Antimicrobial resistance profiles of 5 common bovine mastitis pathogens in large Chinese dairy herds

The prevalence of antimicrobial resistance (AMR) is increasing in human and animal pathogens, becoming a concern worldwide. However, prevalence and characteristics of AMR of bovine mastitis pathogens in large Chinese dairy herds are still unclear. Therefore, our objective was to determine the AMR profile of bacteria isolated from clinical mastitis in large (>500 cows) Chinese dairy herds. A total of 541 isolates of the 5 most common species, Staphylococcus aureus (n = 103), non-aureus staphylococci (NAS; n = 107), Streptococcus species (n = 101), Klebsiella species (n = 130), and Escherichia coli (n = 100), isolated from bovine clinical mastitis on 45 dairy farms located in 10 provinces of China were included. Presence of AMR was determined by minimum inhibitory concentrations using the microdilution method. Prevalence of multidrug resistance (resistance to >2 antimicrobials) was 27% (148/541). A very wide distribution of minimum inhibitory concentrations was screened in all isolates, including Staph. aureus isolates, which were resistant to penicillin (66%). In addition, NAS (30%) were more resistant than Staph. aureus to oxacillin (84%), penicillin (62%), tetracycline (34%), and clindamycin (33%). Prevalence of resistance to tetracycline was high (59%) in Streptococcus spp. Additionally, prevalence of resistance of both E. coli and Klebsiella spp. was high to amoxicillin/clavulanate potassium (81 and 38%, respectively), followed by tetracycline (only Klebsiella spp. 32%). A high proportion (27%) of isolates were multidrug resistant; the most frequent combinations were clindamycin-cefalexin-tetracycline or enrofloxacin-cefalexin-penicillin patterns for Staph. aureus; enrofloxacin-oxacillin-penicillin-tetracycline patterns for NAS; clindamycin-enrofloxacin-tetracycline patterns for Streptococcus spp.; amoxicillin/clavulanate potassium-ceftiofur-polymyxin B patterns for Klebsiella spp.; and amoxicillin/clavulanate potassium-ceftiofur-polymyxin B patterns for E. coli. Resistance for 4 kinds of antimicrobials highly critical for human medicine, including daptomycin, vancomycin, imipenem, and polymyxin B, ranged from 0 to 24%. In conclusion, prevalence of AMR in mastitis pathogens was high on large Chinese dairy farms, potentially jeopardizing both antimicrobial efficacy and public health. Results of this study highlighted the need for improvements in antimicrobial stewardship and infection control programs in large Chinese dairy farms to reduce emergence of AMR.     

The incidence and antibiotic resistance profiles of Salmonella spp. on Irish retail meat products

Irish retail meat (n=74) and poultry samples (n=106) were tested for the presence of naturally occurring Salmonella spp. The pathogen was detected in 28 poultry (n=106), two pork (n=22) and one cooked meat samples (n=20) examined. Salmonella was not isolated from minced beef or lamb samples tested. Initial counts on samples ranged from 0 to log₁₀2·5 cfu g⁻¹. The most commonly isolated serotype was S. bredeney accounting for 48·4%, followed by S. kentucky (35·5%) and S. enteritidis (6·5%). Salmonella spp. (n=31) isolated from food products were also examined for antibiotic resistance. A total of 155 strains (five strains from each isolate) were tested for resistance to 26 antibiotics using the Bauer method. The percentage of samples showing antibiotic resistance amongstSalmonella isolates were as follows: Riampicin (100%); Tetracycline (92·92%); Oxytetracycline (86·26%); Sulphamethoxazole (86·25%) and Streptomycin (80·92%).     

