头颈部放疗期间口腔细菌菌群变化及其与放射性口腔黏膜炎相关性研究

目的 探索口腔细菌菌群在头颈部肿瘤放疗期间的变化及其与放射性口腔黏膜炎(ROM)的相关性。方法 获取入组鼻咽癌患者和陪护家属在放疗前和结束时口腔细菌标本,利用高通量测序技术检测。C57BL/6小鼠构建ROM模型,收集照射后第9天和阴性对照组口腔细菌标本;另一批小鼠解剖获取阴性对照组和小鼠照射后第3、5、7、9天舌头组织,检测炎症因子和HE染色。结果 患者放疗后的口腔细菌多样性与患者放疗前和陪护家属在患者放疗前、后Observed species、Chao1、Simpson指数不同(均 P<0.05)。重度和轻、中度ROM患者的Shannon指数不同(P=0.036)。LEfSe分析显示重度ROM患者链球菌属、链球菌科含量较高,而Familyxl菌科、孪生球菌属、芽孢杆菌目含量较低。小鼠阴性对照组和照射组口腔细菌菌群的Simpson指数和PCoA结果也不同(均 P<0.01)。结论 放疗会引起口腔细菌菌群失调,且失调的口腔细菌菌群与ROM加重关系密切。     

Antimicrobial action and pharmacokinetics/pharmacodynamics: the use of AUIC to improve efficacy and avoid resistance

In in-vitro and in animal models, antibiotics show good relationships between concentration and response, when response is quantified as the rate of bacterial eradication. The strength of these in-vitro relationships promises their utility for dosage regimen design and predictable cure of human infections. Resistance is also predictable from these parameters, fostering a rational means of using dosing adjustments to avoid or minimize the development of resistant organisms. Newly developed computerized methods for the quantitation of susceptibility allow testing of integrated kinetic-susceptibility models in patients. Our attention has focused recently on fluoroquinolones, since they are relatively non-toxic and provide the necessary range of dosage needed to elucidate correlations between concentration and response in the Intensive Care Unit patient. Studies conducted in patients with nosocomial gram-negative pneumonia reveal good correlations between bacterial eradication and integration of concentration with bacterial susceptibility. In patients, the best correlation parameters are time over MIC, and the ratio of 24-hour AUC to MIC (AUIC). Patients with serious infections like nosocomial pneumonia require bactericidal antimicrobial activity. Studies in our laboratory demonstrate that the minimum effective antimicrobial action is an area under the inhibitory titer (AUIC) of 125, where AUIC is calculated as the 24-hour serum AUC divided by the MIC of the pathogen. This target AUIC may be achieved with either a single antibiotic or it can be the sum of AUIC values of two or more antibiotics. There is considerable variability in the actual AUIC value for patients when antibiotics are given in their usually recommended dosages. Examples of this variance will be provided using aminoglycosides, fluoroquinolones, beta-lactams, macrolides and vancomycin. The achievement of minimally effective antibiotic action, consisting of an AUIC of at least 125, is associated with bacterial eradication in about 7 days for beta-lactams and quinolones. When AUIC is increased to 250, the quinolone ciprofloxacin (which displays in vivo concentration dependent bacterial killing) can eliminate the bacterial pathogen in 1-2 days. Beta lactams, even when dosed to an AUIC of 250, often require longer treatment duration to eliminate the bacterial pathogen, because the in vivo bacterial killing rate is slower with beta-lactams than with the quinolones. This remains true even at AUIC values of 250 for both compounds, which is theoretically identical dosing. Antibiotic activity indices allow clinicians to evaluate individualized patient regimens. Furthermore, antibiotic activity is a predictable clinical endpoint with predictable clinical outcome. This value is also highly predictive of the development of bacterial resistance. Antimicrobial regimens that do not achieve an AUIC of at least 125 cannot prevent the selective pressure that leads to overgrowth of resistant bacterial sub-populations. Indeed, there is considerable anxiety that conventional respiratory tract infection management strategies, which prescribe antibacterial dosages that may attain AUIC values below 125, are contributing to the pandemic rise in bacterial resistance levels.     

