International Journal of Food Microbiology 197 (2015) 40–44

Contents lists available at ScienceDirect

International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro

Short Communication

Airborne dissemination of Escherichia coli in a dairy cattle farm and its environment Susana Sanz a,⁎, Carmen Olarte a, Roberto Martínez-Olarte a, Enrique V. Navajas-Benito b, C. Andrea Alonso b, Sara Hidalgo-Sanz c, Sergio Somalo b, Carmen Torres b a b c

Tecnología de los Alimentos, Universidad de La Rioja, Logroño, Spain Bioquímica y Biología Molecular, Universidad de La Rioja, Spain CINFA, Pamplona, Spain

a r t i c l e

i n f o

Article history: Received 30 July 2014 Received in revised form 5 November 2014 Accepted 12 December 2014 Available online 18 December 2014 Keywords: Air Dissemination E. coli

a b s t r a c t There are multiple ways bacteria can be transported from its origin to another area or substrate. Water, food handlers, insects and other animals are known to serve as a vehicle for bacterial dispersion. However, the importance of the air in open areas as a possible way of bacterial dissemination has not been so well analyzed. In this study, we investigated the airborne dissemination of Escherichia coli from the inside of a dairy cattle farm to the immediate environment. The air samples were taken inside the farm (area 0) and from the immediate outside farm surroundings at distance of 50, 100 and 150 m in four directions (north, south, east, and west). At each point, the air was collected at different heights: 40 cm, 70 cm and 1 m. The sampling was carried out in two weather seasons (November and July). E. coli was isolated in both inside and outside air, even in samples taken 150 m from the farm. A seasonal effect was observed with more bacterial isolates when temperature was higher. Regarding the distribution of the isolates, wind direction appeared as a determining factor. In order to verify that E. coli strains isolated from animal housing facilities were identical to those isolated from the air of the immediate farm environment, their genomic DNA profiles were analyzed by pulsed-field gel electrophoresis (PFGE) after digestion with the endonuclease XbaI. The comparison of genetic profiles suggested that the strains isolated from inside and outside the farm were related, leading to the conclusion that the air is an important vehicle for E. coli dissemination. © 2014 Elsevier B.V. All rights reserved.

1. Introduction In recent years, the contamination of vegetables with enteric bacteria has reached concerning proportions due to the potential health, social and economic impacts. Numerous outbreaks associated with the consumption of raw fruits and vegetables have been reported in industrialized countries. Thus, pathogenic strains of Escherichia coli (in most cases linked to the animal environment) have been isolated from fresh vegetables, causing severe foodborne outbreaks (EFSA, 2011; Friesema et al., 2008; Michino et al., 1999; Mora et al., 2011; Södeström et al., 2008; Wendel et al., 2009). Nowadays, consumers demand food products that can be prepared quickly and with little effort. This has led to the development of a new line of minimally processed plant food, which is subjected to minimal processing operations prior to being packaged and commercialized. However, disinfection treatments sometimes can be ineffective in re⁎ Corresponding author at: Dpto. Agricultura y Alimentación, Universidad de La Rioja, CCT, C/Madre de Dios, 51, 26006 Logroño, La Rioja, Spain. Tel.: +34 941299729; fax: +34 941299720. E-mail address: [email protected] (S. Sanz).

http://dx.doi.org/10.1016/j.ijfoodmicro.2014.12.010 0168-1605/© 2014 Elsevier B.V. All rights reserved.

moving potential pathogens from the raw material, especially in the presence of high levels of contamination. Moreover, the presence of organic material (dirt) and the difficulties to remove it (cleaning step) in the case of food products, could make disinfectant solutions useless (Giménez et al., 2003a,b; Sanz et al., 2002, 2003). Several studies have revealed different routes by which microbial contamination of crops may occur. The irrigation of vegetables with contaminated water or the addition of inadequately amended manure to the soil is considered as important sources of contamination by enteric bacteria. Food handlers, insect vectors and other animals have also been identified as a vehicle for bacterial dissemination. However, these routes do not explain all of the cases and there are some evidences to support other routes of propagation (Mora et al., 2011). The air, for instance, appears as an additional vehicle of dissemination that may contribute to explain the contamination of vegetables by enteric bacteria. This hypothesis is supported by previous works carried out in wineries, in which we showed that the air is an important vehicle for the dissemination of microorganisms of oenological interest; this dissemination through the air has been demonstrated in molds (Ocón et al., 2011), yeasts and lactic acid bacteria (Garijo et al., 2008, 2009, 2011).

