Comparative 16SrDNA Gene-Based Microbiota Profiles of the Pacific Oyster (Crassostrea gigas) and the Mediterranean Mussel (Mytilus galloprovincialis) from a Shellfish Farm (Ligurian Sea, Italy).

The pacific oyster Crassostrea gigas and the Mediterranean mussel Mytilus galloprovincialis are two widely farmed bivalve species which show contrasting behaviour in relation to microbial diseases, with C. gigas being more susceptible and M. galloprovincialis being generally resistant. In a recent study, we showed that different susceptibility to infection exhibited by these two bivalve species may depend on their different capability to kill invading pathogens (e.g., Vibrio spp.) through the action of haemolymph components. Specific microbial-host interactions may also impact bivalve microbiome structure and further influence susceptibility/resistance to microbial diseases. To further investigate this concept, a comparative study of haemolymph and digestive gland 16SrDNA gene-based bacterial microbiota profiles in C. gigas and M. galloprovincialis co-cultivated at the same aquaculture site was carried out using pyrosequencing. Bacterial communities associated with bivalve tissues (hemolymph and digestive gland) were significantly different from those of seawater, and were dominated by relatively few genera such as Vibrio and Pseudoalteromonas. In general, Vibrio accounted for a larger fraction of the microbiota in C. gigas (on average 1.7-fold in the haemolymph) compared to M. galloprovincialis, suggesting that C. gigas may provide better conditions for survival for these bacteria, including potential pathogenic species such as V. aestuarianus. Vibrios appeared to be important members of C. gigas and M. galloprovincialis microbiota and might play a contrasting role in health and disease of bivalve species. Accordingly, microbiome analyses performed on bivalve specimens subjected to commercial depuration highlighted the ineffectiveness of such practice in removing Vibrio species from bivalve tissues.

Whole-Genome Enrichment Provides Deep Insights into Vibrio cholerae Metagenome from an African River.

The detection and typing of Vibrio cholerae in natural aquatic environments encounter major methodological challenges related to the fact that the bacterium is often present in environmental matrices at very low abundance in nonculturable state. This study applied, for the first time to our knowledge, a whole-genome enrichment (WGE) and next-generation sequencing (NGS) approach for direct genotyping and metagenomic analysis of low abundant V. cholerae DNA (<50 genome unit/L) from natural water collected in the Morogoro river (Tanzania). The protocol is based on the use of biotinylated RNA baits for target enrichment of V. cholerae metagenomic DNA via hybridization. An enriched V. cholerae metagenome library was generated and sequenced on an Illumina MiSeq platform. Up to 1.8 × 107 bp (4.5× mean read depth) were found to map against V. cholerae reference genome sequences representing an increase of about 2500 times in target DNA coverage compared to theoretical calculations of performance for shotgun metagenomics. Analysis of metagenomic data revealed the presence of several V. cholerae virulence and virulence associated genes in river water including major virulence regions (e.g. CTX prophage and Vibrio pathogenicity island-1) and genetic markers of epidemic strains (e.g. O1-antigen biosynthesis gene cluster) that were not detectable by standard culture and molecular techniques. Overall, besides providing a powerful tool for direct genotyping of V. cholerae in complex environmental matrices, this study provides a 'proof of concept' on the methodological gap that might currently preclude a more comprehensive understanding of toxigenic V. cholerae emergence from natural aquatic environments.

A European epidemiological survey of Vibrio splendidus clade shows unexplored diversity and massive exchange of virulence factors.

The Vibrio splendidus clade has previously been associated with epidemic outbreaks of various aquatic animals, as in the case of the cupped oyster, Crassostrea gigas. To investigate whether involved strains could present a clonal origin and to identify possible alternative background carriage animals or zooplankton, a large epidemiological survey was conducted on isolates of the splendidus clade. For this purpose, Vibrio strains were isolated from various samples including oysters, mussels, sediments, zooplankton, and sea water on the basis of a North/South gradient of the European sea water zone (Ireland, The Netherlands, France, Italy, and Spain). A total of 435 isolates were successfully associated to the V. splendidus clade using real time polymerase chain reaction with 16S specific primers and probes. A multiple-locus variable-number tandem-repeat analysis (VNTR) was conducted on all isolates based on a multiplex PCR-VNTR with a set of primer pairs designed from the V. tasmaniensis LGP32 genome. Preliminary validation of the primers on a set of collection strains from the V. splendidus clade confirmed that the former V. splendidus-related LGP32 and relative strains were related to V. tasmaniensis rather than to the type strain V. splendidus LMG 4042. The VNTR analysis was then successfully conducted on 335 isolates which led to the characterization of 87 different profiles. Our results showed that (1) the high diversity of VNTR did not enlighten significant correlation between a specific pattern and the origin of collected samples. However, populations isolated from animal samples tend to differ from those of the background environment; (2) oyster mortality events could not be linked to the clonal proliferation of a particular VNTR type. However, few different patterns seemed successively associated with samples collected during peaks of oyster's mortality. (3) Finally, no correlation could be seen between specific VNTR patterns and sequence phylogeny of the virulence factors vsm and ompU that were detected among strains isolated during as well as outside mortality events. These results, combined with incongruence observed between the ompU and vsm phylogenetic trees, suggested both large diffusion of strains and massive lateral gene transfer within the V. splendidus clade.

