Microbial assessment of irrigation water used for production of fruit and vegetables in Ontario, Canada

Five hundred one irrigation water samples were collected from 27 irrigation water sources on 17 farms in southern Ontario, Canada, over a single irrigation season in 2002. The water samples were tested for the presence of the following bacterial water quality indicators: total coliform bacteria, fecal coliforms, Escherichia coli, and fecal streptococci. The median values per 100 ml of these indicators in the irrigation water samples were 3,000, 33, 15, and 1, respectively. Between 70.6 and 98.2% of irrigation water samples contained acceptable levels of fecal coliforms or E. coli, according to published irrigation water quality guidelines. Significant correlations (P < 0.05) were observed between the concentrations of different bacterial indicators and the degree of recent precipitation and concentrations of total coliforms and fecal streptococci. With the exception of fecal streptococci, which increased in number toward the end of the study, none of the indicators displayed a significant trend over the course of the season, as determined by linear regression analysis of indicator concentrations over time (P > 0.05).     

Retail food safety risks for populations of different races, ethnicities, and income levels

Research has found that populations with low socioeconomic status (SES) and minority populations have greater access to small corner markets and less access to supermarkets than high-SES and Caucasian populations. This represents a significant difference in the farm-to-fork continuum that these populations experience. This research examined whether differential retail access to foods results in different food safety risks at the retail level for consumers with different demographics. U.S. Census Bureau census tracts with high African American, Asian, Hispanic, Caucasian, low-SES, and high-SES populations were identified in Philadelphia, PA. Approximately 60 retail food establishments were sampled in each census tract category from June 2008 to June 2010. Food samples collected at stores included milk, eggs, lunchmeat, sandwiches, and ready-to-eat (RTE) fresh fruit, greens, and herbs, when available. With the exception of milk and eggs, only food that had been handled and/or prepared at the retail level was sampled. Food samples were tested for temperature, aerobic plate count, coliforms, fecal coliforms, Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes. The results indicated that internal egg temperatures were higher in samples from low-SES census tracts than in eggs from Caucasian census tracts, and eggs were more often found unrefrigerated in markets in low-SES and Asian census tracts. Milk samples from markets in Hispanic and low-SES census tracts had higher aerobic plate counts than high-SES census tract samples. Sandwiches from markets in high-SES census tracts had higher coliform counts than sandwiches from markets in all other census tract categories. Markets in Asian census tracts had a higher incidence of fecal coliform contamination on sandwiches than markets in Caucasian census tracts. Fecal coliforms were present in a percentage of RTE greens from markets in all census tracts except African American, with the highest percentages of RTE greens positive for fecal coliforms in low-SES (100%), Asian (71.4%), and Caucasian (45.5%) markets.     

Feedstock optimization of in-vessel food waste composting systems for inactivation of pathogenic microorganisms

An optimum composting recipe was investigated to reduce pathogenic microorganisms in a forced-aerated in-vessel system (55 liters). The feedstocks used for in-vessel composting were food waste, cow manure, and bulking materials (wood shavings and mulch hay). A statistical extreme vertices mixture design method was used to design the composting experiments and analyze the collected data. Each mixture (nine total) was replicated randomly three times. Temperature was monitored as an indicator of the efficiency of the composting experiments. The maximum temperature values of the mixtures were used as a response for both extreme vertices mixture design and statistical analyses. Chemical changes (moisture content, carbon/nitrogen ratio, volatile solids, and pH) and reductions of indicator (fecal coliforms and fecal streptococci) and pathogenic microorganisms (Salmonella and Escherichia coli O157:H7) were measured by the most-probable-number method before and after a 12-day composting period. Maximum temperatures for the tested compost mixtures were in the range of 37.0 to 54.7 degrees C. Extreme vertices mixture design analysis of the surface plot suggested an optimum mixture containing 50% food waste, 40% manure, and 10% bulking agents. This optimum mixture achieved maximum temperatures of 54.7 to 56.6 degrees C for about 3.3 days. The total reduction of Salmonella and E. coli O157:H7 were 92.3%, whereas fecal coliforms and fecal streptococci reductions were lower (59.3 and 27.1%, respectively). Future study is neededto evaluate the extreme vertices mixture design method for optimization of large-scale composting.     