S. Sanz et al. / International Journal of Food Microbiology 197 (2015) 40–44

The purpose of this work was to study the airborne dissemination of E. coli from the inside of a dairy cattle farm to the immediate outside environment in order to evaluate the real importance of the air in the transmission of enteric microorganisms (and potentially pathogenic bacteria) from animal environments to fresh vegetables. 2. Materials and methods 2.1. Air and organic exudates sampling The air samples were taken from different areas of a dairy cattle farm located in La Rioja (Spain). It occupies a total area of 21,000 m2 and is bordered to the north by a motorway that separates the farm from a gravel pit, and to the south, east and west by cultivated fields. The dairy cattle farm accommodates 500 animals and produces around 4.5 million L of milk per year. The air samples were taken inside the farm (area 0) and from the immediate farm outside surroundings at distance of 50, 100 and 150 m in four directions (north, south, east, and west). Sticks were set firmly in the middle of the farm and in the established sampling points (stationary method). At each stick, six culture plates were placed at three different heights (40 cm, 70 cm and 1 m). The sample plates were exposed to the air for 4 h. Simultaneously, in each sampling point, 1000 L of air was sampled with an AirIdeal air sampler (Biomerieux) (mechanical method). This device allowed the passage of a specific air volume through a grid and the direct impact onto agar plates to facilitate the detection of viable microorganisms. The sampling was carried out in different weather seasons (November 2012 and July 2013). All air sampling occurred between 8:00 a.m. and 1:00 p.m., coinciding with the maximum activity period at the farm. Organic exudates were also collected aseptically from dirty straw and manure. The diluted samples were spread onto the surface of agar plates. Chromocult Coliform Agar (Merck) was used for the isolation and enumeration of E. coli from the air and organic exudate samples. 2.2. Identification of E. coli isolates After an incubation period of 24 h, suspicious colonies were selected and isolated on BHIA (Brain Heart Infusion Agar, Difco) agar plates. Confirmation of suspicious E. coli colonies was carried out using Gram staining, biochemical techniques (indole test and inoculation into TSI — triple sugar iron-agar slant), and PCR amplification of the speciesspecific uidA gene (Heininger et al., 1999). In order to determine the clonal relationship of E. coli isolates, the genomic DNA profiles obtained by pulsed-field gel electrophoresis (PFGE) after digestion with the endonuclease XbaI were analyzed (Sáenz et al., 2004) and PFGE patterns were compared as previously recommended Tenover et al. (1995). A comparison of different methods used for the detection of genetic differences in E. coli has demonstrated that PFGE has a high discriminatory power (McLellan et al., 2003). 3. Results and discussion While numerous studies have been done to examine the microbiological quality of indoor air (buildings, hospitals, food processing plants, wine cellars, animal farms), the methodology to be used for the collection of outdoor air involves greater difficulties. Firstly, it should be kept in mind that the large volume of air exerts a diluting effect, which affects the detection and capture of microorganisms, unless they are in a very high concentration. Such is the case of molds, for which the main route of dissemination is the air, but this is not so common in other microorganisms such as bacteria, whose presence in the air is usually transitory and typically associated with water droplets, dust particles and lightweight materials in suspension (Shale and Lues, 2007). In addition, bacteria found in the air are normally stressed due to a lack of nutrients and dehydration, so they may not be able to grow in selective agar, as a result

