.

RESULTS

A total of 812 patients were identified. There were 32 late deaths (4%), of which 28% were attributable to IAA and multiple organ failure. IAA rates for isolated stomach or colon wounds were 0 and 4.2%, respectively. The presence of associated injuries increased IAA rates to 7.5 and 8.8%, respectively. Independent predictors of IAA determined by multivariate analysis included age, transfusions, gunshot wounds, and associated injuries to the liver, pancreas, and kidney.

CONCLUSION

Gastric injuries are equivalent to colon wounds in their contribution to IAA. Contamination from either organ without associated injury is minimally associated with IAA, but injury to both appears synergistic. The immunosuppressive effects of age and hemorrhage, in addition to significant associated injury, enhance the development of IAA.

Improved success in nonoperative management of blunt splenic injuries: embolization of splenic artery pseudoaneurysms

OBJECTIVES

By using abdominal computed tomographic scans in the evaluation of blunt splenic trauma, we previously identified the presence of vascular blush as a predictor of failure, with a failure of nonoperative management of 13% in that series. This finding led to an alteration in our management scheme, which now includes the aggressive identification and embolization of splenic artery pseudoaneurysms.

METHODS

The medical records of 524 consecutive patients with blunt splenic injury managed over a 4.5-year period were reviewed for the following information: age, Injury Severity Score (ISS), American Association for the Surgery of Trauma splenic injury grade (SIG), method and outcome of management.

RESULTS

Of the patients, 66% were male with a mean age of 32 +/- 16, and mean ISS of 25 +/- 13. A total of 180 patients (34%) were managed with urgent operation on admission (81% splenectomy (SIG 4.0), 19% splenorrhaphy (SIG 2.6)). The remaining 344 patients (66%) were hemodynamically stable and underwent computed tomographic scan and planned nonoperative management. Of these patients, 322 patients (94%) were successfully managed nonoperatively (61% of total splenic injuries). In 26 patients (8%), a contrast blush identified on computed tomographic scan was confirmed as a parenchymal pseudoaneurysm on arteriography. Twenty patients (SIG, 2.8) were successfully embolized. In six patients, technical failure precluded embolization; all required splenectomy (SIG, 4.0). A total of 22 patients (6%) failed nonoperative management, including the six with unsuccessful embolization attempts. Sixteen patients (SIG, 3.0) who had no evidence of pseudoaneurysm were explored for a falling hematocrit, hemodynamic instability, or a worsening follow-up computed tomography: 13 patients had splenectomy, and three patients had splenorrhaphy.

CONCLUSIONS

Aggressive surveillance for and embolization of posttraumatic splenic artery pseudoaneurysms improved the rate of successful nonoperative management of blunt splenic trauma to 61%, with a nonoperative failure rate of only 6%. In comparison with our previous work, this reduction in failure of nonoperative management is a significant improvement (p < 0.03).

Utility of Gram's stain and efficacy of quantitative cultures for posttraumatic pneumonia: a prospective study

OBJECTIVE

This prospective trial examined the efficacy of using bronchoalveolar lavage (BAL) for the diagnosis of pneumonia (PN) and the utility of Gram's stain (GS) for dictating empiric therapy.

SUMMARY BACKGROUND DATA

Posttraumatic nosocomial PN remains a significant cause of morbidity and mortality. However, its diagnosis is elusive, especially in multiply injured patients. The systemic inflammatory response syndrome of fever, leukocytosis, and a hyperdynamic state is common in trauma patients, especially patients with pulmonary contusion. Bronchoscopy with BAL with quantitative cultures of the lavage effluent may distinguish between PN and systemic inflammatory response syndrome, and GS of the lavage effluent may guide empiric therapy before quantitative culture results.