Antimicrobial Action and Pharmacokinetics/Pharmacodynamics: The Use of AUIC to Improve Efficacy and Avoid Resistance

Abstract

In in-vitro and in animal models, antibiotics show good relationships between concentration and response, when response is quantified as the rate of bacterial eradication. The strength of these in-vitro relationships promises their utility for dosage regimen design and predictable cure of human infections. Resistance is also predictable from these parameters, fostering a rational means of using dosing adjustments to avoid or minimize the development of resistant organisms.

Newly developed computerized methods for the quantitation of susceptibility allow testing of integrated kinetic-susceptibility models in patients. Our attention has focused recently on fluoroquinolones, since they are relatively nontoxic and provide the necessary range of dosage needed to elucidate correlations between concentration and response in the Intensive Care Unit patient. Studies conducted in patients with nosocomial Gram-negative pneumonia reveal good correlations between bacterial eradication and integration of concentration with bacterial susceptibility. In patients, the best correlation parameters are time over MIC, and the ratio of 24-hour AUC to MIC (AUIC).

Patients with serious infections like nosocomial pneumonia require bactericidal antimicrobial activity. Studies in our laboratory demonstrate that the minimum effective antimicrobial action is an area under the inhibitory titer (AUIC) of 125, where AUIC is calculated as the 24-hour serum AUC divided by the MIC of the pathogen. This target AUIC may be achieved with either a single antibiotic or it can be the sum of AUIC values of two or more antibiotics. There is considerable variability in the actual AUIC value for patients when antibiotics are given in their usually recommended dosages. Examples of this variance will be provided using aminoglycosides, fluoroquinolones, beta-lactams, macrolides and vancomycin. The achievement of minimally effective antibiotic action, consisting of an AUIC of at least 125, is associated with bacterial eradication in about 7 days for beta-lactams and quinolones. When AUIC is increased to 250, the quinolone ciprofloxacin (which displays in vivo concentration dependent bacterial killing) can eliminate the bacterial pathogen in 1-2 days. Beta lactams, even when dosed to an AUIC of 250, often require longer treatment duration to eliminate the bacterial pathogen, because the in vivo bacterial killing rate is slower with beta-lactams than with the quinolones. This remains true even at AUIC values of 250 for both compounds, which is theoretically identical dosing.

Antibiotic activity indices allow clinicians to evaluate individualized patient regimens. Furthermore, antibiotic activity is a predictable clinical endpoint with predictable clinical outcome. This value is also highly predictive of the development of bacterial resistance. Antimicrobial regimens that do not achieve an AUIC of at least 125 cannot prevent the selective pressure that leads to overgrowth of resistant bacterial sub-populations. Indeed, there is considerable anxiety that conventional respiratory tract infection management strategies, which prescribe antibacterial dosages that may attain AUIC values below 125, are contributing to the pandemic rise in bacterial resistance levels.     

上消化道癌前病变患者舌苔与土壤菌群相关性初步分析

目的:探讨扬中地区上消化道癌前病变患者舌苔与土壤菌群的相关性。方法:收集22例上消化道癌前病变患者的舌苔和自留地土壤,采用16S rDNA高通量测序检测菌群,生物信息学分析菌群多样性、菌群结构、共生关系等。结果:舌苔菌群多样性和丰富度均显著低于土壤,菌群组成显著不同。舌苔与土壤之间有17个分类单元（1门、2纲、3目、3科、4属和4种）显著相关。然而,舌苔与土壤菌群预测功能中脂质运输与代谢、翻译后修饰-蛋白翻转-蛋白伴侣、信号转导机制、防御机制等均为显著负相关,胞内运输-分泌-囊泡运输为显著正相关。结论:舌苔与土壤菌群存在相关性,土壤菌群可能是扬中地区上消化道癌地域性高发的关键因素。     

