Prevalence and serovar diversity of Salmonella spp. in primary horticultural fruit production environments

Genomic Diversity and Potential Transmission and Persistence of Salmonella in the Cambodian Vegetable Supply Chain

S. enterica isolates (n = 78) obtained from the vegetable supply chain (farms, distribution centers, markets) in two Cambodian provinces (Siem Reap, Battambang) were sequenced and analyzed. In silico identification of serotypes and detection of antimicrobial resistance genes was performed using SISTR and ABRicate, respectively. Isolates' relatedness was assessed based on high-quality single nucleotide polymorphisms (hqSNPs) identified within each serotype using the CFSAN SNP pipeline. Among 29 detected serotypes, Paratyphi B var. Java was most abundant (n = 14), followed by Hvittingfoss (n = 11) and Thompson (n = 7). Paratyphi B var. Java was mostly found in farms (n = 5) and markets (n = 6), Hvittingfoss within distribution centers (n = 8), and Thompson at markets (n = 4) and farms (n = 3). Among Paratyphi B var. Java isolates, one phylogenetic clade contained four closely related isolates (0-1 SNP difference), collected at markets in different provinces on different days. Another clade contained two isolates that differed by one SNP, one obtained from a Battambang farm and one from a Siem Reap distribution center, suggesting a broad spread of Paratyphi B var. Java in the Cambodian vegetable supply chain. Hvittingfoss isolates clustered in two clades; one contained five identical isolates, four of which were obtained in different months from the distribution center and a farm in Battambang, suggesting possible transmission among supply chain stages. The second clade contained three isolates from the Battambang distribution center that differed by 0-1 SNP and were isolated in October and November, indicating possible persistence. Lastly, among 78 analyzed isolates, 14 carried antimicrobial resistance genes and seven out of these 14 carried genes with predicted resistance to more than three classes of antibiotics. Overall, highly similar isolates of Salmonella were identified over time and at different supply chain stages, suggesting possible persistence and transmission of Salmonella within and between supply chain stages.

Transfer of Salmonella enterica and Enterococcus faecium from food-contact surfaces to stone fruits

Contaminated food-contact surfaces are a potential route for spreading microorganisms to stone fruit during postharvest handling. The objective of this study was to investigate the factors that affect the transfer of bacteria from food-contact surfaces to stone fruits. Coupons (1 × 1 cm) of polyurethane (PU) or polyvinyl chloride (PVC) were inoculated with rifampin-resistant variants of Salmonella (five-strain cocktail) or Enterococcus faecium NRRL B-2354 at ~5 or ~7 log CFU/cm2. Inoculated coupons (n = 8-11) were attached to a texture analyzer, and uniform contact conditions (5 N, 5 s) were used to explore the impact of bacterial species, inoculation level, donor surface, the presence of dried peach juice or wax, recipient produce commodity, and the dryness of inoculum. Whole fruits were transferred to 20 mL of 0.1 % peptone, rubbed for 2 min, and then the diluent was plated onto tryptic soy agar supplemented with rifampin at 50 μg/mL. Whole fruits were enriched when populations were anticipated to fall below the limit of detection (1.6 log CFU/fruit). At an inoculum of ~5 log CFU/coupon, Salmonella and E. faecium were recovered from the fruit by enrichment but not by plating. At ~7 log CFU/coupon, transfer rates, i.e., ratio of populations on recipient fruit to donor surface, were not significantly (P > 0.05) influenced by either bacterial species (Salmonella [0.26 % ± 0.77 %] versus E. faecium [0.068 % ± 0.071 %]) or donor surface (PU [0.085 % ± 0.098 %] versus PVC [0.16 % ± 0.16 %]). The rates of transfer of E. faecium from contaminated PU to peaches (0.050 % ± 0.031 %), nectarines (0.066 % ± 0.076 %), and onion skins (0.048 % ± 0.059 %) were not significantly different. The mean transfer rates of E. faecium increased significantly (P < 0.05) in the presence of dried wax (18 % ± 16 %) or peach juice (1.3 % ± 2.6 %) on the PU surface compared with the control (0.080 % ± 0.086 %). The transfer rates of E. faecium from contaminated surfaces were also significantly influenced by the drying time post-inoculation; the drier the inoculum, the lower the transfer rates. The presence of residues or moisture on food-contact surfaces facilitated the transfer of microorganisms during dry handling of fresh stone fruits. The results underscore the importance of implementing adequate cleaning, sanitation and, where appropriate, drying of equipment surfaces to effectively remove organic residues and mitigate the risks of cross-contamination.

