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1.
    
This work investigated the prevalence of Escherichia coli O157:H7 and the antibiotic susceptibility, genetic diversity and virulence genes of isolated strains from four beef slaughter plants in China. A total of 510 samples (feces, hide, carcasses and raw meat) were tested for E. coli O157:H7 using enrichment, immunomagnetic separation, and plating on selective media. The prevalence of E. coli O157:H7 in the feces, hide, pre-evisceration carcass, post-evisceration carcass, post-washing carcass, chilled carcass, and raw meat samples was 1.43%, 1.43%, 0%, 0%, 0%, 1.25%, and 0%, respectively. Multiplex PCR assays were used for serotype confirmation and virulence gene detection. stx2, eaeA and EHEC-hlyA genes were present in all six of the strains, and the stx1 gene was not present. Fluorescence amplified fragment length polymorphism (FAFLP) was used to determine the genetic diversity of E. coli O157:H7 and revealed a high similarity between the strains isolated from feces and those isolated from carcasses. None of the isolated strains were found to be resistant to sixteen commonly used antimicrobial agents. The results of this study indicate that although E. coli O157:H7 contamination in the Chinese beef industry is sporadic and not as common as reported in other counties, all of the isolates contained three major virulence genes, presenting a high risk of disease for humans. The current research provides baseline information on E. coli O157:H7 prevalence and character profiles in Chinese beef-processing plants that can be used for future studies.  相似文献   

2.
    
The objective of this study was to investigate the prevalence and characteristics of Listeria monocytogenes isolated from Chinese food, including frozen dumplings, flavored raw meat, roasted meat, braised meat, and a cold vegetable dish with sauce. A total of 900 food samples were collected from supermarkets, open-air markets, and delicatessens in three large cities in the central area of China to examine the presence of L. monocytogenes; 21 (2.3%) of the samples were positive for this pathogen. Among the different samples, braised meat showed the highest L. monocytogenes detection rate (4.4%). Samples obtained from delicatessens showed a much higher L. monocytogenes contamination rate (8.3%) than those from open-air markets (6.7%) or supermarkets (0%). Multilocus sequence typing (MLST) analysis indicated that the 21 bacterial isolates belonged to 12 ST subgroups. ST5 was the largest and contained 7 isolates (33.3%); it was followed by ST474, ST121 and ST9 (each containing 2 isolates [10.5%]). Antibiotic susceptibility analysis showed that the 21 L. monocytogenes isolates were thoroughly resistant to cefoxitin but highly susceptible to doxycycline and ciprofloxacin. The presence of 10 virulence genes was evaluated by PCR, which showed that inlA, inlC, inlJ, prfA, hlyA, and plcB were present in all isolates and that inlB, actA, plcA and iap were present in 71.4–90.5% of the isolates. This study provides a useful reference for risk assessment and control of L. monocytogenes contamination in Chinese food and for the treatment of clinical listeriosis.  相似文献   

3.
    
