Determination of changes in the microbial and chemical composition of Țaga cheese during maturation.

Țaga cheese is a traditional Romanian smear-ripened cheese made from bovine milk and identified with the name of the village and caves where it is produced. As no previously reported microbiological and chemical studies have been undertaken on this product, this research aimed to investigate the microbiological and biochemical characteristics which ensure the uniqueness of Țaga cheese during the ripening process, to inform producers as to key quality determinants. Cheese samples, consisting of retail blocks, were collected on days 2, 5, 12, 18, and 25 of the ripening process. The evolution of lactic microbiota during the production and maturation of traditional cheeses involves isolating lactic acid microorganisms present in cheese. Cheese samples were analyzed for pH, fat, NaCl, fatty acids, and volatile compounds. The microbial ecosystem naturally changes during the maturation process, leading to variation in the microorganisms involved during ripening. Our results show that specific bacteria were identified in high levels during the entire ripening process and may be responsible for milk fat lipolysis contributing directly to cheese flavor by imparting detailed fatty acid flavor notes, or indirectly as precursors formation of other flavor compounds.

Phytochemical Composition and Biological Activity of Berries and Leaves from Four Romanian Sea Buckthorn (Hippophae Rhamnoides L.) Varieties.

Hippophae rhamnoides L. is an important source of natural antioxidant and antimicrobial agents. Phytochemical compounds, antioxidant and antibacterial properties of berries, and leaf extracts from four Romanian sea buckthorn cultivars were investigated. Large differences in the content of total polyphenols and flavonoids between the varieties were observed. HPLC analysis of the polyphenolic compounds showed greater differences in content in leaves than in berries. This study confirmed that sea buckthorn leaves and berries are a rich source of phenolic compounds, especially quercetin derivatives and hydrocinnamic acid derivatives. Five carotenoid compounds were identified in the berries: lutein, zeaxanthin, ß-cryptoxanthin, cis-ß-carotene, and ß-carotene. From the results obtained in this study, it can be stated that the varieties whose berries yielded the highest quantities of polyphenols, flavonoids, and antioxidant activity, can be ranked as follows: SF6 > Golden Abundant > Carmen > Colosal, and for leaf extracts the ranked order is SF6 > Golden Abundant > Colosal > Carmen. A strong correlation between the total flavonoid yield and antioxidant activity (r = 0.96), was observed. All extracts showed antibacterial activity against S. aureus, B. cereus, and P. aeruginosa, however extracts from berries were less potent than extracts from leaves.

Virulence characteristics of hcp (+) Campylobacter jejuni and Campylobacter coli isolates from retail chicken.

BACKGROUND: Recently the Type VI secretion system (T6SS), which can play a significant role in bacterial survival and pathogenesis, was reported in Campylobacter spp., having the hcp gene as a key component. METHODS: Campylobacteriosis is associated with the consumption of infected chicken meat. Our study aimed to explore the presence of T6SS in C. jejuni (n = 59) and C. coli (n = 57) isolates, from retail raw chicken and to investigate their pathogenic potential. The hcp gene was used as an indicator for the T6SS presence. RESULTS: Using multiplex PCR we have identified a significantly higher prevalence of hcp in C. coli isolates (56.1%) than in C. jejuni (28.8%) and AFLP analysis of the isolates showed a high degree of genetic similarity between the isolates carrying the hcp gene. Genome sequencing data showed that 84.3% of the C. coli and 93.7% of the C. jejuni isolates had all 13 T6SS open reading frames. Moreover, the virulence characteristics of hcp + isolates, including motility and the ability to invade human intestinal epithelial cells in vitro, were significantly greater than in the control strain C. jejuni 12502; a human isolate which is hcp positive. CONCLUSION: Overall, it was discovered that hcp (+) C. coli and C. jejuni isolated from retail chicken isolates posses genetic and phenotypic properties associated with enhanced virulence. However, since human infections with C. coli are significantly less frequent than those of C. jejuni, the relationship between virulence factors and pathogenesis requires further study.

Prevalence of Campylobacter and Salmonella in raw chicken on retail sale in the republic of Ireland.