Survival of Salmonella enterica and Enterococcus faecium on Abiotic Surfaces During Storage at Low Relative Humidity

Currently, there is limited knowledge on the survival of bacteria on surfaces during postharvest handling of dry products such as onions. Extended survival of microorganisms, coupled with a lack of established and regular, validated cleaning or sanitation methods could enable cross-contamination of these products. The aim of the study was to evaluate the survival of a potential surrogate, Enterococcus faecium, and Salmonella enterica on typical onion handling surfaces, polyurethane (PU), and stainless steel (SS), under low relative humidity. The influence of onion extract on the survival of E. faecium and Salmonella on PU and SS was also investigated. Rifampin-resistant E. faecium NRRL B-2354 and a five-strain cocktail of Salmonella suspended in 0.1% peptone or onion extract were separately inoculated onto PU and SS coupons (2 × 2 cm), at high, moderate, or low (7, 5, or 3 log CFU/cm2) levels. The inoculated surfaces were stored at ∼34% relative humidity and 21°C for up to 84 days. Triplicate samples were enumerated at regular intervals in replicate trials. Samples were enriched when populations fell below the limit of detection by plating (0.48 log CFU/cm2). Scanning electron microscopy was used to observe the cell distribution on the coupons. Reductions of E. faecium of less than ∼2 log were observed on PU and SS over 12 weeks at all inoculum levels and with both inoculum carriers. In 0.1% peptone, Salmonella populations declined by 2 to 3 log over 12 weeks at the high and moderate inoculum levels; at the low inoculum level, Salmonella could not be recovered by enrichment at 84 days. Survival of E. faecium and Salmonella was significantly (P < 0.05) enhanced over 84 days of storage when suspended in onion extract, where cells were covered by a layer of onion extract. E. faecium might have utility as a conservative surrogate for Salmonella when evaluating microbial survival on dry food-contact surfaces.

Serotype Distribution, Antimicrobial Resistance, Virulence Genes, and Genetic Diversity of Salmonella spp. Isolated from small-scale Leafy Green Vegetable Supply Chains in South Africa

Salmonella have been implicated in foodborne disease outbreaks globally and is a pressing concern in the South African small-scale sector due to inadequate hygiene standards and limited regulatory oversight, leading to a higher risk of foodborne diseases. By investigating irrigation water and leafy green vegetables produced by small-scale growers and sold through unregulated supply chains, this study was able to determine the presence, serotype distribution, virulence gene profiles, antibiotic resistance, and genetic diversity of Salmonella isolated from these sources. From 426 samples, 21 Salmonella-positive samples were identified, providing 53 Salmonella isolates. Of these, six different Salmonella serotypes and sequence types (STs) were identified, including Salmonella II 42:r: ST1208 (33.96%; n = 18), Salmonella Enteritidis: ST11 (22.64%; n = 12), Salmonella II 42:z29: ST4395 (16.98%; n = 9), Salmonella Havana: ST1524 (15.09%; n = 8), Salmonella Typhimurium: ST19 (9.43%; n = 5), and Salmonella IIIb 47:i:z: ST7890 (1.89%; n = 1). A total of 92.45% of the isolates were found to be multidrug-resistant, showing high rates of resistance to aztreonam (88.68%; n = 47), ceftazidime (86.79%; n = 46), nalidixic acid (77.36%; n = 41), cefotaxime (75.47%; n = 40), cefepime (71.70%; n = 38), and streptomycin (69.81%; n = 37). All isolates possessed the aac(6')-Iaa antimicrobial resistance gene, with a range of between 9 and 256 virulence genes. Eleven cluster patterns were observed from Enterobacterial Repetitive Intergenic Consensus sequence analyses, demonstrating high diversity among the Salmonella spp., with water and fresh produce isolates clustering, suggesting water as a potential contamination source. Plasmid replicon types were identified in 41.51% (n = 22) of the isolates, including Col(pHAD28) in Salmonella Havana (5.66%; n = 3), Col156 in Salmonella II 42:z29:- (1.89%; n = 1) and both IncFIB(S) and IncFII(S) in Salmonella Enteritidis (22.64; n = 12), Salmonella Typhimurium (9.43%; n = 5), and Salmonella Havana (1.89%; n = 1). This study highlights the presence of multidrug-resistant and multivirulent Salmonella spp. in the small-scale leafy green vegetable supply chains, underscoring the need for the development of a "fit-for-purpose" food safety management system within this system.