Shiga toxin-producing Escherichia coli (STEC) have caused numerous foodborne outbreaks. Compared with the most well-known STEC E. coli O157:H7, importance of non-O157 STEC has been underestimated and they have gained far less attention till increasing outbreaks recently. Using natural plant materials as antimicrobial agents is a heated area. Therefore in this study, Cinnamomum cassia, a widely used spice in cuisine, was tested for its antibacterial efficacy on CDC “top six” non-O157 STECs including O26, O45, O103, O111, O121, O145. Gas chromatography-mass spectrometry analysis showed that the major component of C. cassia oil was cinnamaldehyde (59.96%). The disk diffusion assay indicated that 20 μL 4% (v/v) C. cassia oil per disk resulted in inhibition zones of 15.0 mm, 18.5 mm, 15.7 mm, 19.3 mm, 18.8 mm, and 25.3 mm for O26:H11, O45:NM, O103:H2, O111:H2, O121:H19, and O145:NT, respectively. Minimum inhibitory concentration for all tested non-O157 STECs were 0.025% (v/v). Minimum bactericidal concentration was strain dependent, which was 0.05% (v/v) for O26:H11, O121:H19, O145:NT, while 0.1% (v/v) for O45:NM, O103:H2 and O111:H2. Growth kinetics showed that at the low inoculation of approximate 2.5 × 105 CFU/mL, C. cassia oil at the concentration of 0.01875% (v/v) completely inhibited the growth of O26:H11 and O145:NT for at least 24 h, and increased the duration of lag phase of O45:NM, O103:H2, O111:H2, O121:H19 by18, 12, 6, and 16 h, respectively. Including 0.025% (v/v) C. cassia oil completely inhibited the growth of all tested non-O157 STECs for at least 24 h. At high inoculation of 5 × 106 CFU/mL, inhibition effect of C. cassia oil decreased. Death curve showed that including as low as 0.05% (v/v) C. cassia oil could kill non-O157 STECs. 0.1% (v/v) C. cassia oil showed bactericidal effects on all tested non-O157 STECs within 15 min. C. cassia oil at the concentration of 0.15% (v/v) killed all O26:H11, O121:H19 and O145:NT within 30 min, while O45:NM, O103:H2 and O111:H2 at 120, 60, and 60 min, respectively. In conclusion, C. cassia oil can effectively inhibit the growth of non-O157 STECs at concentration as low as 0.025% (v/v). Our data suggest that C. cassia oil has the potential to be used as a natural antibacterial agent in food industry.  相似文献   

4.
    
The goals of this study were to assess the prevalence, antimicrobial susceptibility and the presence of virulence genes of arcobacters recovered from edible bivalve molluscs. A total of 106 samples (21 clams, 18 mussels, 20 oysters, 20 razor clams, 11 scallops and 16 surf clams) were analysed by culture between 2010 and 2013. The obtained colonies were identified by multiplex PCR and PCR-RFLP and genotyped by ERIC-PCR. Furthermore, nine putative virulence genes (cadF, ciaB, cjl349, irgA, hecA, hecB, mviN, pldA and tlyA) were assessed by PCR and the antimicrobial resistance was tested by the dilution agar method. The global prevalence was 40.5%, with the highest value in surf clams (87.5%) followed by razor clams (65.0%), mussels (33.3%), clams (23.8%), scallops (18.0%) and oysters (15.0%). The most commonly found species was Arcobacter butzleri (62%) followed by Arcobacter cryaerophilus (21%), Arcobacter skirrowii (16%) and Arcobacter defluvii (1%). A high resistance was found to nalidixic acid and ampicillin, while the predominant detected virulence genes were mviN (83.8%), ciaB (82.8%) and tlyA (72.7%). Our results indicate a high prevalence of arcobacters in shellfish and the pathogenic potential of the recovered isolates suggests that this type of food could be a plausible transmission route of virulent strains to humans.  相似文献   

5.
    
The aim of this study was to investigate the occurrence of Campylobacter spp. in poultry meat available in retail stores in the northern part of Poland during a five-year period (2009–2013). A total of 742 poultry meat samples were collected from butcher shops and supermarkets including the following types of samples: chicken breast filets (n = 133), turkey breast filets (n = 112), chicken wings (n = 135), chicken leg quarters (n = 128), chicken drumsticks (n = 115), and chicken giblets (n = 119).The results indicated that 41.6% of the samples were positive for Campylobacter spp., and Campylobacter jejuni was predominant in this study. The prevalence of Campylobacter spp. changed during the study period, decreasing from 60.2% in 2009 to 32% in 2013.The characterization of the isolates revealed a high prevalence of Campylobacter virulence genes. All Campylobacter spp. isolates from poultry meat contained the cadF gene, which is responsible for adherence. The flaA gene, which is involved in motility, was present in all C. jejuni and Campylobacter coli strains. The cdtB, which is associated with toxin production, was present in 93.3% of C. jejuni strains and 89.6% of C. coli strains. The iam gene, which is associated with the invasiveness of Campylobacter spp., was predominant in C. coli strains (95.6%) compared to C. jejuni strains (84.5%).Resistance to four antimicrobials was also examined. The prevalence of resistance among the obtained C. jejuni and C. coli isolates was as follows: ciprofloxacin (62.8% and 72.2%, respectively), tetracycline (42.3% and 42.6%, respectively), erythromycin (3% and 1.7%, respectively) and azithromycin (1%). Multidrug resistance was more frequent among C. jejuni isolates (29.8%) than among C. coli isolates (18.2%).In conclusion, the results of this study demonstrated the importance of poultry meat as a source of Campylobacter spp., especially macrolide-resistant strains. The trend of decreasing Campylobacter spp. occurrence in retail poultry meat in this region of Poland requires further investigation, and monitoring.  相似文献   

6.
    
