Salmonella Infections

• Salmonella infections are a major public health concern due to acute diarrheal disease. Preventative measures have not stopped it.
• Salmonellosis ranges from gastroenteritis to life-threatening enteric fevers that need fast antibiotic treatment.
• There have been numerous outbreaks of Salmonella reported worldwide, which indicates the requirement for improved prevention, control measures, and disease surveillance across the globe.
• Acute diarrheal diseases cause significant mortality and morbidity.
• The World Health Organization (WHO) reports that over 2 billion people worldwide suffer from diarrheal diseases annually.
• Food is implicated as the source of infection in a third of cases.
• Salmonellosis is one of the most common foodborne infections.
• Infections caused by Salmonella is divided into minor and major diseases.
• Minor salmonellosis caused by nontyphoid Salmonella strains is characterized by self-limiting diarrhea that rarely leads to bacteremia or meningitis.
• Major salmonellosis is represented by typhoid fever with symptoms of fever, headache, malaise, and sometimes cough.

Salmonella Discovery and Classification

• Salmonella was first discovered in 1884 by D. E. Salmon, an American bacteriologist.
• The organism was isolated from porcine intestine.
• Up to 80% of salmonellosis cases go unrecognized as part of a known outbreak and are considered sporadic cases.
• Salmonella nomenclature is complex with many classifications.
• The first classification of Salmonella was based on biochemical characteristics.
• The Kauffman-White classification is based on O and H antigens and follows the serotype-one species principle.
• The Kauffman-White classification subdivides the Salmonella genus into more than 2500 species.
• Current Salmonella taxonomy includes two species: enterica and bongori.
• S. enterica contains 6 subspecies: enterica, salamae, arizonae, diarizonae, houtenae, and indica, and are subdivided into serogroups (O antigen) and serovars (H antigen).
• Over 2500 serovars are known.
• Recent research uses molecular methods for serotyping, which are better in standardization, reproducibility, and discrimination than traditional serotyping.
• These techniques detect serovars are based on molecular subtype or specific genomic markers that identify genes encoding certain antigens.
• Equipment and reagents for molecular methods are less accessible for developing countries.

Transmission Routes

• The main reservoir of Salmonella is the intestine of humans and animals, though it has also been identified in reptiles and insects.
• Sources of Salmonella infection include eggs, meat, dairy products, vegetables, and water.
• In developed countries, the most common source of infection is food, and identifying the source is important to prevent spread.
• A study in PLoS One showed an increase in cases of Salmonella infection in Australia from 2000-2013, involving Salmonella Typhimurium and Salmonella non-Typhimurium.
• The study estimates that food was the source in over 70% of cases in Australia.
• Water can be a contamination source.
• Eggs and meat (chicken, pork) are the most important sources, but vegetables and fruits should not be neglected.
• Chicken and other birds can carry the microorganism, and exposure is associated with infection acquisition.
• Cases of infection have been reported after contact with pets, which are often asymptomatic, and person-to-person transmission is possible.
• Some serotypes are host-specific, while others infect any warm-blooded animal, i.e. S. typhi infects only humans.
• Around 50 serovars are involved in human and animal diseases.

