Effects of subinhibitory concentrations of menthol on adaptation, morphological, and gene expression changes in enterohemorrhagic Escherichia coli.

Menthol (C(10)H(20)O) possesses antibacterial activity; nevertheless, bacterial adaptation to this compound has never been studied. Here we report that precultivation of enterohemorrhagic Escherichia coli (EHEC) strains in increasing subinhibitory (SI) concentrations of menthol significantly elevates (4- to 16-fold) their resistance to menthol. Concomitant morphological alterations included the appearance of mucoid colonies and reduced biofilm production. Scanning electron microscopy (SEM) examination revealed suppressed curli formation in menthol-adapted cells. Expression of the gene cpsB10 (encoding one of the enzymes responsible for colanic acid production) was elevated in response to SI concentrations of menthol in a laboratory E. coli strain, whereas expression in an rcsC null mutant was reduced, implicating a partial role for the Rcs phosphorelay system in mediating the menthol signal. Adaptation to menthol also reduced expression of the locus of enterocyte effacement-encoded regulator (Ler). This reduction, together with reduced curli and biofilm formation and elevated mucoidity, suggests a general reduction in bacterial virulence following adaptation to menthol. Our results thus suggest menthol as a potential lead in the recently emerging alternative strategy of targeting bacterial virulence factors to develop new types of anti-infective agents.

Epigallocatechin gallate induces upregulation of the two-component VraSR system by evoking a cell wall stress response in Staphylococcus aureus.

We previously found that a short exposure of Staphylococcus aureus to subinhibitory (SI) doses of epigallocatechin gallate (EGCG) results in increased cell wall thickness, adaptation, and enhanced tolerance to cell-wall-targeted antibiotics. In this study, the response to EGCG of sigB and vraSR transcription factor mutants was characterized. We show that in contrast to the results observed for wild-type (WT) strains, an S. aureus 315 vraSR null mutant exposed to SI doses of EGCG did not exhibit increased tolerance to EGCG and oxacillin. A diminished increase in tolerance to ampicillin (from 16-fold to 4-fold) and no change in the magnitude of resistance to vancomycin were observed. Preexposure to EGCG enhanced the tolerance of wild-type and sigB null mutant cells to lysostaphin, but this enhancement was much weaker in the vraSR null mutant. Marked upregulation (about 60-fold) of vraR and upregulation of the peptidoglycan biosynthesis-associated genes murA, murF, and pbp2 (2-, 5-, and 6-fold, respectively) in response to SI doses of EGCG were determined by quantitative reverse transcription-PCR (qRT-PCR). EGCG also induced the promoter of sas016 (encoding a cell wall stress protein of unknown function which is not induced in vraSR null mutants) in a concentration-dependent manner, showing kinetics comparable to those of cell-wall-targeting antibiotics. Taken together, our results suggest that the two-component VraSR system is involved in modulating the cell response to SI doses of EGCG.

Longitudinal study on the effects of growth-promoting and therapeutic antibiotics on the dynamics of chicken cloacal and litter microbiomes and resistomes.

BACKGROUND: Therapeutic and growth-promoting antibiotics are frequently used in broiler production. Indirect evidence indicates that these practices are linked to the proliferation of antimicrobial resistance (AMR), the spread of antibiotic-resistant bacteria from food animals to humans, and the environment, but there is a lack of comprehensive experimental data supporting this. We investigated the effects of growth promotor (bacitracin) and therapeutic (enrofloxacin) antibiotic administration on AMR in broilers for the duration of a production cycle, using a holistic approach that integrated both culture-dependent and culture-independent methods. We specifically focused on pathogen-harboring families (Enterobacteriaceae, Enterococcaceae, and Staphylococcaceae). RESULTS: Antibiotic-resistant bacteria and antibiotic resistance genes were ubiquitous in chicken cloaca and litter regardless of antibiotic administration. Environment (cloaca vs. litter) and growth stage were the primary drivers of variation in the microbiomes and resistomes, with increased bacterial diversity and a general decrease in abundance of the pathogen-harboring families with age. Bacitracin-fed groups had higher levels of bacitracin resistance genes and of vancomycin-resistant Enterococcaceae (total Enterococcaceae counts were not higher). Although metagenomic analyses classified 28-76% of the Enterococcaceae as the commensal human pathogens E. faecalis and E. faecium, culture-based analysis suggested that approximately 98% of the vancomycin-resistant Enterococcaceae were avian and not human-associated, suggesting differences in the taxonomic profiles of the resistant and non-resistant strains. Enrofloxacin treatments had varying effects, but generally facilitated increased relative abundance of multidrug-resistant Enterobacteriaceae strains, which were primarily E. coli. Metagenomic approaches revealed a diverse array of Staphylococcus spp., but the opportunistic pathogen S. aureus and methicillin resistance genes were not detected in culture-based or metagenomic analyses. Camphylobacteriaceae were significantly more abundant in the cloacal samples, especially in enrofloxacin-treated chickens, where a metagenome-assembled C. jejuni genome harboring fluoroquinolone and ß-lactam resistance genes was identified. CONCLUSIONS: Within a "farm-to-fork, one health" perspective, considering the evidence that bacitracin and enrofloxacin used in poultry production can select for resistance, we recommend their use be regulated. Furthermore, we suggest routine surveillance of ESBL E. coli, vancomycin-resistant E. faecalis and E. faecium, and fluoroquinolone-resistant C. jejuni strains considering their pathogenic nature and capacity to disseminate AMR to the environment. Video Abstract.