Interactions between Mytilus galloprovincialis hemocytes and the bivalve pathogens Vibrio aestuarianus 01/032 and Vibrio splendidus LGP32.

Marine bivalves can accumulate large numbers of bacteria, in particular Vibrio species, whose persistence in bivalve tissues largely depends on their sensitivity to the bactericidal activity of circulating hemocytes and hemolymph soluble factors. The interactions between vibrios and hemolymph have been investigated, in particular in bivalve species susceptible to infection by certain Vibrio spp. and strains. In this work, the effects of two bivalve pathogens, Vibrio splendidus LGP32 (V.s.) and Vibrio aestuarianus 01/032 (V.a.), isolated from oyster mortality outbreaks, on the hemocytes of Mytilus galloprovincialis were investigated. In vitro, V.s., but not V.a., induced a dramatic decrease in lysosomal membrane stability-LMS in the hemocytes; both vibrios induced a moderate lysozyme release, with V.s. > V.a.. The V.s.-induced decrease in LMS was mediated by activation of PI-3Kinase, as shown by use of different kinase inhibitors. TEM analysis showed rapid internalization of both vibrios; however, V.s. lead to cellular and lysosomal damage and was able to survive within the hemocytes, whereas significant killing of V.a. was observed. In vivo, in mussels challenged with either vibrio and sampled at 6, 24 and 96 h post-injection, transient decreases in hemocyte LMS and progressive increases in serum lysozyme activity were observed, with V.s. > V.a.. Moreover, whereas V.a. was efficiently cleared from hemolymph, V.s. showed significant growth, that was maximal at 24 h p.i. when lowest LMS values were recorded in the hemocytes. Both vibrios also induced significant decreases in LMS in the digestive gland, again with V.s. > V.a.. The results indicate distinct interactions between mussel hemocytes and the two vibrio strains tested. The effects of V.s. may be due to the capacity of this strain to interfere with the signaling pathways involved in hemocyte function, thus escaping the bactericidal activity of the host cell, as observed for certain mammalian pathogens. Although V.s. is considered not pathogenic to Mytilus, this vibrio strain can affect the lysosomal function at the cellular and tissue level, thus leading to stressful conditions.

Evaluation of plant and fungal extracts for their potential antigingivitis and anticaries activity.

The link between diet and health has lead to the promotion of functional foods which can enhance health. In this study, the oral health benefits of a number of food homogenates and high molecular mass and low molecular mass fractions were investigated. A comprehensive range of assays were performed to assess the action of these foods on the development of gingivitis and caries using bacterial species associated with these diseases. Both antigingivitis and anticaries effects were investigated by assays examining the prevention of biofilm formation and coaggregation, disruption of preexisting biofilms, and the foods' antibacterial effects. Assays investigating interactions with gingival epithelial cells and cytokine production were carried out to assess the foods' anti- gingivitis properties. Anti-caries properties such as interactions with hydroxyapatite, disruption of signal transduction, and the inhibition of acid production were investigated. The mushroom and chicory homogenates and low molecular mass fractions show promise as anti-caries and anti-gingivitis agents, and further testing and clinical trials will need to be performed to evaluate their true effectiveness in humans.

Effects of demethylfruticuline A and fruticuline A from Salvia corrugata Vahl. on biofilm production in vitro by multiresistant strains of Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis.