This work investigated the prevalence of Salmonella, the serotypes and antibiotic resistance of the isolated strains from four beef processing plants of China. The prevalence of Salmonella in hide (n = 70), feces (n = 70), pre-evisceration carcass (n = 70), post-evisceration carcass (n = 70), post-washing carcass (n = 70), chilled carcass (n = 80), and raw meat (n = 80) samples was 20.0%, 18.6%, 1.4%, 1.4%, 2.9%, 1.3%, and 1.3%, respectively. Among the four plants, there were significant differences in the prevalence of Salmonella on hides and in feces. During the processing, Salmonella was significantly reduced after hide removal. Seven serotypes of Salmonella were identified among the eighty-three isolates. Salmonella Agona was the dominant serotype (p < 0.05, 53.0%), followed by Salmonella Senftenberg (16.9%), Salmonella Meleagridis (10.8%), and Salmonella Derby (9.6%). None of the isolated strains were found to be resistant to sixteen commonly used antimicrobial agents. The results of this study indicate that Salmonella contamination is common in samples along the production line, with S. Agona as dominant serotype. Specific measures should be taken to prevent and/or treat Salmonella contamination in corresponding products in Chinese beef processing plants. Furthermore, the current research might provide baseline information of Salmonella prevalence profile in Chinese beef processing plant, which could be used for the future study.  相似文献   

7.
Yersinia enterocolitica is an important food-borne enteropathogen that causes gastrointestinal syndromes. The aims of this study were to identify Y. enterocolitica in food samples in China, and to assess the pathogenic potential and antimicrobial resistance, and to characterize the genotypes of the isolates. From July 2011 to May 2014, a total of 2320 food samples were obtained, and 47 (2.03%) were found positive for Y. enterocolitica, while 706 retail-level ready-to-eat products and 249 vegetable samples were negative. A total of 58 Y. enterocolitica strains were isolated. All isolates belonged to biotype 1A, and the primary serotype was O:8. All strains lacked the ail, virF, ystA, and ystC virulence genes, but harbored the ystB, fepD, ymoA, fes, and sat genes. All 58 strains were sensitive to kanamycin and sulfonamide, but were resistant to two or more antibiotics. Most of the strains expressed the β-lactamase genes; the presence of blaA and blaB was detected in 97% and 100% of isolates, respectively. Many strains were resistant to trimethoprim/sulfamethoxazole (79.3%), ampicillin (91.4%), and cephalothin (91.4%). The 58 strains were grouped into three clusters and one singleton by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) at a similarity coefficient of 70%, and each cluster was largely organized by geographical region. This study provides a valuable accounting of the prevalence of Y. enterocolitica from a nationwide survey of foods in China, and highlights the seasonal effects of Y. enterocolitica prevalence in foods in China for the first time.  相似文献   

8.
The aim of this study was to evaluate the prevalence of Cronobacter spp. in indigenous infant flours sold in public health care centres within Abidjan (Côte d'Ivoire) and to assess their antimicrobial susceptibility. A total of 133 samples of cereal-based indigenous flours were collected from randomly selected public health care centres within Abidjan and subjected to Cronobacter spp. isolation and identification by using biochemical tests, API 20E system and duplex PCR detection. Subsequently, the antimicrobial susceptibility test was performed for confirmed isolates. Our results showed that the samples contained Cronobacter spp. in addition to 18 other Enterobacteriaceae species among with Enterobacter cloacae (21.84% of total isolates) and Pantoea spp. (14.08%) were the most frequently isolated species. Ninety samples (67.7%) were contaminated by Enterobacteriaceae and 16 samples (12.0%) by Cronobacter spp. Gentamycin, colistine, tobramycin, ticarcillin–clavunate and trimethoprim–sulphamethoxazole remained the most potent antimicrobial agents against Cronobacter spp. while resistance occurred most often to nalidixic acid (87.5%), aztreonam (75.0%), amoxicillin–clavunate (68.7%), ampicillin (62.5%) and cefotaxime (62.5%). Twelve resistant phenotypes were defined among Cronobacter spp. isolates and the most common phenotype (25% of isolates) was amoxicillin–clavunate/cefotaxime/aztreonam/tetracycline/nalidixic acid resistant. Furthermore, all the strains tested were resistant to at least four antibiotics.  相似文献   