Quorum sensing pathways in Gram-positive and -negative bacteria: potential of their interruption in abating drug resistance

Quorum sensing (QS) is an inter-cell communication between bacterial populations through release of tiny diffusible compounds as signalling agents, called auto-inducers, abetting bacteria to track population density. QS allows bacterial population to perform collectively in coordination to wide phenotypes like alterations in expression of virulence genes to achieve advancement over their competitors, drug resistance and biofilm formation. Several classes of autoinducers have been described that are involved in bacterial virulence. This review gives an insight into the multitudinous QS systems in Gram-positive and Gram-negative bacteria to explore their role in microbial physiology and pathogenesis. Bacterial resistance to antibiotics has clinically become a super challenge. Strategies to interrupt QS pathways by natural and synthetic QS inhibitors or quorum quenchers or analogs provide a potential treatment. We highlight the advancements in discovery of promising new targets for development of next generation antimicrobials to control infections caused by multidrug resistant bacterial pathogens.     

Post-translational modifications of the C-terminal region of the rho protein are important for its interaction with membranes and the stimulatory and inhibitory GDP/GTP exchange proteins

We have recently found, by use of the rhoA p21 purified from bovine aortic smooth muscle, that it is similarly post-translationally processed as described for ras p21s: it is first geranylgeranylated at the cysteine residue in the C-terminal region followed by removal of the three C-terminal amino acids and the subsequent carboxyl methylation of the revealed C-terminal cysteine residue. In the present study, we investigated the function(s) of these post-translational modifications of the C-terminal region of rhoA p21 by use of the rhoA p21s purified from bovine aortic smooth muscle and rhoA p21-overexpressing Escherichia coli since the bacterial protein was not modified with a geranylgeranyl moiety. Bovine rhoA p21 bound to plasma membranes and phosphatidylserine-linked Affigel, but bacterial rhoA p21 did not bind to them. The inhibitory GDP/GTP exchange protein for rhoA p21, named GDP dissociation inhibitor (GDI), made a complex with the GDP-bound form of bovine rhoA p21 and thereby inhibited the dissociation of GDP from and the subsequent binding of GTP to it. However, rho GDI neither made a complex with the GDP-bound form of bacterial rhoA p21 nor affected these reactions of the bacterial protein. The stimulatory GDP/GTP exchange protein for rhoA p21, named GDP dissociation stimulator (GDS), stimulated the dissociation of GDP from bovine rhoA p21, but was inactive for the bacterial protein. In contrast, the GTPase activating protein for rhoA p21 is active not only for bovine rhoA p21 but also for the bacterial protein. These results suggest that the post-translational modifications of the C-terminal region of bovine rhoA p21, most presumably the geranylgeranylation, which are absent in bacterial rhoA p21, play important roles in its interaction with membranes and the stimulatory and inhibitory GDP/GTP exchange proteins but not with the GAP.     

Effect of moxifloxacin on bacterial pathogenicity factors in comparison with amoxicillin, clarithromycin and ceftriaxone

Moxifloxacin is a recent fluoroquinolone with an antibacterial spectrum encompassing both aerobic Gram-negative and Gram-positive strains, as well as anaerobic bacteria. In this study the activity of moxifloxacin against Streptococcus pneumoniae, Staphylococcus aureus, Moraxella catarrhalis, Haemophilus influenzae, Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa, and effects of subinhibitory concentrations on bacterial morphology and adhesion properties were compared with those of amoxicillin, clarithromycin and ceftriaxone. The in vitro activity of moxifloxacin against Gram-positive and Gram-negative pathogens was equal to or better than that of comparators. Subinhibitory concentrations of moxifloxacin significantly affected bacterial morphology of S. pneumoniae, M. catarrhalis, H. influenzae and P. aeruginosa, leading to formation of spherical forms and filaments. Moreover, bacterial adhesion to buccal cells and fibroblasts was reduced after treatment with 1/4 and 1/8 X MIC of moxifloxacin. In conclusion, subinhibitory concentrations of moxifloxacin remarkably interfere with some bacterial pathogenic factors, thereby contributing to its antimicrobial activity.     