Microbial quality of “doubles” sold in Trinidad

A cross-sectional study was conducted to determine the prevalence and characteristics of Escherichia coli, Staphylococcus aureus, Bacillus spp. and Salmonella spp. in “bara”, “channa”, condiments/spices and ready-to-eat “doubles” sold by vendors in the St. George and Caroni counties of Trinidad. Of 196 samples of each of “bara”, “channa”, condiments/spices and ready-to-eat “doubles” examined, E. coli was detected in 0 (0.0%), 14 (7.1%), 96 (49.0%) and 67 (34.2%), respectively; Staphylococci were isolated from 104 (53.1%), 71 (36.2%), 129 (65.8%) and 123 (62.8%) samples, respectively; and Bacillus spp. were recovered from 22 (11.2%), 85 (43.4%), 100 (51.0%) and 88 (44.9%) samples, respectively. Salmonella spp. were not isolated from any sample. Of the 177 isolates of E. coli recovered from all sources, 9 (5.1%), 7 (4.0%) and 47 (26.6%) were mucoid, haemolytic and non-sorbitol fermenters (NSF), respectively, but none agglutinated with O157 antiserum. Of 427 staphylococcal isolates, 130 (30.4%) were confirmed as S. aureus of which 20 (15.4%) were haemolytic and 84 (64.6%) pigmented, while 17 (20.7%) of 82 strains of S. aureus tested produced enterotoxins. Ready-to-eat “doubles”, a popular food in Trinidad, therefore pose a potential health risk to consumers due to the high level of contamination with bacteria.     

Prevalence of E. coli,Salmonella, and Listeria spp. as potential pathogens: A comparative study for biofilm of sink drain environment

Since knowledge and understanding of waterborne pathogens and their diseases are well illuminated, a few research publications on the prevalence of pathogenic microorganisms in various household sink drain pipes are often not extensively examined. Therefore, this study aims to (a) assess and monitor the densities of the bacterial community in the different natural biofilm that grow on plastic pipelines, (b) to detect Escherichia coli, Salmonella, and Listeria spp. from natural biofilm samples that are collected from the kitchen (n = 30), bathroom (n = 10), laboratories (n = 13), and hospital (n = 8) sink drainage pipes. Three bacterial species selected were assessed using a culture-dependent approach followed by verification of isolates using both BIOLOG GEN III and polymerase chain reaction. The estimated number of each bacterium was 122 isolates, while 60, 20, 26, and 16 isolates were obtained from the natural biofilm samples, kitchen, bathroom, laboratories, and hospital, respectively. As for the tests, in all types of biofilm samples, the overall bacterial counts at low temperature (22°C) were higher than those at high temperature (37°C). Meanwhile, E. coli had the most significant number of bacterial microorganisms compared to the other two pathogens. Additionally, the most massive cell densities of E. coli, Salmonella, and Listeria species were discovered in the biofilm collected from the kitchen, then the hospital. Statistically, the results reveal that there is a positive correlation (p ≥ .0001) with significance between the sources of biofilm. This work certainly makes the potential of household sink drain pipes for reservoir contagious pathogens more explicitly noticeable. Such knowledge would also be beneficial for prospective consideration of the threat to human public health and the environment.     

Prevalence and Characterization of Salmonella Isolated from Chicken Meat in Turkey

This study was conducted in a Turkish province to investigate the presence of Salmonella spp. in 150 chicken meat samples using 2 phenotyping techniques: classic culture technique (CCT) and immunomagnetic separation (IMS). For the confirmation of the isolates at molecular levels, invA gene was detected in these isolates. The presence of invA, class 1 (Cls1) integrons, and integrase (Int1) genes was demonstrated by PCR assay; and the resistance of the isolated Salmonella spp. strains to antibiotics was determined by disk diffusion test. All the cultural and PCR results were evaluated together; Salmonella spp. were detected in a total of 64 (42.66%) chicken meat samples. Contamination rate was higher in carcasses (53.33%, n = 75) than in meat pieces (32%, n = 75). When results of standard culture were compared with IMS technique, IMS (n = 54) showed a clear superiority over the CCT (n = 38). A very high resistance rate (≥89.28%) to vancomycin, tetracycline, streptomycin, or nalidixic acid was found. Trimethoprim‐sulfamethoxazole resistance was present in 32.14%. Relatively lower incidence of resistance (≤8.33%) to gentamicin, chloramphenicol, ampicillin, and ceftriaxone was observed. Concurrent resistance to at least 4 antibiotics was detected in 92.85% of the isolates. Cls1 integrons and Int1 were positive in 80.95% and 95.23% of the isolates, respectively. However, Int1 alone was detected in 15.47% (n = 13). In conclusion, the high prevalence of Salmonella spp. in chicken meat may pose a potential public health risk, and the presence of antibiotic‐resistant Salmonella spp. isolate together with Cls1 integron and/or integrase might play an important role in horizontal antibiotic gene transfer.     

