Non-Invasive Providencia alcalifaciens Strains Fail to Attach to HEp-2 Cells

We investigated the adherence properties of six P. alcalifaciens strains with previously characterized differential invasive capabilities in HEp-2 cells. Highly invasive strains were found to attach to HEp-2 cell monolayers within 2 h post-infection and in large numbers on the eukaryotic cell surfaces within 3 h post-infection. In contrast, weakly or non-invasive P. alcalifaciens strains were non-adherent to HEp-2 cells even at 3 h post-infection. Highly invasive isolates were found to weakly bind F-actin using the fluorescent actin staining assay although these strains were negative for Escherichia coli attachment and effacing gene (eaeA) of enteropathogenic E. coli (EPEC). These results suggest that the strain variation in the ability of P. alcalifaciens to invade HEp-2 cells previously noted by several investigators may be linked to expression of key adhesin(s) on the cell surface of invasive isolates. Received: 10 April 2001 / Accepted: 17 April 2001     

Berberine inhibits HEp-2 cell invasion induced by <Emphasis Type="Italic">Chlamydophila pneumoniae</Emphasis> infection

This study investigated the inhibitory effects of berberine on Chlamydophila (Chlamydia) pneumoniae infection-induced HEp-2 cell invasion and explored the possible mechanisms involved in this process. C. pneumoniae infection resulted in a significant increase in HEp-2 cell invasion when compared with the control cells (P<0.01) in a Matrigel invasion assay. This enhanced cell invasion was strongly suppressed by berberine (50 μM) (P<0.01). In a cell adhesion assay, the infection-induced HEp-2 cell adhesion to Matrigel was also significantly inhibited by berberine (P<0.01). C. pneumoniae infection was found to promote HEp-2 cell migration remarkably (P<0.01), which was markedly suppressed by berberine (P<0.01) in the cell migration assays. There were no statistically significant differences in the expression of matrix metalloproteinase-1 (MMP-1) and MMP-9 in the infected cells and berberine did not change the expression of MMP-1 and MMP-9. These data suggest that berberine inhibits C. pneumoniae infection-induced HEp-2 cell invasion through suppressing HEp-2 cell adhesion and migration, but not through changing the expression of MMP-1 and MMP-9.     

Adherence Patterns and DNA Probe Types of Escherichia coli Isolated from Diarrheal Patients in China

One hundred and seventy-two strains of Escherichia coli isolated from diarrheal patients in Beijing, P. R. China, were analyzed for plasmid DNA profile, HEp-2 cell adherence ability and reactivity to 10 previously described DNA probes. They had not been recognized as pathogenic E. coli in China. Of the 110 strains tested, 76 (69%) contained one or multiple large plasmids. Of the 71 strains with the large plasmids 64 could adhere to HEp-2 cells. Of the 172 strains, 102 (59.3%) were hybridized with at least one of the 10 probes. Of those, seven strains hybridized with enteroaggregative E. coli (EAggEC) probe. Their serotypes were O128 (two strains), O6 (one strain), and O111 (one strain). Three strains were untypable. Six and three strains were hybridized with enteropathogenic E. coli (EPEC) attaching and effacing genes (eae) or EPEC adherence factor (EAF) probe, respectively. Two non-O157: H7 strains hybridized with enterohemorrhagic E. coli (EHEC) probe. Seventy-two strains (41.9%) hybridized with shiga-like toxin 2 or 1 (SLT2 or SLT1) probes. Among the SLT1 or SLT2 probe-positive strains, 54 hybridized with invasive (INV) plasmid probe developed for identification of enteroinvasive E. coli (EIEC) and Shigella species. The INV and SLT probe-positive strains might represent a new variety of verotoxin-producing E. coli (VTEC).     

