Staphylococcus aureus as Food-Borne Disease: An Ongoing Threat in Public Health in the Kingdom of Saudi Arabia

Majority of the global population have been affected by food-borne diseases, and Staphylococcus aureus is one of the causes of this disease. S. aureus can be transmitted through contaminated food and is a risk to universal human health because of its ability to produce toxins-staphylococcal enterotoxins. Additionally, methicillin resistant Staphylococcus aureus (MRSA) furthered public health concerns. Although MRSA has been identified in food worldwide, little information is available on this topic locally and internationally. This review presents information on MRSA that was collected as evidence of such infections globally and in Saudi Arabia.


INTRODUCTION
Staphylococcal species are opportunistic pathogens that can cause various types of infections with varying levels of severity.S. saprophyticus is the second main cause of urinary tract infections, and S. simulans, S. warneri, and S. haemolyticus can cause device-related infections.Additionally, S. aureus is a serious human pathogen that can cause lethal diseases such as pneumonia, endocarditis, toxic shock syndrome, and sepsis (Figure 1).Moreover, S. aureus and S. epidermidis can cause nosocomial infections in indwelling devices. 1 S. aureus can cause alternative diseases, particularly methicillin-resistant Staphylococcus aureus (MRSA), which forms approximately 13-74% of S. aureus infections.
MRSA infection and colonization can be negatively affected by factors such as obesity; however, the mechanism has not yet been revealed. 2According to origin of the outbreaks, MRSA is divided into two groups: healthcareassociated MRSA (HA-MRSA) and communityassociated MRSA (CA-MRSA). 3CA-MRSA clones differ from country-to-country; e.g., ST8 (USA300) and ST1 (USA400) clones were found essentially in the USA and Canada, whereas ST80 clones were found in Europe. 4Although the MRSA USA300 clone was mainly found in the USA and Canada, it was also infrequently detected in wild pig meat in Germany, Switzerland, and Spain. 5The probability of MRSA infection in patients colonized with CA-MRSA (13%) are lower than those with HA-MRSA (37%).Hence, patients colonized with HA-MRSA exhibit longer recovery time than those colonized with CA-MRSA. 6Additionally, the major cause of this infectious disease is that S. aureus is resistant to several types of antibiotics, and the susceptibility of HA-MRSA to antibiotics is lower than that of CA-MERSA. 7,8ivestock is considered a major source of staphylococci species, particularly S. aureus, causing livestock-associated MRSA (LA-MRSA).Thus, LA-MRSA can occur by direct contact with animals or by use of animal products obtained from animals such as lambs, calves, and goats.However, the spread rate of S. aureus was lower in calves (12.5%) and goats (1 %) than in lambs (30%).LA-MRSA was first discovered in France and the Netherlands and was found in pig populations in several countries of Europe.Furthermore, CA-MRSA, HA-MRSA and LA-MRSA clones vary between countries; e.g., the CC398 clone was detected in Europe and the USA, whereas the CC9 clone was found in Asia. 5,9