Influence of farming methods on microbiological contamination and prevalence of resistance to antimicrobial drugs in isolates from beef

The presence of Escherichia coli, Staphylococcus aureus, Listeria monocytogenes and Salmonella spp. was determined in 75 samples of conventional beef and in 75 samples of organic beef. All samples came from cattle slaughtered and processed in the same slaughterhouse and quartering room. A total of 180 E. coli, 180 S. aureus and 98 L. monocytogenes strains were analyzed by an agar disk diffusion assay for their resistance to 11 antimicrobials, for the case of E. coli and S. aureus, or 9 antimicrobials, for the case of L. monocytogenes. Salmonella spp. were not isolated from any of the beef samples. No significant differences in prevalence were obtained for any of the bacterial species tested between organic and conventional beef. E. coli isolated from organic beef exhibited significant differences in antimicrobial resistance against 5 of the 11 antimicrobials tested as compared to isolates recovered from conventional beef. In the case of S. aureus, these differences were only found for 3 of the 11 antimicrobials tested and for L. monocytogenes, no differences were obtained between isolates obtained from organic or conventional beef. Although no significant differences were obtained in microbiological contamination, E. coli and S. aureus isolates from organically farmed beef samples showed significantly lower rates of antimicrobial resistance in E. coli and S. aureus isolates.     

Untersuchungen zum mikrobiellen und viralen Kontaminationsstatus von Garnelen aus Aquakultur

In der vorliegenden Untersuchung wurden 111 Proben roher, aus Drittl?ndern importierter Garnelen aus Aquakultur auf bakterielle Erreger und auf humanpathogene Viren untersucht. Die Garnelen stammten bis auf acht lateinamerikanische Proben aus Südostasien. Am h?ufigsten waren Proben aus Bangladesh vertreten (n=40). Das Untersuchungsspektrum umfasste die Ermittlung des aeroben mesophilen Gesamtkeimgehalts, die quantitative Untersuchung auf Escherichia coli und Staphylococcus aureus und den qualitativen Nachweis von Salmonella spp., Vibrio spp. und Listeria monocytogenes. Der Nachweis des humanpathogenen Rotavirus, des Norovirus und des Hepatitis A-Virus erfolgten jeweils mittels einer nested RT-PCR. Bei den untersuchten Proben wurden Gesamtkeimgehalte von 4,8×10² bis 1,3×10⁹ KbE/g ermittelt. Davon hatten vierzehn Proben (12,6%) einen aeroben mesophilen Gesamtkeimgehalt >10⁷ KbE/g. In einer Probe konnte Escherichia coli mit einer Keimzahl von 1,9×10³ KbE/g isoliert werden. In 16 Proben wurde Staphylococcus aureus nachgewiesen. Aus keiner der Garnelenproben lie? sich Listeria monocytogenes isolieren. Salmonella spp. war in acht der untersuchten Proben nachweisbar. Das am h?ufigsten isolierte Serovar war Salmonella Weltevreden.     

Variations in Radiation Sensitivity of Foodborne Pathogens Associated with the Suspending Meat

Longissimus dorsi from beef, pork, and lamb and turkey breast and leg meats were inoculated with Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus, and the gamma radiation resistance of the pathogens were determined under identical conditions. At 5°C the respective radiation D-values of E. coli O157:H7 and L. monocytogenes did not vary with the suspending meat. The D-value for a mixture of Salmonella spp. was significantly lower on pork than on beef, lamb, turkey breast, and turkey leg meats. The D-value for S. aureus was significantly lower on lamb and mechanically deboned chicken meat than on the other meats. All values were, nevertheless, within expected ranges.     