A FORENSIC AND PHYLOGENETIC SURVEY OF CAULERPA SPECIES (CAULERPALES,CHLOROPHYTA) FROM THE FLORIDA COAST,LOCAL AQUARIUM SHOPS,AND E‐COMMERCE: ESTABLISHING A PROACTIVE BASELINE FOR EARLY DETECTION1

Baseline genotypes were established for 256 individuals of Caulerpa collected from 27 field locations in Florida (including the Keys), the Bahamas, US Virgin Islands, and Honduras, nearly doubling the number of available GenBank sequences. On the basis of sequences from the nuclear rDNA‐ITS 1+2 and the chloroplast tufA regions, the phylogeny of Caulerpa was reassessed and the presence of invasive strains was determined. Surveys in central Florida and southern California of >100 saltwater aquarium shops and 90 internet sites revealed that >50% sold Caulerpa. Of the 14 Caulerpa species encountered, Caulerpa racemosa was the most common, followed by Caulerpa sertularioides, Caulerpa prolifera, Caulerpa mexicana, and Caulerpa serrulata. None of the >180 field‐collected individuals (representing 13 species) was the invasive strain of Caulerpa taxifolia or C. racemosa. With one exception (a sample of C. racemosa from a shop in southern California belonged to the invasive Clade III strain), no invasive strains were found in saltwater aquarium stores in Florida or on any of the internet sites. Although these results are encouraging, we recommend a ban on the sale of all Caulerpa species (including “live rock”) because: morphological identification of Caulerpa species is unreliable (>12% misidentification rate) and invasive strains can only be identified by their aligned DNA sequences, and because the potential capacity for invasive behavior in other Caulerpa species is far from clear. The addition of the Florida region to the genetic data base for Caulerpa provides a valuable proactive resource for invasion biologists as well as researchers interested in the evolution and speciation of Caulerpa.     

Putative Virulence Factor Expression by Clinical and Food Isolates of Bacillus spp. after Growth in Reconstituted Infant Milk Formulae

Forty-seven strains representing 14 different Bacillus species isolated from clinical and food samples were grown in reconstituted infant milk formulae (IMF) and subsequently assessed for adherence to, invasion of, and cytotoxicity toward HEp-2 and Caco-2 cells. Cell-free supernatant fluids from 38 strains (81%) were shown to be cytotoxic, 43 strains (91%) adhered to the test cell lines, and 23 strains (49%) demonstrated various levels of invasion. Of the 21 Bacillus cereus strains examined, 5 (24%) were invasive. A larger percentage of clinically derived Bacillus species (20%) than of similar species tested from the food environment were invasive. Increased invasion occurred after growth of selected Bacillus species in reconstituted IMF containing glucose. While PCR primer studies revealed that many different Bacillus species contained DNA sequences encoding the hemolysin BL (HBL) enterotoxin complex and B. cereus enterotoxin T, not all of these isolates expressed these diarrheagenic genes after growth in reconstituted IMF. Of the 47 Bacillus isolates examined, 3 isolates of B. cereus and 1 isolate of B. subtilis produced the HBL enterotoxin after 18 h of growth in brain heart infusion broth. However, eight isolates belonging to the species B. cereus, B. licheniformis, B. circulans, and B. megaterium were found to produce this enterotoxin after growth in reconstituted IMF when assessed with the B. cereus enterotoxin (diarrheal type) reversed passive latex agglutination (RPLA) kit. It is concluded that several Bacillus species occurring occasionally in clinical specimens and food samples are of potential medical significance due to the expression of putative virulence factors.     

Inactivation of Adhesion and Invasion of Food-Borne Listeria monocytogenes by Bacteriocin-Producing Bifidobacterium Strains of Human Origin

Three bacteriocin-producing bifidobacterial isolates from newborns were identified as Bifidobacterium thermacidophilum (two strains) and B. thermophilum (one strain). This study was undertaken to evaluate the ability of these strains to compete with food-borne Listeria monocytogenes for adhesion and invasion sites on Caco-2 and HT-29 cells. The bifidobacteria adhered at levels ranging from 4% to 10% of the CFU added, but none of the bifidobacteria were able to invade cells. The abilities of Listeria to adhere to and to invade cells varied widely depending on the strain tested. Three groups of Listeria were identified based on invasiveness: weakly invasive, moderately invasive, and highly invasive strains. One strain from each group was tested in competition with bifidobacteria. B. thermacidophilum RBL70 was the most effective in blocking invasion of Listeria, and the decreases in invasion ranged from 38% to 90%. For all three bifidobacterial strains, contact between the cell monolayer and the bifidobacteria for 1 h before exposure to Listeria increased the degree of inhibition. Finally, visualization of competition for adhesion sites on cells by fluorescent in situ hybridization suggested that the two bacteria tended to adhere in close proximity.     