41

of additional stress caused by the selective agents. Furthermore, plate counts could be subjected to error because microorganisms exposed to the air may remain viable but have lost the ability to form colonies, i.e., they become viable but nonculturable. In fact, and according to several authors (Al-Dagal and Fung, 1990; Crozier-Dodson and Fung, 2002), the number of viable airborne microorganisms may be underreported. In our study, different culture media with distinct specificities for the detection of E. coli were studied. PCA (Plate Count Agar) and MuellerHinton Agar showed very low selectivity level and high number of invasive microorganisms grew. However the selectivity of VRB Agar (Violet Red Bile Agar) and EMB-Levine (Eosin Methylene Blue Lactose Sucrose Agar) media was too high mostly due to the presence of bile salts and no growth was observed. Furthermore, these media showed dehydration problems with 1–2 h of exposition to air. On the other hand, ENDO Agar was not used because of the occurrence of color changes due to oxidation processes. Finally, Chromocult-Coliform Agar (Merck) was selected for the isolation and enumeration of bacterial colonies. This is a selective and differential medium for the detection of total coliforms and E. coli that, after incubation (37 °C, 24 h), enables the detection and differentiation of E. coli colonies due to the acquisition of a violet color. This medium has been widely used for the detection of E. coli and coliforms from drinking water and processed food. Moreover, the lack of bile salts in its composition has been shown to be effective for the recovery of sublethally injured coliforms (González et al., 2002; Ogden et al., 1998; Turner et al., 2000). In this study, two different methods were used for the collection of E. coli from the air. On the one hand, a conventional mechanical procedure was employed by using an AirIdeal air sampler. On the other hand, a stationary method was designed by setting sticks at different distances from the farm. At each stick, three sterilized mesh bags containing opened agar plates were placed at three different heights (two agar plates at each height). The exposure period was limited to 4 h because the culture medium suffered an important dehydration after that period of time. Organic exudates were also collected from dirty straw and manure. In these kinds of samples, the presence of suspicious E. coli colonies, as expected, was very high with an average value of 4.8 × 104 cfu/mL and 7.8 × 106 cfu/mL in samples collected in winter and summer, respectively. The higher recorded temperatures in summer with respect to winter (the average temperature was 20.3 °C in July and 11.1 °C in November) may be the cause of the higher bacterial counts in summer. However, the growth of related bacteria in some agar plates, some of them invasive (such as Proteus), made the isolation of E. coli complicated. Finally, a total of 42 isolates were obtained from manure, 13 isolates of E. coli from the winter sampling and 29 from the summer sampling, and they were typified in order to be compared with the colonies isolated from air samples. The sampling method used in this work was effective in the recovery of E. coli strains from air. A total of 149 suspicious colonies were obtained, of which 75 were verified as belonging to the E. coli species. Table 1 shows the origin of these 75 isolates, recovered from the sampled air in both the mechanical (AirIdeal) and the stationary procedure. Thus, in area 0 (inside the farm), 47 E. coli isolates were obtained. In winter, 18 E. coli strains (12 by the stationary method and 6 by the mechanical one) were isolated, while in summer the number of isolated strains was slightly higher, 29 (4 and 25 by the stationary and the mechanical methods, respectively). The higher bacterial counts obtained in the summer sampling from organic exudates may explain the greater amount of bacteria isolated from the air in this season. A total of 28 E. coli (7 by the stationary method and 21 by the mechanical one) isolates were recovered in the air samples taken from farm surroundings, including in the sampling points located further away from the animal housing facilities (Table 1). It is noted that, unlike in area 0, the air sampler (mechanical method) was less successful in isolating E. coli at a distance from the farm than the stationary method. This difference in the effectiveness of the two sampling

42

S. Sanz et al. / International Journal of Food Microbiology 197 (2015) 40–44

Table 1 Number of E. coli strains isolated from air samples considering the origin, the method and time of sampling. Number of strains at: Sampling point

Method

Winter

Summer

Area 0

0m

East

50 m

Stationary, 40 cm height Stationary, 70 cm height Stationary, 100 cm height Mechanical (AirIdeal) Stationary, 40 cm height Stationary, 70 cm height Stationary, 100 cm height Mechanical (AirIdeal) Stationary, 40 cm height Stationary, 70 cm height Stationary, 100 cm height Mechanical (AirIdeal) Stationary, 40 cm height Stationary, 70 cm height Stationary, 100 cm height Mechanical Stationary, 40, 70, 100 cm height Mechanical (AirIdeal) Stationary, 40, 70, 100 cm height Mechanical (AirIdeal) Stationary, 40 cm height Stationary, 70 cm height Stationary, 100 cm height Mechanical (AirIdeal) Stationary, 40, 70, 100 cm height Mechanical (AirIdeal) Stationary, 40, 70, 100 cm height Mechanical (AirIdeal) Stationary, 40, 70, 100 cm height Mechanical (AirIdeal) Stationary, 40, 70, 100 cm height Mechanical (AirIdeal) Stationary, 40, 70, 100 cm height Mechanical (AirIdeal) Stationary, 40, 70, 100 cm height Mechanical (AirIdeal)