To assess the current risks to consumers from Campylobacter and Salmonella in raw chicken products sold in the Republic of Ireland, a retail survey was undertaken to define their prevalence. Samples (n = 510) were analyzed using protocols based on ISO 10272-1:2006 and ISO 6579:2002. Processor codes on pack labels showed that 67% of samples were produced in the Republic of Ireland and 25% in the United Kingdom. Salmonella was present in 5.1% of samples, but the eight serovars found caused less than 7% of human salmonellosis reported in the Republic of Ireland. The results suggest that on-farm controls to limit Salmonella infection of broilers have been successful and that in Ireland raw chicken is not a significant cause of salmonellosis in humans. The overall prevalence of Campylobacter spp. was 84.3%. Isolation by the ISO method found 52.7% of samples to be positive, but overgrowth by contaminants was frequently evident. Therefore, in addition to enrichment, an homogenized sample was plated directly onto modified charcoal cefoperazone deoxycholate agar, and this detected a further 31.6%. Speciation of isolates (n = 426) determined that 67% were Campylobacter jejuni and 32% were Campylobacter coli. These species are the most common cause of campylobacteriosis in man. The results indicate that there is a need for poultry producers to introduce interventions to minimize the exposure of consumers in the Republic of Ireland to Campylobacter spp., as has been successfully done for Salmonella.

Genotypic characterisation and cluster analysis of Campylobacter jejuni isolates from domestic pets, human clinical cases and retail food.

The genetic similarity of Campylobacter jejuni isolates from pets, compared to human clinical cases and retail food isolates collected in Ireland over 2001-2006 was investigated by cluster analysis of pulsed-field gel electrophoresis (PFGE) fingerprinting profiles. Comparison of the PFGE profiles of 60 pet isolates and 109 human isolates revealed that seven (4.1%) profiles were grouped in clusters including at least one human and one pet C. jejuni isolate. In total six (1.6%) of 60 pet and 310 food profiles were in clusters with at least one food and one pet C. jejuni isolate. The detection of only a small number of genetically indistinguishable isolates by PFGE profile cluster analysis from pets and from humans with enteritis in this study suggests that pets are unlikely to be an important reservoir for human campylobacteriosis in Ireland. However, genetically indistinguishable isolates were detected and C. jejuni from pets may circulate and may contribute to clinical infections in humans. In addition, contaminated food fed to pets may be a potential source of Campylobacter infection in pets, which may subsequently pose a risk to humans.

Pulsed field gel electrophoresis typing of human and retail foodstuff Campylobacters: an Irish perspective.

Campylobacter enteritis is a zoonosis, an infectious disease transmissible under normal conditions from vertebrate animals to man, presenting a major global public health burden. In this study, Pulsed Field Gel Electrophoresis (PFGE) was employed to identify common genotypes in a collection of 600 Campylobacter isolates in order to investigate if profiles obtained from retail samples of foodstuffs matched genotypes causing illness in the community in Ireland. The Campylobacters were isolated from retail foodstuffs, and cases of gastroenteritis, over the same 20-month period in three population centres in Ireland. The major observation made was of a high level of PFGE-genotype heterogeneity; 236 SmaI discrete genotypes were found in 507 strains successfully analysed. Analysis of the PFGE profiles revealed 22 common profiles amongst food isolates and those causing enteritis in humans. These cojoint PFGE genotypes indicate that 56 (38%) of the human clinical isolates are genetically related to 129 (36%) of the food isolates. The identification of these recurrent PFGE types, in the sampled Campylobacter coli and Campylobacter jejuni populations, indicates that a high proportion of Campylobacter isolates found in foods of animal origin also occur in patients with symptoms of enteritis. This data adds weight to the epidemiological hypothesis that a high proportion of human Campylobacter cases are contracted via the handling and consumption of contaminated foodstuffs, in particular poultry.

Prevalence of Campylobacter spp. in raw retail poultry on sale in Northern Ireland.

A year-long survey of fresh, retail poultry products on sale in Northern Ireland was undertaken to define the prevalence of Campylobacter spp. by using protocols based on ISO (standard) 10272-1:2006. Incubation at 37 and 42 degrees C was undertaken to increase the diversity of isolates obtained. Overall, 652 isolates were identified as Campylobacter spp. by using PCR and amplified fragment length polymorphic typing. Phenotyping wrongly identified 21% of isolates. Prevalences of Campylobacter found were chicken, 91% (n = 336); turkey, 56% (n = 77); and duck, 100% (n = 17). Prevalence rates for chicken produced in Northern Ireland, Scotland, England, and Wales were similar, with a mean value of 91%. The prevalences in product from the latter two countries were much higher than were found in two United Kingdom-wide surveys of chicken. The incubation temperature did not affect the relative proportions of the species isolated (P > 0.05). Campylobacter jejuni composed 64.6% of isolates, Campylobacter coli, 27.4%, and Campylobacter lari, 1%. Most cases of human campylobacteriosis are caused by C. jejuni and C. coli. The overall Campylobacter prevalence results are consistent with Northern Ireland surveys undertaken since 2000, and indicate that United Kingdom strategies to control Campylobacter in chicken have not had a significant effecton the prevalence of this pathogen in retail products on sale in Northern Ireland.