Outcome of thick (> 4 mm) node-negative melanomas.

BACKGROUND: Patients with thick melanomas > 4 mm deep are at great risk for regional and distant metastatic disease. Historically, the appropriate management of thick melanomas has remained unclear and there is no consensus in the literature. Many have taken the nihilistic view that surgical intervention to excise regional nodal basins is not justified in light of the poor overall prognosis and risk of occult distant disease. OBJECTIVES: To review the outcome of patients with thick node negative melanoma treated at a multidisciplinary academic center METHODS: We retrospectively reviewed a database of melanoma patients to identify patients with thick melanomas, > 4 mm, who were either clinically or sentinel node biopsy negative, staged T4N0, stage IIb or IIc. The charts of these patients were reviewed and updated, with a median follow-up of 4 years. RESULTS: We identified 23 patients who fit these criteria. Of these, 18 (78%) remain alive with a median follow-up of 4 years. Five patients died of metastatic disease. Of the 18 surviving patients, 14 remained with no evidence of disease after initial resection of their primary lesions. The majority of the recurrences were non-nodal. CONCLUSIONS: The overall survival of patients in our study remains above 75% at median follow-up of 4 years, even with thick initial index tumor depths. Most of the failures were due to hematogenous spread with lymphatic sparing. Tumor biology that may inhibit lymphatic spread could be a target of future investigation.

Emergence of novel Streptococcus iniae exopolysaccharide-producing strains following vaccination with nonproducing strains.

Streptococcus iniae is a major pathogen of fish, producing fatal disease among fish species living in very diverse environments. Recently, reoccurrences of disease outbreaks were recorded in rainbow trout (Oncorhynchus mykiss, Walbaum) farms where the entire fish population was routinely vaccinated. New strains are distinguished from previous strains by their ability to produce large amounts of extracellular polysaccharide that is released into the medium. Present findings indicate that the extracellular polysaccharide is a major antigenic factor, suggesting an evolutionary selection of strains capable of extracellular polysaccharide production.

Isolation and characterization of Escherichia coli mutants exhibiting altered response to thymol.

The antimicrobial mode of action of the plant essential oil thymol was studied with Escherichia coli. Random transposon-insertion mutants were screened for altered response to thymol. Of four mutants showing more sensitivity, three were found in rfaQ, whose product is involved in lipopolysaccharide biosynthesis, and the fourth in the quorum-sensing gene qseC. Mutants showing more resistance had mutations in genes whose products are involved in the degradation of short-lived regulatory and abnormal proteins (the lon gene), menaquinone biosynthesis (menA), an unknown function of a putative membrane protein (yagF), synthesis of a small hypothetical protein (an intergene region between the two small genes yiiE and yiiF), and the efflux pump of cadaverine and lysine (cadB). The antibacterial activities of carvacrol, menthol, and cymene, essential oils structurally similar to thymol, were also determined. Although the level of resistance toward thymol was conserved in the respective mutants qseC, menA, and cadB, knockout mutants displayed different levels of tolerance to carvacrol; inconsistencies in resistance levels were also noted in mutants challenged with menthol. Wild-type and mutant E. coli responded to thymol exposure with a massive potassium efflux that generally corresponded to the resistant rate. The verity of the loci accounting for E. coli response suggests a multitarget mode of the antimicrobial activity of thymol and multitolerance mechanisms.