Introduction of new multidrug-resistant Salmonella enterica strains into commercial dairy herds

A longitudinal observational study of 59 dairy herds was conducted in Washington State to estimate the rate of introduction of new multidrug-resistant (MDR) Salmonella enterica strains onto commercial dairy herds. Samples were collected on these herds over 7 visits separated by intervals of 2 to 4 mo over a period of 15 to 21 mo. Samples were cultured for Salmonella spp. and serogroup, serovar, and antimicrobial susceptibility patterns were identified for MDR Salmonella isolates. Fingerprinting generated by pulsed-field gel electrophoresis (PFGE) using XbaI restriction enzyme digestion generated genotyping profiles for all MDR isolates identified in the study. The rate of new MDR Salmonella strain introduction was 0.9 per herd-year (95% confidence interval: 0.6-1.4). The rates for the most commonly introduced MDR Salmonella serovars were 0.4/herd-year for Typhimurium, 1.2/herd-year for Newport, and 0.1/herd-year for Dublin. Thirty-three of 59 herds (56%) had at least one new MDR Salmonella introduction during the study period. The number of new MDR Salmonella strains acquired by dairy herds ranged from zero to 8. Thirteen of the 59 herds had a history of clinical salmonellosis. Among these 13 herds, 6 herds acquired new MDR Salmonella strains, although these strains were different than historical clinical strains. These data indicate that acquisition of new MDR Salmonella strains by dairy herds was a common event in participating herds, although the number of strains introduced varied greatly among herds.     

Impact of Rearing Conditions on the Microbiological Quality of Raw Retail Poultry Meat

There is a gap in knowledge of microbiological quality in raw chicken products produced by nonconventional methods and no studies have reported the microbiological quality of turkeys produced under different rearing environments. Thus, the aim of this study was to compare the microbiological quality of conventionally and organically reared whole chicken and turkey carcasses purchased from 3 retail outlets in Knoxville, Tenn., U.S.A. A total of 100 raw broiler chickens organically (n = 50) and 50 raw turkey carcasses consisting of 3 brands reared either conventionally (n = 25) or organically (n = 25) were evaluated. The FDA BAM protocol for rinsing poultry carcasses was used to enumerate of aerobic bacteria, Campylobacter, and Staphylococcus spp., and for qualitative analysis of Salmonella. Organic chickens from one brand had the highest average counts of aerobic bacteria, Staphylococcus spp. and Campylobacter (4.8, 4.8, and 4.7 Log₁₀ CFU/mL rinsate, respectively) while the other organic brand had the lowest average counts (3.4, 3.3, and 3.1, respectively) of all 4 brands evaluated. The organic turkeys had the highest average counts of these same bacteria (4, 3.9, and 3.8, respectively) compared to the 2 brands of conventional turkeys evaluated. Salmonella (5% prevalence) was isolated only from organic chickens and turkeys. From these data, it appears that the microbiological quality of the raw product was not dependent on rearing conditions and, thus, it cannot be assumed that organic raw poultry is safer than conventionally raised poultry in terms of microbiological quality.     

Antimicrobial resistant genes associated with Salmonella from retail meats and street foods