In this study, demethylfruticuline A (dfA) and fruticuline A (fA), two quinones representing the major diterpenoid components of the exudate produced by the aerial parts of Salvia corrugata, were assessed for their ability to modify surface characteristics, such as hydrophobicity, and to inhibit synthesis of biofilm in vitro by multiresistant Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis. Five strains of S. aureus (three meticillin-resistant and two meticillin-susceptible), five strains of S. epidermidis (four meticillin-resistant and one meticillin-susceptible) and eight vancomycin-resistant E. faecalis, all recently isolated from clinical specimens and capable of slime production, were studied. fA decrease by at least two-fold the hydrophobic properties of the S. aureus cell membrane but did not affect S. epidermidis or E. faecalis. Biofilm formation on polystyrene plates was quantified spectrophotometrically by established methodologies. Inhibition of biofilm formation was also confirmed by the Congo red agar plate assay. dfA and fA were more effective against S. aureus strains (>70% effect at subinhibitory concentrations) than against S. epidermidis in inhibiting slime synthesis. Against E. faecalis, dfA at subinhibitory concentration induced an inhibition of biofilm production of ca. 60%; fA was less active and more strain-dependent. Moreover, the two compounds were shown to possess chelating activity on divalent and trivalent metal cations. Interactions of fA and dfA with bacteria could be very complex, possibly being species-specific, and could depend not only on inhibition of exopolysaccharide synthesis but also on their chelating activity and on changes in the microorganism's surface, including cell hydrophobicity.

SPECT/CT preoperatorio, una nueva herramienta diagnóstica para localizar adenomas paratiroideos: presentación de 2 casos clínicos / Localization of functioning parathyroid adenomas by SPECT/CT: report of two cases

Single photon emission computed tomography and computed tomography (SPECT/CT), integrates a gamma camera and a CT scan and is effective for the location of parathyroid adenomas. We report a 55 years old male and a 80 years old female with primary hyperparathyroidism. In both cases the 99mTc-Sestamibi parathyroid scintigraphy detected a functioning nodule whose presence was confirmed with SPECT/CT.

El SPECT/CT integra una gamacámara y un escáner radiológico en un solo equipo híbrido que fusiona la imagen de la cintigrafía SPECT (tomografía computada de fotón único) con la imagen morfológica obtenida con un escáner de baja intensidad, sin movilizar al paciente, en una perfecta correspondencia anátomo-funcional, permitiendo identificar con exactitud la localización de un adenoma paratiroideo. Se describen dos pacientes con hiperparatiroidismo primario, con ecotomografía convencional negativa, donde el SPECT/CT demostró la localización exacta de adenomas de ubicación no habitual.

Compromiso muscular por linfoma no hodgkin: caso clínico y revisión del tema / Muscle infiltration by non-hodgkin lymphoma: a case and bibliographic review

A case report of a patient with treated Non-Hodgkin Lymphoma is presented. In his usual tomographic control patient was requested a PET-CT scan to supplement prior study that showed a metabo-lically active focus on the left adductor muscle without evident tomographic correlation. Lesion underwent both a soft tissue ultrasound study and a directed biopsy, the latter being positive for secondary infiltration by lymphoma. This case has demonstrated the usefulness of applying complementary techniques in the management of these lesions, mainly of PET-CT scans in the study of unusual sites of spread. This combined medical imaging technique allows accurate lesion localization, which in turn permits performance of a subsequent directed study.

Se presenta un caso clínico de paciente con linfoma no Hodgkin tratado; en control tomográfico habitual se le solicitó PET-CT para complementar su estudio, que demuestra un foco metabólicamente activo en el espesor de músculo aductor izquierdo sin traducción tomográfica evidente. La lesión fue estudiada con ultrasonografia de partes blandas y biopsia dirigida, que resultó positiva para infiltración secundaria por linfoma. Este caso demuestra la utilidad de las técnicas complementarias en el manejo de estos pacientes, en especial la utilidad del PET-CT en el estudio de sitios inhabituales de diseminación. En este examen existe la posibilidad de identificar con precisión la localización de las lesiones mediante la TC complementaria, lo que permite efectuar posteriormente el estudio dirigido.

Aporte del SPECT-CT en la detección y localización de hiperplasia nodular focal del hígado / Usefulness of SPECT-CT in detection and location of focal nodular hyperplasia

Se presenta el caso clínico de una mujer de 39 años de edad que consulta por dolor abdominal. Los hallazgos en el Ultrasonido efectuado con Doppler y la Resonancia Magnética dinámica no lograron establecer el diagnóstico diferencial entre adenoma e hiperplasia nodular focal. Se complementó el estudio con una cintigrafía de vía biliar detectándose en controles tardíos dos focos de retención del radiofármaco. El estudio tomográfico del hígado con Tc99m-coloidal se efectuó en gamma cámara híbrida (SPECT-CT) obteniéndose imágenes fusionadas anátomo-funcionales que demostraron la existencia y la localización exacta de tres focos de hiperplasia nodular focal.