4 3 5 6 – – – – – – – – – – – – – – – – – 2 1 – – – – – – – – – – – – –

1 1 2 25 3 3 2 3 5 1 3 3 – – 1 – – – – 1 – – – – – – – – – – – – – – – –

100 m

150 m

West

50 m 100 m 150 m

North

50 m 100 m 150 m

South

50 m 100 m 150 m

methods could be explained by the fact that microbial density in the air decreases with increasing the distance from the source. The mechanical procedure takes only 10 min for sampling while the stationary method needs longer time (4 h), increasing the chance of bacterial recovery. In the winter sampling only 3 isolates were recovered and in summer 25 colonies of E. coli were obtained in the surrounding areas. The difference between the number of isolates obtained in summer and those obtained in winter can be attributed to the higher bacterial load present in area 0 in summer. However, considering the bacterial load detected in exudates (4.8 × 104 cfu/mL and 7.8 × 106 cfu/mL in winter and summer, respectively) and, estimating the amount of exudate present in the farm during the sampling period, the rate of bacteria recovered from the air (21 in winter and 54 in summer) was 1/108 in winter and 1/1010 in summer. These low rates of bacterial recovery should be attributed to the fact that only a small fraction of the microorganisms found in the exudates are transferred to the air. In addition, we must take into account the diluting effect of the air and the stressful conditions of the environment, such as light exposure and dehydration. However, this last aspect might explain the differences in bacterial recovery rates between winter and summer; in winter the relative humidity was higher (74%) than in summer (54%). The 3 isolates of the winter sampling were recovered from the west sampling point. Regarding to the 25 colonies of E. coli collected in summer, 24 were obtained from the east and 1 from the west sampling point. The predominant wind direction in the area where the farm is located was, effectively, east/west. It should be noted that, in sampling days, the wind speed was similar, around 5.5–5.8 km/h, but the

direction was opposite: from west to east in summer and from east to west in winter. The predominant wind direction could justify the absence of isolates in any of the sampling points located in north/south direction. Regarding to these data, we may conclude that the wind is a determining factor in bacterial dispersion through the air. The influence of the wind in the microorganism dissemination through the air has already been reported by other authors, especially in molds (Haas et al., 2010; Sen and Asan, 2009). Furthermore, Crozier-Dodson and Fung (2002) studied the airborne microorganisms at an indoor dairy cattle facility and showed the importance of the wind direction in the recovery of microorganisms from air samples. It should be pointed out that, in summer sampling, E. coli was detected in air samples obtained at all the distances: 50, 100 and 150 m. However, in winter sampling, the 3 isolated strains of E. coli were taken at the greatest distance (150 m) from the farm. The sampling height did not seem to be a determining factor and E. coli strains were isolated either at 40, 70 and 100 cm. It is also worth mentioning that the farm was bordered to the east and the west by cultivated fields. Therefore, the continuous emission of enteric and potentially pathogenic bacteria via aerosol from animal housing facilities can increase the likelihood of microbial contamination of crops and, consequently, the risk of foodborne illness associated with consumption of fresh vegetables and fruits. Quantitatively, the risk of vegetable contamination due to the dissemination of bacteria through the air seems to be much lower than the one caused by other vehicles of propagation such as irrigation water or manure (De Roever, 1998; Harrison et al., 2013; Park et al., 2013; Rangarajan et al., 2002; Strawn et al., 2013). However, the data indicate that this dissemination pathway should not be discarded. In addition, is important to mention that air involves a continuous flow of microorganisms. The risk assessment of bacterial contamination by airborne dissemination should be estimated for each specific situation. In order to verify that E. coli strains isolated from the air of the immediate farm environment came from the animal housing facilities, the genomic DNA profiles of E. coli isolates recovered from organic exudates (n = 42) and from air obtained both inside (area 0) and outside of the farm (n = 75) were analyzed and compared by pulsed-field gel electrophoresis (PFGE) after digestion with the endonuclease XbaI. Fig. 1 shows representative PFGE patterns of E. coli strains isolated from different origins. According to the interpretation criteria established by Tenover et al. (1995), the restriction endonuclease XbaI revealed 78 distinct PFGE profiles among the 117 E. coli isolates (67%) obtained in this study from organic exudates and air samples. 18 different PFGE profiles were identified among the 34 isolates of winter period (53%), and, 61 1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Fig. 1. Representative PFGE patterns of E. coli strains isolated from different origins. Molecular size standards (lambda oligomers) are in lanes 1 and 20. Lanes 4 and 16 (P44), 10 and 11 (P53), and 13, 14 and 15 (P50) show indistinguishable banding pattern.