Probabilistic model for contamination of egg dishes with Salmonella spp. made from shell eggs produced on the island of Ireland.

A quantitative model was constructed to estimate the probability that a serving of food containing eggs produced on the island of Ireland is contaminated with Salmonella spp. The model is based on the prevalence of contaminated eggs at the time of lay and a set of parameters which describe the pooling of eggs in the home and in catering situations. Both external and internal contamination of the eggs by Salmonella spp. was considered. The model estimates that there is a 90% chance that the probability of a serving of food being contaminated is between 0.0043% and 0.038%. Sensitivity analysis demonstrated that egg prevalence drives this low probability and that, at the current level of egg prevalence at the time of lay, pooling of eggs has a minor effect. These results indicate the importance of maintaining the low prevalence of contaminated eggs at the time of lay to minimise the risk of human cases of salmonellosis from consumption of eggs.

Qualitative exposure assessment for Salmonella spp. in shell eggs produced on the island of Ireland.

A qualitative exposure assessment for Salmonella in eggs produced on the island of Ireland was developed. The assessment was divided into three main modules (production and packing, distribution and storage, and preparation and consumption), and each of these stages into defined steps in the exposure pathway. In the production and packing stage the initial prevalences of Salmonella in the contents and on the shell of eggs were estimated to be negligible and low respectively. Numbers of Salmonella both in and on eggs were estimated to be low. At each subsequent step in the pathway, qualitative assessments were made of the impact of events on the probability and level of Salmonella contamination on the shells and in the contents of eggs. At the end of each module assessments were combined to give an overall probability and level of Salmonella contamination. In the first two modules the assessment focused on the effect of the duration and temperature of storage on yolk membrane integrity and the likelihood of shell penetration. During the final stage the influence of factors such as safe-handling procedures, pooling practices, consumption patterns and the effectiveness of cooking, on the prevalence and level of Salmonella contamination in a food item at time of consumption was assessed. The outcome of this assessment was an estimate of a low probability and level of Salmonella contamination of egg-containing foods, prepared with eggs produced on the island of Ireland.

A comparison of media for the isolation of Arcobacter spp. from retail packs of beef.

In order to determine the most effective protocol for the isolation of Arcobacter spp. from retail packs of beef, three published methods (A, B, and C) were selected. In addition, a modified version of method B was studied (method D). The ability of the four methods to isolate Arcobacter from standardized beef samples (n = 80) was compared with presumptive Arcobacter isolates being identified to genus and species level, using multiplex PCR methods. The presence of Arcobacter in enrichment broths was also investigated using PCR techniques. Overall, the modified enrichment and selection media of Johnson and Murano (method D) gave the highest recovery of Arcobacter. Recovery using these media was enhanced by incubating the enrichment and selection media in a microaerobic cabinet rather than air, and the inclusion of streaking the enrichment broth onto selective agar after 24 h in addition to 48 h. Method D yielded significantly more Arcobacter-positive samples of beef (P < 0.01) than did the three other methods investigated.

Prevalence of Salmonella in grade A whole shell eggs in the island of Ireland.

Following the emergence of Salmonella Enteritidis as a widespread contaminant of eggs and the role of eggs in the transmission of human salmonellosis, control measures were introduced to curb the spread of infection. Two approaches to Salmonella control are currently used by egg producers in Ireland, because Northern Ireland producers, like those in the rest of the United Kingdom, widely adopted a vaccination regime, whereas the Republic of Ireland does not permit vaccination but introduced controls based on routine monitoring for specific Salmonella serovars and subsequent culling of infected flocks. To compare the efficacy of these two approaches and determine the prevalence of salmonellae in eggs produced for retail sale in the island of Ireland, a major survey of approximately 30,000 grade A eggs was undertaken. Egg shells and contents were analyzed separately for salmonellae by procedures based on International Organization for Standardization methodology. The survey yielded only two positive samples, with Salmonella Infantis and Salmonella Montevideo isolated from shells; no egg contents yielded salmonellae. There was no statistically significant difference in the prevalence of salmonellae between eggs produced in Northern Ireland and those from the Republic of Ireland; hence, both regimes appeared to be equally effective in controlling salmonellae. The prevalence was also significantly lower than that found in a recent major United Kingdom survey. Hence, shell eggs produced in the island of Ireland are unlikely to be a source of human salmonellosis.