We examined the antimicrobial resistance of Salmonella isolates from 300 meat products (raw beef, chicken meat and street foods). A total of 88 non-duplicate Salmonella from 66 (22.0%) retail meat and 22 (7.5%) street food samples were recovered and 11 serovars were identified. Among the 88 Salmonella isolates, the highest resistance was to tetracycline (73.8%), followed by sulfonamide (63.6%), streptomycin (57.9%), nalidixic acid (44.3%), trimethoprim–sulfamethoxazole (19.3%), ampicillin (17.0%), chloramphenicol (10.2%), cephalotin (8.0%), kanamycin (6.8%), ciprofloxacin (2.2%) gentamycin (2.2%), cefoxitin (2.2%), amoxicillin–clavulanate (1.0%) and amikacin (1.0%). Sixty-seven percent of the isolates (59/88) were multidrug resistant (MDR). Ten out of 17 resistance genes (bla_TEM-1, strA, strB, aadA, sulI, sulII, tetA, tetB, floR, cmlA) were detected. Twelve of the 59 MDR Salmonella isolates from serovars Typhimurium (6), Newport (3), Agona (1), Albany (1) and Weltevreden (1) had class 1 integrons. The gene cassettes identified were dfrA1, dfrV, dfrA12, aadA2, sul1 genes and an open reading frame orfC of unknown function. Four integron-positive isolates could transfer resistance phenotypes to the recipient strain, E. coli J53 via conjugation. These data revealed that the Salmonella isolates recovered from the retail meats and cooked street foods were resistant to multiple antimicrobials, which can be transmitted to humans through food products. The occurrence of mobile genetic elements such as integrons reiterates the roles of food of animal origins as a reservoir of MDR Salmonella.     

In vitro inactivation of Escherichia coli, Staphylococcus aureus and Salmonella spp. using slightly acidic electrolyzed water

In the current study, the effectiveness of slightly acidic electrolyzed water (SAEW) on an in vitro inactivation of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Salmonella spp. was evaluated and compared with other sanitizers. SAEW (pH 5.6, 23 mg/l available chlorine concentration; ACC; and 940 mV oxidation reduction potential; ORP) was generated by electrolysis of dilute solution of HCl (2%) in a chamber of a non-membrane electrolytic cell. One milliliter of bacteria suspension (ca. 10–11 log₁₀CFU/ml) was mixed with 9 ml of SAEW, strong acidic electrolyzed water (StAEW; ca. 50 mg/l ACC), sodium hypochlorite solution (NaOCl; ca.120 mg/l ACC) and distilled water (DW) as control and treated for 60 s. SAEW effectively reduced the population of E. coli, S. aureus and Salmonella spp. by 5.1, 4.8, and 5.2 log₁₀CFU/ml. Although, ACC of SAEW was more than 5 times lower than that of NaOCl solution, they showed no significant bactericidal difference (p > 0.05). However, the bactericidal effect of StAEW was significantly higher (p < 0.05) than SAEW and NaOCl solution in all cases. When tested with each individual test solution, E. coli, S. aureus and Salmonella spp. reductions were not significantly different (p > 0.05). These findings indicate that SAEW with low available chlorine concentration can equally inactivate E. coli, S. aureus and Salmonella spp. as NaOCl solution and therefore SAEW shows a high potential of application in agriculture and food industry as an environmentally friendly disinfection agent.     

Microbiological characterisation of artisanal farmhouse cheeses manufactured in Scotland

Twenty‐eight Scottish artisanal farmhouse cheeses were examined in respect of 16 microbial groups of significance for food safety and cheese character development. Microbial populations were diverse and although Escherichia coli O157 and Salmonella spp. were not detected the occurrence of potential foodborne pathogens was confirmed in 86% of the samples analysed. Mycobacterium avium subsp. paratuberculosis was detected in 25% of the cheeses tested and some Staphylococcus aureus and the Bacillus cereus isolates were enterotoxigenic. Resistance to methicillin and vancomycin and other clinically important antibiotics was detected in some S. aureus and Enterococcus strains. The inappropriate labelling of some raw milk cheeses and the consequences of the complexity of the microbial population on isolation media specificity is discussed.     