Transcytosis of Streptococcus iniae through skin epithelial barriers: an in vitro study.

By constructing a biological model based on in vitro culture of polarized rainbow trout primary skin epithelial cell monolayers, the series of early events that precede Streptococcus iniae infection, particularly colonization and translocation through external barriers, were analyzed. Streptococcus iniae promptly invades skin epithelial cells, but the rapid decline of viable intracellular bacteria points out the limited capability of intracellular survival for this bacterium. Translocation assays, supported by electron microscopy microphotographs, demonstrate that following successful in vitro invasion of skin epithelial cell, the bacterium exists free in the cytoplasm after release from the endosome, and translocates through the skin barrier. Bacterial invasion and transcytosis is not accompanied by apparent cell-line damages or disruption of host cells' tight junctions. It is hypothesized that the phenomenon of epithelial invasion coupled to the rapid translocation through the barrier plays a crucial role in Streptococcus iniae infection.

Nitrite reduction in Paracoccus sp. is affected by a novel plasmid pYR1.

Two relatively low-copy plasmids of 9 and 16 kb were found to comprise the extrachromosomal DNA of a Paracoccus strain. Reduction of nitrate by plasmid-cured cells resulted in a significant intermediate nitrite accumulation as compared to wild-type cells. By examining nitrate reduction by transformants containing one of the two plasmids, it was found that nitrite accumulation was influenced by the 9.0-kb plasmid, designated as pYR1. Subcloning analysis showed that a 1.8-kb fragment of this plasmid affected nitrite accumulation. Sequence analysis of this fragment revealed the presence of five open reading frames. One of the six deduced proteins showed a strong homology to ABC transporters.

Adoptive cell therapy with autologous tumor-infiltrating lymphocytes and high-dose interleukin-2 for metastatic melanoma: The surgeon's perspective.

Tumor-infiltrating lymphocytes (TILs) are produced by resecting tumor tissue and growing and expanding ex vivo large quantities of autologous T cells. Once the TILs are ready for infusion, the patient undergoes a non-myeloablative lympho-depleting course of chemotherapy and subsequent TIL infusion with high-dose bolus IL-2. This study reviews the surgical experience of the TIL program at the Chaim Sheba Cancer Research Center in Israel. Eligible patients underwent surgical consultation to determine what tumorectomy would be beneficial for harvesting appropriate tissue. Factors involved in the decision included tumor mass size, location and morbidity of the procedure. Between January 2006 and May 2010, 44 patients underwent 47 procedures of adoptive transfer of TILs. Three patients underwent the procedure twice for recurrence after initial good responses, including an additional surgical procedure to produce fresh tumor. Thirty-seven excisions were with general anesthesia and 10 were with local anesthesia. Of the 37 general anesthesia procedures, 27 were open procedures involving a thoracotomy, a laparotomy or dissection of a major lymph node basin. Ten used minimally invasive techniques such as thorascopy or laparoscopy. Tumorectomy sites included 18 lymph node metastasis, 13 subcutaneous nodules, 11 lung specimens and 5 abdominal visceral metastasis including 2 liver lesions. Surgical mortality and major morbidity was 0%. Minor morbidity included only wound complications. Maximal number of TILs were derived from lymph node specimens, while liver metastasis procured the fewest TILs. Adoptive cell transfer technology affords a maximal tumor response with minimal surgical morbidity in metastatic patients.

Staphylococcal strains adapted to epigallocathechin gallate (EGCG) show reduced susceptibility to vancomycin, oxacillin and ampicillin, increased heat tolerance, and altered cell morphology.