Pathogenesis of Staphylococcal Disease and Virulence Factors
Genetically, one of the many types of staphylococcal cassette chromosome mec complex gene (SCCmec) would be sufficient to induce an MRSA infection.Elements of SCCmec carry mecA gene, which encodes penicillinbinding protein 2a (PBP2a) that is responsible for bacterial resistance to methicillin, as shown in Figure 2. PBP2a has low similarity to betalactamases, which are responsible for resistance against extended-spectrum cephalosporins, monobactams, penicillins, and carbapenems. 10,11,12urthermore, the Panton-Valentine Leukocidin (PVL) gene is a genetic marker of MRSA (first identified in 2003) (Figure 2).Strains that produce PVL may cause skin infection or serious diseases such as pneumonia.However, PVL gene was more prevalent in CA-MRSA than in HA-MRSA and was found in approximately 60%-100% of CA-MRSA strains.Consequently, PVL develops the pathogenicity of CA-MRSA strains, and the prevalence of PVL between strains relies on mobile genetic elements, particularly bacteriophages. 8,13,14. aureus also causes Staphylococcus scalded skin syndrome by producing the epidermolytic toxins A and B, which affect the skin all over the body.It commonly affects children aged <5 years, in addition to adults with kidney disease.15 Some species of Staphylococci can cause a very prevalent disease called food-borne poisoning that occurs after consumption of contaminated food.It is mainly caused by S. aureus or occasionally by other Staphylococcus species, such as S. intermedius.Symptoms (vomiting, fever, nausea, diarrhea, dizziness, low blood pressure, and headache) present 30 min to 8 h post consumption of contaminated food.16 S. aureus live in various habitats and can contaminate foods such as sandwich fillings, salads, milk, sausages, canned meat, cheeses, and cooked meals.17 However, staphylococci can be killed by different methods for food preservation, such as cooking food with high heat and pasteurization.18 Bacteria can also contaminate food during food preparation and milk processing or storage. Coquently, Staphylococci produce enterotoxins, which include more than 20 types of toxins.16

Statement of the Problem
MRSA infections spread rapidly throughout Saudi Arabia.A group of clinicians reported that the percentage of such infections in King Fahad Medical City in Riyadh reached 50% during 2011, and there are no sufficient studies addressing this problem. 19Although MRSA in Saudi Arabia was discovered in the 1990s, the number of studies on MRSA infection in Saudi Arabia is limited compared to that in other countries around the world. 20According to PubMed, there were only 141 studies conducted on MRSA in Saudi Arabia over past 5 years (2015-2019), of which majority have been conducted on HA-MRSA.Nevertheless, until May 2014, there were only 12 articles on MRSA infections, of which ten were published in Riyadh and Dammam. 10Despite conducting investigations and discussions on HA-MRSA, there is still a shortage in the number of studies on HA-MRSA in children, and surprisingly, HA-MRSA is primarily found in men than in women. 21Based on the prevalence of CA-MRSA, the number of patients significantly increased from 9.9 per 10,000 in 2001 to 67 per 10,000 in 2008. 21,22Furthermore, between 2000 and 2008, the spread rate of CA-MRSA in the eastern region of Riyadh increased sixfold. 19Furthermore, CA-MRSA samples collected from Qatif city, Saudi Arabia, showed that CA-MRSA percentages increased gradually from 23% in 2006 to 60% in 2015. 23There is still a lack of studies that aimed to investigate LA-MRSA. 24

MRSA in the Capital City of Saudi Arabia
According to the Center of Disease Control, two in 100 individuals develop MRSA infections, and 33% of persons colonize with Staphylococcus. 25S. aureus strains (n=135) have been collected from main public health centers and hospital laboratories in Riyadh city between 2008 and 2009 to examine the presence of CA-MRSA infections.As a result, scientists have announced that the CA-MRSA infection rate was amplified in Riyadh city. 22Al Yousef et al. reported that 94% of MRSA strains have been detected in Riyadh. 26In addition, all 37 isolates of S. aureus, which were collected from King Khalid University Hospital in Riyadh (2007), were MRSA, and only two of them carried mecA gene. 27oreover, SCCmec type IV was tested in Riyadh to determine the type of strains; subsequently, CC22-MRSA-IV was found to be a common strain associated with strains collected from India and the Middle East rather than that from the Western European countries. 28Senok et al. obtained 117 samples of MRSA infections over a 6-year period (2009-2015) in Riyadh city and examined them to identify the most derived strains related to CA-MRSA; CC5, CC22, CC6, and CC80 (13, 12, 15, and 35 strains, respectively) were the most commonly identified strains.This study identified three new MRSA clones in Saudi Arabia ( CC15-MRSA). 29laklobi et al. estimated the growth of CA-MRSA levels among children in Riyadh city, which ranged from 0%-9%, and 164/824 samples in this study were colonized with S. aureus; however, only 38 samples were MRSA, and 23% of the MRSA infections were reported in children. 30In addition, another study examined 100 raw retail meat samples: 24 lamb (mutton), 24 camel, 23 beef, and 29 poultry (chicken parts) in Riyadh.Of the 100 meat samples, 25 were contaminated with S. aureus.While meat samples from poultry assets were recorded to have the lowest contamination among the tested samples, the meat sample from camel had the highest level of contamination. 24oreover, 80 camel milk samples were collected from different places throughout Riyadh city, and strains of bacteria that carried the 16s RNA gene similar to many pathogens such as MRSA were found. 31