METHODS

Mechanically ventilated trauma patients with a clinical diagnosis of PN (fever, leukocytosis, purulent sputum, and new or changing infiltrate on chest radiograph) underwent bronchoscopy with BAL. Effluent was sent for GS and quantitative cultures. The diagnostic threshold for PN was > or =10(5) colony-forming units (CFU)/mL, and antibiotics were continued. Antibiotics were stopped for < 10(5) CFU/mL and the diagnosis of systemic inflammatory response syndrome was made. Causative organisms for PN were compared to GS.

RESULTS

Over a 2-year period, 232 patients underwent 443 bronchoscopies with BAL (71% men, 29% women; mean age, 41). The mean injury severity score was 30. Sixty percent of the patients had pulmonary contusion, and 59% were cigarette smokers. The overall incidence of PN was 39% and was no different regardless of the number of BALs a patient had. The false-negative rate of BAL was 7%. GS identified gram-positive organisms in 80% of patients with gram-positive PN and 40% of patients with gram-negative PN. GS identified gram-negative organisms in 52% of patients with gram-positive PN and 77% with gram-negative PN. The duration of the intensive care unit stay relative to the timing of BAL was beneficial for guiding empiric therapy. BAL in week 1 primarily identified Haemophilus influenzae and gram-positive organisms; Acinetobacter sp. and Pseudomonas sp. were more common after week 1.

CONCLUSIONS

Bronchoscopy with BAL is an effective method to diagnose PN and avoids prolonged, unnecessary antibiotic therapy. Empiric therapy should be adjusted to the duration of the intensive care unit stay because the causative bacteria flora changes over time. GS of BAL effluent correlates poorly with quantitative cultures and is not reliable for dictating empiric therapy.

Nutritional support and infection: does the route matter?

Questions regarding the effects of the route of nutrition began to surface shortly after the introduction of total parenteral nutrition (TPN). Although TPN has become a life-saving therapy for patients who cannot tolerate enteral nutrition, it is not the panacea it was hoped to be. It appears that the enteral route of nutrition decreases rates of infectious complications compared with parenteral feeding. Reasons for this phenomenon are not clear, but it seems that enteral nutrition supports the gut barrier and gut-associated lymphoid tissue, which may have effects on infections at distant sites such as the lung. These effects do not appear to be due solely to prevention to malnutrition, as the infectious complications develop early after injury or illness. However, the lack of understanding of the mechanisms does not negate the fact that in many clinical studies the enteral route of nutrition is superior to the parenteral route in terms of reducing infectious complications in critically ill or injured patients.

Postoperative nutrition in surgery for major trauma

Research in the area of the nutritional support of trauma patients has continued to focus on a few main areas: the effect that the route, timing and type of feeding has on patient outcome, nutritional assessment and mucosal immunity. This year a nutritional conference has released a paper, summarizing the current state of research in this area, that generated some controversy.

Pancreatic trauma: a simplified management guideline

INTRODUCTION

Recent literature supports a conservative trend in the management of pancreatic injuries. Contrary to this trend, some recommend defining ductal integrity by pancreatography, implying that the results alter management. This study examines our recent 5-year experience with a simplified approach to all pancreatic injuries.

METHODS

Retrospective analysis of patients sustaining pancreatic injuries was performed.

RESULTS

One hundred thirty-four patients were identified. Overall mortality was 13%, and pancreatic-related mortality was 2%. Analyses were based on 124 pancreatic injuries among patients who survived >12 hours. Thirty-seven proximal injuries were treated with drainage alone, with a pancreatic morbidity of 11%. Eighty-seven distal pancreatic injuries occurred, 54 with indeterminate ductal status. Twenty-four had high probability for duct injury and were treated by distal resection; 30 with a low probability of ductal injury were drained. Pancreatic morbidity was not different between these groups.

CONCLUSIONS

Pancreatic injuries including those with indeterminate ductal status can be successfully managed with low morbidity and mortality using this simplified management protocol.

