Survey of nasal carriage of Staphylococcus aureus and intestinal parasites among food handlers working at Gondar University, Northwest Ethiopia

Food borne diseases are major health problems in developed and developing countries. The World Health Organization (WHO) estimated that in developed countries, up to 30% of the population suffer from food borne diseases each year, whereas in developing countries up to 2 million deaths are estimated per year [1, 2].

The spread of food borne diseases via food handlers are a common and persistent problem worldwide [3, 4]. Many diseases are communicable and caused by micro-organisms that enter into the body via food [5]. Numerous outbreaks of gastroenteritis have been associated with ingestion of raw foods, foods incorporating raw ingredients or foods obtained from unsafe sources [6, 7].

Food poisoning has been reported to be a result of infection with enterotoxigenic strains of staphylococcus aureus[8‐13]. It accounts for 14–20% of outbreaks involving contaminated food in the USA [14], and in the United Kingdom restaurants are the second most important place for acquiring staphylococcal food poisoning [15]. This organism may exist on food handler’s nose or skin, from which it may be transmitted to cooked moist protein-rich foods, and become intoxication agent, if these foods are then kept for several hours without refrigeration or stored in containers.

Antibiotic resistant staphylococci are major public health concern since the bacteria can be easily circulated in the environment. Infections due to methicilin-resistant S. aureus (MRSA) have increased world-wide during the past twenty years [16, 17]. Multiple drug-resistant S. aureus have been frequently recovered from foodstuffs [18], nasal mucosa of humans [19].

Likewise intestinal parasitic infections remain important public health problems in developing countries. Infection of intestinal parasites usually occurs primarily by ingestion of eggs and cysts via a fecal-oral route or directly from human to human through poor personal hygiene [20, 21]. In Ethiopia amoebiasis and giardiasis are common causes of intestinal protozoa infections throughout the nation. The prevalence of amoebiasis ranges from 0–4% and that of giardiasis is 3–23% [22]. Food-handlers with poor personal hygiene working in food-serving establishments could be potential sources of infections of many intestinal helminthes, protozoa, and entero pathogenic bacteria [23]. Food-handlers who harbour and excrete intestinal parasites may contaminate foods from their faeces via their fingers, then to food processing, and finally to healthy individuals [21].

In this study, nasal swab culture and stool microscopic examination of 200 food handlers had been investigated for the presence of bacteria and intestinal parasites. The rate of isolation of S. aureus from the nasal cultures in our study 41 (20.5%) was found to be similar to those reported by several researchers as 26.6%, 23.1% and 21.6% [26‐29]. However, our finding was found to be higher than the rate 69(0.77%) obtained from a study conducted in Turkey [30] and much lower than the findings reported in Brazil and Botswana as 30%, and 44.6%; respectively [31, 32]. Nasal carriage rates reported by several workers vary and the variation has been attributed to the ecological differences of the study population.

It is very important to note that although S. aureus causes severe infections it may also be as a member of the normal flora of the nasal cavity [33]. If by chance, a food handlers carries, an enterotoxin producer S. aureus he/she may contaminate the food and causes staphylococcal food poisoning outbreak in the students population. However, in our nasal carriage strains isolated from food handlers, we were not able to identify the presence or the absence enterotoxin producer strains because of lack of reagent enterotoxin kit, Phage typing and PCR techniques.

Our study demonstrated that 4(9.8%) strains of S. aureus were resistant to methicillin. It is important to note that the emergence and dissemination of MRSA (Methicillin Resistant Staphylococcus aureus) is an increasing global health problem that complicates the therapeutic management of staphylococcal infections. However, the rate of resistance in our study was much lower than that reported as 3(20%) the study done in Gondar from nasal swab isolate of health professionals (unpublished). The possible explanation for the higher rate of MRSA in the previous study may be due to cross transmission with hospital strains. In this study isolates of S. aureus resistant to ampicilin was 19(46.3%) in line with reported as 45% in Brazil [27]. However, the resistance of S. aureus to penicillin in our study was lower than from the reported 70% in Brazil [31]. In our study all isolates were sensitive to vancomycin in line with a finding by Acco et al.[31]. However, a study conducted in Botswana showed that 9(27.3%) of the isolates were resistant to vancomycin [32].

In this study, the overall prevalence of intestinal parasite among food handlers were 50(25%) consistent with the study done in Gondar town (29%) and in Sudan 23.1% [29, 34]. However, this prevalence was much lower compared to previous study done at Bahir Dar town [34], reported as 158(41.1%) and in Jimma which was 59(58.4%) [35]. The possible explanation may be more than half of the food handlers in this study had taken medical examination and might be treated for intestinal parasites or this study did not use sensitive techniques like Kato-thick smear for most of intestinal helminthes especially for Schistosoma mansoni, water emergency technique for Strongloides stercolaris and the adhesive scotch tape for E. vermicularis.

It was noted that 12 (6%) and 2(1%) of food handlers working in the kitchens were suffering from diarrhea and dysentery; respectively. Active trophozoites forms of E. histolytica, G. lamblia and larva of S. stercolaris were associated with diarrheic food handlers. Infections with the protozoan parasites like E. histolytica and G. lamblia are common causes of diarrhoea worldwide [35]. G. lamblia and E. histolytica infected food handlers can directly transmit to consumers if ingested via contaminated food and water because G. lamblia cysts and E. histolytica cyst do not need environmental maturation. Thus, food handlers should be in a good health and those suffering from diarrhea and dysentery must be excluded from work until they have been completely free of symptoms and must get rest.

In this study, majority of food handlers working in the cafeterias were young adults 135 (67.5%) but which was older than study done in Bahir Dar 371(96.6%) [37]. More than half of (53.5%) the food handlers had medical check-up in the past. However, none of the food handlers had medical check-up in the past in Bahir Dar study [34].