Prevalence of Arcobacter spp. in raw milk and retail raw meats in Northern Ireland.

A 1-year study was undertaken to determine the prevalence of Arcobacter spp. in raw milk and retail raw meats on sale in Northern Ireland. Retail raw poultry samples (n = 94), pork samples (n = 101), and beef samples (n = 108) were obtained from supermarkets in Northern Ireland, and raw milk samples (n = 101) were kindly provided by the Milk Research Laboratory, Department of Agriculture and Rural Development, Belfast, Northern Ireland. Presumptive arcobacters were identified by previously described genus-specific and species-specific PCR assays. Arcobacter spp. were found to be common contaminants of retail raw meats and raw milk in Northern Ireland. Poultry meat (62%) had the highest prevalence, but frequent isolations were made from pork (35%), beef (34%), and raw milk (46%). Arcobacter butzleri was the predominant species isolated from retail raw meats and was the only species isolated from raw milk samples. Arcobacter cryaerophilus was detected less frequently, and Arcobacter skirrowii was detected only as a cocontaminant. To our knowledge, this is the first report of Arcobacter spp. prevalence in a diverse range of products of animal origin in Northern Ireland.

Determination of the principal points of product contamination during beef carcass dressing processes in Northern Ireland.

To determine the principal points of microbial contamination of carcasses during beef carcass dressing in Northern Ireland, 190 carcasses were sampled by swabbing 1,000 cm2 of the brisket. A detailed survey of one abattoir was initially conducted, with sampling of a total of 100 carcasses immediately after hide removal (H), after carcass splitting (S), and immediately after washing (W) before dispatch to the chiller. The total bacterial counts after incubation at both 22 and 37 degrees C indicated that there was no significant increase in the numbers of bacteria after the first sampling point, H (P > 0.05). To determine whether this was the case in the majority of Northern Ireland abattoirs, 15 carcasses were then sampled at each of an additional six abattoirs, at points H and W only. Total bacterial counts were significantly higher (P < 0.05) at H than at W, indicating that hide pulling was the major point of bacterial contamination of beef carcasses and hence a critical control point for the final microbiological quality of the carcasses. Mean counts of Enterobacteriaceae at both incubation temperatures were very low (< 10 CFU/cm2) but were higher at W than at H, probably indicating that washing was redistributing bacteria from the posterior to the anterior region.

A comparison of three methods for the isolation of Arcobacter spp. from retail raw poultry in Northern Ireland.

Recent evidence suggests that arcobacters, especially Arcobacter butzleri, are potential foodborne pathogens, but standardized detection methods have yet to be established. A study was undertaken to determine which of three isolation methods was the most effective for the isolation of Arcobacter spp. from fresh raw poultry. Methods 1 was microaerobic and involved a membrane filtration step followed by plating onto blood agar. Method 2 was also microaerobic and involved enrichment and plating media containing a five-antibiotic cocktail. Method 3 was aerobic and was based on enrichment in a charcoal-based broth containing two antibiotics. Retail poultry samples (n = 50) were obtained from supermarkets in Northern Ireland; the European Community license number was recorded to ensure sample diversity. Presumptive arcobacters were identified using genus-specific and species-specific primers. Methods 1 resulted in the lowest recovery of arcobacters (28% of samples positive). The detection rate for method 2 (68%) was higher than that for method 3 (50%), but the difference was not significant (P > 0.05). Modification of method 3 by plating the enrichment broth at 24 h, as well as at 48 h, increased recovery to 68%. Use of methods 2 and 3 together increased the number of positive samples detected by approximately 25% compared with use of either method alone. A. butzleri was the most commonly isolated species using all methods. Method 3 detected Arcobacter cryaerophilus in more samples (n = 3) than did method 1 and 2 (n = 1). Arcobacter skirrowii was detected by only method 3 (n = 1). In terms of sensitivity, ease of use, and diversity of species recovered, modified method 3 was the overall method of choice.