9.
The beef industry continues to be interested in reliable rapid detection technologies for shiga toxin-producing Escherichia coli (STEC). Current rapid technologies require several hours of pre-enrichment and additional time on the rapid technology instrument. A flow cytometer-based system (RAPID-B®) has been shown to improve the turn-around for results with a more rapid pre-enrichment requiring only 6.5 h pre-enrichment for a 25 g and 8.5 h for a 375 g sample, followed by an additional 30 min time to achieve final results using the screening technology. The purpose of this study was to validate the RAPID-B® technology for non-O157 STEC detection as compared to the USDA-FSIS reference method which utilizes the BAX® system. A total of 180 STEC isolates from various sources and 20 non-STEC strains were used to evaluate specificity and sensitivity using the RAPID-B® flow cytometer. Also, three different weights (25, 325 and 375 g) of beef trim and ground beef samples were spiked with each STEC to verify detection sensitivity of BAX® system and RAPID-B® flow cytometer. For both methods, samples were confirmed by culturing using the USDA-FSIS reference method regardless of the screening result. The RAPID-B® flow cytometer showed that 180 isolates were all positive and the 20 non-STEC strains were all negative. For spiked beef samples, overall detection sensitivity was the same for both the BAX® system and RAPID-B® flow cytometer. When detection sensitivity was based on sample weight, there was no differences in 25 and 375 g samples between RAPID-B® flow cytometer and USDA-FSIS reference method. The RAPID-B® system yielded the same sensitivity as the reference method with a decrease of over 10 h of pre-enrichment time and 3 h of rapid screening detection time. In conclusion, the RAPID-B® flow cytometer based on whole cell detection generated similar results as BAX® system therefore the RAPID-B® flow cytometer system could be a valuable rapid method for the detection of non-O157 STEC in beef products.  相似文献   

10.
    
This study determined the prevalence, serotypes and virulence genes distribution of non-O157 Shiga toxin-producing Escherichia coli in meat products collected from butchers shops and supermarkets in Mansoura city, Egypt. We have characterized 18 non-O157 STEC strains among the identified 100 E. coli isolates recovered from the examined 87 meat product samples. The prevalence of non-O157 STEC strains in fresh beef, ground beef and beef burger samples were 11.1% (3/27), 16.7% (5/30), and 33.3% (10/30), respectively. The eighteen non-O157 STEC isolated strains were serotyped into seven (38.9%) O111:H8, six (33.3%) O26:H11, two (11.1%) O111:H–, and one (5.56%) for each of O55:H7, O126:H5 and O128:H2. PCR assays for different virulence genes showed that nine (50%), eleven (61.1%), and nine (50%) strains carry stx1, stx2, and eae genes, respectively. The distribution of shiga toxin genes among the isolated strains indicated that seven (38.9%) strains harbored stx1 only, nine (50%) strains harbored stx2 only, and two (11.1%) strains harbored both stx1 and stx2. The eae gene was present in association with five (27.8%), three (16.7%), and one (5.6%) strains that harbored stx1 only, stx2 only, and both stx1 and stx2, respectively. This study concluded that the examined meat products, particularly beef burger, consumed in Egypt are considerably contaminated with a variety of non-O157 STEC serotypes, and hence consumption of such products may constitute a potential health risk for consumers.  相似文献   

11.
    