S. Sanz et al. / International Journal of Food Microbiology 197 (2015) 40–44

distinct PFGE profiles among the 83 isolates of summer period, (74%). It should be noted that one of the PFGE profiles was recovered both in the summer and the winter sampling. The greatest variability was found among E. coli strains isolated from the samples taken inside the farm. Thus, 37 distinct PFGE profiles were identified among the 42 isolates obtained from the exudates (88%). Thirteen E. coli strains isolated from exudates in winter exhibited 10 different PFGE profiles (77%), while 29 strains isolated in summer showed 27 distinct PFGE profiles (93%). The observed genetic diversity of studied strains is coherent with previous works that showed the high genetic diversity of E. coli isolates from various environments (McLellan et al., 2003; McLellan, 2004; Souza et al., 1999; Walk et al., 2007). The same high levels of genetic diversity were reported for the E. coli isolates collected from the air of area 0. Thus, 37 distinct PFGE profiles were identified among the 47 isolates obtained from air samples (79%). Eighteen E. coli strains isolated from air of area 0 in winter exhibited 14 different PFGE profiles (78%) while 29 strains isolated in summer showed 22 distinct PFGE profiles (76%). Regarding the strains isolated from outside air, 21 distinct PFGE profiles were identified among 28 obtained E. coli (75%). Three isolates collected in the winter sampling belonged to the same PFGE profile (P3) (33%) and 25 E. coli obtained in the summer sampling exhibited 20 distinct PFGE profiles (80%). Despite the large number of different profiles obtained (n = 78), 12 of them were present in more than one sampling point (Table 2). Thus, some E. coli isolated from exudates showed indistinguishable PFGE profiles with strains isolated from the air of area 0 (P3, P5, P13, P17, P21, P24, P38 and P65). This result indicates that E. coli strains isolated from air of area 0 had their origin in organic exudates. It is also worth mentioning that one of the PFGE profiles (P21) found in summer in the air of area 0 was also present in the winter sampling. Moreover, identical PFGE profiles were observed in strains recovered in air of area 0 and at different distances of the outside surrounding areas (P50, P53 and P56). Finally, and most interestingly, identical PFGE profiles

43

were detected in strains recovered from organic exudates and in the outside farm sampling, either at 50 m of distance (P38 and P44) or even at 150 m of distance (P3). In the case of P3 and P38, the same profile was also identified in strains of the air of the zone 0 (Table 2). Although only 10 of the 28 (about 35%) E. coli isolates recovered from the air distant to the dairy farm could be genetically linked to the farm, it is necessary to note that the genetic heterogeneity of intestinal E. coli of animals and also of humans is very high. For this reason, is more relevant the similar PFGE patterns detected than those that look different. In addition, we cannot discard the farm as the origin of those clones that look different because only a group of isolates recovered, and not all the E. coli that could be in the manure ecosystem, have been studied. Nonetheless, other potential sources (wild animals, human activity) could also be the origin of some air isolates. The detection of identical genomic DNA profiles in E. coli strains recovered from inside and outside samples leads to the conclusion that the air was involved in E. coli dissemination from the inside of the dairy cattle farm to the immediate environment. 4. Conclusion The sampling methodology used in this study, which includes a mechanical and a stationary procedure, was effective for collecting E. coli strains from outside air. This study shows that E. coli can disseminate from the organic exudates present in the farm to the inside and outside air, leading to the conclusion that the air is an important vehicle for the bacterial dissemination between different ecosystems. The wind direction appears as a determining factor in bacterial dispersion through the air. Cattle are an important source of human infections (beef, dairy products, bovine fecal contamination) by pathogenic E. coli (Friesema et al., 2010). The fact that the studied farm is bordered by agricultural fields increases the likelihood of microbial contamination of crops. Taking into account that the air is involved in bacterial dissemination,