Occurrence of verocytotoxin-producing Escherichia coli in dairy and meat processing environments.

From June 1999 to June 2000, 480 environmental swabs were collected from two abattoirs in Northern Ireland. In addition, from July 1999 to July 2000, 420 samples originating from raw cow's milk were collected from two Northern Ireland dairies. All samples were examined for the presence of verocytotoxin-producing Escherichia coli (VTEC). O157 with the use of selective enrichment in tryptone soya broth (TSB) and double-strength MacConkey broth purple (MBP) followed by immunomagnetic separation and selective plating onto sorbitol MacConkey agar supplemented with cefixime tellurite. Non-O157 VTEC was detected by selective enrichment in TSB-MBP and plating on MacConkey agar. A multiplex polymerase chain reaction assay was also used to detect the presence of the VT1, VT2, and eae genes. Two (0.42%) of the 480 abattoir samples tested positive for VTEC; one isolate carried the VT2 gene only, and the other carried both the VT2 and the eae genes. Nine (2.14%) of the 420 dairy samples tested positive for VTEC; four carried the VT2 gene only, four carried both the VT2 and the eae genes, and one carried both the VT1 and the eae genes. These results indicate that the incidence of VTEC was low in the dairy and meat processing environment samples tested, and this finding may help to explain the low incidence of VTEC reported for the local human population.

Effect of incubation temperature on isolation of Campylobacter jejuni genotypes from foodstuffs enriched in Preston broth.

Preston broth and agar incubated at either 37 or 42 degrees C have been widely used to isolate campylobacters from foodstuffs. The consequences of using either incubation temperature were investigated. Retail packs of raw chicken (n = 24) and raw lamb liver (n = 30) were purchased. Samples were incubated in Preston broth at 37 and 42 degrees C and then streaked onto Preston agar and incubated as before. Two Campylobacter isolates per treatment were characterized. Poultry isolates were genotyped by random amplification of polymorphic DNA (RAPD), pulsed-field gel electrophoresis (PFGE), and flagellin PCR-restriction fragment length polymorphism, and lamb isolates were genotyped by RAPD only. In total, 96% of the poultry and 73% of the lamb samples yielded campylobacters. The lamb isolates were all Campylobacter jejuni, as were 96% of the poultry isolates, with the remainder being Campylobacter lari. The incubation temperature had no significant effect on the number of positive samples or on the species isolated. However, genotyping of the C. jejuni isolates revealed profound differences in the types obtained. Overall (from poultry and lamb), the use of a single incubation temperature, 37 degrees C, gave 56% of the total number of RAPD C. jejuni genotypes, and hence, 44% remained undetected. The effect was especially marked in the poultry samples, where incubation at 37 degrees C gave 47% of the PFGE genotypes but 53% were exclusively recovered after incubation at 42 degrees C. Thus, the incubation temperature of Preston media selects for certain genotypes of C. jejuni, and to detect the widest range, samples should be incubated at both 37 and 42 degrees C. Conversely, genotyping results arising from the use of a single incubation temperature should be interpreted with caution.

Comparison of eight phenotypic methods for subspecies characterization of thermophilic Campylobacter spp. isolated from pig liver.