《Food Control》2013,33(2):440-449
Due to their high market value, meat products are often targets for species substitution and adulteration. DNA-based methods are recognized as the most appropriate means to detect such fraudulent practices, however, these have not been extensively employed for the authentication of meat products available in South Africa. The aim of this study was to utilize a variety of molecular techniques to evaluate the extent of meat product mislabelling prevailing on the local market. A total of 139 processed meat products (minced meats, burger patties, deli meats, sausages and dried meats) were collected from retail outlets and butcheries in South Africa. The enzyme-linked immunosorbent assay (ELISA) was employed for the detection of undeclared plant proteins (soya and gluten) in the samples. A commercial DNA-based LCD array was used to screen the samples for the presence of 14 animal species, the results of which were confirmed by species-specific polymerase chain reaction (PCR) and in some cases also DNA sequencing. The results revealed that 95 of 139 (68%) samples contained species which were not declared on the product labelling, with the incidence being highest in sausages, burger patties and deli meats. Soya and gluten were identified as undeclared plant proteins in a large number of samples (>28%), while pork (37%) and chicken (23%) were the most commonly detected animal species. Unconventional species such as donkey, goat and water buffalo were also discovered in a number of products. Overall, this study confirmed that the mislabelling of processed meats is commonplace in South Africa and not only violates food labelling regulations, but also poses economic, religious, ethical and health impacts.  相似文献   

12.
Listeria monocytogenes is an important food-borne pathogen causing meningitis, meningoencephalitis and abortion. To assess the potential risk to consumer health, the presence of L. monocytogenes was investigated using qualitative and quantitative methods. Ten (6.33%) of 158 retail RTE food samples were positive for L. monocytogenes and the contamination levels were less than 10 MPN/g,while none of 65 dairy products was positive for L. monocytogenes. The 37 strains were grouped into five clusters and two singletons, five clusters and two singletons, and three clusters and one singleton by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) and RAPD fingerprint respectively, at similarity coefficient of 80%. The susceptibility test showed that 83.8% were susceptible to 15 antimicrobials; two were penicillin-resistant, and one was multidrug-resistant to kanamycin, tetracycline, sulfamethoxazole, rifampin, gentamycin, penicillin, and ampicillin. Virulent L. monocytogenes that possess partial antimicrobial resistance, and serotypes frequently associated with listeriosis were recovered from RTE foods. Consumers may, therefore, be exposed to potential risks of L. monocytogenes infection in South China. This study contributed to the prevalence and contamination levels of L. monocytogenes in RTE foods in South China for the first time, providing baseline information for Chinese regulatory authorities to formulate a regulatory framework for controlling L. monocytogenes to improve the microbiological safety of RTE foods.  相似文献   

13.
    
The present study sought to determine the prevalence of molecular markers for Salmonella and Shiga toxigenic Escherichia coli (STEC) serogroups O26, O45, O103, O111, O121, O145, and O157 in whole-muscle beef cuts sold at retail in urban and semi-rural areas of Costa Rica. A total of 279 (171 urban, 108 semi-rural) samples were purchased from 93 butcher shops between August of 2012 and August of 2013 and tested for the presence of molecular markers characteristic of Salmonella and STEC using the DuPont Qualicon BAX® System. The overall prevalence of Salmonella and STEC markers was 3.6% (10/279) and 4.7% (13/279), respectively. Salmonella markers were more frequently found in semi-rural (6.5%; 7/108) than in urban (1.8%; 3/171) areas. Similarly, STEC markers were more commonly detected in semi-rural (7.4%; 8/108) than in urban (2.9%; 5/171) areas. A marginal association was found between Salmonella markers and sampling location (P = 0.0496), whereas the presence of STEC markers and sampling location were considered independent (P = 0.1416). Among the 13 positive samples for STEC, 38 O-antigen gene fragments were amplified, with serogroups O45 and O121 being the predominant (28.9 and 21.1%, respectively). Markers for somatic antigens O111 and O157 were not detected in any of the samples. The present investigation is the first of its kind in Central America and shows that both Salmonella and STEC may be commonly present in whole-muscle raw beef cuts sold at retail markets in Costa Rica. Consequently, consumers may be directly at risk of foodborne illness due if meat products are not adequately cooked and handled in food service or domestic settings. Future work should emphasize continuous monitoring of the presence of these and other zoonotic pathogens in meat and meat products and on the implementation and validation of adequate food safety controls along the farm-to-table continuum.  相似文献   