A survey on the microbiological quality of various cheeses in Turkey

A survey was made at the retail level in the Erzurum, Erzincan and Van markets to study the microbial characteristics of pickled white cheese, Erzincan (Savak) Tulum cheese and Van herby cheese, the most typical cheeses of Turkey. Significant variation was found in their microbiological quality. Microbiological analysis revealed the presence of extremely high numbers of total bacteria, faecal streptococci, other microorganisms including coliforms, Staphylococcus aureus, yeast and mould, lipolytic and proteolytic microorganisms and lactic acid bacteria. A statistical relationship between the number of microorganisms and variety of cheese type was investigated.     

Quantitative application of fecal sterols using gas chromatography-mass spectrometry to investigate fecal pollution in tropical waters: western Malaysia and Mekong Delta,Vietnam

This is the first report on fecal pollution using molecular markers in Southeast Asia where serious sewage pollution has occurred. A simple and sensitive analytical method using gas chromatography-mass spectrometry for 10 sterols in various environmental samples was developed to monitor extensive areas of tropical Asia. First, the method was applied to wastewater to confirm that >95% of sterols existed in the particulate phase. Then the approach was applied to a tropical Asian region, Malaysia and Vietnam, with a selection of 59 sampling stations in total. River water and sediment samples were collected and analyzed for chemical markers (coprostanol and other sterols) and microbiological markers (fecal coliforms and fecal streptococci). Particulate coprostanol concentrations ranged from <0.0001 to 13.47 microg/L in tropical river and estuarine waters, indicating severe fecal pollution in populous areas. Coprostanol concentrations in the sediments ranged from 0.005 to 15.5 microg/g-dry. The sedimentary coprostanol concentrations were lower than those reported in some urban areas of industrialized countries. This is probably because frequent heavy rain induces intensive input of eroded soil, which dilutes fecal material in river sediments. The relationship between the concentrations of fecal sterols and bacterial indicators was examined in an attempt to develop public health criteria for coprostanol levels applicable to the tropical region. Coprostanol concentrations of 30-100 ng/L or percent coprostanol levels of 2% corresponded to approximately 1000 fecal coliforms per 100 mL, which is set for secondary contact limit in many countries. These coprostanol concentrations were lower than those proposed as criteria in temperate countries, probably owing to greater survival of bacteria in warmer tropical waters. On the basis of these criteria, extensive monitoring of sediments suggests that poor sanitary conditions exist in most of the urbanized area of Malaysia and in several urban and rural sites in Vietnam.     

Coliphage as an indicator of fecal contamination in hydroponic cucumber (Cucumis sativus L) greenhouses

A preliminary study has been performed to evaluate the utility of somatic and F⁺‐specific coliphage as quality indicators of irrigation water used in hydroponic cucumber greenhouse operations. Samples of incoming water, waste hydroponic solution, cucumber fruit and plant roots derived from two greenhouses were screened for bacterial fecal indicators (generic Escherichia coli, fecal coliforms, total coliforms and Clostridium perfringens) and coliphage. Bacterial fecal indicators were present in incoming water and in spent hydroponic solution with coliphage only being sporadically recovered. However, both somatic and F⁺‐specific coliphage were consistently recovered from the roots of cucumber plants along with bacterial fecal indicators. Despite the heavy contamination of plant roots, the cucumber fruits were within acceptable microbiological limits. F⁺‐specific coliphage was recovered from 1 out of 25 cucumbers tested along with generic E coli. In contrast, no somatic coliphage was recovered from cucumbers despite coliforms being present on 15 out of 25 units. In conclusion, coliphage represents a poor index of hydroponic irrigation water quality but presence on cucumber fruit and roots can be used to highlight the presence of fecal indicator bacteria within greenhouse operations. Copyright © 2005 Society of Chemical Industry     

Market survey of Vibrio spp. and other microrganisms in Italian shellfish

A survey was conducted of Vibrio spp., Escherichia coli, fecal coliforms, and Salmonella in 644 molluscan shellfish samples marketed in the Apulia region of southern Italy. Vibrios were found in 278 samples (43%), and levels of E. coli and fecal coliforms were above the Italian legal limit in 27 and 34 samples (4 and 5%), respectively. Salmonella was not detected in any of the samples. Because the majority of the vibrio isolates were found in samples that were compliant with Italian regulations, there appears to be no relationship between the presence of microorganisms of fecal origin and the presence of vibrios potentially harmful to human health.     