Four hundred pork livers from bacon pigs (37 herds) obtained at six pig-processing plants were studied to assess the Campylobacter contamination rate. Deep tissue areas were sampled immediately after evisceration. Approximately 6% of livers were infected with Campylobacter spp., including Campylobacter coli (67%), Campylobacter jejuni (30%), and Campylobacter lari (3%). The 60 resulting isolates (39 C. coli isolates, 19 C. jejuni isolates, and 2 C. lari isolates) employed in this study were characterized at the subspecies level in a comparison of eight phenotyping schemes, including four biotyping, two serotyping, and two phage-typing schemes. The Skirrow-Benjamin biotyping scheme produced two biotypes for C. jejuni, i.e., biotype 2 (95%) and biotype 1 (5%). The Lior biotyping scheme subdivided C. coli into biotype 1 (41%) and biotype 2 (59%), while biotype 4 was the dominant type (95%) for C. jejuni. The Roop scheme allowed further differentiation of C. coli into three biovars, i.e., biovar 1 (57%), biovar 2 (40%), and biovar 3 (3%), and it subdivided C. jejuni into two biotypes, i.e., biovar 1 (95%) and biovar 2 (5%). Preston biotyping produced the largest degree of subspecies differentiation, with 18 C. coli biotypes and 7 C. jejuni biotypes being identified. The most common were biotypes 2650 and 6030, representing 18 and 42% of all C. coli and C. jejuni isolates, respectively. The Penner-Hennessy serotyping scheme successfully serotyped 89% of the isolates, with 10 serotypes being identified; 30% of the serotypeable isolates were accounted for by Penner 23, followed by Penner 20 (16%) and Penner 39 (14%). The Lior serotyping scheme successfully serotyped only 45% of the strains, and eight serogroups were identified, with Lior 36 (31%), Lior 20 (23%), and Lior 5 being the most frequent. The Preston scheme and the Khakhria-Lior phage-typing scheme were able to type 16 and 25% of the isolates, respectively. The Preston scheme produced three phage groups, i.e., 69 (56%), 90 (22%), and 116 (22%), and the Khakhria-Lior scheme also produced three phage types, i.e., 44 (40%), 27 (33%), and 37 (20%), as well as atypical lysis patterns (7%). The results of this study demonstrate the role of Preston biotyping in the phenotyping of isolates, particularly in diagnostic laboratories that have no access or limited access to molecular typing equipment.

Impediometric detection of Campylobacter coli.

The rapid automated bacterial impedance technique (RABIT) was examined as a method for the detection of two wild-type isolates of Campylobacter coli in broth media. Both isolates failed to produce a change in impedance that was sufficient for detection in any combination of six nonselective basal broth media, including Mueller-Hinton broth, nutrient broth no. 2, brain heart infusion broth supplemented with yeast extract (0.5% [wt/vol]), brucella broth, Campy broth supplemented with yeast extract (0.5% [wt/voll), and Whitley impedance broth, at 37 and 42 degrees C. Although the strains did proliferate in the media, changes in conductivity were very small (ranging from 0 to 1,000 microS) and were not significantly greater than the drift in conductance observed in the control broth medium. Additional work is therefore required to define a nonionic growth substrate that will produce charged ions upon metabolism that are detectable by RABIT.

Preservation of Vacuum-Packaged Pork Liver Paté by Fermentation.

Fermentation with Lactobacillus plantarum and Pediococcus cerevisiae was evaluated as a natural method of preservation for use in pork liver paté. Addition of both starter strains to a raw meat mix (108 CFU g-1) lowered the pH to 4.0 in 15 h at 30°C. Subsequent cooking to a core temperature of 70°C followed by vacuum packaging resulted in a product which remained acceptable for longer than 22 days when stored at 4°C and 10°C. Addition of glucose did not increase the activity of the lactic acid starter organisms, indicating the presence of endogenous fermentable substrate in the raw ingredients. Challenge test studies employing Staphylococcus aureus , Salmonella infantis , and Clostridium sporogenes were carried out in finished product at 37°C. No recovery was observed 7 days postinoculation. Results from this investigation indicate the potential use of lactic acid starter cultures to obtain a microbiologically stable product with enhanced safety.

Hygienic Quality of Raw Pork and Chorizo (Raw Pork Sausage) on Retail Sale in Mexico City.

A survey of raw pork and a raw fermented pork sausage, chorizo, was undertaken in Mexico City to assess the hygienic quality of these two products on retail sale in a variety of outlets. Total bacterial counts and Enterobacteriaceae counts were determined and the samples were analyzed for the presence of Salmonella spp. Pork sold from refrigerated display cabinets in supermarkets and butchers' shops was of a poor microbial quality similar to that sold in street markets. In all types of outlets, a high proportion (76%) of samples contained Salmonella spp. Hygiene scores for vendors did not correlate with microbiological quality. For chorizo, the microbial quality was related to the type of producer. The product of major commercial companies had a lower mean Enterobacteriaceae count than that of small-scale producers, but although this difference was statistically significant, counts were high for a fermented meat product. Twenty percent of chorizo samples from major producers were positive for Salmonella spp. Small-scale or "back-shop" production resulted in 72% of samples being positive for Salmonella spp. Thus neither type of chorizo could be described as being a good quality and hygienic product. It is apparent that both animal husbandry and slaughter procedures for pigs require further study, as does the pork-processing industry, in order to define how the meat becomes so heavily contaminated. Improving the quality of the raw meat will benefit consumers in the Mexico City area and will be an essential prerequisite for improving the quality of chorizo.