Table 2 Origin and sampling characteristics of the E. coli isolated from air and organic exudates samples that showed indistinguishable PFGE profiles. PFGE profile

Number of isolates

Origin

Distance from Area 0 (m)

Sampling method

Sampling season

P3

2 1 1 1 1 1 1 1 1 2 1 1 1 1 2 1 1 1 2 1 1 1 1 1 1 2 1 1 1 1 2 1

Air west Air west Air area 0 Exudate Air area 0 Exudate Air area 0 Air area 0 Air area 0 Exudate Air area 0 Exudate Air area 0 Exudate Air area 0 Exudate Air area 0 Exudate Air east Air east Air area 0 Exudate Air east Exudate Air east Air area 0 Air east Air area 0 Air east Air area 0 Air area 0 Exudate

150 150 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 50 50 0 0 50 0 100 0 100 0 100 0 0 0

Stationary, 70 cm height Stationary, 100 cm height Mechanical (AirIdeal)

Winter Winter Winter Winter Winter Winter Winter Winter Winter Winter Winter Winter Winter Winter Summer Summer Winter Winter Summer Summer Summer Summer Summer Summer Summer Summer Summer Summer Summer Summer Summer Summer

P5 P13

P17 P21

P24 P38

P44 P50 P53 P56 P65

Mechanical (AirIdeal) Stationary, 40 cm height Stationary, 70 cm height Mechanical (AirIdeal) Stationary, 40 cm height Stationary, 100 cm height Mechanical (AirIdeal) Mechanical (AirIdeal) Stationary, 40 cm height Stationary, 70 cm height Mechanical (AirIdeal) Stationary, 100 cm height Stationary, 40 cm height Mechanical (AirIdeal) Stationary, 40 cm height Stationary, 40 cm height Stationary, 100 cm height Mechanical (AirIdeal) Mechanical (AirIdeal)