Incidence of faecal streptococci as an indicator of sanitation in ice-cream and frozen vegetables

Fifty-three ice-cream and fifty-five frozen vegetable samples, collected from two different factories, were analysed for total coliform bacteria, faecal coliform bacteria and faecal streptococci so that the value of faecal streptococci as an indicator of faecal contamination and sanitation in ice-cream and frozen vegetables could be evaluated. Thirty-two per cent of the ice-cream samples and 73% of the frozen vegetable samples were positive for coliform bacteria, whereas only 4% of the ice-cream samples and 24% of the frozen vegetable samples contained faecal coliform bacteria. Occurrence of faecal streptococci in the ice-cream and frozen vegetable samples were 81 and 75%, respectively. These results indicate that there is no direct relationship between the presence of faecal coliforms and faecal streptococci, and the high occurrence of faecal streptococci in frozen foods examined suggests that faecal streptococci is a better sanitary indicator in frozen food products.     

Suitability of log-linear models to evaluate the microbiological quality of baby clams (Chamelea gallina L.) harvested in the Adriatic Sea

The presence of fecal coliforms or Escherichia coli in baby clams (Chamelea gallina L.) is considered an indicator related to their safety because they can be correlated with the presence of pathogenic bacteria. For this reason the Italian regulation has defined limits for these microorganisms. The presence of these microbial indicators is dependent on various environmental variables. In this work all the variables considered are categorical and, consequently, the traditional approach of predictive microbiology was not applicable. The data were summarized by means of a cross-tabulation and analyzed using the log-linear model technique. This statistical technique is widely used in social and economic studies but only partially developed in food microbiology. The suitability of the log-linear model to analyse microbiological data in relation to environmental variables was evaluated. In particular, the microbiological quality of baby clams harvested in five different areas of the Adriatic Sea coast in Emilia Romagna (Italy) was considered. The influence of the season and geographical origin on microbiological standards was assessed. A logit model was developed to predict the frequencies, depending on geographical origin and season, of samples with concentrations of the indicator organisms below or above the legal standards provided by Italian regulation.     

Salmonella and the sanitary quality of aquacultured shrimp

In this study, we examined the prevalence of Salmonella and coliform bacteria on shrimp aquaculture farms to develop guidelines or preventative measures for reducing Salmonella and fecal contamination on products harvested from these farms. The U.S. Food and Drug Administration, in conjunction with foreign government regulatory agencies, the aquaculture industry, and academia affiliates, analyzed 1,234 samples from 103 shrimp aquaculture farms representing six countries between July 2001 and June 2003 for fecal coliforms, Escherichia coli, and Salmonella. A significant relationship was found (P = 0.0342) between the log number of fecal bacteria and the probability that any given sample would contain Salmonella. The likelihood of any given sample containing Salmonella was increased by 1.2 times with each 10-fold increase in either fecal coliform or E. coli concentration. The statistical relationship between Salmonella concentration and that of both fecal coliforms and E. coli was highest in grow-out pond water (P = 0.0042 for fecal coliforms and P = 0.0021 for E. coli). The likelihood of finding Salmonella in grow-out pond water increased 2.7 times with each log unit increase in fecal coliform concentration and 3.0 times with each log unit increase in E. coli concentration. Salmonella is not part of the natural flora of the shrimp culture environment nor is it inherently present in shrimp grow-out ponds. The occurrence of Salmonella bacteria in shrimp from aquaculture operations is related to the concentration of fecal bacteria in the source and grow-out pond water.     