Combined hydrothermal and biological treatments for valorization of fruit and vegetable waste into liquid organic fertilizer

This study investigated the effects of hydrothermal treatment, biological treatment and their combination on nutrients recovery from fruit and vegetable waste (FVW) and evaluated the feasibility of fruit and vegetable waste juice (FVWJ) from the combined treatment as liquid organic fertilizer. In this study, following conditions were determined suitable for FVW treatment: the temperature of 165 °C and retention time of 45 min for hydrothermal treatment, 20 h for biological treatment, and Weissella, as the dominant microbial genus present in FVW, was suggested as inoculum for biological treatment. In the combined treatment, based on the above conditions of hydrothermal and biological treatments, the yield of FVWJ was 93.03 g out of 100 g FVW, and concentrations of organic matter (1.45%, w/w), primary nutrients (0.51%, w/w), and toxic components in the FVWJ complied with the requirements for use concentration in both Chinese and European standards for liquid organic fertilizer. The economic analysis showed the net saving of 13.60 USD per ton FVW, indicating that it is an economical approach to valorize fruit and vegetable waste into liquid organic fertilizer through the combined treatment.

Salmonella Behavior in Meat during Cool Storage: A Systematic Review and Meta-Analysis

The aim of the present study was to investigate Salmonella behavior in meat stored in cool conditions (between 0 °C and 7.5 °C), by employing a systematic review and meta-analysis. The data were obtained from research articles published in SciELO, PubMed, the Web of Science, and Scopus databases. The results of the retrieved studies were obtained from meat (beef, chicken, pork, poultry, and turkey), fish, shellfish, and broth media samples The data were extracted as sample size (n), initial concentration (Xi), final concentration (Xf), standard deviation (SD), standard error (SE), and microbial behavior effects (reduction or growth). A meta-analysis was carried out using the metaphor package from R software. A total of 654 articles were initially retrieved. After applying the exclusion criteria, 83 articles were selected for the systematic review, and 61 of these were used for the meta-analysis. Most studies were conducted at 0 °C to 4.4 °C storage temperatures under normal atmosphere package conditions. Salmonella Typhimurium, S. Enteritidis, and a cocktail (strain mixture) were inoculated at 5.0 and 6.0 log CFU mL−1. Articles both with and without the addition of antimicrobial compounds were found. Salmonella concentration decreases were observed in most studies, estimated for all study combinations as −0.8429 ± 0.0931 log CFU g−1 (95% CI; −1.0254, −0.6604) (p < 0.001), varying for each subgroup analysis. According to this survey, Salmonella concentration decreases are frequent during cool storage, although concentration increases and no bacterial inactivation were observed in some studies.

One Health Perspective of Salmonella Serovars in South Africa Using Pooled Prevalence: Systematic Review and Meta-Analysis