Epigallocathechin gallate (EGCG) possesses many beneficial properties, such as anticarcinogenicity, antiatherogenicity, as well as antioxidant and antibacterial activities. However, the bacterial response to sublethal concentrations of EGCG has not been studied. Here we investigated whether short exposure of staphylococci strains to sublethal doses of EGCG can lead to adaptation and cross-resistance. Two-hour exposure of five strains to 20 microg/ml of EGCG did not affect the growth rate but significantly elevated the resistance towards antibiotics targeting the bacterial cell wall. The magnitude of cross-resistance towards such antibiotics varied with the staphylococci strain, with Staphylococcus aureus Newman exhibiting the highest magnitude of cross-resistance, showing a 2, 4 and 8-fold increase in resistance towards vancomycin, oxacillin and ampicillin respectively. All EGCG-adapted strains were also more heat tolerant than their control counterparts as derived from the Weibull model. Adaptation to EGCG led to a moderate increase in heat resistance of the adapted strains S. epidermis ATCC 12228, S. aureus Newman, and S. aureus ATCC 29213, and an extremely pronounced increase for S. aureus ATCC 6538 and S. aureus RN4220. The shape of the survival curve also varied with the staphylococci strain. Transmission electron microscopy (TEM) analysis revealed suppressed separation of daughter cells in cultures exposed to EGCG, as evidenced by the pseudomulticellular appearance and by more than 2-fold increase in cell wall thickness. These observations raise concerns over the potential of EGCG utilization in therapy in that it may contribute to the development and enhancement of microbial resistance mechanisms.

A pivotal role for the Streptococcus iniae extracellular polysaccharide in triggering proinflammatory cytokines transcription and inducing death in rainbow trout.

Streptococcus iniae is a major pathogen of fish, causing considerable economic losses in Israel, the United States and the Far East. Containment of mortalities through vaccination was recently compromised due to the emergence of novel vaccine-escape strains that are distinguished from previous strains by their ability to produce large amounts of extracellular polysaccharide (EPS) that is released to the medium. In vitro and in vivo data now indicate that the EPS is a major virulence factor, capable of triggering the proinflammatory cytokine machinery and inducing mortality of fish. Streptococcus iniae EPS might therefore be considered to be responsible for sepsis and death just as lipopolysaccharide is for Gram-negative pathogens.

The role of the outer membrane in formaldehyde tolerance in Escherichia coli VU3695 and Halomonas sp. MAC.

To investigate the mechanism of formaldehyde tolerance in Gram-negative bacteria, two formaldehyde-tolerant strains, Escherichia coli VU3695 and Halomonas sp. MAC (DSM 7328), and formaldehyde-sensitive revertants obtained by ethidium bromide or novobiocin treatment were studied. The presence of high levels of formaldehyde dehydrogenase activity alone proved insufficient to confer tolerance to high formaldehyde concentrations, as shown by high activity displayed by formaldehyde-sensitive revertants of Halomonas MAC. Moreover, formaldehyde-tolerant strains also proved to be tolerant to high concentrations of acetaldehyde and glutaraldehyde, which are not oxidized by formaldehyde dehydrogenase. Treatment with sublethal concentrations of EDTA rendered the resistant strains highly sensitive to formaldehyde without affecting the activity of formaldehyde dehydrogenase. Comparison of the outer membrane proteins of formaldehyde-resistant strains with those of their sensitive revertants showed the presence of at least one additional high molecular mass protein in the tolerant strains. It is concluded that formaldehyde tolerance in the bacteria studied depends on the composition and structure of the outer membrane.

Immunodetection of the bacteriocin lacticin RM: analysis of the influence of temperature and Tween 80 on its expression and activity.

Immunoassays with specific antibodies offer higher sensitivity than do bioassays with indicator strains in the detection and quantification of several bacteriocins. Here we present the purification of lacticin RM and the production of specific polyclonal antibodies to a synthetic peptide resembling an internal fragment of the mature bacteriocin. The specificity and sensitivity of the generated polyclonal antibodies were evaluated in various immunoassays. The detection limits of lacticin RM were found to be 1.9, 0.16, and 0.18 micro g ml(-1) for Western blot, immuno-dot blot, and noncompetitive indirect enzyme-linked immunosorbent assays, respectively. Immunoassay sensitivities were 12.5-fold higher than that of the agar diffusion test (ADT). The production of lacticin RM showed temperature dependency, with 3, 4.2, 12.7, 28.9, 37.8, and 12 micro g ml(-1) at 37, 30, 20, 15, 10, and 4 degrees C, respectively. Temperature-stability analysis demonstrated that lacticin RM is sensitive to mild temperature, but the loss of activity does not seem to result from protein degradation. Tween 80 increased the concentration of lacticin RM eightfold and probably affected the results of the ADT either by enhancing the activity of lacticin RM or by increasing the sensitivity of the indicator strain. The use of antibodies for the specific detection and quantification of lacticin RM can expand our knowledge of its production and stability, with important implications for further investigation and future application.