Development and application of a loop-mediated isothermal amplification method on rapid detection of Pseudomonas aeruginosa strains

We developed and evaluated the specificity and sensitivity of a simple loop-mediated isothermal amplification (LAMP) method for rapid detection of P. aeruginosa strains. The optimal reaction condition was found to be 65°C for 45 min, with the detection limit as 100 fg DNA/tube and 10 CFU/reaction. Application of LAMP assays were performed 426 clinical samples (including 252 P. aeruginosa and 174 non- P. aeruginosa isolates) using a rapid procedure and easy result confirmation. Sensitivity of LAMP and PCR assays was found to be 97.6% (246/252) and 90.5% (228/252), respectively; with a 100% specificity for both assays.     

Development and Analysis of qPCR for the Identification of Arthroconidial Yeasts of the Genus Magnusiomyces

The arthroconidial yeasts Magnusiomyces capitatus and M. clavatus are emerging opportunistic pulmonary pathogens. They are closely related and difficult to distinguish based on morphological and physiological traits. We applied an SYBR^® green-based quantitative PCR (qPCR) assay to identify the species. We analyzed 30 reference strains originating from clinical and environmental sources by targeting the Rpb2 gene encoding the second largest subunit of RNA polymerase II. The qPCR assays were tested by direct identification of M. capitatus and M. clavatus in spiked sputum and household dishwasher swabs, respectively, as models for clinical and environmental samples. The assays were proved to be reliable for species-level identification of both species, with 100% sensitivity and 100% specificity, lowest inter-assay deviations (RSDr?≤?1.65%, R² values >0.99), detection limit of 10 theoretical copy number of target DNA, and detection cell limit of ≥5000 yeast cells from spiked sputum samples. The developed qPCR assay is a practical molecular approach for the detection of M. capitatus and M. clavatus that can be used as a stand-alone assay or in conjunction with culture-dependent approaches.

     

Hyper-invasive mutants define a novel Pho-regulated invasion pathway in Escherichia coli

We have isolated two transposon insertion mutations of the pst–phoU operon which result in the constitutive expression of the phoA gene product, alkaline phosphatase. The two mutations also render Escherichia coli invasive towards cultured HEp-2 cells and define a novel Pho-regulated invasion pathway. The presence of the large‘invasion’plasmid derived from an entero-invasive E. coli (EIEC) clinical isolate in these mutants leads to enhanced invasiveness toward cultured HEp-2 cells, a phenomenon referred to as the‘hyper-invasive’phenotype. Transduction of a pst–phoU insertion mutation into clinical isolates of EIEC and Shigella flexneri results in constitutive PhoA expression and coupled hyper-invasiveness in the former but not the latter. We speculate that the Pho-regulated invasion pathway described here, while silent in bacteria grown in standard laboratory rich media, may become functional in the host when invasive bacteria encounter nutrient starvation and/or other related stress conditions.     

Real-Time PCR Assays for the Specific Identification of Probiotic Strains Lactobacillus gasseri BNR17 and Lactobacillus reuteri LRC (NCIMB 30242)

The broad spectrum of health benefits attributed to probiotics has contributed to a rapid increase in the value of the probiotic market. Probiotic health benefits can be strain specific. Thus, strain-level identification of probiotic strains is of paramount importance to ensure probiotic efficacy. Both Lactobacillus gasseri BNR17 and Lactobacillus reuteri LRC (NCIMB 30242) strains have clinically proven health benefits; however, no assays were developed to enable strain-level identification of either of these strains. The objective of this study is to develop strain-specific PCR-based methods for Lactobacillus gasseri BNR17 and Lactobacillus reuteri LRC strains, and to validate these assays according to the guidelines for validating qualitative real-time PCR assays. Using RAST (Rapid Annotation using Subsystem Technology), unique sequence regions were identified in the genome sequences of both strains. Probe-based assays were designed and validated for specificity, sensitivity, efficiency, repeatability, and reproducibility. Both assays were specific to target strain with 100% true positive and 0% false positive rates. Reaction efficiency for both assays was in the range of 90 to 108% with R square values > 0.99. Repeatability and reproducibility were evaluated using five samples at three DNA concentrations each and relative standard deviation was < 4% for repeatability and < 8% for reproducibility. Both of the assays developed and validated in this study for the specific identification of Lactobacillus gasseri BNR17 and Lactobacillus reuteri LRC strains are specific, sensitive, and precise. These assays can be applied to evaluate and ensure compliance in probiotic products.