A general role for surface membrane proteins in attachment to chitin particles and copepods of environmental and clinical vibrios.

AIMS: To investigate the role of surface membrane proteins (MP) to promote attachment to chitin particles and copepods of different environmental and clinical vibrios. METHOD AND RESULTS: The role of surface MP to promote attachment to chitin particles and the copepod Tigriopus fulvus was investigated in several environmental and clinical Vibrio strains by inhibition test methods. Attachment to both substrates was significantly inhibited by homologous MP treatment in all strains and percentages of inhibition were comparable with the ones observed with N-acetyl glucosamine (GlcNAc). Sarkosyl-insoluble MP extracted from tested strains were added to chitin particles either in the presence or in the absence of GlcNAc and the fraction bound to chitin in both conditions was visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Chitin-binding proteins (CBP) defined as Sarkosyl-insoluble MP that bound chitin in the absence of GlcNAc but did not in the presence of the sugar were isolated in all strains. CONCLUSION: CBP are common in both environmental and clinical Vibrio strains and they have an important general role in mediating cell interactions with chitin-containing surfaces. SIGNIFICANT AND IMPACT OF THE STUDY: The role of CBP should be taken into account when investigating environmental persistence of aquatic vibrios.

VanA-type enterococci from humans, animals, and food: species distribution, population structure, Tn1546 typing and location, and virulence determinants.

VanA-type human (n=69), animal (n=49), and food (n=36) glycopeptide-resistant enterococci (GRE) from different geographic areas were investigated to study their possible reservoirs and transmission routes. Pulsed-field gel electrophoresis (PFGE) revealed two small genetically related clusters, M39 (n=4) and M49 (n=13), representing Enterococcus faecium isolates from animal and human feces and from clinical and fecal human samples. Multilocus sequence typing showed that both belonged to the epidemic lineage of CC17. purK allele analysis of 28 selected isolates revealed that type 1 was prevalent in human strains (8/11) and types 6 and 3 (14/15) were prevalent in poultry (animals and meat). One hundred and five of the 154 VanA GRE isolates, encompassing different species, origins, and PFGE types, were examined for Tn1546 type and location (plasmid or chromosome) and the incidence of virulence determinants. Hybridization of S1- and I-CeuI-digested total DNA revealed a plasmid location in 98% of the isolates. Human intestinal and animal E. faecium isolates bore large (>150 kb) vanA plasmids. Results of PCR-restriction fragment length polymorphism and sequencing showed the presence of prototype Tn1546 in 80% of strains and the G-to-T mutation at position 8234 in three human intestinal and two pork E. faecium isolates. There were no significant associations (P>0.5) between Tn1546 type and GRE source or enterococcal species. Virulence determinants were detected in all reservoirs but were significantly more frequent (P<0.02) among clinical strains. Multiple determinants were found in clinical and meat Enterococcus faecalis isolates. The presence of indistinguishable vanA elements (mostly plasmid borne) and virulence determinants in different species and PFGE-diverse populations in the presence of host-specific purK housekeeping genes suggested that all GRE might be potential reservoirs of resistance determinants and virulence traits transferable to human-adapted clusters.

Comparison of different biochemical and molecular methods for the identification of Vibrio parahaemolyticus.

AIMS: Multicentre evaluation of biochemical and molecular methods for the identification of Vibrio parahaemolyticus. METHODS AND RESULTS: For the biochemical identification methods, API 20E and API 20NE and Alsina's scheme were evaluated in intra- and interlaboratory tests in order to determine the accuracy and concordance of each method. Both in intra- and interlaboratory tests, the Alsina's scheme showed the highest sensitivity (86% of correct identifications in the interlaboratory test). False-positive results were obtained by all methods (specificity was 95% for API 20E, 73% for API 20NE and 84% for Alsina's scheme) and concordance varied from 65% of API 20NE to 84% of API 20E. For the molecular identifications, polymerase chain reaction (PCR) for the detection of toxR gene, tl gene and pR72H fragment were tested on 30 strains by two laboratories. The PCR for toxR showed the highest inclusivity (96%), exclusivity (100%) and concordance (97%). CONCLUSIONS: Among the biochemical identification methods tested, the Alsina's scheme gave more reliable results; however, in order to avoid false-positive results, all the biochemical identifications should be confirmed by means of molecular methods. SIGNIFICANCE AND IMPACT OF THE STUDY: Availability of an efficient identification method of Vibrio parahaemolyticus to use in official control of fisheries products.