Salmonella is a bacterium that is commonly associated with food-borne infections and is regarded as one of the most important pathogens in public health. Salmonella serovars, particularly Typhimurium and Enteritidis, which are widely distributed globally, mainly result in outbreaks commonly linked to the consumption of animal products. This study is a systematic review and meta-analysis of studies reporting the prevalence of Salmonella serovars from one health perspective that included human, environmental, and animal samples in South Africa. PubMed, ScienceDirect, African Journals Online, and Scopus databases were used to conduct extensive searches of articles which were ultimately included or excluded following the Systematic Reviews and Meta-Analysis (PRISMA) guidelines. According to the data obtained in this review, the overall pooled prevalence estimates (PPE) of Salmonella serovars detection were 79.6%, 61.6%, 56.5%, and 43.2% for human, environment, animal, and environment/animal samples in South Africa, respectively. The majority of the studies (50%) used the polymerase chain reaction (PCR) technique for the detection of Salmonella serovars, followed by culture methods (26.7%), while 20% used serotyping. The PPE for nontyphoidal Salmonellae (NTS) was 65.6% and 34.4% for Salmonella Typhimurium and Salmonella Enteritidis, respectively. Our data further shows that 3 serovars, namely, Salmonella Typhimurium, Salmonella Enteriditis, and Salmonella Hadar, have been isolated from animals, humans, and the environment in South Africa. Our results highlight the ongoing spread of Salmonella spp. especially on animals which might end up infecting humans via direct contact with infected animals or eating infected animal products. This calls for deliberate “One Health” epidemiological studies in order to document information on the transmission between humans, animals, and the environment. This will ultimately result in the formulation of a consolidated salmonellosis control policy by the environmental, human, and veterinary health sectors.

Mango Endophyte and Epiphyte Microbiome Composition during Fruit Development and Post-Harvest Stages

The influence of the development stage and post-harvest handling on the microbial composition of mango fruit plays a central role in fruit health. Hence, the composition of fungal and bacterial microbiota on the anthoplane, fructoplane, stems and stem-end pulp of mango during fruit development and post-harvest handling were determined using next-generation sequencing of the internal transcribed spacer and 16S rRNA regions. At full bloom, the inflorescence had the richest fungal and bacterial communities. The young developing fruit exhibited lower fungal richness and diversities in comparison to the intermediate and fully developed fruit stages on the fructoplane. At the post-harvest stage, lower fungal and bacterial diversities were observed following prochloraz treatment both on the fructoplane and stem-end pulp. Ascomycota (52.8%) and Basidiomycota (43.2%) were the most dominant fungal phyla, while Penicillium, Botryosphaeria, Alternaria and Mucor were detected as the known post-harvest decay-causing fungal genera. The Cyanobacteria (35.6%), Firmicutes (26.1%) and Proteobacteria (23.1%) were the most dominant bacterial phyla. Changes in the presence of Bacillus subtilis following post-harvest interventions such as prochloraz suggested a non-target effect of the fungicide. The present study, therefore, provides the primary baseline data on mango fungal and bacterial diversity and composition, which can be foundational in the development of effective disease (stem-end rot) management strategies.

Antimicrobial Resistance Profiles of Diarrheagenic E. coli (DEC) and Salmonella Species Recovered from Diarrheal Patients in Selected Rural Communities of the Amathole District Municipality, Eastern Cape Province, South Africa

Purpose

The emergence of multidrug-resistant bacteria remains as one of the major impediments towards the prevention and treatment of microbial infections and continues to be a serious threat to medicine. Henceforth, this study aimed at elucidating the antimicrobial resistance profiles of diarrheagenic E. coli (DEC) and Salmonella species recovered from diarrheal patients in selected rural communities of the Amathole District Municipality (ADM), Eastern Cape Province, South Africa (SA).

Methods

The antimicrobial resistance profiles of diarrheagenic E. coli (DEC) and Salmonella isolates were evaluated using antimicrobial susceptibility tests and the relevant antimicrobial resistance factors were elucidated by the Polymerase Chain Reaction technique.

Results

A sum of 324 diarrheagenic E. coli (DEC) and 62 Salmonella isolates were recovered from diarrheal stool specimens collected amongst diarrheal patients admitted in medical facilities/health-care centers within the ADM in the Eastern Cape Province, South Africa. Multiple antimicrobial resistance index mean values of 0.7 and 0.5 for DEC and Salmonella isolates, respectively, were observed in this study, indicating that these isolates were from sources where antimicrobials were frequently used. The antimicrobial resistance factors ampC, bla_TEM, SulI and II, tet A and aadA were detected among antimicrobial-resistant DEC pathotypes and Salmonella isolates recovered in this study.

Conclusion

The occurrence of the multiple antimicrobial-resistant DEC and Salmonella isolates with the relevant antimicrobial resistance factors in this study suggests a portentous human health threat associated with diarrhea and a major deterrent in medicine.