MRSA in Different Cities of Saudi Arabia
As shown in figure 3, MRSA's types have been spotted in variant cities of Saudi Arabia such as Dhahran, Dammam, Medina, Jeddah, Taif, Asir, etc.In 2019; moreover, Farah et al. reported that there was a high level of multidrug resistance among seven different locations and 12 hospitals in Saudi Arabia.During the same period, HA-MRSA cases declined significantly from 0.17/1000 to 0.03/1000. 25In Saudi Arabia, HA-MRSA was first discovered, followed by CA-MRSA and LA-MRSA.However, CA-MRSA has been reported to be less serious than HA-MRSA; hence, researchers in Saudi Arabia are more focused on HA-MRSA. 32,33In addition, investigators have tended to use PVL as an indicator of CA-MRSA presence, which has been recorded to be present at high levels in Riyadh since 2012. 19,32dditionally, a group of scientists in Riyadh and Taif focused on CA-MRSA and found that since SCCmec IV and V can easily be transmitted among organisms, they are predominant than SCCmec I, II, and III. 22,34wing to the Hajj season, 31 studies were conducted in Mecca, Mina, and Medina, and the authors examined food workers, hospitalized patients, and pilgrims between 2000 and 2015.Subsequently, a sharp increase in MRSA infections in pilgrims was observed (from 1% in 2000 to 63% in 2015).The rate of MRSA isolated from food handlers has also increased remarkably (i.e., from 0% in 2001 to 20% in 2014). 35Additionally, certain restaurants in Makkah city have tested and reported that the food samples were contaminated with S. aureus. 33In addition, many food samples (e.g., raw milk and cheese) in Makkah City were found to have a significant incidence of multidrug-resistant S. aureus and coagulase-negative staphylococci. 36he western region of Saudi Arabia has been similarly investigated by El amin and Faidah, and the most isolated MRSA infections (87%) were from soft tissue, skin, and wounds.In addition, the prevalence of HA-MRSA was 53%, whereas that of CA-MRSA was 31.5%. 37Approximately 5% of MRSA infections were also reported in Madinah city by Ghanem et al. during the time of fourteen-month.Most of them were isolated from men (237 MRSA strains), including 37 recovered strains from nasal swabs, 120 strains from sputum, and 124 strains from wound swabs.Moreover, MRSA isolated from catheter tips and pus samples was higher in women than in men, and the rate of MRSA infections reached a peak in the summer season throughout the Hajj term (51%), which decreased during other seasons: 21% in autumn, 18.5% in winter, and 10% in spring. 38part from Mecca city, different cities in Saudi Arabia have been examined for MRSA infections; e.g., a study conducted in Qatif city from January 1, 2006, to December 31, 2015, highlighted that 25/100,000 patients were diagnosed with MRSA infection, and 20%-35% of all patients in the examined city were children. 23oreover, MRSA was detected in 101 samples from public health centers and large hospital laboratories in Jeddah city between August 2009 and May 2011.MRSA strains carry mecA gene and are positive for PVL; therefore, the common type of SCCmec in that study was type V, followed by type III (42.5% and 39%, respectively). 39Four different strains of S. aureus (CC22, CC8, CC5, and CC80) were isolated from 206 nasal swabs (103 from Saudi Arabia and 103 from Egypt).The prevalence of MRSA in Saudi Arabia was lower than that in Egypt (12% and 15%, respectively).In this study, mecA gene was positive, and the most common types of SCCmec were IVa and V. 40 A recent study in Jeddah city, conducted by Al-Zahrani et al. recorded the highest ratio of MRSA infections (CA-MRSA comprised majority of the infections).During Hajj, pilgrims travel from Jeddah to Mecca, which lead to a rise in MRSA cases (>61%), and these cases majorly include foreigners (from Pakistan, Sudan, Syria, Yamen, Somalia, Egypt, and Chad). 41n addition, a 7-year study from 2001 to 2008 was conducted in the eastern region of Saudi Arabia, which revealed that the rate of CA-MRSA infections increased from 9.9/10,000 in 2001 to 67/10,000 in 2008.This investigation was divided into two stages.The presence of CA-MRSA was 67 (20%) and 176 (59%) in the first (2001-2004) and second stages (2005-2008), respectively. 42Furthermore, Dhahran city in Saudi Arabia was among the places that attracted the attention of researchers for further investigation of MRSA.Khanfar et   44 Throughout the southern region of Saudi Arabia, from Asir Central Hospital and Abha General Hospital, 210/9831 infectious samples contained S. aureus.The samples were collected from three dissimilar sources (ten from the hospital environment, 100 from community-acquired infections, and 100 from hospital-acquired infections).Hence, the hospital environment is a serious threat to all hospital staff, visitors, and hospitalized patients in terms of MRSA dissemination. 45everal CA-MRSA + HA-MRSA and LA-MRSA infections have been reported in several cities of Saudi Arabia.For example, 20 isolates from 775 nasal swabs and 235 milk samples taken from a goat farm in eastern Saudi Arabia were MRSA.The maximum prevalence of MRSA in this study was 2%, and most of them were from mastitic milk (9%) and a few were from normal milk (0.6%). 46Furthermore, in Al-Hasa city, 20 out of 187 fresh raw camel meat samples consisted of S. aureus strains, and three of 20 isolates were reported as MRSA. 47n Qassim city, 90/400 animal-derived samples (from goat, sheep, cow, and camels) were identified as LA-MRSA (57%).The smallest level of LA-MRSA isolates was from cow and goat samples, whereas the highest level was from sheep and camel samples. 48