POULTRY PRODUCT QUALITY. 5. Microbiological Evaluation of Mechanically Deboned Poultry Meat

SUMMARY —Samples of deboned meat from broiler necks and backs, whole fowl and turkey racks were obtained from commercial sources and examined for total aerobic counts, fecal coliforms, salmonellae, Clostridium perfringens, coagulase positive staphylococci and psychrotolerant microorganisms. The raw materials were either deboned immediately after birds were processed (conventional processing) or held in the plants at 3–5°C for 5 days prior to deboning (delayed processing). The storage studies were conducted by holding the deboned meat at 3°C for 0, 3, 6 and 12 days and at -15°C for periods of 3, 6 and 9 months. The total aerobic counts of delayed processed samples were shown to be higher than conventionally processed meat and remained the same throughout the storage period. In all instances, the total aerobic counts increased during the storage at 3°C. The MPN fecal coliforms were high for all samples and remained relatively the same throughout the storage period at 3°C. Freezing resulted in a significant reduction of fecal coliforms. Only six out of 54 samples were contaminated with salmonellae while four showed the presence of C. perfringens and none was contaminated with S. aureus. Pseudomonas, Achromobac-ter and Flavobacterium dominated the psychrotolerant genera isolated in this investigation.     

Comparison of destructive and nondestructive sampling techniques of retail chicken carcasses for enumeration of hygiene indicator microorganisms

The type of sampling technique used to obtain food samples is fundamental to the success of microbiological analysis. Destructive and nondestructive techniques, such as tissue excision and rinsing, respectively, are widely employed in obtaining samples from chicken carcasses. In this study, four sampling techniques used for chicken carcasses were compared to evaluate their performances in the enumeration of hygiene indicator microorganisms. Sixty fresh chicken carcasses were sampled by rinsing, tissue excision, superficial swabbing, and skin excision. All samples were submitted for enumeration of mesophilic aerobes, Enterobacteriaceae, coliforms, and Escherichia coli. The results were compared to determine the statistical significance of differences and correlation (P < 0.05). Tissue excision provided the highest microbial counts compared with the other procedures, with significant differences obtained only for coliforms and E. coli (P < 0.05). Significant correlations (P < 0.05) were observed for all the sampling techniques evaluated for most of the hygiene indicators. Despite presenting a higher recovery ability, tissue excision did not present significant differences for microorganism enumeration compared with other nondestructive techniques, such as rinsing, indicating its adequacy for microbiological analysis of chicken carcasses.     

Microbiological survey of retail herbs and spices from Mexican markets

In the present study, 304 samples of herbs and spices (garlic powder, cumin seeds, black pepper, oregano, and bay leaves) widely used in Mexico were analyzed for the presence of Bacillus cereus, Salmonella Typhi, Shigella dysenteriae, Escherichia coli, total and fecal coliforms, total mesophilic aerobic organisms, and fungi. Samples were nonpackaged or packaged in polyethylene bags or glass containers. High levels (10(5) to 10(7) CFU/g) of mesophilic aerobic microorganisms were found in most of the samples of garlic powder, cumin seed, and black pepper. Lower levels (<102 CFU/g) were found in oregano and bay leaves. Total and fecal coliforms counts were dependent on the type of packaging. More than 70% of the polyethylene-packaged samples had less than 10(3) CFU/g of microorganisms. Glass and nonpackaged spices showed lower levels of these microorganisms. B. cereus was present in 32 samples of which most were polyethylene packaged. The other pathogenic bacteria were not detected. Aspergillus niger was detected in 29% of the samples, Rhizopus sp. in 19%, and Penicillum sp. and Cunninghamella in 8%.     

Assessment of the microbiological quality and wash treatments of lettuce served in University restaurants

One hundred and forty-four samples of lettuce from 16 University restaurants were analyzed. The mesophilic aerobic counts of all samples ranged from 3.01 to 7.81 log10 CFU g(-1). Results of total coliforms ranged from < 0.47 to > 3.38 log10 most probable number (MPN) g(-1). Of the lettuce samples, 25.7% harbored Escherichia coli, 22.9% Staphylococcus aureus and 84% group D streptococci. Similarly, 10.4% of the samples harbored Aeromonas hydrophila, 2.8% Pseudomonas aeruginosa, and coliforms such as 14.6% Citrobacter freundii, 8.3% Klebsiella pneumoniae, 4.2% Enterobacter cloacae and 1.4% Providencia spp. Salmonella, Shigella and E. coli O157:H7 were not detected. When sodium hypochlorite or potassium permanganate solutions were used in washing procedures, the aerobic microorganisms were reduced by more than two log units, and total coliforms by at least one log.     