     

Comparison of multiplex PCR, enzyme immunoassay and cell culture methods for the detection of enterotoxinogenic Bacillus cereus

Fast and reliable methods are needed for the detection of pathogenic Bacillus cereus which should provide consistent results. Therefore, we tested a panel of 176 strains, including B. cereus strains, B. cereus group strains and other Bacillus spp. with polymerase chain reaction, immunoassays and cytotoxicity tests and assessed the consistency of the results. A screening multiplex PCR for the detection of hbl, nhe, ces and cytK1 as well as two multiplex PCRs for the differentiation of Hbl genes (hblC, hblD, hblA) and Nhe genes (nheA, nheB, nheC) was applied. All PCRs included an internal amplification control. Component specific antibody based immunoassays were used for the detection of the three components of Hbl and Nhe and the overall cytotoxicity to Vero cells and HEp-2 cells was checked. An overall excellent correlation was obtained for the results of the three, methodically independent assays and no false-negative PCR results were seen for any of the strains tested positive in immunoassays and cytotoxicity tests. The three multiplex PCRs proved to be a facile method for the identification of enterotoxinogenic B. cereus isolates.     

Comparison of in vitro cytotoxicity of Fusarium mycotoxins,deoxynivalenol, T-2 toxin and zearalenone on selected human epithelial cell lines

Three human epithelial cell lines (CaCo-2, HEp-2 and HeLa) implicated as potential targets for three Fusarium toxins were tested for the extent of survival on exposure to increasing toxin concentration and incubation periods. Cytotoxicity assay using 3(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT) was carried out with deoxynivalenol (DON), T-2 toxins and zearalenone (ZON) on CaCo-2, HEp-2 and HeLa cell lines. Of the three cell lines used, HeLa was the most sensitive, eliciting cell death after 2 days exposure at 100 ng ml^–1with T-2 toxin. HeLa was the only cell line to exhibit cytotoxicity towards ZON showing cell death at 1000 ng ml^–1after 2 days which increased to 4 days, showing substantial cell death at 200 ng ml^–1. HEp-2 was sensitive to DON showing cell death after 2 days (100 ng ml^–1) with complete cell death occurring at 200 ng ml^–1 after 4 days of exposure. Substantial cytoxicity of T-2 towards HEp-2 occurred after 2 days at 1000 ng ml^–1 and complete cell death occurred with 100 ng ml^–1 at day 4. The CaCo-2 cell line was generally resistant to the mycotoxins tested between 100 and 1000 ng ml^–1. This study shows that cytotoxicity of Fusarium toxins to epithelium cell lines is concentration- and time- dependant and results from ZON–HeLa interaction indicate possible cell type-mycotoxin specificity.     

入侵植物印加孔雀草在不同生境的种群构件生物量及其分配特征

印加孔雀草是中国西藏新近入侵种,其危害已初见端倪,但我国鲜有对其入侵机理的研究.为探究印加孔雀草在异质环境下的种群构件生物量及其分配特征,进一步深入了解其生存策略和易入侵生境.该研究在菜园、果园、路边、荒地和河滩等五种典型入侵生境内对其花果期的种群构件生物量进行了测定和分析,计算了表型可塑性指标值.结果表明:(1)印加...     

The role of DNA base excision repair in filamentation in Escherichia coli K-12 adhered to epithelial HEp-2 cells

Base excision repair (BER) is dedicated to the repair of oxidative DNA damage caused by reactive oxygen species generated by chemical and physical agents or by metabolism which can react with DNA and cause a variety of mutations. Epithelial cells are typically the first type of host cell to come into contact with potential microbial invaders. In this work, we have evaluated whether the adherence to human epithelial cells causes DNA damage and associated filamentation. Experiments concerning adherence to HEp-2 cells were carried out with mutants deficient in BER that were derived from Escherichia coli K-12. Since the removal of mannose during bacterial interaction with HEp-2 cells allows adhesion through mannose-sensitive adhesins, the experiments were also performed in the presence and the absence of mannose. Our results showed enhanced filamentation for the single xth (BW9091) and triple xth nfo nth (BW535) mutants in adherence assays with HEp-2 cells performed without d-mannose. The increased filamentation growth was inhibited by complementation of BER mutants with a wild type xth gene. Moreover, we measured SOS induction of bacteria adhered to HEp-2 cells in the presence and absence of d-mannose through of SOS-chromotest assay and we observed a higher β-galactosidase expression in the absence of mannose. In this context, data showed evidence that bacterial attachment to HEp-2 epithelial surfaces can generate DNA lesions and SOS induction.     

