Potential Risk of Transmission of Escherichia coli and Salmonella spp. Infections by the Musca domestica Fly and the Periplaneta americana Cockroach in the City of Cotonou (South Benin)

Background: The occurrence of bacterial infections sometimes involves synanthropic flies and cockroaches, as mechanical vectors of pathogenic microorganisms. The aim of this study was to identify the different species of flies and cockroaches that cohabit with humans in the city of Cotonou and determine the contribution of Musca domestica and Periplaneta americana in the transmission of bacteria responsible for infections in humans. Methods: Capture sessions during the day for flies and at night for cockroaches were carried out in 4 arrondissements of the city of Cotonou. The insects collected were transported to the Center of Research Entomological of Cotonou for identification, then sent to the Section Hygiene of Water and Food for microbiological analysis, enumeration and testing for human pathogenic bacteria. Results: A total of 351 flies and 26 cockroaches were collected at the sites, including two synanthropic species belonging to two families each. Musca domestica and Periplaneta americana were the most abundant species found after identification in the city of Cotonou. Thermo-tolerant coliforms and Escherichia coli were found on all specimens at varying concentrations. Salmonella spp. bacteria were identified in the fly population from the Dantokpa dump. Conclusion: Flies and cockroaches can transmit microorganisms to humans. The presence of Salmonella spp. among the specimens revealed that infections frequently caused by contaminated food or water are also transmitted to humans by flies. The presence of these germs on flies and cockroaches represents a potential risk of mechanical transmission to humans. It is, therefore, essential to continue investigations in order to assess the species of bacteria propagated, improve control strategies against these troublesome insects and adopt better hygiene conditions for better living.

Morphological Changes of Hemocytes of Musca domestica Larva in vitro Infected by Escherichia coli

[Objective] The research aimed to observe the effects of Escherichia coli infection on the morphology of hemocytes of the 3rd stage larva of Musca domestica in vitro and understand the hemocytes types that take part in the cell immunity of Musca domestica larval.[Method] The hemcytes of the 3rd stage larva of Musca domestica were cultured in vitro and the hemocyte morphology was observed about 2,4,6,8 h after culture in vitro.After Escherichia coli were injected into the hemocytes of the 3rd stage larva of Musca domestica in vitro,the morphology changes of hemocytes were observed at different time after infection.[Result] The hemocytes of of the 3rd stage larva of Musca domestica was divided into five types about 2 h after hemoculture.The hemocytes partly adherence was seen about 6 h after hemoculture.The vacuolation and morpholysis was found in plasmatocytes after being infected by E.coli and a great quantity bacterium were gathered around granulocyte,but the morphology changes of hemocytes were not found in the prohemocyte,shprulocyte and oenocytoid.[Conclusion] The plasmatocyte and granulocyte were primary participants of the cell immunity of Musca domestica larval,but the prohemocyte,sphrulocyte and oenocytoid do not participate in the cell immune reactions.

Musca domestica cecropin协同头孢曲松钠抗鼠伤寒沙门氏菌及生物被膜作用研究

目的研究家蝇抗菌肽cecropin(Musca domestica cecropin,MDC)和头孢曲松钠的协同抗鼠伤寒沙门氏菌作用及抗生物被膜作用。方法采用微量肉汤稀释法、棋盘法、结晶紫染色等方法研究2种药的协同抗菌效果和抗生物被膜作用;用荧光染色、流式细胞术(FCM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)观察联合用药的抗菌机制。结果棋盘法计算FIC指数为0.218,结果表明MDC与头孢曲松钠之间存在协同抗菌作用;96孔板法联合结晶紫染色等结果显示联合用药对鼠伤寒沙门氏菌初始生物被膜具有抑制作用,并且能协同破坏成熟生物被膜;采用荧光染色与流式细胞术考察细胞膜的完整性,同浓度下MDC组对细胞膜的破坏为47%,头孢曲松钠组为30%,联合组能破坏89%的细胞膜。扫描电子显微镜和透射电子显微镜观察到联合用药组中细菌细胞壁破损,细胞膜不完整,胞质内容物坏死溶解导致细胞肿胀破裂,药效强于单独用药组。结论体外联合使用抗菌肽MDC与头孢曲松钠具有协同抗鼠伤寒沙门氏菌及生物被膜的作用。