Popliteal artery trauma. Systemic anticoagulation and intraoperative thrombolysis improves limb salvage

OBJECTIVE

This study was conducted to evaluate those factors associated with popliteal artery injury that influence amputation, with emphasis placed on those that the surgeon can control.

SUMMARY BACKGROUND DATA

Generally accepted factors impacting amputation after popliteal artery injury include blunt trauma, prolonged ischemic times, musculoskeletal injuries, and venous disruption. Amputation ultimately results from microvascular thrombosis and subsequent tissue necrosis, predisposed by the paucity of collaterals around the knee.

METHODS

Patients with popliteal artery injuries over the 10-year period ending November 1995 were identified from the trauma registry. Preoperative (demographics, mechanism and severity of injury, vascular examination, ischemic times) and operative (methods of arterial repair, venous repair-ligation, anticoagulation-thrombolytic therapy, fasciotomy) variables were studied. Severity of extremity injury was quantitated by the Mangled Extremity Severity Score (MESS). Amputations were classified as primary (no attempt at vascular repair) or secondary (after vascular repair). After univariate analysis, logistic regression analysis was performed to identify the independent risk factors for limb loss.

RESULTS

One hundred two patients were identified; 88 (86%) were males and 14 (14%) were females. Forty injuries resulted from blunt and 62 from penetrating trauma. There were 25 amputations (25%; 11 primary and 14 secondary). Patients with totally ischemic extremities (no palpable or Doppler pulse) more likely were to be amputated (31% vs. 13%; p < 0.04). All requiring primary amputations had severe soft tissue injury and three had posterior tibial nerve transection; the average MESS was 7.6. Logistic regression analysis identified independent factors associated with secondary amputation: blunt injury (p = 0.06), vein injury (p = 0.06), MESS (p = 0.0001), heparin-urokinase therapy (p = 0.05). There were no complications with either heparin or urokinase.

CONCLUSIONS

Minimizing ischemia is an important factor in maximizing limb salvage. Severity of limb injury, as measured by the MESS, is highly predictive of amputation. Intraoperative use of systemic heparin or local urokinase or both was the only directly controllable factor associated with limb salvage. The authors recommend the use of these agents to maximize limb salvage in association with repair of popliteal artery injuries.

A randomized trial of isonitrogenous enteral diets after severe trauma. An immune-enhancing diet reduces septic complications

OBJECTIVE

The authors randomized patients to an enteral diet containing glutamine, arginine, omega-3 fatty acids, and nucleotides or to an isonitrogenous, isocaloric diet to investigate the effect of septic outcome. A third group of patients, without enteral access but eligible by severity of injury, served as unfed controls and were studied prospectively to determine the risk of infection.

SUMMARY BACKGROUND DATA

Laboratory and clinical studies suggest that diets containing specialty nutrients, such as arginine, glutamine, nucleotides, and omega-3 fatty acids, reduce septic complications. Unfortunately, most clinical trials have not compared these diets versus isonitrogenous, isocaloric controls. This prospective, blinded study randomized 35 severely injured patients with an Abdominal Trauma Index > or = 25 or a Injury Severity Score > or = 21 who had early enteral access to an immune-enhancing diet ([IED] Immun-Aid, McGaw, Inc., Irvine, CA; n = 17) or an isonitrogenous, isocaloric diet (Promote [Ross Laboratories, Columbus, OH] and Casec [Mead-Johnson Nutritionals, Evansville, IN]; n = 18) diet. Patients without early enteral access but eligible by severity of injury served as contemporaneous controls (n = 19). Patients were evaluated for septic complications, antibiotic usage, hospital and intensive care unit (ICU) stay, and hospital costs.

RESULTS

Two patients died in the treatment group and were dropped from the study. Significantly fewer major infectious complications (6%) developed in patients randomized to the IED than patients in the isonitrogenous group (41%, p = 0.02) or the control group (58%, p = 0.002). Hospital stay, therapeutic antibiotics, and the development of intra-abdominal abscess was significantly lower in patients receiving the IED than the other two groups. This improved clinical outcome was reflected in reduced hospital costs.