血清C反应蛋白、降钙素原及髓样细胞触发受体-1对非小细胞肺癌术后肺部细菌感染的诊断价值

目的探讨血清C反应蛋白(CRP)、降钙素原(PCT)及髓样细胞触发受体-1(sTREM-1)联合检查对非小细胞肺癌(NSCLC)患者术后并发肺部细菌感染的诊断价值。方法选取实施肺癌根治性手术的NSCLC患者212例进行前瞻性研究,根据术后是否发生肺部感染分为感染组44例、非感染组168例,对比两组患者术后第1 d、术后第3 d、术后第5 d、术后第7 d的血清CRP、PCT、sTREM-1水平,绘制ROC曲线分析三项指标单用或联合应用诊断肺部细菌感染的价值。结果感染组患者的血清CRP、PCT、sTREM-1水平在术后第1 d与非感染组比较差异无统计学意义(P>0.05);感染组患者的血清CRP、PCT、sTREM-1水平在术后第3~7 d均显著高于非感染组(P<0.05);以术后第5d的结果绘制ROC曲线,血清CRP鉴别诊断肺部发生细菌感染的灵敏度84.29%、特异度74.03%、AUC值为0.790;血清PCT鉴别诊断肺部发生细菌感染灵敏度88.17%、特异度78.30%、AUC值为0.835;血清sTREM-1鉴别诊断肺部发生细菌感染灵敏度67.48%、特异度77.04%、AUC值为0.738;三项指标联合应用鉴别诊断肺部发生细菌感染灵敏度95.28%、特异度87.31%、AUC值为0.911。结论血清CRP、PCT、sTREM-1联合检测对于NSCLC患者根治术后发生肺部细菌感染具有较高的临床诊断价值。     

Cellular and molecular mechanisms of metastasis as applied to carcinomatous meningitis

Cancer cells as well as bacteria metastasize to the subarachnoidal space (SAS) causing meningitis. Primary brain tumors, although not forming distant metastases, disseminate via the cerebrospinal fluid and occupy the meninges. The multistep process of cancer or bacterial dissemination is regulated through molecular crosstalk between invaders and host cells. Such crosstalks establish invasion-promoter and invasion-suppressor complexes. In carcinomatous and bacterial meningitis, the participation of host cells is prominent since leukocytes and inflammatory cytokines are the major determinants of malignancy. We propose a model in which bacterial breakdown products activate endothelial cells, a process leading to leukocyte extravasation. This initiates a cascade of inflammatory processes opening up the blood cerebrospinal fluid barrier and producing access for new invaders.     

鼠伤寒沙门氏菌回复突变试验中通过吸光度值测定菌液浓度的方法研究

目的：研究鼠伤寒沙门氏菌回复突变试验（Ames试验）中菌液浓度和吸光度值[D（λ）值，λ为波长数值]的关系，开发通过吸光度值测定菌液浓度的方法。方法：选取Ames试验中常用的营养缺陷型鼠伤寒沙门氏菌TA102作为试验菌株，严格控制菌液扩增条件，对比分析540和600 nm波长下菌液的吸光度值的高低以确定最佳测定波长，对比分析菌株扩增0、2、4、6、8、10、12、14 h后的菌液浓度以确定最佳扩增时间。在最佳测定波长和最佳扩增时间下，测定菌液吸光度值，并通过平板菌落计数法测定菌液浓度，获得菌液浓度和吸光度值的回归方程。结果：菌株TA102的最佳测定波长为540 nm，最佳培养条件为37℃、100 r/min、10 h，菌液浓度和D（540）值的直线回归方程为y=4×10⁹x[方程中x为D（540）值；y为菌液浓度，单位为个/mL]。结论：应用上述菌液浓度和D（540）值的直线回归方程，可通过测定D（540）值实时控制菌液达到要求浓度，从而确保试验菌液的质量。     