Characterization of Salmonella bacteriophages and their potential use in dishwashing materials

AIMS

The aims of this study were to isolate and characterize novel Salmonella phages and to evaluate the effectiveness of phage cocktails used as antibacterial agents in dishwashing materials.

METHODS AND RESULTS

The effective phages, vB_STy-RN5i1 and vB_STy-RN29, were isolated from drain water samples collected from open markets using Salmonella Typhimurium as the host strain. These phages were identified as members of Podoviridae and Siphoviridae, respectively. Both phages infected at least six Salmonella serovars and rapidly lysed their host within one hour. They were stable at 4-45°C and at pH 6-9 for at least an hour while being evaluated in this study. The phage application results indicated that bacterial cells were reduced by 3⋅1 and 2⋅7 log CFU per ml at room temperature when they encountered the phage cocktail on scouring pads (SPs) and dishwashing sponges (DSs), respectively.

CONCLUSIONS

The isolated Salmonella phages, vB_STy-RN5i1 and vB_STy-RN29, had potential against Salm. Typhimurium and could reduce the occurrence of bacterial-cross-contamination from dishwashing materials, which have been reported to be a source of bacteria, to other kitchen utensils and food.

SIGNIFICANCE AND IMPACT OF THE STUDY

The successful reduction of bacterial contamination in dishwashing materials by the phage cocktail consisting of vB_STy-RN5i1 and vB_STy-RN29 reveals its potential to be an alternative antimicrobial agent for SPs and DSs.

Technological Advances in Phytopathogen Detection and Metagenome Profiling Techniques

The use of advanced molecular methods in plant pathology and applied microbiology has necessitated for more accurate, rapid detection and identification of plant pathogens. This is particularly significant given accelerated emergence of virulence that leads to increased prevalence of plant pathogens. Thus, the capacity to contain plant pathogens and ultimately disease progression is key to ensuring crop biosecurity and overall food security. Of recent, research on pathogens utilizes a holistic approach focusing on elucidating growth dynamics within the entire biome rather than studying individual or closely related isolates in unison. This has advanced knowledge and information of microbial ecosystem within natural environments in the twenty first century. Applied technological platforms used for rapid detection and profiling microbial biomes in this regard include digital PCR, pyrosequencing, Illumina, DNA microarray and barcoding, Ion torrent, and nanopore. These technologies have been applied in various fields including human health and medicine, marine and animal biology, crop production and water quality research, to mention but a few. Although much has been done and achieved through the development of several technologies, more accuracy is required to circumvent the shortfalls still experienced. This includes integrating existing methods with new applications such as viability PCRs and microbial viability testing. Hence, this review provides critical analysis of some widely used latest technologies in rapid detection and identification of plant pathogens, and profiling plant associated microbiomes that reveal growth dynamics and population diversity. The advantages and limitations of the technologies are also discussed.

Precipitation and Salmonellosis Incidence in Georgia, USA: Interactions between Extreme Rainfall Events and Antecedent Rainfall Conditions

BACKGROUND

The southeastern United States consistently has high salmonellosis incidence, but disease drivers remain unknown. Salmonella is regularly detected in this region's natural environment, leading to numerous exposure opportunities. Rainfall patterns may impact the survival/transport of environmental Salmonella in ways that can affect disease transmission.

OBJECTIVES

This study investigated associations between short-term precipitation (extreme rainfall events) and longer-term precipitation (rainfall conditions antecedent to these extreme events) on salmonellosis counts in the state of Georgia in the United States.

METHODS

For the period 1997-2016, negative binomial models estimated associations between weekly county-level extreme rainfall events (≥90th percentile of daily rainfall) and antecedent conditions (8-week precipitation sums, categorized into tertiles) and weekly county-level salmonellosis counts.