Absceso y flegmón periamigdalino: ¿lo estamos haciendo bien? / Abscess and cellulitis peritonsillar: are we doing it right?

El flegmón (celulitis) y el absceso periamigdalino son infecciones difusas o una colección ubicada entre la cápsula fibrosa de la amígdala palatina, las fibras horizontales del músculo constrictor superior de la faringe y las verticales del músculo palatofaríngeo. Constituye la infección de tejidos y espacios profundos del cuello más frecuente. Material y método: Revisión retrospectiva de las fichas de pacientes adultos y niños hospitalizados con diagnóstico de absceso o flegmón periamigdalino en el Servicio de Otorrinolaringología del Hospital San Juan de Dios entre los años 1995 y 2001. Resultados y discusión: Se analizaron 124 pacientes. Se observó un acierto del diagnóstico clínico en 85,5 por ciento de los casos. El 100 por ciento de los pacientes presentó evolución clínica favorable según la modalidad terapéutica indicada. La mayoría de los pacientes con absceso periamigdalino fue tratado con drenaje y antimicrobiano, y los con flegmón periamigdalino con antimicrobiano. El antibiótico utilizado con mayor frecuencia fue penicilina. No existió diferencia significativa al usarlo en esquema asociado. La penicilina sódica sigue siendo un antimicrobiano de primera elección para este cuadro y no requeriría de asociaciones; dosis de 3 millones de Ul cada 6 horas endovenosa pueden ser recomendadas. El tratamiento en el Servicio de Otorrinolaringología del Hospital San Juan de Dios se ciñe a las reglas internacionales.

Detección del linfonodo centinela en cáncer de mama en estadíos precoces: estudio multicéntrico / Sentinel lymph node detection in patients with early stage breast cancer: multicenter study

La extracción y análisis del linfonodo centinela (LNC) en cáncer de mama en estadío inicial es una alternativa válida en la etapificación de la axila, reduciendo la morbilidad asociada al vaciamiento axilar. Su marcación y localización requiere de experiencia para reducir la tasa de falsos negativos. El objetivo de este trabajo fue evaluar la seguridad en la identificación del linfonodo centinela en nuestro medio. Se estudiaron 46 mujeres con cáncer de mama infiltrante T1, T2 inyectándose Tc99m Nanocint y azul patente 1 por ciento peritumoral y posteriormente se modificó a periareolar. El 80 por ciento de los casos correspondió histológicamente a un carcinoma ductal infiltrante. En el 46.5 por ciento de las pacientes el LNC fue negativo para metástasis, al igual que el resto de los ganglios linfáticos axilares. El 53,5 por ciento restante presentó un LNC (+), en 15 de 20 pacientes, el LNC fue el único ganglio comprometido por tumor. Las 5 restantes tenían varios ganglios comprometidos, incluido el LNC. La tasa global de identificación en pabellón fue de 100 por ciento; 95 por ciento con radiocoloides y 95 por ciento con azul. El azul patente mostró 2 casos de falsos negativos y no hubo falsos negativo con radiocoloides. En conclusión, la técnica empleada sumado a la experiencia quirúrgica permiten una elevada y correcta detección del LNC.

Molecular vs culture methods for the detection of bacterial faecal indicators in groundwater for human use.

AIMS: The current standard culture methods are unable to detect nongrowing bacteria and, thus, might not be sufficient for precise monitoring of the microbiological quality of waters. The use of a molecular method such as PCR could be a valid alternative to detect bacterial faecal contamination indicators such as Escherichia coli and Enterococcus faecalis and reveal the presence of culturable and nonculturable bacterial forms. METHODS AND RESULTS: The presence of E. coli and Ent. faecalis cells in 30 groundwater samples was evaluated with the standard culture method and compared with a specific PCR protocol. A substantial percentage (50%) of the samples not containing culturable cells proved positive in the search for Ent. faecalis DNA by PCR. Quantification by competitive PCR (cPCR) of the DNA detected allowed us to calculate the number of nonculturable cells present in water samples: the number varied from 2 to 120 cells ml(-1). Only four samples were positive for E. coli DNA and the corresponding nonculturable cells varied from 24 to 70 ml(-1). CONCLUSIONS: This study demonstrates that the standard culture methods in use are unable to detect a substantial proportion of the bacterial population which is nonculturable but, as previously demonstrated, potentially still viable and able to express those pathogenic factors needed for causing infections in humans. SIGNIFICANCE AND IMPACT OF THE STUDY: To protect human health it is necessary to develop and use methods which detect the nonculturable as well as culturable bacteria present in water.