44

S. Sanz et al. / International Journal of Food Microbiology 197 (2015) 40–44

sewage treatment plants, farms, and compost plants, among others, should be considered as a potential source of bacteria that might be implicated in foodborne outbreaks. Acknowledgments This study has been undertaken with a grant from the University of La Rioja: PROFAI13/04 Project. C. Andrea Alonso has a predoctoral FPI fellowship of the Ministerio de Economía y Competitividad of Spain (BES-2013-063105) References Al-Dagal, M., Fung, D.Y.C., 1990. Aeromicrobiology — a review. Food Sci. Nutr. 29, 333–340. Crozier-Dodson, B.A., Fung, D.Y.C., 2002. Comparison of recovery of airborne microorganisms in a dairy cattle facility using selective agar and thin agar layer resuscitation media. J. Food Prot. 65, 1488–1492. De Roever, C., 1998. Microbial safety evaluations and recommendations of fresh produce. Food Control 6, 321–347. EFSA (European Food Safety Authority), 2011. Urgent advice on the public health risk of Shiga-toxin producing Escherichia coli in fresh vegetables. EFSA J. 9, 2274–2324. Friesema, I., Sigmundsdottir, G., van der Zwaluw, K., Heuvelink, A., Schimmer, B., de Jager, C., Rump, B., Briem, H., Hardardottir, H., Atladottir, A., Gudmundsdottir, E., van Pelt, W., 2008. An international outbreak of Shiga toxin-producing Escherichia coli O157 infection due to lettuce, September–October 2007. Euro Surveill. 13 (50) (Pii:19065). Friesema, I.H., van de Kassteele, J., de Jager, C.M., Heuvelink, A.E., van Pelt, W., 2010. Geographical association between lives tock density and human Shiga toxin-producing Escherichia coli O157 infections. Epidemiol. Infect. 8, 1–7. Garijo, P., Santamaría, P., López, R., Sanz, S., Olarte, C., Gutiérrez, A.R., 2008. The occurrence of fungi, yeasts and bacteria in the air of a Spanish winery during vintage. Int. J. Food Microbiol. 125, 141–145. Garijo, P., Santamaría, P., Ocón, E., López, R., Sanz, S., Olarte, C., Gutiérrez, A.R., 2009. Presence of lactic acid bacteria in the air of a winery along one vintage. Int. J. Food Microbiol. 136, 142–146. Garijo, P., López, R., Santamaría, P., Ocón, E., Olarte, C., Sanz, S., Gutiérrez, A.R., 2011. Presence of enological microorganisms in the air of a vineyard during the ripening period. Int. Eur. Food Res. Technol. 233, 359–365. Giménez, M., Olarte, C., Sanz, S., Lomas, C., Echávarri, J.F., Ayala, F., 2003a. Influence of packaging films on microbiological and sensorial evolution of minimally processed borage (Borago officinalis). J. Food Sci. 68, 1051–1058. Giménez, M., Olarte, C., Sanz, S., Lomas, C., Echávarri, J.F., Ayala, F., 2003b. Relation between spoilage and microbial quality in minimally processed artichoke packaged with different films. Food Microbiol. 20, 231–242. González, R.D., Tamagnini, L.M., Olmos, P.D., De Sousa, G.B., 2002. Evaluation of a chromogenic medium for total coliforms and Escherichia coli determination in ready-to-eat food. Food Microbiol. 20, 601–604. Haas, D., Galler, H., Habib, J., Melkes, A., Schlacher, R., Buzina, W., Friedl, H., Marth, E., Reinthaler, F.F., 2010. Concentrations of viable airborne fungal spores and trichloroanisole in wine cellars. Int. J. Food Microbiol. 144, 126–132. Harrison, J.A., Gaskin, J.W., Harrison, M.A., Cannon, J.L., Boyer, R.R., Zehnder, J.W., 2013. Survey of food safety practices on small to medium-sized farms and in farmers markets. J. Food Prot. 11, 1989–1993. Heininger, A., Binder, M., Schmidt, S., Unertl, K., Botzenhart, K., Döring, G., 1999. PCR and blood culture for detection of Escherichia coli bacteremia in rats. J. Clin. Microbiol. 37, 2479–2482. McLellan, S.L., 2004. Genetic diversity of Escherichia coli isolated from urban rivers and beach waters. Appl. Environ. Microbiol. 70, 4658–4665.