Prevalence,Distribution, and Diversity of Salmonella spp. in Meat Samples Collected from Italian Slaughterhouses

Recently worldwide food safety authorities indicated the rise of foodborne outbreaks linked to Salmonella: this highlighted the need to intensify monitoring and apply more targeted controls to help manage the spread of the disease. The aim of this study was to assess the prevalence and distribution of Salmonella serotypes in 7 slaughterhouses, located in different areas of Naples province (Regione Campania, Italy). Meat samples collected from the slaughterhouses were submitted for standardized microbiological analysis in 2015. Results of routine testing for Salmonella spp. were analyzed and then compared to biochemical and molecular evaluations. Salmonella spp. were detected in 12% of 320 samples examined (39/320) and the isolation rates ranged from 87% (32 samples) for raw poultry meat to 13% (7 samples) for pork meat. Biochemical serotyping showed that approximately 50% of the isolates belonged to Salmonella enterica serotype Choleraesuis. Rapid detection methods, such as molecular analysis (polymerase chain reaction and gel electrophoresis), able to confirm food matrices contamination, represent a valid support to the fast identification of Salmonella species. A further aspect of the study consisted, indeed, on analyzing isolated strains through molecular evaluations. By amplifying bacterial DNA—using invA primers, selective for Salmonella—it was possible, in less than 3 h, to classify the isolates as Salmonella spp., confirming the results of microbiological outcomes. Results of distribution analysis, supported by rapid molecular approaches, showed the difficulty of reducing Salmonella risk on food chain. This emphasized the importance of periodic surveillance to prevent outbreaks.     

Bacterial populations associated with poultry processing in a South African abattoir

Bacteria were isolated from yeast extract supplemented tryptone soya agar (TSAYE) plates (357 isolates) and violet red bile glucose agar (VRBGA) plates (311 isolates) of micro- biological surveys in a South African Grade B poultry abattoir. Bacterial populations from TSAYE plates of carcasses (neck skin) were dominated byAcinetobacterspp.,Escherichia coli, Micrococcusspp. andFlavobacteriumspp., which collectively comprised 75.4% of isolates, while isolates from VRBGA plates showed dominance ofEscherichia coli(80.0%). Environmental isolates dominant on TSAYE plates wereMicrococcusspp. from equipment surfaces and air samples of the defeathering area of the abattoir (48.5 and 68.7%, respectively) andBacillusspp. from air samples of the packaging area (37.4%). Isolates from TSAYE plates of scald tank water were dominated byE. coli(47.8%) andMicrococcusspp. (39.1%), while isolates from immersion chiller water were predominantlyE. coli(54.1%). Environmental isolates dominant on VRBGA plates wereE. coliin water samples and air of the defeathering and packaging areas (from 93.7 to 100%).E. coli, Enterobacterspp. andSerratiaspp. were dominant on VRBGA plates of equipment surfaces, collectively comprising 77.8% of isolates.     

Untersuchungen zum mikrobiellen und viralen Kontaminationsstatus von Garnelen aus Aquakultur

Zusammenfassung: In der vorliegenden Untersuchung wurden 111 Proben roher, aus Drittl?ndern importierter Garnelen aus Aquakultur auf bakterielle Erreger und auf humanpathogene Viren untersucht. Die Garnelen stammten bis auf acht lateinamerikanische Proben aus Südostasien. Am h?ufigsten waren Proben aus Bangladesh vertreten (n=40). Das Untersuchungsspektrum umfasste die Ermittlung des aeroben mesophilen Gesamtkeimgehalts, die quantitative Untersuchung auf Escherichia coli und Staphylococcus aureus und den qualitativen Nachweis von Salmonella spp., Vibrio spp. und Listeria monocytogenes. Der Nachweis des humanpathogenen Rotavirus, des Norovirus und des Hepatitis A-Virus erfolgten jeweils mittels einer nested RT-PCR. Bei den untersuchten Proben wurden Gesamtkeimgehalte von 4,8×10² bis 1,3×10⁹ KbE/g ermittelt. Davon hatten vierzehn Proben (12,6%) einen aeroben mesophilen Gesamtkeimgehalt >10⁷ KbE/g. In einer Probe konnte Escherichia coli mit einer Keimzahl von 1,9×10³ KbE/g isoliert werden. In 16 Proben wurde Staphylococcus aureus nachgewiesen. Aus keiner der Garnelenproben lie? sich Listeria monocytogenes isolieren. Salmonella spp. war in acht der untersuchten Proben nachweisbar. Das am h?ufigsten isolierte Serovar war Salmonella Weltevreden. Vibrio spp. konnte mit 60 Isolaten in 49 Proben (44%) nachgewiesen werden. Am h?ufigsten wurde Vibrio cholerae non-O1 non-O139 isoliert (n=34). Aus 14 Proben konnte Vibrio parahaemolyticus isoliert werden und in fünf Proben konnte Vibrio vulnificusnachgewiesen werden. Erstmals konnte Norovirus in Garnelen nachgewiesen werden. 21 (18,9%) der untersuchten Proben waren positiv. Sowohl Rotavirus als auch Hepatitis A-Virus konnten hingegen nicht nachgewiesen werden.