RESULTS

In Georgia's Coastal Plain counties, extreme and antecedent rainfall were associated with significant differences in salmonellosis counts. In these counties, extreme rainfall was associated with a 5% increase in salmonellosis risk (95% CI: 1%, 10%) compared with weeks with no extreme rainfall. Antecedent dry periods were associated with a 9% risk decrease (95% CI: 5%, 12%), whereas wet periods were associated with a 5% increase (95% CI: 1%, 9%), compared with periods of moderate rainfall. In models considering the interaction between extreme and antecedent rainfall conditions, wet periods were associated with a 13% risk increase (95% CI: 6%, 19%), whereas wet periods followed by extreme events were associated with an 11% increase (95% CI: 5%, 18%). Associations were substantially magnified when analyses were restricted to cases attributed to serovars commonly isolated from wildlife/environment (e.g., Javiana). For example, wet periods followed by extreme rainfall were associated with a 34% risk increase (95% CI: 20%, 49%) in environmental serovar infection.

CONCLUSIONS

Given the associations of short-term extreme rainfall events and longer-term rainfall conditions on salmonellosis incidence, our findings suggest that avoiding contact with environmental reservoirs of Salmonella following heavy rainfall events, especially during the rainy season, may reduce the risk of salmonellosis. https://doi.org/10.1289/EHP4621.

Behavior of Salmonella Typhimurium on Fresh Strawberries Under Different Storage Temperatures and Wash Treatments

Fresh strawberries are one of the most popular fruits in China and are vulnerable to microbial contamination. In this study, the behavior of Salmonella Typhimurium on fresh strawberries stored at refrigeration and room temperatures, as well as the effectiveness of mild heat wash treatments at 47, 50, and 53°C on bacterial survival was investigated. The modified Gompertz, Huang, log-linear, and Weibull models were used to fit bacterial growth and survival curves under different treatments. A secondary model based on linear regression was developed to describe the effect of washing temperature on the kinetic parameters of S. Typhimurium survival derived from the Weibull model. During 72 h storage, S. Typhimurium on fresh strawberries stored at 4°C was reduced by 1.35 log CFU/g and growth of 5.64 log CFU/g was observed when strawberries were stored at 25°C. Bacterial reductions of 1.22 ± 0.15, 1.92 ± 0.06, 2.27 ± 0.07 log CFU/g were obtained when washing was carried out at 47, 50 and 53°C for 240 s, respectively. The wash temperature was an important parameter for bacterial inactivation and bacterial populations declined significantly in conjunction with washing time (p < 0.05). Warm wash treatments lead the visible color changes of strawberries, showing a slightly darker appearance while acceptable. The goodness-of-fit indices indicated that the log-linear model provided a satisfactory fit to describe the bacterial survival at 4°C. According to the smaller Akaike information criterion (AIC) value, the modified Gompertz model performed slightly better than the Huang model in describing bacterial growth at 25°C. The high adj-R2 (≥0.90) and small RMSE (≤0.22) indicated the Weibull model better described bacterial behavior under mild heat treatments. We found a close linear relationship between wash temperatures and ln k and ln n. These models were validated by independent experimental data and the values of the bias and accuracy factors fell into the acceptable range.

Characterization of fungal communities of developmental stages in table grape grown in the northern region of South Africa

AIMS

To determine fungal communities that characterize table grapes during berry development.

METHODS AND RESULTS

Two agro-ecologically different table grape commercial farms (site A and B) were used in this study. Samples were collected at full bloom, pea size and mature stages, from three positions (inside centre, eastern and western peripheral ends) per site. Total DNA extraction, Illumina sequencing and analysis of 18 pooled samples for fungal diversity targeting ITS1-2 generated a total of 2 035 933 high-quality sequences. The phylum Ascomycota (77.0%) and Basidiomycota (23.0%) were the most dominant, while the genera, Alternaria (33.1%) and Cladosporium (24.2%) were the overall dominant postharvest decay causing fungi throughout the developmental stages. Inside centre of site A were more diverse at full bloom (3.82) than those at the peripheral ends (<3.8), while at site B, the peripheral ends showed better diversity, particularly the eastern part at both full bloom (3.3) and pea size (3.7).

CONCLUSION

Fungal population diversity varies with different phenological table grape growth stages and is further influenced by site and vine position within a specific vineyard.

SIGNIFICANCE AND IMPACT OF THE STUDY

The information on fungal diversity and succession in table grapes during preharvest growth stages is critical in the development of a more targeted control strategy, to improve postharvest quality of table grapes.