14.
Enteropathogenic (EPEC) and Shigatoxigenic Escherichia coli (STEC) are foodborne pathogens that cause potentially fatal infant diarrhea and hemolytic uremic syndrome, respectively. We investigated the presence of intimin and Shiga toxin encoding genes, as indicators of EPEC and STEC presence in cloacae and chicken products. The analyzed products were hamburgers, giblets and carcasses obtained from poultry and butcher shops. EPEC contamination predominated over STEC contamination in cloacae and chicken products, although some differences were detected when the kind of food or shop was taken into account. In particular, among chicken hamburgers we found a greater proportion of EPEC than STEC-positive samples at poultry shops, while in butcheries STEC was predominant. This finding could suggest cross contamination during handling at butcheries. The results indicate that it is necessary to improve hygienic measures both during slaughtering and manipulation of chicken products at retail stores, to provide a safe product to consumers.  相似文献   

15.
    
Shiga toxin-producing Escherichia coli (STEC) strains are one of the most important recently emerged groups of food borne pathogens. This study investigated the prevalence of molecular markers for STEC and characteristics of E. coli O157 isolates from foods sold at retail markets in Wuhan, China. A total of 489 samples (350 meat products and 139 raw vegetables) were purchased from 22 large scale markets between July of 2011 and September of 2013. The meat samples consisted of frozen chicken products, raw pork, raw beef, frozen fish products and processed duck products. The raw vegetable samples consisted of lettuce, bok choy, radish, spinach, cucumber, and tomato. Shiga toxin genes (stx1 and stx2) and an O-group marker of the seven main pathogenic STEC serogroups (O157, O26, O45, O103, O111, O121, and O145) were detected in the samples by using PCR. 100% agreement was obtained between the results of the PCR targeting for wzyO157 and the PCR targeting for rfbEO157 gene. The result demonstrated that PCR assay targeting for wzyO157 gene can be employed as an effective screening method for E. coli O157 in food sample. In the study, E. coli O157 and non-O157 STEC were detected in 55 (11.2%) and 75 (15.3%) samples by PCR screening, respectively. There was significant difference in the occurrence of STEC contamination between supermarkets (19/127, 15.0%) and open markets (111/362, 30.7%) (P < 0.05). Out of 489 samples, 5 samples carried O45, 1 sample carried O145 and 1 sample carried O111. Markers for O103, O26 and O121 were not detected. This result differed from other reports. Immunomagnetic separation based cultivation technique was used to isolate E. coli O157 from 27 food samples collected in 2013. Finally 7 E. coli O157 isolates were obtained. Among the 7 isolates, the prevalent stx genotype was stx1a and stx2a. Four E. coli O157 strains exhibited toxic effects on Vero cells, while 3 isolates had no detectable cytotoxicity effects even though they contained stx genes. All E. coli O157 isolates were sensitive to the 12 antimicrobials tested except for roxithromycin. There are some inconsistencies between the PCR screening and culture results. Characteristics of STEC isolates should be evaluated and considered for monitoring STEC contamination in foods.  相似文献   

16.
    
Antimicrobial resistance phenotypes (18 antimicrobials; disk diffusion method) and genotypes (38 antimicrobial resistance genes; PCR) of 20 pathogenic Vibrio parahaemolyticus strains isolated from seafood in Shanghai wholesale markets between 2009 and 2013 were evaluated. Seventeen isolates (85%) were resistant to one or more antimicrobials, and highest resistance was observed to ampicillin (85%) and cephazolin (30%). And the isolates with tdh displayed higher resistant rates than isolates with trh. Eight antimicrobial resistance genes (strB, aadA2, strA, tetA, floR, sulI, sulII, and sulIII) were detected in these isolates. Surprisingly, the antimicrobial resistance phenotypes and genotypes of these isolates were not consistent: some isolates were resistant to β-lactam or aminoglycoside, whereas the corresponding genes were negative. Comparatively, aminoglycoside, tetracycline and chloramphenicol resistance genes occurred in susceptibility isolates. This research reveals the mismatch phenomenon between the antimicrobial resistance phenotype and genotype of seafood-derived pathogenic V. parahaemolyticus, and that susceptibility isolates might be a potential risk source for storage and transmission of resistance genes.  相似文献   

17.
    