Frequent and preferential infection of Treponema denticola, Streptococcus mitis, and Streptococcus anginosus in esophageal cancers

Multiple cancers frequently occur in the upper digestive tract. One possible explanation is that specific bacterial infection stimulates the normal epithelium to initiate inflammation and/or promotes carcinogenesis. This study was undertaken to determine which bacterial species is predominantly associated with esophageal cancer. We examined the bacterial diversity in this type of cancer and in the saliva from healthy people by using a culture-independent molecular method. Here we report the preferential and frequent infection of the oral periodontopathic spirochete Treponema denticola (T. denticola), Streptococcus mitis (S. mitis), and Streptococus anginosus (S. anginosus) in esophageal cancer from different regions of the world, and we also describe the induction of inflammatory cytokines by infection of S. anginosus and S. mitis. Our present data suggest that these three bacteria could have significant roles in the carcinogenic process of many cases of esophageal cancer by causing inflammation and by promoting the carcinogenic process, and that eradication of these three bacteria may decrease the risk of recurrence.     

Bacterial Vaginosis and Cervical Intraepithelial Neoplasia: Is there an Association or is Co-Existence Incidental?

Objectives: To determine associations, if any, of bacterial vaginosis with cervical pre-neoplastic lesions and evaluate any effects of sub-categorization of smears with bacterial vaginosis. Methods: All cervico-vaginal smears reported as positive for bacterial vaginosis over a five-year period were reviewed and sub-categorized into ‘type I (dysbacteriosis)’ and ‘type II (pure Gardenerella infection)’ smears by two cytopathologists (PS, SG). The proportion of smears with healthy flora and pre-neoplastic lesions was compared with those having bacterial vaginosis in conjunction with such changes. In addition, a comparison was also attempted between the frequencies of pre-neoplastic lesions with the two categories of bacterial vaginosis smears. Results: Bacterial vaginosis was diagnosed in 28.6% (7017 of the 24,565) of the 24,565 smears received in the Institute during the study period. Of these 7,017 smears with bacterial vaginosis, 53% (3717) were categorized as type I and 42.7% (3000) as type II by both cytopathologists. Pre-neoplastic lesions were detected in 10.2% of smears with bacterial vaginosis compared to 5.7% of those with healthy flora (P<0.0001). Of the sub-categories of bacterial vaginosis, the risk of detecting precancerous lesion was higher for type II smears (P<0.001). Conclusion: Sub-categorization of bacterial vaginosis, as performed in the Dutch coding system, may be worthwhile due to the strikingly different risk of associated preneoplasia.     

In tumors Salmonella migrate away from vasculature toward the transition zone and induce apoptosis

Motile bacteria can overcome diffusion resistances that substantially reduce the efficacy of standard cancer therapies. Many reports have also recently described the ability of Salmonella to deliver therapeutic molecules to tumors. Despite this potential, little is known about the spatiotemporal dynamics of bacterial accumulation in solid tumors. Ultimately this timing will affect how these microbes are used therapeutically. To determine how bacteria localize, we intravenously injected Salmonella typhimurium into BALB/c mice with 4T1 mammary carcinoma and measured the average bacterial content as a function of time. Immunohistochemistry was used to measure the extent of apoptosis, the average distance of bacteria from tumor vasculature and the location of bacteria in four different regions: the core, transition, body and edge. Bacteria accumulation was also measured in pulmonary and hepatic metastases. The doubling time of bacterial colonies in tumors was measured to be 16.8 h, and colonization was determined to delay tumor growth by 48 h. From 12 and 48 h after injection, the average distance between bacterial colonies and functional vasculature significantly increased from 130 to 310 μm. After 48 h, bacteria migrated away from the tumor edge toward the central core and induced apoptosis. After 96 h, bacteria began to marginate to the tumor transition zone. All observed metastases contained Salmonella and the extent of bacterial colocalization with metastatic tissue was 44% compared with 0.5% with normal liver parenchyma. These results demonstrate that Salmonella can penetrate tumor tissue and can selectively target metastases, two critical characteristics of a targeted cancer therapeutic.     