Bacterial killing by Mytilus hemocyte monolayers as a model for investigating the signaling pathways involved in mussel immune defence.

The signaling pathways involved in mussel immune defence were investigated utilizing a model of killing of Escherichia coli by Mytilus galloprovincialis hemocytes in a co-culture setting. In particular, the role played by different mitogen activated protein kinases (MAPKs) and by the production of eicosanoids were investigated utilising specific cell permeant, pharmacological enzyme inhibitors. Hemocyte pretreatment with the p38 MAPK inhibitor SB203580 significantly reduced bacterial killing, whereas PD98059 (an inhibitor of ERK--extracellularly regulated kinase--MAPK activation) had no significant effect. Wortmannin also inhibited bacterial killing, indicating a crucial role for PI3-kinase activation in the immune response. Killing of E. coli was also reduced by inhibitors of both PLA2 and cyclooxygenase activities, indicating that eicosanoid production is involved in mediating the response to bacterial challenge. The results demonstrate that bacterial killing by mussel hemocytes is particularly sensitive to inhibitors of the key steps involved in the transduction of bacterial signals into the host cell. Moreover, these data indicate that the hemocyte bactericidal activity can be suitably utilized not only for identifying the signaling pathways involved in the response to bacterial infection, but also as a potential investigative-toxicology model to test drugs and contaminants for their effect on the overall mussel immune defence.

Antiadhesive effect of green and roasted coffee on Streptococcus mutans' adhesive properties on saliva-coated hydroxyapatite beads.

Green and roasted coffees of the two most used species, Coffea arabica and Coffea robusta, several commercial coffee samples, and known coffee components were analyzed for their ability to interfere with Streptococcus mutans' sucrose-independent adsorption to saliva-coated hydroxyapatite (HA) beads. All coffee solutions showed high antiadhesive properties. The inhibition of S. mutans' adsorption to HA beads was observed both when coffee was present in the adsorption mixture and when it was used to pretreat the beads, suggesting that coffee active molecules may adsorb to a host surface, preventing the tooth receptor from interacting with any bacterial adhesions. Among the known tested coffee components, trigonelline and nicotinic and chlorogenic acids have been shown to be very active. Dialysis separation of roasted coffee components also showed that a coffee component fraction with 1000 Da < MW < 3500 Da, commonly considered as low MW coffee melanoidins, may sensibly contribute to the roasted coffee's antiadhesive properties. The obtained results showed that all coffee solutions have antiadhesive properties, which are due to both naturally occurring and roasting-induced molecules.

Surface interactions between Escherichia coli and hemocytes of the Mediterranean mussel Mytilus galloprovincialis lam. leading to efficient bacterial clearance.

The role of type 1 fimbriae in the interactions between Escherichia coli and Mytilus galloprovincialis Lam. hemocytes was evaluated. The association of fimbriated strain MG155 with hemocyte monolayers at 18 degrees C was 1.5- and 3- to 4-fold greater than the association of unfimbriated mutant AAEC072 in artificial seawater and in hemolymph serum, respectively. Such differences were apparently due to different adhesive properties since MG155 adhered more efficiently than AAEC072 when hemocytes were incubated at 4 degrees C to inhibit the internalization process. Hemolymph serum increased both association and adherence of MG155 two- to threefold but did not affect association and adherence of AAEC072. MG155 was also 1.5- to 1.7-fold more sensitive to killing by hemocytes than AAEC072, as evaluated by the number of culturable bacteria after 60 and 120 min of incubation. The role of type 1 fimbriae in MG155 interactions with hemocytes was confirmed by the inhibitory effect of D-mannose. In in vivo experiments MG155 cells were cleared from circulating hemolymph more rapidly than AAEC072 cells were cleared. These results confirm that surface properties are crucial in influencing bacterial persistence and survival within mussel hemolymph.