Recent Outbreaks

• ProMED-mail was used to select several worldwide Salmonella outbreaks reported in recent year and European outbreaks are discussed in a separate section.
• In 2015, a frozen raw breaded chicken product outbreak in Canada affected 4 provinces, resulting in 44 cases.
• Raw mung bean sprouts caused an outbreak in South Australia in 2016, with 230 Salmonella cases reported. Also. rockmelon caused an outbreak in New South Wales(Australia), with 97 cases reported.
• In 2016, a raw meal organic shake outbreak in the USA infected over 27 people.
• A Salmonella Poona serotype outbreak originated from cucumbers imported from Mexico, affected 40 states, and infected 907 people in 2016.
• In 2019, most outbreaks reported by promedmail.org took place in the USA.
• In 2017, several Australian restaurant outbreaks had unknown sources.
• In Japan, fever and vomiting cases in 87 kindergartners were recorded. Salmonella was the most common isolated pathogen.
• Salmonella Typhimurium sequence type (ST)313 emerged as an invasive and virulent strain in Sub-Saharan Africa.
• Several outbreaks were reported in the USA in 2017.
• The US CDC reported 24 cases of Salmonella infection in 16 states.
• Raw turkey products, ground beef, eggs, fast food, pre-cut melon, and frozen coconut were sources of infection in the USA in 2018.
• Tahini products caused a Salmonella Concord outbreak in Israel around that same time.
• 49 Australians had acute diarrheal disease caused by Salmonella after consuming chicken-sandwich products in 2018.
• A sushi-related salmonellosis outbreak was reported, and it affected 80 people in Chile.
• Contact with backyard poultry led to an infections outbreak in the USA, infecting over 1,000 people in 49 states. Additionally, vegetables were found as a source of related infection.
• Until June 24, 2020, 473 persons were reported ill in USA (Salmonella Braenderup, Muenchen, Thompson, and Typhimurium).
• There were a total of 938 reported cases across 48 states as of July 28, 2020.
• Multiple other outbreaks emerged with Salmonella Newport, Salmonella Thompson, Salmonella Enteritidis, Salmonella Potsdam and Salmonella Miami being identified.
• The last two outbreaks are still ongoing and account for nearly 200 people sick.

Salmonella Causing Enteric Fever

• Cases of illness were reported in several US states after eating Paratyphi-isolated raw fish. in 2015.
• A chloramphenicol, ampicillin, trimethoprim-sulfamethoxazole, fluoroquinolones, and 3rd-generation cephalosporins-resistant Salmonella enterica serotype Typhi outbreak was reported in Pakistan between November 2016 and September 2017 involving 5,372 extensive-drug resistant (XDR) Typhi cases and 5 travel-related cases in the USA.
• Multidrug-resistant (MDR) typhoid fever cases were reported in Pakistan among children due to a water crisis in the area in 2017. Resistant Salmonella Typhi strains have been identified in Kenya.
• Typhoid fever cases increased in India in 2017 due to the consumption of polluted water. Typhoid fever was also reported in Zambia.
• New Zealand reported an outbreak of paratyphoid fever from mussel contamination.
• Typhoid fever cases were reported among Iraqi refugees and displaced Syrians due to drinking water in 2018.
• Consumption of contaminated water caused multiple cases of typhoid fever in the Woraiyur area of India.
• According to the CDC, about 350 cases of typhoid fever are reported each year in the United States.
• A police detective in California was diagnosed with typhoid fever in 2019, and 6 colleagues had similar symptoms.
• Paratyphoid fever cases were reported in North Korea in 2019 after typhoon Lingling hit.
• Salmonella Paratyphi B was reported at the end of 2020, causing illness in 18 people, and the outbreak is deemed as closed.