不同颜色对比对舍蝇(Musca domestica vicina)引诱效果的比较

舍蝇对目标的视觉反应主要与目标/背景间颜色的对比有关,并且偏爱黑色背景.在黑色背景下,观察了目标颜色分别为白、暗红、黄、黑、绿、蓝、玫瑰红时不同颜色对比对舍蝇的引诱效果,发现2种颜色组合(目标/背景)与白/黑组合对舍蝇的引诱效果之间存在显著差异(P<0.05):暗红/黑、黄/黑>

不同诱导条件下家蝇(Musca domestica)三龄幼虫免疫相关基因的表达研究

旨在研究在不同诱导条件下家蝇三龄幼虫先天性免疫基因的表达情况。采用冷刺激、热刺激及革兰氏阴性菌、革兰氏阳性菌和真菌注射诱导12 h后提取家蝇三龄幼虫总RNA。根据GenBank公布的家蝇磷酸甘油醛脱氢酶(GAPDH)基因、攻击素(Attacin)、天蚕素(Cecropin)、防御素(Defensin)、双翅肽(Diptericin)、溶菌酶(Lysozyme)、热休克蛋白(Heat shock protein,HSP)及家蝇抗真菌肽(MAF-1)基因序列进行RT-PCR反应,以GAPDH基因为内参照,分析在不同诱导条件下家蝇三龄幼虫先天性免疫基因的表达情况。结果显示,不同条件诱导下,家蝇免疫相关基因表达显现较大差异,微生物诱导比物理刺激诱导后家蝇免疫相关基因表达水平高;真菌、阳性菌诱导后家蝇免疫相关基因表达量最高,阴性菌次之;冷刺激诱导最低。微生物及物理刺激均能激活家蝇的免疫系统,在不同条件刺激下,家蝇幼虫机体免疫应激反应不同。

舍蝇(Musca domestica vicina)幼虫分泌物及血淋巴活性研究

首次报告舍蝇幼虫分泌物具有抗根结线虫 (Meloigyne sp.)活性 ,同时未经外源诱导的舍蝇幼虫 ,其分泌物和血淋巴提取液也有抗菌活性 .IEF- PAGE电泳分析表明 ,幼虫分泌物和血淋巴提取液呈微酸性至弱碱性 ,前者电泳带为 6条 ,后者 7条 。

3个家蝇(Musca domestica L.)种群及其乙酰胆碱酯酶对杀虫剂的敏感性研究

采用药膜法测定了3个家蝇(Musca domestica L.)种群对12种有机磷和氨基甲酸酯类杀虫剂的敏感性,采用酶动力学方法测定了不同杀虫剂对家蝇乙酰胆碱酯酶(acetylcholinesterase,AChE)的体外抑制作用。结果表明,Org种群对抗蚜威(LC50=18.654mg·L-1)、速灭威(LC50=17.387mg·L-1)比FAAS种群(LC50分别为26.011、26.632mg·L-1)更为敏感,FAAS种群对仲丁威(LC50=8.271mg·L-1)比Org种群(LC50=12.539mg·L-1)更为敏感;除了与乙酰甲胺磷无显著差异外,FZ种群对其他供试杀虫剂的敏感性均显著低于Org种群和FAAS种群(95%CI没有重叠)。Org种群AChE对二嗪磷(IC50=0.025mg·L-1)比FAAS种群AChE(IC50=0.048mg·L-1)更为敏感,FAAS种群AChE对辛硫磷(IC50=0.021mg·L-1)比Org种群AChE(IC50=0.026mg·L-1)更为敏感;FZ种群AChE对所有供试杀虫剂的敏感性均显著低于Org种群和FAAS种群AChE(95%CI没有重叠)。

北京地区家蝇(Musca domestica L.)乙酰胆碱酯酶(AChE)动力学性质研究

实验结果表明,在北京地区家蝇种群以及实验室敏感系和用残杀威选育的抗性种群中,其乙酰胆碱酯酶(AChE)对乙酰硫代胆碱的米氏常数(K_m)值最大相差4倍,最大反应速度(V_(max))相差近8倍。敌百虫与家蝇AChE的双分子速率常数(Ki)值,农大敏感品系(SA)为7.41×10~4(L/mol,分^(-1)),而北京宜武种群AChE的Ki值仅为5.13×10~2,相差达144倍,崇文、密云和回龙观种群AChE的Ki值和SA品系相比,差异也在10倍以上,说明北京地区家蝇AChE对敌百虫的敏感度明显降低了。这些家蝇种群的AChE对敌百虫的亲合力(解离常数Kd)和SA品系相比,宜武种群相差近2890倍,其它种群也相差50倍以上,而磷酸化速率常数(k_2)则相差不大,说明北京地区家蝇对敌百虫的敏感度降低是由于解离常数—Kd值的改变造成的。