McLellan, S.L., Daniels, A.D., Salmore, A.K., 2003. Genetic characterization of Escherichia coli populations from host sources of fecal pollution by using the DNA fingerprints. Appl. Environ. Microbiol. 69, 2587–2594. Michino, H., Araki, K., Minami, S., Takaya, S., Sakai, N., Miyazaki, M., Ono, A., Yanagawa, H., 1999. Massive outbreak of Escherichia coli O157:H7 infection in schoolchildren in Sakai City, Japan associated with consumption of white radish sprouts. Am. J. Epidemiol. 150, 787–796. Mora, A., Herrera, A., López, C., Dahbi, G., Mamani, R., Pita, J.M., Alonso, M.P., Llovo, J., Bernárdez, M.I., Blanco, J.E., Blanco, M., Blanco, J., 2011. Characteristics of the Shiga-toxin-producing enteroaggregative Escherichia coli O104:H4 German outbreak strain and of STEC strains isolated in Spain. Int. Microbiol. 14, 121–141. Ocón, E., Gutiérrez, A.R., Garijo, P., Santamaría, P., López, R., Olarte, C., Sanz, S., 2011. Factors of influence in the distribution of mold in the air in a wine cellar. J. Food Sci. 76, 169–174. Ogden, I.D., Brown, G.C., Gallacher, S., Garthwaite, P.H., Gennari, M., González, M.P., Jørgensen, L.B., Lunestad, B.T., MacRae, M., Nunes, M.C., Petersen, A.C., Rosnes, J.T., Vliegenthart, J., 1998. An interlaboratoy study to find an alternative to the MNP technique for enumerating Escherichia coli in shellfish. Int. J. Food Microbiol. 40, 57–64. Park, S., Navratil, S., Gregory, A., Bauer, A., Srinath, I., Jun, M., Szonyi, B., Nightingale, K., Anciso, J., Ivanek, R., 2013. Generic Escherichia coli contamination of spinach at the preharvest stage: effects of farm management and environmental factors. Appl. Environ. Microbiol. 14, 4347–4358. Rangarajan, A., Pritts, M.P., Reiners, S., Pedersen, L.H., 2002. Focusing food safety training based on current grower practices and farm scale. HortTechnology 1, 126–131. Sáenz, Y., Brinas, L., Domínguez, E., Ruiz, J., Zarazaga, M., Vila, J., Torres, C., 2004. Mechanisms of resistance in multiple-antibiotic-resistant Escherichia coli strains of human, animal, and food origins. Antimicrob. Agents Chemother. 48, 3996–4001. Sanz, S., Giménez, M., Lomas, C., Olarte, C., Portu, J., 2002. Effectiveness of chlorine washing disinfection and effects on the appearance of artichoke and borage. J. Appl. Microbiol. 93, 986–993. Sanz, S., Giménez, M., Olarte, C., 2003. Survival and growth of enterohemorrhagic Escherichia coli O157:H7 and Listeria monocytogenes in minimally processed artichoke. J. Food Prot. 66, 2203–2209. Sen, B., Asan, A., 2009. Fungal flora in indoor and outdoor air of different houses in Tekirdag City (Turkey): seasonal distribution and relationship with climatic factors. Environ. Monit. Assess. 151, 209–219. Shale, K., Lues, J.F.R., 2007. The aetiology of bioaerosols in food environments. Food Rev. Int. 23, 73–90. Södeström, A., Osterberg, P., Lindqvist, A., Jönsson, B., Lindberg, A., Blide Ulander, S., Welinder-Olsson, C., Löfdahl, S., Kaijser, B., De Jong, B., Kühlmann-Berenzon, S., Boqvist, S., Eriksson, E., Szanto, E., Andersson, S., Allestam, G., Hedenström, I., Ledet Muller, L., Andersson, Y., 2008. A large Escherichia coli O157 outbreak in Sweden associated with locally produced lettuce. Foodborne Pathog. Dis. 5, 339–349. Souza, V., Rocha, M., Valera, A., Eguiarte, L.E., 1999. Genetic structure of natural populations of Escherichia coli in wild host and different continents. Appl. Environ. Microbiol. 65, 3373–3385. Strawn, L., Grohn, Y.T., Warchocki, S., Worobo, R.W., Bihn, E.A., Wiedmann, M., 2013. Risk factors associated with Salmonella and Listeria monocytogenes contamination on produced fields. Appl. Environ. Microbiol. 24, 7618–7627. Tenover, F.C., Arbeit, R.D., Goering, R.V., Mikelsen, P.A., Murray, B.E., Persing, D.H., Swaminathan, B., 1995. Interpreting chromosomal DNA restriction patterns produced by pulsed-filed gel electrophoresis criteria for bacterial strain typing. J. Clin. Microbiol. 33, 2233–2239. Turner, K.M., Restaino, L., Frampton, E.W., 2000. Efficacy of Chromocult Coliform Agar for Coliform and Escherichia coli detection in foods. J. Food Prot. 63, 539–541. Walk, S.T., Alm, E.W., Calhoun, L.M., Mladonicky, J.M., Whittam, T.S., 2007. Genetic diversity and population structure of Escherichia coli isolated from fresh water beaches. Environ. Microbiol. 9, 2274–2288. Wendel, A.M., Jonhson, D.H., Sharapov, U., Grant, J., Archer, J.R., Monson, T., Koschmann, C., Dacis, J.P., 2009. Multistate of Escherichia coli O157:H7 infection associated with consumption of packaged spinach, August–September 2006: the Wisconsim investigation. Clin. Infect. Dis. 48, 1079–1086.

Airborne dissemination of Escherichia coli in a dairy cattle farm and its environment.

There are multiple ways bacteria can be transported from its origin to another area or substrate. Water, food handlers, insects and other animals are ...
421KB Sizes 0 Downloads 7 Views