Minimally processed vegetable salads: microbial quality evaluation

The increasing demand for fresh fruits and vegetables and for convenience foods is causing an expansion of the market share for minimally processed vegetables. Among the more common pathogenic microorganisms that can be transmitted to humans by these products are Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella. The aim of this study was to evaluate the microbial quality of a selection of minimally processed vegetables. A total of 181 samples of minimally processed leafy salads were collected from retailers in the city of Sao Paulo, Brazil. Counts of total coliforms, fecal coliforms, Enterobacteriaceae, psychrotrophic microorganisms, and Salmonella were conducted for 133 samples. L. monocytogenes was assessed in 181 samples using the BAX System and by plating the enrichment broth onto Palcam and Oxford agars. Suspected Listeria colonies were submitted to classical biochemical tests. Populations of psychrotrophic microorganisms >10(6) CFU/g were found in 51% of the 133 samples, and Enterobacteriaceae populations between 10(5) and 106 CFU/g were found in 42% of the samples. Fecal coliform concentrations higher than 10(2) CFU/g (Brazilian standard) were found in 97 (73%) of the samples, and Salmonella was detected in 4 (3%) of the samples. Two of the Salmonella-positive samples had <10(2) CFU/g concentrations of fecal coliforms. L. monocytogenes was detected in only 1 (0.6%) of the 181 samples examined. This positive sample was simultaneously detected by both methods. The other Listeria species identified by plating were L. welshimeri (one sample of curly lettuce) and L. innocua (2 samples of watercress). The results indicate that minimally processed vegetables had poor microbiological quality, and these products could be a vehicle for pathogens such as Salmonella and L. monocytogenes.     

Relationship among fecal coliforms and <Emphasis Type="Italic"> Escherichia coli </Emphasis>in various foods

For much of the twentieth century, coliform bacteria and especially Escherichia coli have been used as indicators of possible post-processing contamination and the presence of E. coli as an indicator of fecal contamination in foods. In this study, 500 foods in 10 different groups, mainly dairy products, delicatessen products, salads, spices, cream cakes and fresh fruit and vegetable samples, were analyzed for the natural contamination of fecal coliforms and E. coli by the standard most probable number (MPN) method. The difference between weighted means of fecal coliforms and E. coli counts were only 0.246 log₁₀ MPN/g-ml (MPN/gram for solid samples, and MPN/milliliter for liquids). Enumeration results were also evaluated by Pearson's correlation coefficient ( r), Cronbach's alpha (f) and determination coefficient ( r ²) analysis. According to results, although 33 samples contained only non- E. coli fecal coliforms, the results of reliability analyses indicated that fecal coliform counts and E. coli counts may be used interchangeably ( P <0.0001). It can be said that fecal coliform or, preferably E. coli analysis is sufficient for rapid routine determination of fecal contamination, at least for those food groups analyzed in this research.     

Prevalence of Salmonellae on Beef Products at Butcheries and their Antibiotic Resistance Profiles

We determined the aerobic plate count at 5 and 25 °C, presence of total coliforms, fecal coliforms, and Escherichia coli, and prevalence of Salmonella species in 354 meat products collected from butcheries. The aerobic counts varied from 3.5 to 10.7 log₁₀ CFU/g. Most of the microorganisms were psychrotrophic. Coliforms were present in all samples except kidneys. Escherichia coli was present at ≥2 log₁₀ CFU/g in ≥50% of the minced meat, liver, and stew. Salmonella species were present in 9.9% of the samples. Minced meat and tripe contained more salmonellae than the other beef. Serogroup E or G (57.1%) was the most predominant serotype. Tetracycline resistance (33.3%) was higher than that of other antibiotics.     