Low Prevalence of Human Pathogens on Fresh Produce on Farms and in Packing Facilities: A Systematic Review

Foodborne illness burdens individuals around the world and may be caused by consuming fresh produce contaminated with bacterial, parasite, and viral pathogens. Pathogen contamination on produce may originate at the farm and packing facility. This research aimed to determine the prevalence of human pathogens (bacteria, parasites, and viruses) on fresh produce (fruits, herbs, and vegetables) on farms and in packing facilities worldwide through a systematic review of 38 peer-reviewed articles. The median and range of the prevalence was calculated, and Kruskal-Wallis tests and logistic regression were performed to compare prevalence among pooled samples of produce groups, pathogen types, and sampling locations. Results indicated a low median percentage of fresh produce contaminated with pathogens (0%). Both viruses (p-value = 0.017) and parasites (p-value = 0.033), on fresh produce, exhibited higher prevalence than bacteria. No significant differences between fresh produce types or between farm and packing facility were observed. These results may help to better quantify produce contamination in the production environment and inform strategies to prevent future foodborne illness.

Microbial Load of Fresh Produce and Paired Equipment Surfaces in Packing Facilities Near the U.S. and Mexico Border

Several produce-associated outbreaks have been linked to the packing facility. Equipment surfaces may be an important source of contamination. The goal was to assess whether the microbial load of packing facility surfaces is associated with the microbial load of produce. From November 2000 to December 2003, 487 matched produce (14 types) and equipment surfaces (six production steps) were sampled from eight packing facilities in the United States near the border with Mexico and enumerated for aerobic plate counts (APC), Escherichia coli , Enterococcus, and coliforms. Bivariate correlations were assessed by Spearman's ρ, and adjusted associations were assessed by multilevel mixed linear regression models. In general, the microbial load both increased and decreased on produce (0.2 to 1.0 log CFU/g) and equipment surfaces (0.5 to 3.0 log CFU/cm²) across production steps. Equipment surface and produce microbial loads were correlated, but correlations varied from none to high depending on the equipment surface. For example, significant correlations (P < 0.01) included APC (ρ = 0.386) and Enterococcus (ρ = 0.562) with the harvest bin, E. coli (ρ = 0.372) and Enterococcus (ρ = 0.355) with the merry-go-round, Enterococcus (ρ = 0.679) with rinse cycle equipment, APC (ρ = 0.542) with the conveyer belt, and for all indicators with the packing box (ρ = 0.310 to 0.657). After controlling for crop type, sample replicate group, and sample location, there were significant positive associations between the log concentration of Enterococcus on produce and the harvest bin (β = 0.259, P < 0.01) and the rinse cycle (β = 0.010, P = 0.01), and between the log concentration of all indicators on produce and the packing box (β = 0.155 to 0.500, all P < 0.01). These statistically significant associations between microbial loads on packing facility surfaces and fresh produce confirm the importance of packing facility sanitation to protect produce quality and safety.

Microbial quality and suitability of roof-harvested rainwater in rural villages for crop irrigation and domestic use

The study aimed at assessing the microbiological quality and suitability of roof-harvested rainwater (RHRW) for crop irrigation and domestic use. In total, 80 rainwater tanks (246 samples) across three rural villages (Ga-Molepane, Jericho and Luthngele) were visited. Culture-based techniques were used to isolate bacterial microbes and identities were confirmed using matrix-assisted laser desorption/ionization time of flight (MALDI-TOF-MS). Uncultured fungal populations were also identified using pyrosequencing. Salmonella spp. (3%), Listeria monocytogenes (22%), total coliforms (57.7%), Escherichia coli (30.5%), Enterococcus spp. (48.8%), Pseudomonas spp. (21.5%) were detected in RHRW samples after rainfall. Fungal sequences belonging to species known to cause fever, coughing and shortness of breath in humans (Cryptococcus spp.) were identified. This study indicates that RHRW quality can be affected by external factors such as faecal material and debris on rooftops. The use of untreated RHRW could pose a potential health risk if used for irrigation of crops or domestic use, especially in the case of a relative high population of immunocompromised individuals. This study does not dispute the fact that RHRW is an alternative irrigation water source but it recommends treatment before use for domestic purposes or for watering crops.