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In this study 111 samples of raw imported aqua-cultured shrimps have been examined for bacterial pathogens and for pathogen viruses. The samples originated from South-East Asia except for eight Latin-American samples. Most samples were taken from Bangladesh (n=40). The bacteriological quality of these samples was analysed in terms of aerobic plate count, Escherichia coli, Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and Vibrio species. Rotavirus, norovirus and hepatitis A-Virus were detected by using a nested RT-PCR. The aerobic plate count was found to be in a range between 4,8×10² to 1,3×10⁹ cfu/g. Fourteen samples (12,6%) showed an aerobic plate count >10⁷ cfu/g. One sample was found to be contaminated with Escherichia coli at a level of 1,9×10³ cfu/g. Staphylococcus aureus was isolated from sixteen samples. Listeria monocytogenes was not detected in any of the shrimp samples examined. Salmonella spp. was found in eight samples. Salmonella Weltevreden was the most frequently isolated serovar. Forty-nine shrimp samples (44%) were positive for Vibrio spp. and 60 Vibrio-isolates could be extracted. Vibrio cholerae non- O1 non-O139 was isolated in 34 samples as the most frequent species. 14 samples contained Vibrio parahaemolyticus, Vibrio vulnificus was present in five samples. For the first time Norovirus could be detected in shrimps. 21 (18,9%) of all examined samples were positive. However, both rotavirus and hepatitis A-virus could not be detected.

Eingegangen: 21. November 2007     

Rapid and simultaneous quantification of viable Escherichia coli O157:H7 and Salmonella spp. in milk through multiplex real-time PCR

Escherichia coli O157:H7 and Salmonella spp. in milk are 2 common pathogens that cause foodborne diseases. An accurate, rapid, specific method has been developed for the simultaneous detection of viable E. coli O157:H7 and Salmonella spp. in milk. Two specific genes, namely, fliC from E. coli O157:H7 and invA from Salmonella spp., were selected to design primers and probes. A combined treatment containing sodium deoxycholate (SDO) and propidium monoazide (PMA) was applied to detect viable E. coli O157:H7 and Salmonella spp. only. Traditional culture methods and SDO-PMA-multiplex real-time (mRT) PCR assay were applied to determine the number of viable E. coli O157:H7 and Salmonella spp. in cell suspensions with different proportions of dead cells. These methods revealed consistent findings regarding the detected viable cells. The detection limit of the SDO-PMA-mRT-PCR assay reached 10² cfu/mL for Salmonella spp. and 10² cfu/mL for E. coli O157:H7 in milk. The detection limit of SDO-PMA-mRT-PCR for E. coli O157:H7 and Salmonella spp. in milk was significantly similar even in the presence of 10⁶ cfu/mL of 2 nontarget bacteria. The proposed SDO-PMA-mRT-PCR assay is a potential approach for the accurate and sensitive detection of viable E. coli O157:H7 and Salmonella spp. in milk.     