CONCLUSIONS

An IED significantly reduces major infectious complications in severely injured patients compared with those receiving isonitrogenous diet or no early enteral nutrition. An IED is the preferred diet for early enteral feeding after severe blunt and penetrating trauma in patients at risk of subsequent septic complications. Unfed patients have the highest complication rate.

Prophylactic Greenfield filters: acute complications and long-term follow-up

The efficacy of prophylactic vena caval filters (VCF) in reducing morbidity and mortality from pulmonary embolism (PE) in high-risk trauma patients has been shown, but minimal follow-up data is currently available. VCFs were prophylactically placed in 110 patients between August 1991 and June 1995. There was an early VCF complication rate of 7%. Twenty-two patients died; the remaining 88 patients formed the basis for the follow-up study. Forty-five patients were located and interviewed by phone, and 30 of these patients (34%) returned for evaluation. The mean follow-up time was 18 months (range, 4-42 months). There was no incidence of caval thrombosis on follow-up. Eleven patients had physical findings, and duplex evidence consistent with postphlebitic syndrome. An additional three patients had evidence of old deep venous thrombosis (DVT) by duplex, but no significant symptomatology. VCF are effective in preventing PE related deaths and have few major complications. The long-term morbidity associated with posttraumatic venous thrombosis is significant. This morbidity is related not to PE or VCF, but to the underlying DVT. Improved strategies against DVT are necessary.

Blunt carotid injury. Importance of early diagnosis and anticoagulant therapy

OBJECTIVE

The incidence, associated injury pattern, diagnostic factors, risk for adverse outcome, and efficacy of anticoagulant therapy in the setting of blunt and carotid injury (BCI) were evaluated.

SUMMARY BACKGROUND DATA

Blunt carotid injury is considered uncommon. The authors believe that it is underdiagnosed. Outcome is thought to be compromised by diagnostic delay. If delay in diagnosis is important, it is implied that therapy is effective. Although anticoagulation is the most frequently used therapy, efficacy has not been proven.

METHODS

Patients with BCI were identified from the registry of a level I trauma center during an 11-year period (ending September 1995). Neurologic examinations and outcomes, brain computed tomography (CT) results, angiographic findings, risk factors, and heparin therapy were evaluated.

RESULTS

Sixty-seven patients with 87 BCIs were treated. Thirty-four percent were diagnosed by incompatible neurologic and CT findings, 43% by new onset of neurologic deficits, and 23% by physical examination (neck injury, Horner's syndrome). There were 54 intimal dissections, 11 pseudoaneurysms, 17 thromboses, 4 carotid cavernous fistulas, and 1 transected internal carotid artery. Thirty-nine patients had follow-up angiograms. Mortality rate was 31%. Of 46 survivors, 63% had good neurologic outcomes, 17% moderate, and 20% bad. Logistic regression analysis demonstrated heparin therapy to be associated independently with survival (p < 0.02) and improvement in neurologic outcome (p < 0.01).

CONCLUSIONS

Blunt carotid injury is more common than appreciated, seen in 0.67% of patients admitted after motor vehicle accidents. Therapy with heparin is highly efficacious, significantly reducing neurologic morbidity and mortality. Heparin therapy, when instituted before onset of symptoms, ameliorates neurologic deterioration. Liberal screening, leading to earlier diagnosis, would improve outcome.

A prospective analysis of transesophageal echocardiography in the diagnosis of traumatic disruption of the aorta

OBJECTIVE

Recently, transesophageal echocardiography (TEE) has been proposed as the standard for the diagnosis of traumatic disruption of the aorta (TDA), replacing aortography. The purpose of this study was to evaluate the accuracy and practicality of TEE in the diagnosis of TDA.

DESIGN

Prospective clinical trial.

MATERIALS AND METHODS

Patients with blunt trauma admitted with a suspected diagnosis of TDA were evaluated with TEE and aortography.