Validation of acid washes as critical control points in hazard analysis and critical control point systems

A 2% lactic acid wash used in a large meat-processing facility was validated as an effective critical control point (CCP) in a hazard analysis and critical control point (HACCP) plan. We examined the microbial profiles of beef carcasses before the acid wash, beef carcasses immediately after the acid wash, beef carcasses 24 h after the acid wash, beef subprimal cuts from the acid-washed carcasses, and on ground beef made from acid-washed carcasses. Total mesophilic, psychrotrophic, coliforms, generic Escherichia coli, lactic acid bacteria, pseudomonads, and acid-tolerant microorganisms were enumerated on all samples. The presence of Salmonella spp. was also determined. Acid washing significantly reduced all counts except for pseudomonads that were present at very low numbers before acid washing. All other counts continued to stay significantly lower (P < 0.05) than those on pre-acid-washed carcasses throughout all processing steps. Total bacteria, coliforms, and generic E. coli enumerated on ground beef samples were more than 1 log cycle lower than those reported in the U.S. Department of Agriculture Baseline data. This study suggests that acid washes may be effective CCPs in HACCP plans and can significantly reduce the total number of microorganisms present on the carcass and during further processing.     

Microbiological evaluation of stuffed mussels

Stuffed mussel is a traditional food, sold by street vendors in coastal parts of Turkey and other Mediterranean countries. In the present study, the microbiological quality of not only the stuffing mixture, but also the outer surface of the stuffed mussels was evaluated for 1 year, and the effect of the ambient temperatures on the prevalence and the count levels of the microorganisms were evaluated. Fifty samples (750 stuffed mussels in total) were collected periodically, and microbiological analyses were performed by standard procedures for aerobic plate count, coliforms, fecal coliforms, Enterobacteriaceae, Staphylococcus aureus, Bacillus cereus, and Vibrio spp. Aerobic plate counts above 5 log CFU/g were obtained in 16 and 72% of stuffing mixture samples at high and low ambient temperatures, respectively, and average aerobic plate counts of outer surface samples at high and low ambient temperatures were 3.21 and 4.34 log CFU/ml, respectively. The prevalence and the count levels of coliforms, fecal coliforms, Enterobacteriaceae, and Vibrio spp. (except for the prevalence of Vibrio spp. in stuffing mixture samples) in the samples at high ambient temperatures were considerably higher compared with those at low ambient temperatures (P < 0.05). High frequencies of pathogens S. aureus and B. cereus were found in stuffing mixture samples at high ambient temperatures, with averages of 2.84 and 2.94 log CFU/g, respectively (P < 0.05). The result of this investigation indicates that stuffed mussels as a street food may constitute a potential health hazard, especially at high ambient temperatures, depending on contamination level and lack of sanitary practices, and therefore, handling practices should require more attention and improvement.     

Fecal shedding of Salmonella spp. by dairy cows on farm and at cull cow markets

As part of a national study of the U.S. dairy cow population, fecal samples were collected from representative cows on 91 dairies and 97 cull dairy cow markets in 19 states. Salmonella spp. were recovered from 5.4% of milk cows, 18.1% of milk cows expected to be culled within 7 days, and 14.9% of culled dairy cows at markets. On a premise basis, Salmonella shedding in milk cows was detected on 21.1% of dairies and 66% of cull dairy cow markets. The percentage of herds with at least one cow with detectable Salmonella fecal shedding was higher during the sampling period from May through July, in herds with at least 100 milk cows, and in herds in the South region. The most common Salmonella serogroups isolated were E (30.8% of isolates) and C1 (28.6%); the most common serotypes isolated were Salmonella Montevideo (21.5% of isolates), Salmonella Cerro (13.3%), and Salmonella Kentucky (8.5%). Fecal shedding of Salmonella Typhimurium or Salmonella Typhimurium var. copenhagen was infrequent (2.8% of isolates). Most isolates (88.9%) were susceptible to all 17 antimicrobials evaluated; multiple resistance was an infrequent occurrence. This study provides information describing the distribution of Salmonella fecal shedding from dairy cows on farm and at markets and will serve as a baseline for future studies.