Salmonella Outbreaks in Europe

• The number of salmonellosis cases has decreased in Europe since 2007, due to preventive measures regarding food product control and hygiene.
• There was a 23.6% increase in the number of outbreaks due to S. Enteritidis at EU level in 2016, with 13 Member States, Salmonella serovars outbreaks are Enteritidis and Typhimurium.
• Increased consumption of fresh produce has led to an increased number of outbreaks associated with contaminated fresh produce. The first outbreak related to fresh produce was registered in the USA in 1990, was tomatoes.
• Salmonellosis survey in the European Union over 15 years (2000-2014) showed that catering services are a very important source, second only to household environment cases.
• Eggs and egg products were the main infection source, followed by meat and vegetables due to proper food preparation.
• A study on Danish meatballs distributed through catering services showed that core temperatures of about 70°C significantly reduced salmonellosis risk.
• In 2013, a Salmonella enterica subspecies enterica serovar Infantis outbreak in Germany lasted from April to October, and the raw pork products infected 267 people, killing one.
• The most affected were the elderly and people receiving medication that decreases gastric acidity, who can adhere to recipient surfaces used by catering services, forming biofilm. Adhesion depends on material like teflon, glass, or polyurethane.
• Salmonella Enteritidis infected 200 children in Bosnia & Herzegovina, where the source was macaroni with cheese and eggs.
• Salmonella enterica serovar Enteritidis was reported in Greece, affecting 56 persons with severe symptoms requiring hospitalization. Symptoms began less than 12 hours after eating cheesy penne pasta.
• It was assumed that cooking temperatures were not adequate, and high-fat cheesy penne pasta formed a capsule around the microorganism, preventing its destruction by gastric acid.
• A rare Salmonella serotypes outbreak took place in Europe regarding 40 cases in Greece, Germany, the Czech Republic and Luxembourg related to sesame-based products. The average per year was 3 cases of Salmonella Stourbridge in 2011-2016.
• In 2017, 92,649 cases of salmonellosis were reported in Europe that resulted to 156 deaths.
• Experts announced “a multi-country outbreak of Salmonella Enteritidis linked to eggs from Poland is ongoing in the EU/EEA".
• Between 1 February 2017 and 28 November 2017, 196 confirmed cases of Salmonella Enteritidis infection were reported.
• "a multi-country outbreak of Salmonella Enteritidis linked to eggs from Poland is ongoing in the EU/EEA".
• "a multi-country outbreak of Salmonella Enteritidis linked to eggs from Poland is ongoing in the EU/EEA".
• Another outbreak investigated by ECDC, involving Salmonella enterica subspecies enterica serovar Agona included 147 cases was linked to ready to eat products that containing cucumbers.
• S Agona is among the 10 most common Salmonella serotypes reported in Europe,
• According to 2018 ECDC report, Salmonella was the most common cause of foodborne outbreaks in Europe.
• Over 60% of Salmonella outbreaks were recorded in Slovakia, Spain and Poland.
• A Salmonella enterica serotype Poona outbreak occurred in France causing 30 confirmed cases, was linked the consumption of infant formula product based on rice proteins.
• 23 EU/EEA countries reported cases from "a multi-country outbreak of Salmonella Enteritidis linked to eggs from Poland is ongoing in the EU/EEA" annual case ranging from 378 to 582 between 2013 and 2017.

Salmonella Causing Enteric Fever

• Typhoid fever is rare in Europe, where most reported cases are travel related, more than a third of typhoid fever cases were related to India in the United Kingdom in 2016.
• In Georgia, a hospital-based surveillance enrolling 537 patients revealed that 3 had Salmonella Typhi infection as of 2008-2011.
• The cases were in Italy, France, and Asia. Worldwide, 11-21 million cases of typhoid and paratyphoid fever are reported annually.
• The isolates detected in Switzerland indicated 11.5% had multidrug resistance, creating an important problem with resistance to fluoroquinolones.
• A case of typhoid fever has been reported being caused by Salmonella enterica serovar Typhi producing an extended-spectrum ß-lactamase (ESBL), and has been identified in Spain.
• Between 1997-2017, 53 cases of Typhoid fever were reported in the Czech Republic. Imported.

Methods to Prevent Salmonella Outbreaks

• Restaurants are a common place for outbreaks.
• The correct washing of employees' hands is a very important action in preventing these outbreaks, and a study showed a 100% reduction in Salmonella pathogens when the hands were washed properly.
• Temperature abuse, the level of undercooking, and contaminated equipment are the significant risks.
• Not only prevalence of Salmonellae but also factors related to virulence of the strain is important. The author cites temperature abuse, the level of undercooking, contamination of ready-to-eat food.

Prevention

• It is important to promote risk consumption behaviors and high-risk customers as linked to infections.
• Fresh and raw foods can be a major concern, and food and water, which are easily overlooked, are important because boiling, peeling, cooking, and forgetting, can prevent traveler's dirrahea
• Eggs are an important the source of multiple infections. Various treatments are available, such as gamma irradiation, freeze drying, hot air, microwave heating, etc
• Rigorous hygiene practices must be implemented in the food processing and preparation industry, especially around environmental controls.
• To reduce the degree of contamination in pathogens, phages in bioactive packaging materials and anti-E. coli may be useful in reducing food pathogens.

Conclusion

• Data on Salmonella infections are not aggregated.
• The lack of communication and preparedness is evidenced to SARS-CoV-2 and begs to question: When the pandemic will subside, will we again go back to ignoring the outbreak?
• There is a need to support the public health units to manage food contamination and prevent the spread. Because “Infections do not respect customs".