Studies on the Antimicrobial Activity of Chitooligosaccharides from Housefly Larvae, Musca domestica vicina Macquart(Diptera: Muscidae)

The inhibition effect of chitooligosaccharides from housefly larvae on pathogens ofcrops seeds, fruits or vegetables was studied and the main factors influencing theantimicrobial activity of chitooligosaccharides were also investigated. It was foundthat chitooligosaccharides from housefly larvae had wide spectrum fungistasis. It canstrongly inhibit the development of 31 kinds of plant pathogenic fungi such as corticiumrolfsii Saccardo. The results indicated that the degree of deacelylation (DD) or theaverage molecular weight(MW)of chitooligosaccharides were related to the antimicrobialactivity. The antimicrobial activity increased with the rising of DD or the declining ofMW. Pot culture results showed that chitooligosaccharide could enhance the rate ofgermination and emergence of the seeds of maize, wheat and cotton. Chitooligosaccharidehad certain effect on corn southern leaf blight caused by Helminthosporium maydis.

Proteomic Analysis of the Peritrophic Matrix from the Midgut of Third Instar Larvae,Musca domestica

Objective To better comprehend the molecular structure and physiological function of the housefly larval peritrophic matrix （PM）, a mass spectrometry approach was used to investigate the PM protein composition. Methods The PM was dissected from the midgut of the third instar larvae, and protein extracted from the PM was evaluated using SDS-PAGE. A 1D-PAGE lane containing all protein bands was cut from top to bottom, the proteins in-gel trypsinised and analysed via shotgun liquid chromatography- tandem mass spectrometry （LC-MS/MS）. Results In total, 374 proteins, with molecular weights varying from 8.225, kD to 996.065 kD and isoelectric points ranging from 3.83 to 11.24 were successfully identified, most identified proteins were mainly related to immunity, digestion, nutrient metabolism and PM structure. Furthermore, many of these proteins were functionally associated with pattern binding, polysaccharide binding, structural constituent of peritrophic membrane and chitin binding, according to Gene Ontology annotation. Conclusion The PM protein composition, which provides a basis for further functional investigations of the identified proteins, will be useful for understanding the housefly larval gut immune system and may help to identify potential targets and exploit new bioinsecticides.

一类具有时空时滞的Musca domestica苍蝇模型的行波解的存在性

通过单调迭代和上、下解技术,研究了一类具有时空时滞的Musca domestica苍蝇模型行波解的存在性,证明了当时滞充分小时,方程具有连接两个平衡点的单调的行波解。

Inhibition of Na^+,K^+-ATPase in Housefly (Musca domestica L.) by Terpinen-4-ol and Its Ester Derivatives

To reveal the insecticidal mechanism of terpinen-4-ol, the activity of Na＋,K＋-ATPase in insects tested were determined in vivo and in vitro. The results showed that terpinen-4-ol and its ester derivatives had strong contact activity to housefly and the contact toxicities of its derivatives except Z3 were all superior or equivalent to terpinen-4-ol. All the 7 compounds had strong inhibition towards activity of Na＋,K＋-ATPase. With poisoning symptom exacerbating, the inhibition rates were gradually increased. In vitro, the IC50 of terpinen-4-ol, Z1, Z2, Z4, Z5, and Z6 was 155.89, 197.98, 96.02, 121.36, 124.85, and 153.74 μg mL% respectively. There was well correlation between the LDs0 of terpinen-4-ol derivatives to housefly and the IC50 of terpinen-4-ol derivatives to Na＋,K＋-ATPase in housefly. In conclusion, Na＋,K＋-ATPase was likely the target of terpinen-4-ol against insects.