Reasons of MRSA Infection
Bhedi et al. stated that the presence of MRSA infections in poultry meat is attributed to many factors, such as dropping meat handling levels in selling shops, hygiene, and sales practices. 49lobally, food handlers are also considered a major cause of food contamination; e.g., in Dhaka city, street food is served with bare hands.Thus, approximately 50-70% of ready-to-eat food (RTE) handlers are transmitters of S. aureus.Moreover, 32% and 1% of food handlers of Zimbabwe and Hong Kong, respectively, are infected with S. aureus.Another study in China confirmed that 3-6% of Hong Kong butchers were affected by LA-MRSA ST9. 50,51

CONCLUSION
This literature review revealed that the rate of MRSA prevalence has significantly increased worldwide, with the emergence of MRSA in food handlers, food samples, and animal-derived food.In Saudi Arabia, studies have emphasized that HA-MRSA is more serious, even though the susceptibility of HA-MRSA to antibiotics is lower than that of CA-MERSA.Lastly, it is worth mentioning that more studies on MRSA are required because of their impact on public health.

Figure 3 .
Figure 3. Spread of HA-MRSA and CA-MRSA in Saudi Arabia al. reported 878 cases of MRSA infections from the Saudi Aramco Dhahran Health Center between 2004 and 2009; 777 (88%) and 101(11.5%)cases were CA-MRSA and HA-MRSA infections, respectively. 43Approximately 30% of MRSA strains have been discovered in approximately 90 minced meat and vegetable sandwiches collected from fast-food canteens in Al-Ahsa city.