Bacterial and fungal infections in patients with the acquired immunodeficiency syndrome

Over a 14-month period, 136 episodes of bacterial and 26 episodes of fungal infection were identified from the microbiology records of 444 patients with acquired immunodeficiency syndrome (AIDS). The respective rates for infection were 31 of 100 admissions (bacterial) and 5 of 100 admissions (fungal). Contributory factors appeared to be therapy with antineoplastic agents, ganciclovir and zidovudine, resulting in neutropenia, corticosteroid therapy, and increased use of central venous catheters. Bacteria isolated most often were Staphylococcus spp., the Enterobacteriaceae, and Pseudomonas aeruginosa. Aspergillus spp. and Candida spp. were the common fungal pathogens. However, several unusual fungal organisms seem to be emerging as important pathogens and can cause disseminated infection. Appropriate and prompt antimicrobial therapy resulted in the resolution of most bacterial infections. Disseminated fungal infections were difficult to treat and responded less often.     

Effects of fluoroquinolones on bacterial adhesion and on preformed biofilm of strains isolated from urinary double J stents

The activity of levofloxacin and ulifloxacin on biofilm formation and persistence was evaluated on microorganisms isolated from urinary double-J-stents. We analyzed 51 bacterial strains and their susceptibility to different antimicrobial classes was determined. We evaluated the bacterial ability to form biofilm and the effects of different concentrations of levofloxacin and ulifloxacin on bacterial adhesion and biofilm persistence. Most of the strains were biofilm producers with no relevant difference in biofilm production at 24 or 48 hours. The fluoroquinolones were able to prevent biofilm formation, but not to eradicate the preformed biofilm. On the basis of our data we advise that antibiotic prophylaxis with fluoroquinolones may be most helpful if given at the time of stent insertion and at high dosage.     

Morphostructural damage and the inhibition of bacterial adhesiveness of Staphylococcus aureus and Moraxella catarrhalis induced by moxifloxacin

The aim of this study was to investigate the ability of moxifloxacin to interfere with the mechanism of bacterial adhesion and disrupt the morphological and structural integrity of bacteria. Three Staphylococcus aureus and three Moraxella catarrhalis strains were grown in the presence of 1/2-1/128 minimum inhibitory concentration (MIC) serial dilutions and incubated with human epithelial cells. A significant decrease in adhesion was observed from 1/2 MIC to 1/64 MIC for S. aureus, and from 1/2 MIC to 1/16 MIC for M. catarrhalis. The use of atomic force microscopy, a new technique capable of revealing surface structures in three-dimensional detail and at very high resolution, showed the rapid onset and time course of the sequence of disruptive morphostructural events following the incubation of both S. aureus and M. catarrhalis with sub-MICs of moxifloxacin. Our findings suggest that less than conventional MIC moxifloxacin concentrations may be effective in reducing bacterial adhesiveness and structural integrity on which the maintenance of bacterial activity depends.     