具离散时滞的扩散Musca domestica苍蝇模型的波前解

本文考虑了一类具离散时滞的扩散Musca domestica苍蝇模型,利用上、下解方法及单调迭代技巧得到了这类模型波前解存在的充分条件。结果表明,当时滞充分小时,该模型连结两一致静态解的波前解仍能得以保持。

具有耗散项的Musca domestica苍蝇模型波前解的持续性

对具有耗散项的Musca domestica苍蝇模型的波前解进行研究,在耗散充分小的情况下,运用几何奇异摄动理论证明其波前解是持续的,即如果开始时种群数量非零,那么它最终将稳定于一个常态。

Larvicidal, pupicidal and oviposition deterrent activities of essential oils from Umbelliferae plants against house fly Musca domestica

To evaluate the toxicity against house fly Musca domestica L.(M. domestica)-larvicidal, pupicidal, and oviposition deterrent activities of essential oils(EOs) from five plants: Anethum graveolens L.(A. graveolens), Centratherum anthelminticum L.(C. anthelminticum), Foeniculum vulgare Mill.(F. vulgare), Pimpinella anisum L.(P. anisum), and Trachyspermum ammi L.(T. ammi) Sprague. Methods: Dipping, topical and dual-choice assays were performed by using each EO at three concentrations(1%, 5% and 10%) as well as cypermethrin(positive control) and ethyl alcohol(negative control) in order to determine their larvicidal, pupicidal and oviposition deterrent activities against M. domestica mortality rate and morphogenic abnormality of larvae and pupae were recorded after 3 and 10 days of incubation. Oviposition deterrent activity was recorded for 5 consecutive days from the beginning of the assay. Results: All EOs at the highest concentration(10%) were highly effective in oviposition deterrent with 100% effective repellency and an oviposition activity index of-1.00. Ten percent of F. vulgare oil exhibited the highest efficacy against the larvae with 89.6% mortality rate at 3 days and an LC50 value of 5.4%. Ten percent of A. graveolens and T. ammi oils showed the highest efficacy against the pupae with 100% mortality and an LC50 value ranging from 1.81%-2.24%. Conclusions: These results indicate that F. vulgare, A. graveolens and T. ammi EOs are effective larvicidal, pupicidal and oviposition deterrent agents against house fly M. domestica.

DIFFERENCES IN SUSCEPTIBILITY TO INSECTICIDES BETWEEN ADULTS AND LARVAE OF HOUSEFLY, MUSCA DOMESTICA(L.)

In this paper,we reported the differences in susceptibility to insecticides between adults and larvae of housefly, Musca domestica (L.),and the mechanisms for the differences.The larvae of housefly were much more tolerant to insecticides than the adults,and the tolerance ratio to cyhalothrin was as high as 205.5 for susceptible strain.Mechanism studies showed that higher GST activity was associated with higher insecticide tolerance in the larvae.The co\|toxicity coefficient of the mixture of cyhalothrin and methylene dithiocyanate(4∶1) on pyrethroid\|resistant houseflies was 188.

Purification and Molecular Identification of an Antifungal Peptide from the Hemolymph of Musca domestica （housefly）

Antibacterial and antifungal peptides found in houseflies （Musca domestica） in large number are indispensable components of its immune defense mechanism. In this study the anterior tip of the larvae of housefly was cut off with a pair of fine scissors and hemolymph was collected and exuded in an ice-cold test tube. From the hemolymph an antifungal substance was isolated by solid-phase extraction combined with reverse phase-high performance liquid chromotography （RP-HPLC） and named as Musca domestica antifungal peptide-1 （MAF-1）. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis （SDS-PAGE） showed its molecular weight was 17 kDa. UV absorption spectra revealed that this antifungal substance possessed the characteristics of protein peptides. Analysis by fingerprint-identification and tandem mass spectrometry suggested MAF-I was an unknown protein. Edman degradation identified the sequence of 30 amino acids of its N-terminal which matched no peptide in the MASCOT search database, indicating MAF-1 was a novel insect antifungal peptide. Mass spectrometry showed the precise molecular weight of MAF-1 was 17203.384 Da. Its isoelectric point was acidic.