Previously, we have isolated a novel bacteriocin, peptide F1 from Tibetan Kefir, and demonstrated its superior antimicrobial activity. However, its antimicrobial mechanism is still undefined. This study was aimed to elucidate the antimicrobial mechanism of peptide F1 against Staphylococcus aureus. The antimicrobial effects of peptide F1 were characterized by the following methods: chemical assay to quantify cytoplasmic β-galactosidase leakage, atomic absorption spectrometry to measure the released potassium ions, transmission electron microscopy to visualize the cellular morphological changes, and electrophoresis analysis and atomic force microscopy together to exam the DNA binding activity. Our results revealed that peptide F1 exerted its bactericidal effects by damaging bacterial cell membranes and by binding to the genomic DNA in the cytoplasm, which both led to rapid cell death.  相似文献   

18.
The aim of this research was to study the incidence of potential virulence factors and antibiotic resistance in 38 Enterococcus faecalis and 43 Enterococcus faecium strains isolated from dairy products and human samples. The presence of the virulence factors agg, ace, esp, gelE, efaA and of the vanA and vanB genes was evaluated by PCR, while antibiotic resistance was tested by the disk diffusion method. Ent. faecalis displayed more virulence determinants than Ent. faecium, with the presence of multiple virulence traits. Virulence determinants were present in both human and dairy strains, while antibiotic resistance patterns of the two groups of strains were very different with a significant higher diffusion of resistances among human enterococci. Considering the results of our study, dairy enterococci cannot be considered the main potential source for dissemination of antibiotic resistances.  相似文献   

19.
Biosurfactants are generally microbial metabolites with the typical amphiphilic structure of a surfactant. This study investigated potential biosurfactants production of Pseudomonas aeruginosa ATCC-10145 and Bacillus subtilis NCTC-1040 using glucose and n-hexadecane as substrates separately and compared it with the production in conventional medium. Pseudomonas aeruginosa growing in BHMS (Bushnell hass mineral salt) medium with glucose as substrate decreased the surface tension from 72 of distilled water to 32 mN/m, this strain had higher reduction than Bacillus subtilis among all the substrates tested. The selection of Pseudomonas aeruginosa for the separation of biosurfactant was determined. The crude biosurfactant was extracted from the supernatant and the yield of the crude biosurfactant was about 1 g/l. Some surface properties of rhamnolipids biosurfactant were evaluated. It also showed antimicrobial activity against different bacteria and fungi strains. The crude biosurfactant showed good action as antimicrobial activity against different bacterial and fungal species.  相似文献   

20.
    
Vibrio parahaemolyticus is a marine and estuarine bacterium that poses the greatest threat to human health worldwide. It has been the leading bacterial cause of seafood-borne illness. This study investigated the prevalence and drug resistance of V. parahaemolyticus isolated from retail shellfish in Shanghai. A total of 140 shellfish samples were collected from February 2014 to February 2015. The occurrence of V. parahaemolyticus in shellfish was 34.3%, which has increased compared to previous reports. In addition, discernible differences of total presumptive V. parahaemolyticus counts (TPVPC) were also observed in shellfish between market A and B. The results from PCR assays indicated that thermostable direct hemolysin (tdh) gene was positive in two isolates (2.1%), and the thermostable direct hemolysin-related hemolysin (trh) gene was not detected in all isolates. Antibiotic resistance profiles of those isolates were as follows: ampicillin (87.5%), cephazolin (31.3%), cephalothin (6.3%), amoxicillin/clavulanic acid (6.3%), piperacillin (6.3%), and amikacin (3.2%). Thirty-three out of 96 isolates were resistant to two or more antimicrobial agents. It is suggested that V. parahaemolyticus in retail shellfish could be a potential risk to consumers in Shanghai.  相似文献   

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