晚期肺癌肺部感染细菌培养及药敏实验

目的:探究晚期肺癌肺部感染患者的细菌感染及药敏实验情况。方法:选择2013年3月-2014年7月收治的100例晚期肺癌并发肺部感染患者进行药敏实验研究,分析细菌感染以及耐药状况。结果:100例晚期肺癌并发肺部感染患者痰液标本中的细菌培养结果显示,共分离出150株病原菌,革兰氏阴性菌77株,比例51.3%,占据首位,其次是真菌53株,比例35.3%,革兰氏阳性菌20株,占据比例最小。革兰氏阴性菌中比例较大的有铜绿假单胞菌、鲍氏不动杆菌、肺炎克雷伯菌以及大肠埃希氏菌等;真菌中比例最大的是白色念珠菌,其次是热带念珠菌与光滑念珠菌;革兰氏阳性菌中比例最大的是金黄色葡萄球菌,为6.7%;通过对铜绿假单胞菌、鲍氏不动杆菌、肺炎克雷伯菌、大肠埃希氏菌、金黄色葡萄球菌以及主要真菌进行药敏实验发现,不同的细菌或真菌对不同的抗菌药物的耐药性不同。结论:晚期肺癌患者发生肺部感染,革兰氏阴性菌比例占据首位,其次是真菌,革兰氏阳性菌比例最小。药敏实验显示不同的细菌或真菌对不同的抗菌药物的耐药性不同,需合理使用抗菌药物。     

An open randomized comparative trial of efficacy and safety of selective alpha-adrenoblocker setegis (terazosin) in therapy of patients with chronic bacterial prostatitis

An open randomized comparative trial of setegis (terazosine) has shown good subjective and objective results in patients with chronic bacterial prostatitis. The drug is well tolerated and produces insignificant side effects. It is also demonstrated that combined therapy with alpha-adrenoblockers is more effective that monotherapy with antibacterial drugs in patients with bacterial prostatitis.     

Lipopolysaccharides increase the amount of CXCR4, and modulate the morphology and invasive activity of oral cancer cells in a CXCL12-dependent manner

Recently, it has been reported that bacterial infections play an important role in the development of cancers of the upper aero digestive tract. To examine the influence of bacterial infections on oral cancer, human oral carcinoma T3M-1 cells were treated with lipopolysaccharide (LPS) for 24 h as a model of infection. The LPS treatment increased the mRNA expression of CXCR4 and invasiveness in T3M-1 cells stimulated with CXCL12.The Rho family of small guanosine triphosphatases regulates the dynamics of the actin cytoskeleton that underlie cellular functions such as cell shape changes, migration and polarity. In T3M-1 cells treated with LPS and stimulated with CXCL12, Rac and Cdc42 were activated and caused an increase in the development of filopodia. The present findings suggest that bacterial infections enhance the invasiveness of T3M-1 cells via CXCL12/CXCR4 interaction and Cdc42-activation. Furthermore, filopodia are critical to this process.     

Salmonella typhimurium lacking ribose chemoreceptors localize in tumor quiescence and induce apoptosis

The effectiveness of most chemotherapeutics is limited by their inability to penetrate deep into tumor tissue and their ineffectiveness against quiescent cells. Motile Salmonella typhimurium, which are specifically attracted to compounds produced by quiescent cancer cells, could overcome this therapeutic barrier. We hypothesized that individual chemoreceptors target S. typhimurium to specific tumor microenvironments. To test this hypothesis, we used time-lapse fluorescent microscopy and tumor cylindroids to quantify the accumulation of chemotaxis machinery knockouts, including strains lacking individual cell surface chemoreceptors, chemotaxis signal transduction pathway enzymes, and the flagella and motor assemblies. To measure the extent of apoptosis induced by individual bacterial strains, caspase-3 activity was measured as a function of time. Our results showed how chemoreceptors directed bacterial chemotaxis within cylindroids: the aspartate receptor initiated chemotaxis toward cylindroids, the serine receptor initiated penetration, and the ribose/galactose receptor directed S. typhimurium toward necrosis. In addition, strains lacking proper flagella constructs, signal transduction proteins, or active motor function did not chemotax toward tumor cylindroids, indicating that directed chemotaxis is necessary to promote accumulation in tumors. By deleting the ribose/galactose receptor, bacterial accumulation localized to tumor quiescence and had a greater individual effect on inducing apoptosis than wild-type S. typhimurium. This new understanding of the mechanisms of Salmonella migration in tumors will allow for the development of bacterial therapies with improved targeting to therapeutically inaccessible regions of tumors.