Modeling the Surface Cross-Contamination of <i>Salmonella</i>spp. on Ready-to-Eat Meat via Slicing Operation

Salmonella spp. surface transfer patterns/models between ready-to-eat (RTE) deli meat and a typical meat slicer are presented. A five-strain cocktail of Salmonella spp. was inoculated directly onto the rim of a round slicer blade at an initial level of ca. 4, 5, 6, 7 or 8 log CFU/blade (ca. 3, 4, 5, 6 or 7 log CFU/cm2 of the blade edge area). Thereafter, a RTE deli meat (ham) was sliced to a thickness of 1.5 - 2.0 mm. In another cross-contamination scenario, a clean blade was initially used to slice ham, which was pre-surface-inoculated with the Salmonella cocktail (ca. 2, 3, 4, 5, 6 or 7 log CFU/cm2 with a total area of 100 cm2), followed by slicing of an un-inoculated ham. The log CFU of Salmonella per ham slice was determined and empirical models were developed. The models, follow the decreasing Power law, predict the surface cross-contamination of Salmonella spp. (at any initial level) for sliced deli meat (ham) and will provide a useful tool in developing RTE meat risk assessments. Surface transfer patterns of three foodborne pathogens, i.e. Listeria monocytogenes, E. coli O157:H7 and Salmonella predicted by models are also presented.

Renewed Focus on the Threat of Cross-Contamination in Molecular Laboratories: Notes from the COVID-19 Testing Experience in Bangladesh

Rapid and accurate laboratory diagnosis of SARS-CoV-2 infection is crucial for the management of COVID-19 patients and control of the spread of the virus. At the start of the COVID-19 pandemic, Bangladesh had only one government molecular laboratory where real-time RT-PCR would be performed to diagnose SARS-CoV-2 infection. With the increasing number of suspected cases requiring confirmation diagnostic testing, there is a requirement to expand capacity for large-scale testing quickly. The government of Bangladesh established over 100 molecular laboratories within one year to test COVID-19. To expand the testing capacity, the government was compelled to recruit laboratory staff with limited experience and technical expertise, especially in molecular assays, to process specimens, interpret results, troubleshoot. As a result, the risk of diagnostic errors, such as cross-contamination, increased, potentially undermining the efficacy of public health policies, public health response, surveillance programs, and restrictive measures aimed toward containing the outbreak. In this piece, we discuss the different sources of cross-contamination in the COVID-19 RT-PCR laboratories and proffer practical preventive measures to avoid them.

The antimicrobial interventions of cilantro(Coriandrum sativum)in mitigating cross-contamination of foodborne pathogens during the retail soaking process

The efficacy of commercially available antimicrobials for fresh produce—electrolyzed water(EW;around 60 mg/L of free chlorine),a combination of lactic acid and phosphoric acid-based(LPA)and citric acid-based(CA)—was compared with tap water(TW)in preventing cross-contamination during the soaking step of crisping at a retail setting.A bunch of cilantro((103.7±14.9)g/bunch)was inoculated with a three-strain cocktail of nalidixic acid-resistant Salmonella enterica(S.enterica)and Escherichia coli(E.coli)O157:H7,S.enterica and Listeria monocytogenes(L.monocytogenes),or E.coli O157:H7 and L.monocytogenes(around 5.0 log CFU/g).One inoculated and seven non-inoculated cilantro bunches were soaked in 76 L of TW,EW,LPA,and CA for 5 min.Two additional soakings,each with eight bunches of non-inoculated cilantro,were performed in the same soaking water.To determine the cross-contamination of inoculated foodborne pathogens via soaking water,the cilantro samples and soaking water following each soaking step were subjected to microbiological analyses using selective media supplemented with nalidixic acid(100μg/mL).During the first soaking,significantly greater reductions in Salmonella((2.9±0.5)log CFU/g),E.coli O157:H7((3.0±0.1)log CFU/g),and L.monocytogenes((2.7±0.3)log CFU/g)on cilantro were achieved with EW compared to soaking with TW,LPA,and CA(P<0.05).Cross-contamination of foodborne pathogens from inoculated cilantro to non-inoculated cilantro was completely mitigated by EW during three subsequent soaking events.With the exception of TW soaking water,no inoculated foodborne pathogens were detected in the 100 mL soaking water of EW,CA,and LPA collected.Including an appropriate concentration of chemical antimicrobial in water during the soaking step of crisping aids in mitigating cross-contamination of foodborne pathogen(s)in cilantro bunches.