MEASUREMENTS AND MAIN RESULTS

Thirty-four patients were evaluated with TEE and aortography. TEE was unsuccessful in five patients (15%). Of the remaining 29 patients, TEE results were true-positive in four and true-negative in 20. TEE results were false-positive in two patients, and three injuries were missed (two were proximal to the left subclavian artery, and one was a localized aortic disruption). Sensitivity and specificity of TEE were 57% and 91%, respectively, compared with aortography, for which sensitivity was 89% and specificity was 100%.

CONCLUSION

Although the use of TEE in the diagnosis of TDA has several advantages, it is not more accurate than aortography. TEE should not replace aortography as the standard for the diagnosis of TDA.

Using bronchoalveolar lavage to distinguish nosocomial pneumonia from systemic inflammatory response syndrome: a prospective analysis

OBJECTIVE

Ventilator-associated pneumonia (PN) is difficult to distinguish from trauma-induced systemic inflammatory response syndrome (SIRS), especially in patients with multiple injuries. Previous work using bronchoscopy and quantitative cultures demonstrated significant bacterial growth in about one-third of patients with clinical evidence of PN. In this prospective study, antibiotic therapy for PN was based solely on quantitative bronchoalveolar lavage (BAL) cultures.

METHODS

Mechanically ventilated trauma patients underwent bronchoscopy with BAL when they developed clinical evidence of PN: fever (temperature > 100.5 degrees F), white blood cells > 10,000 or > 10% immature forms, purulent sputum, and new or changing infiltrate on chest roentgenogram. Patients with other infections or those receiving antibiotics for any other reason were excluded. Empiric antibiotic therapy for PN was started at the time of BAL. If the quantitative cultures revealed > or = 10(5) colony-forming units (CFU)/mL, that patient was defined as having PN and was treated. If the cultures revealed < 10(5) CFU/mL, that patient was defined as having SIRS, and empiric therapy was stopped.

RESULTS

Forty-three patients (88% blunt, 12% penetrating) underwent bronchoscopy with BAL 55 times. Mean age was 40 and Injury Severity Score was 25. Twenty patients had > or = 10(5) CFU/mL (47%) and 23 had < 10(5) CFU/mL (53%). There were no differences in age, Injury Severity Score, temperature, white blood cell count, or ventilator days before BAL between groups. Sixty-five percent of those with SIRS improved after empiric therapy was stopped (average 3.3 days), and 35% underwent repeat BAL. Three patients with the initial diagnosis of SIRS developed PN (13% of SIRS). Mortality for PN was 15%, compared with 17% for SIRS; no deaths were related to antibiotic therapy.

CONCLUSIONS

SIRS, which can mimic PN, is common in trauma patients. These entities can be distinguished by bronchoscopy with BAL. Basing antibiotic therapy solely on quantitative BAL cultures is efficacious in trauma patients.

Management of blunt splenic trauma: computed tomographic contrast blush predicts failure of nonoperative management

Nonoperative management of blunt splenic trauma is widely accepted; however, reported failure rates have ranged as high as 40%. There are few factors available to identify failures reliably. To characterize failures of nonoperative management better, we retrospectively reviewed 309 blunt splenic injuries treated at our level I trauma center over a 5-year period. Eighty-nine patients were initially managed nonoperatively (29%), and 12 patients failed this approach (13%). Upon review of the initial computed tomography scans, a hyperdense collection of contrast media in the splenic parenchyma, or "contrast blush," was noted in 8 of 12 (67%) patients who failed and in 5 of 77 (6%) of those who were successfully managed nonoperatively (p < 0.0001). These data suggest that the presence of a contrast blush is an important consideration when deciding the method for management of the splenic injury. If these results are confirmed in a prospective fashion, the failure rate of nonoperative management of blunt splenic trauma could be reduced by identification of the contrast blush.