The effect of nitrogen and temperature changes on Solidago canadensis phenotypic plasticity and fitness

Phenotypic plasticity is commonly considered to contribute to the invasion success of invasive species. However, the importance of phenotypic plasticity, nitrogen (N) levels and warming to the invasion of invasive species is unclear. The effects of warming and N addition on the morphology, biomass allocation and biochemistry traits of Solidago canadensis and their plasticity were investigated by conducting a pot experiment. The results showed that the effect of N addition on biomass was improved for S. canadensis; whereas warming displayed no significant effect, their positive synergistic interact effect resulted in the overall significant increase in plant performance. The mean phenotypic plasticity indices (MPPI) of biochemistry and total parameters demonstrated a difference between operations, and the higher value was observed in N interaction with temperature treatments than N addition or warming alone. The observed MPPI indicated the biochemistry parameters > morphological parameters > allocation parameters. The MPPI of biochemistry parameters, morphological parameters and total parameters exhibited significant and positive correlations with N level and MPPI of morphological parameters was also significantly positively correlated with the fitness of S. canadensis. These results indicated that the global warming and N addition would make the invaded habitat more suitable for the growth of invasive S. canadensis, and even may effectively increase the invasion risk of S. canadensis through the enhanced phenotypic plasticity, which is a crucial factor to help species deal with the changing environment.     

Aeromonas spp.-mediated cell-contact cytotoxicity is associated with the presence of type III secretion system

In the study we examined the production of cytotonic and cytotoxic toxins and the presence of a type III secretion system (TTSS) in 64 Aeromonas spp. strains isolated from fecal specimens of patients with gastroenteritis. We observed that contact of the bacteria with host epithelial cells is a prerequisite for their cytotoxicity at 3 h incubation. Cell-contact cytotoxic activity of the strains was strongly associated with the presence of the TTSS. Culture supernatants of the strains induced low cytotoxicity effects at the same time of incubation. Cell-free supernatants of 61 (95%) isolates expressed cytotoxic activity which caused the destruction of HEp-2 cells at 24 h. Moreover, 44% strains were cytotonic towards CHO cells and 46% of strains invaded epithelial cells.     

Binding of Selected Extracellular Matrix Proteins to Enterococci and Streptococcus bovis of Animal Origin

Thirty-three enterococcal strains and 10 Streptococcus bovis strains were investigated for their protein-binding cell surface components. Seven extracellular matrix (ECM) proteins were immobilized on Difco latex beads to detect these components on the surface of all enterococcal strains and eight non-autoaggregating S. bovis strains by a particle agglutination assay (PAA). Twenty-three selected strains were also examined in microtiter plate assays. According to the absorbance readings (A_570nm), 11 strains were classified as nonadherent (A_570nm < 0.1), 10 strains as weakly adherent (0.1 < A_570nm > 0.3), and 2 strains as strongly adherent (A_570nm > 0.3) in these assays. A direct correlation was found between the values obtained in PAA and A_570nm readings of microtiter plate assays. Binding of ¹²⁵I-labeled bovine lactoferrin to enterococci and streptococci was in the range of 6%–30% and of ¹²⁵I-labeled human vitronectin in the range of 9%–33% to streptococci. The binding of ¹²⁵I-labeled ECM proteins to selected strains was much more effectively inhibited by sulfated carbohydrates than by non-sulfated hyaluronic acid, indicating the importance of the sulfate groups of these inhibitors. An inhibition effect of heparin on bLf binding to four selected strains was higher in comparison with fucoidan in the microtiter plates. Thirty-five out of 44 strains had agglutinated rabbit erythrocytes. However, these strains showed no ability to agglutinate bovine or sheep erythrocytes. Received: 28 April 1999 / Accepted: 26 July 1999     

Examination of Food Chain-Derived Listeria monocytogenes Strains of Different Serotypes Reveals Considerable Diversity in inlA Genotypes,Mutability, and Adaptation to Cold Temperatures