Molecular characterization and expression analysis of a chicken-type lysozyme gene from housefly (Musca domestica)

Lysozymes can hydrolyze bacteria and play an important role in animal digestion and innate immunity. The cDNA of a chicken-type lysozyme gene （Mdlys） was cloned from housefly （Musca domestica）. The 484 bp full-length cDNA contains a 426 bp open reading frame （ORF） that encodes MdLys of 141 amino acids. Phylogenetic analysis indicated that the MdLys was similar to chicken-type lysozymes. Spatio-temporal expression of Mdlys was analyzed by RT-PCR. The Mdlys transcript can be detected in both midgut and fat body and was expressed at a relatively lower level at the embryo stage. Mdlys mRNA was upregulated 2 h post bacterial challenge, maintained for 2 to 6 h, and slightly declined from 12 to 24 h post-injection. Western blot analysis showed that MdLys was highly expressed in midgut and was also detected in the hemolymph and fat body. MdLys expression was slightly increased in midgut after challenging with Escherichia coli or Staphylococcus aureus. Its expression was also slightly increased in the fat body after challenging with S. aureus, but no obvious change occurred after E. coli challenge. MdLys expression in the hemolymph was not affected by bacterial challenge. In the developmental stages, MdLys expression levels had no obvious change from the first instar to the pupae stage. There was also no variation under 24 h starvation stress. Recombinant MdLys displayed inhibitory activity against Gram-negative and Gram-positive bacteria. Together, these results suggest that MdLys may play an important role in the innate immunity of houseflies.

Campylobacterjejuni in Musca domestica： An examination of survival and transmission potential in light of the innate immune responses of the house flies

The house fly, Musca domestica, has been implicated as a vector of Campy- lobacter spp., a major cause of human disease. Little is known whether house flies serve as biological amplifying hosts or mechanical vectors for Campylobacterjejuni. We in- vestigated the period after C. jejuni had been ingested by house flies in which viable C. jejuni colonies could be isolated from whole bodies, the vomitus and the excreta of adult M. domestica and evaluated the activation of innate immune responses of house flies to ingested C. jejuni over time. C. jejuni could be cultured from infected houseflies soon after ingestion but no countable C. jejuni colonies were observed 〉 24 h postingestion. We detected viable C. jejuni in house fly vomitus and excreta up to 4 h after ingestion, but no viable bacteria were detected 〉 8 h. Suppression subtractive hybridization identi- fied pathogen-induced gene expression in the intestinal tracts of adult house flies 4-24 h after ingesting C. jejuni. We measured the expression of immune regulatory （thor, JNK, and spheroide） and effector （cecropin, diptericin, attacin, defensing, and lysozyme） genes in C. jejuni-infected and -uninfected house flies using quantitative real time PCR. Some house fly factor, or combination of factors, eliminates C. jejuni within 24 h postingestion. Because C. jejuni is not amplified within the body of the housefly, this insect likely serves as a mechanical vector rather than as a true biological, amplifying vector for C. jejuni, and adds to our understanding of insect pathogen interactions.

Studying the ＂fly factor＂ phenomenon and its underlying mechanisms in house flies Musca domestica

The ＂fly factor＂ was first discovered 〉60 years ago and describes the phe- nomenon that food currently or previously fed on by flies attracts more foraging flies than the same type and amount of food kept inaccessible to flies. Since then, there has been little progress made to understanding this phenomenon. Our objectives were （i） to demonstrate the existence of the fly factor in house flies, Musca domestica and （ii） to study underlying mechanisms that may cause or contribute to the fly factor. In 2-choice laboratory bioassays, we obtained unambiguous evidence for a fly factor phenomenon in house flies, in that we demonstrated that feeding flies are more attractive to foraging flies than are nonfeeding flies, and that fed-on food is more attractive to foraging flies than is ＂clean＂ food. Of the potential mechanisms （fly excreta, metabolic output parameters [elevated temperature, relative humidity, carbon dioxide]）, causing the fly factor, fly feces, and regurgitate do at- tract foraging flies but none of the metabolic output parameters of feeding flies does. Even though feeding flies produce significantly more CO2 than nonfeeding flies, elevated levels of CO2 have no behavior-modifying effect on flies. Preferential attraction of house flies to fly feces and regurgitate indicates that the flies sense airborne semiochemicals emana- ting from these sources. Hypothesizing that these semiochemicals are microbe-produced, future studies will aim at isolating and mass producing these microbes to accumulate semiochemicals for identification.