Prognostic factors after acute subdural hematoma

Factors that have been shown to affect outcome after acute subdural hematoma (ASDH) include age, Injury Severity Score (ISS), intracranial pressure (ICP), direct admission to a trauma center, presence of subarachnoid hemorrhage, score on the Glasgow Coma Scale (GCS), and timing of operation. However, these data come from selected patient populations (e.g., operated, comatose, or minimally symptomatic patients, etc.). In an effort to evaluate factors that predict outcome for the entire spectrum of ASDH patients, we evaluated 211 patients with ASDH and GCS scores of 3 to 15. One hundred twenty-eight patients (61%) were managed nonoperatively (Nonop), whereas 83 (39%) were managed with craniotomy [operatively (Op)]. Op patients had more severe brain injuries, as evidenced by their lower GCS scores (Op 7.8 vs. Nonop 10.7, p = 0.0001), higher incidence of large ASDH with midline shift (Op 61% large ASDH, 83% midline shift vs. Nonop 16% large ASDH, 30% midline shift, p = 0.001 for each comparison), and higher incidence of basilar cistern effacement (Op 61% vs. Nonop 21%, p = 0.001). Thirty-five percent of the Op patients had their hematoma evacuated within 4 hours (early), whereas 65% did not (delayed). Early Op patients had a significantly lower incidence of functional survival (early = 24% vs. delayed = 51%, p = 0.02). The early patients seem to have had more significant head injuries, as evidenced by their lower GCS scores (early = 7.0 vs. delayed = 8.4), higher incidence of associated intracranial injuries (early = 1.14 vs. delayed = 0.85), and higher incidence of cistern effacement (early = 76% vs. delayed = 53%, p = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Nonoperative management of blunt hepatic trauma is the treatment of choice for hemodynamically stable patients. Results of a prospective trial

BACKGROUND

A number of retrospective studies recently have been published concerning nonoperative management of minor liver injuries, with cumulative success rates greater than 95%. However, no prospective analysis that involves a large number of higher grade injuries has been reported. The current study was conducted to evaluate the safety of nonoperative management of blunt hepatic trauma in hemodynamically stable patients regardless of injury severity.

METHODS

Over a 22-month period, patients with blunt hepatic injury were evaluated prospectively. Unstable patients underwent laparotomies, and stable patients had abdominal computed tomography (CT) scans. Those with nonhepatic operative indications underwent exploration, and the remainder were managed nonoperatively in the trauma intensive care unit. This group was compared with a hemodynamically matched operated cohort of blunt hepatic trauma patients (control subjects) who had been prospectively analyzed.

RESULTS

One hundred thirty-six patients had blunt hepatic trauma. Twenty-four (18%) underwent emergent exploration. Of the remaining 112 patients, 12 (11%) failed observation and underwent celiotomy--5 were liver-related failures (5%) and 7 were nonliver related (6%). Liver related failure rates for CT grades I through V were 20%, 3%, 3%, 0%, and 12%, respectively, and rates according to hemoperitoneum were 2% for minimal, 6% for moderate, and 7% for large. The remaining 100 patients were successfully treated without operation--30% had minor injuries (grades I-II) and 70% had major (grades III-V) injuries. There were no differences in admission characteristics between nonoperative success or failures, except admission systolic blood pressure (127 vs. 104; p < 0.04). Comparing the nonoperative group to the control group, there were no differences in admission hemodynamics or hospital length of stay, but nonoperative patients had significantly fewer blood transfusions (1.9 vs. 4.0 units; p < 0.02) and fewer abdominal complications (3% vs. 11%; p < 0.04).

CONCLUSIONS

Nonoperative management is safe for hemodynamically stable patients with blunt hepatic injury, regardless of injury severity. There are fewer abdominal complications and less transfusions when compared with a matched cohort of operated patients. Based on admission characteristics or CT scan, it is not possible to predict failures; therefore, intensive care unit monitoring is necessary.