Characterization of Extended Spectrum Β‐Lactamase Producing Enterobacteria and Methicillin‐Resistant Staphylococcus aureus Isolated from Raw Pork and Cooked Pork Products in South China

In this study, we assessed the co‐colonization with extended spectrum β‐lactamase producing Enterobacteria (ESBL‐E) and methicillin‐resistant Staphylococcus aureus (MRSA) in raw pork and cooked pork products in south China. In total, 240 raw pork and 240 cooked pork samples collected from supermarkets (n = 20) and local butcher shops (n = 20) in the city of Guangzhou (China) were investigated. Raw pork and cooked pork was more frequent colonization with ESBL‐E (7.5% in raw pork and 0.4% in cooked pork products) than with MRSA (4.2% in raw pork). Two of samples were contaminated with both tested types of multidrug‐resistant bacteria. High antibiotic‐resistance rate with wide spectrums of both ESBL‐E and MRSA isolated were observed. In ESBL‐E isolates, TEM (n = 15), CTX‐M‐1 (n = 3), CTX‐M‐9 (n = 1), and SHV (n = 1) genes were detected. TEM and SHV genes were associated with CTX‐M‐1 in 2 isolates, respectively. The CTX‐M‐9 gene of 1 isolate from cooked pork samples was found to be transferred to Escherichia coli J53 by conjugation. Detected MLST‐types of MRSA were livestock‐associated ST7 (n = 5) and ST9 (n = 4), as well as hospital‐acquired ST239 (n = 1), suggesting contamination from human source(s) during meat processing. These findings confirmed a contamination of raw pork and cooked pork with ESBL‐E and MRSA and emphasized the necessity of enforcing hygienic practices and specific detection of MRSA and ESBL‐producing bacteria in meat processing and storage.     

Prevalence of Salmonella serotypes S. Enteritidis and S. Typhimurium in poultry and poultry products

Salmonella continues to be a major food safety and public health threat. In the present study, Salmonella enterica subsp. enterica serotypes Enteritidis (SE) and Typhimurium (ST) were isolated from poultry and characterized for virulence, antimicrobial susceptibility, and biofilm formation. Prevalence of Salmonella serotypes in poultry was 3.35%; predominant serotypes isolated were S. Enteritidis (68.1%) and S. Typhimurium (31.8%). Source-wise, Salmonella were isolated from retail market chicken meat (4.8%), live chicken at farm (2.5%), and table eggs (2.1%). Salmonella isolates produced invA gene of 284 bp (100%), spvR gene of 310 bp (77.27%), spvC gene of 571 bp (22.72%), and stn gene of 260 bp (100%) as virulence/ pathogenicity determinants. Salmonella isolates exhibited resistance to common antimicrobials; 72.7% isolates showed multiple resistance (≥3 antimicrobial class), highest resistance was observed for polymyxin-B (81.8%) followed by nalidixic acid (72.7%), colistin (59.1%), ampicillin/tetracyline (45.5%), ampicillin + sulbactam (40.9%), cefodroxil (18.2%), streptomycin (9.1%), and cefazidine/ceftriaxone-tazobactam (4.5%). Multiple antimicrobial resistance (MAR) index of poultry Salmonella isolates ranged from 0.11 to 0.35; wherein, 59.1% isolates showed MAR of >0.2. About 81.8% Salmonella isolates produced biofilm and were categorized as strong (13.6%), moderate (45.4%), and weak (22.7%) biofilm producers. Occurrence of antimicrobial resistant virulent Salmonella strains in poultry requires implementation of suitable strategies so as to protect the public health.     

Outbreaks and factors influencing microbiological contamination of fresh produce

Fresh fruits and vegetables are nutritionally well‐recognised as healthy components in diets. The microbiological foodborne outbreaks associated with the consumption of fresh produce have been increasing. Salmonella spp., Escherichia coli O157:H7, Staphylococcus aureus, Campylobacter spp. and Listeria monocytogenes are the most common pathogens that contaminate fresh produce. This review discusses recent foodborne outbreaks linked to fresh produce, factors that affect microbiological contamination and measures that could be adopted to reduce the foodborne illnesses. © 2016 Society of Chemical Industry