Flashlight contamination and effectiveness of two disinfectants in a stomatology hospital

Aim: This study aims to assess the infection risks of flashlight contamination in a stomatology hospital and compare the disinfection effectiveness of alcohol (75%) and disinfecting wipes.Background: The flashlight is a basic non-critical medical device in oral and maxillofacial surgery wards. Wounds are mostly found in oral cavities;therefore, reusable flashlights may be a potential source of nosocomial infections (NIs). However, the microbial flora present in flashlights used in hospitals has not yet been explored. Methods: This study investigated the microbial contamination of 41 flashlights used in a stomatology hospital in Guangzhou in March 2016. Results: Results indicated that 75.6%(31/41) of the flashlights had microbial contamination. Gram-positive bacteria accounted for 72.7%(24/33)of the microbial groups contaminating the flashlights, and Gram-negative bacteria (21.2%, 7/33), and fungi (6.1%, 2/33) constituted the remaining contaminants. The predominantly isolated species was Staphyloccus (66.7%, 22/33), especially Staphylococcus aureus (24.2%, 8/33). Approximately 77.3%(17/22) of the types of bacteria detected in the hands were same as those in the corresponding flashlights. Both the bacterial overstandard and S. aureus detection rates of doctors' flashlights were higher than those of nurses' flashlights (16/17 vs. 14/23, 7/17 vs. 1/23, respectively) (P < 0.05). Moreover, both disinfectants performed excellently, and their eligibility rates were not significantly different (17/17 vs. 14/14) (P>0.05). Conclusion: Flashlights are potential causes of NIs. Disinfecting flashlights could be an effective and practical infection control method.

Spread of Staphylococcus aureus between medical staff and high-frequency contact surfaces in a large metropolitan hospital

Objective:To examine whether bacteria are transferred between the hands of medical staff and high-frequency contact surfaces within and between departments of a major metropolitan hospital,and to further analyze the patterns of cross-transmission.Methods:Microbiological samples were collected from the hands of 112 hospital employees as well as from 120 high-frequency contact surfaces in four hospital departments.Samples were collected on agar plates,analyzed for the presence of Staphylococcus aureus or methicillin-resistant S.aureus(MRSA)by standard microbiology testing,and partially genotyped using pulsed-field gel electrophoresis.Results:Genetically identical MRSA was identified on the surface of an electrocardiography device in the medical intensive care unit and on the same type of device in the neurosurgical unit.Genetically similar S.aureus was identified on an infusion pump in the medical intensive care unit and on the hands of several doctors in a different department who regularly use that pump.Genetically identical S.aureus was also identified on bedside rail restraint in the medical intensive care unit and on the hands of the nurse in the neurosurgical unit.Finally,genetically similar MRSA was identified both on the surface of an electrocardiography device and on the suction apparatus in the medical intensive care unit.Conclusion:Cross-contamination of S.aureus or MRSA on medical workers'hands and contact surfaces was demonstrated within and between departments of a large metropolitan hospital.Improvements are needed in medical staff hygiene habits and in the cleaning of highfrequency contact surfaces to help prevent and control nosocomial infections.

Microbiological Contamination and Disinfection Procedures of Kitchen Sponges used in Food Services

Kitchen sponges continue to be heavily used in Brazilian food services, even though they may be very contaminated. The objective of this study was to evaluate the microbiological contamination and the efficacy of two procedures for the disinfection of kitchen sponges used in Brazilian food services. Eighty sponges were collected from food services and then analyzed for the quantification heterotrophic microorganisms (HM), fecal coliforms (CF), Staphylococcus coagulase-positive (SA) microorganisms and to the investigation of the presence of Salmonella sp. (SAM). After that, the sponges were disinfected, separately, by either boiling water for five minutes or immersed in 200ppm sodium hypochlorite, for 10 minutes, added to a rinse with potable water. The results showed that sponges presented HM counts between 3.4 and 10.4 log CFU/sponge, with an average of 9.1 log CFU/sponge, and 76.25% of them presented CF with average counts of 8.4 log CFU/sponge. SA and SAM were found in 2.5% of samples. Both disinfection procedures were able to significantly reduce the bacterial counts, but the boiling method showed a greater reduction (99.9999%) than the method of disinfection by 200 ppm sodium hypochlorite (99.9%). Based on the results it was possible to conclude that kitchen sponges can be very contaminated, but simple disinfection procedure can be applied to significantly reduce the microbial contamination.

How to achieve energy efficiency in buildings without compromising indoor air quality:A case study on enthalpy exchangers

As a representative heat recovery device,the fixed-plate enthalpy exchanger possesses the advantages of high recovery effectiveness,low pressure drop,and small space occupied.Still,indoor contaminants may transfer to fresh air through the enthalpy exchanger simultaneously,causing cross-contamination risk.However,the cross-contamination risk of the fixed-plate enthalpy exchanger has been under-researched in previous studies.As a result,this study experimentally investigates the energy performance,formaldehyde and ammonia transfer rates of paper-based and membrane-based enthalpy exchangers.The results illustrate that the enthalpy recovery effectiveness of the plate exchangers ranges from 60%–85%.The formaldehyde transfer rate through the exchangers varies from 5%–23%,and the ammonia transfer rate is 0–15%.The high effectiveness and low contaminant transfer rates are conducive to the promising application of the fixed-plate enthalpy exchangers.In addition,the energy reclaimed increases with the increase of the absolute indoor-outdoor enthalpy difference.The formaldehyde and ammonia transfer rates and cross-contamination risk slightly decrease with increasing temperature but significantly increase with increasing humidity.Moreover,the experimental results demonstrate that the contaminant transfer rates through the membranebased exchanger are lower than those of the paper-based exchanger.This study provides a reference for the fixed-plate enthalpy exchanger design in practical applications.