Listeria monocytogenes strains belonging to serotypes 1/2a and 4b are frequently linked to listeriosis. While inlA mutations leading to premature stop codons (PMSCs) and attenuated virulence are common in 1/2a, they are rare in serotype 4b. We observed PMSCs in 35% of L. monocytogenes isolates (n = 54) recovered from the British Columbia food supply, including serotypes 1/2a (30%), 1/2c (100%), and 3a (100%), and a 3-codon deletion (amino acid positions 738 to 740) seen in 57% of 4b isolates from fish-processing facilities. Caco-2 invasion assays showed that two isolates with the deletion were significantly more invasive than EGD-SmR (P < 0.0001) and were either as (FF19-1) or more (FE13-1) invasive than a clinical control strain (08-5578) (P = 0.006). To examine whether serotype 1/2a was more likely to acquire mutations than other serotypes, strains were plated on agar with rifampin, revealing 4b isolates to be significantly more mutable than 1/2a, 1/2c, and 3a serotypes (P = 0.0002). We also examined the ability of 33 strains to adapt to cold temperature following a downshift from 37°C to 4°C. Overall, three distinct cold-adapting groups (CAG) were observed: 46% were fast (<70 h), 39% were intermediate (70 to 200 h), and 15% were slow (>200 h) adaptors. Intermediate CAG strains (70%) more frequently possessed inlA PMSCs than did fast (20%) and slow (10%) CAGs; in contrast, 87% of fast adaptors lacked inlA PMSCs. In conclusion, we report food chain-derived 1/2a and 4b serotypes with a 3-codon deletion possessing invasive behavior and the novel association of inlA genotypes encoding a full-length InlA with fast cold-adaptation phenotypes.     

Comparison of adherence to and penetration of a human laryngeal epithelial cell line by group A streptococci of various M protein types

Clinically isolated group A streptococci (GAS) of different M protein types were studied using aminoglycoside exclusion and [2,8-3H]adenine radiolabeled GAS assays to compare the abilities of different strains to adhere to and internalize within human laryngeal epithelial (HEp-2) cells. GAS isolated from patients with pharyngitis and GAS isolated from patients with more severe disease, such as necrotizing fasciitis, adhered to and penetrated HEp-2 cells equally well. M3, M4, M6, and M12 strains adhered to and were internalized within HEp-2 cells more than M1 strains. M18 GAS producing hyaluronic acid capsules were less adherent and less invasive than the M3, M4, M6, and M12 strains. An M3-producing GAS strain and its M protein-deficient isogenic strain adhered similarly to HEp-2 cells, but the M protein-deficient strain exhibited greater penetration. Preincubation of HEp-2 cells with an N-terminal synthetic M3 peptide did not alter the adherence or penetration by an M3 strain. In summary, this study demonstrates that GAS from invasive and non-invasive disease adhere to and penetrate HEp-2 cells equally well and that multiple strains of GAS with various M protein types have the ability to adhere to and penetrate HEp-2 cells.     

Non-encapsulated strains reveal novel insights in invasion and survival of Streptococcus suis in epithelial cells

Streptococcus suis is a porcine and human pathogen causing invasive diseases, such as meningitis or septicaemia. Host cell interactions of S. suis have been studied mainly with serotype 2 strains, but multiple capsular serotypes as well as non-typeable strains exist with diverse virulence features. At present, S. suis is considered an extracellular pathogen. However, whether or not it can also invade host cells is a matter of controversial discussions. We have assessed adherence and invasion of S. suis for HEp-2 epithelial cells by comparing 10 serotype 2 strains and four non-typeable (NT) strains. Only the NT strains and a non-encapsulated serotype 2 mutant strain, but none of the serotype 2 strains, adhered strongly and were invasive. Invasion seemed to be affected by environmental signals, as suggested from comparison of strains grown in different media. Further phenotypic and genotypic characterization revealed a high diversity among the different strains. Electron microscopic analysis of invasion of selected invasive NT strains indicated different uptake mechanisms. One strain induced large invaginations comparable to those seen in 'caveolae' mediated uptake, whereas invasion of the other strains was accompanied by formation of filipodia-like membrane protrusions. Invasion of all strains, however, was similarly susceptible to hypertonic sucrose, which inhibits receptor-mediated endocytosis. Irrespective of the uptake pathway, streptococci resided in acidified phago-lysosome like vacuoles. All strains, except one, survived intracellularly as well as extracellular acidic conditions. Survival seemed to be associated with the AdiS protein, an environmentally regulated arginine deiminase of S. suis. Concluding, invasion and survival of NT strains of S. suis in epithelial cells revealed novel evidence that S. suis exhibits a broad variety of virulence-associated features depending on genetic variation and regulation.