CRONOBACTER SAKAZAKII: AN EMERGING PATHOGEN

INTRODUCTION

Cronobacter spp. are opportunistic food borne pathogens associated with infections in neonates and infants, particularly those that are premature or immune-compromised. Symptoms of Cronobacter infection are severe, including meningitis, septicemia and necrotizing enterocolitis (Bar et al.,2001:Van et al 2001). The frequency of C. sakazakii infections appears to be low, prognosis is poor. Reported case-mortality rates vary from 40% to 80% among infected infants (Willis et al.,1988). Low contamination levels (1 cfu.100 g-1) of Cronobacter sakazakii can have a severe impact on health and the rapid detection and correct identification of these pathogens are important for food safety(Van et al.,2001). Only 3 Cronobacter species associated with neonatal infections, namely C. sakazakii, C. malonaticus and C. turicensis have the genes encoding for a cation efflux system which allows bacteria to invade brain micro vascular endothelial cells. As it is still unclear whether all of the species are virulent, the genus is currently classified as pathogenic. However, infant formula(IF) is the only source that has been epidemiologically linked to disease outbreaks caused by Cronobacter (Van et al.,2001:Muytjenes et al.,1983:Himelright et al.,2002:Pagotto et al.,2009). The risk of Cronobacter contamination is further increased as it has been reported that regularly used disinfectants are insufficient to kill Cronobacter cells imbedded in biofilm(Kim et al .,2007). Case-reports of C. sakazakii- infections in adults are rarely published because of the less severe nature of the illness in comparison with the high lethality of C. sakazakii- infections occurring in new-born infants(Lai,2001). Oral and intestinal colonization with C. sakazakii (Farmer et al.,1980:Ohara et al.,2003) may be associated with ingestion of contaminated food. The original reservoir of Cronobacter is still unknown but there are indications that these pathogens might be of plant origin.

Cronobacter strains have been isolated from various food products such as mixed salad vegetables, meat, milk and cheese (Iversen et al.,2003:Kim et al., 2005:Beuchat et al.,2009). Foods other than infant formula have been rarely investigated for the presence of C. sakazakii. Nevertheless, this microorganism could be isolated from a wide spectrum of foods and food ingredients. Although C. sakazakii contaminated food do not have general public health significance, measures for prevention should consider the presence of C. sakazakii in foods, food ingredients, their processing and preparation as possible source of contamination, colonization or infection.( Farmer et al.,1980) recommended that Cronobacter isolates could be tested for susceptibility to the antibiotics cephalothin and Ampicilin. These researchers found that 13% of Cronobacter isolates were susceptible to cephalothin and that all the isolates tested were susceptible to Ampicilin. Other studies have confirmed the susceptibility of Cronobacter to Ampicilin(Kim et al.,2006). Ampicilin resistance in Cronobacter has, however, also been reported(Kuzina et al., 2001:Lai et al., 2001). It was suggested by (Lai KK,2001) that this resistance was likely due to the overall increasing trend of antibiotic resistance in members of the Enterobacteriaceae in general. It has been determined that API 20E biochemical kits are not reliable or consistent tools for the correct identification of Cronobacter strains(Iversen et al ., 2007). The polymerase chain reaction (PCR) has been shown to be a more reliable approach to identifying Cronobacter in comparison with the conventional identification techniques(Lehner et al.,2005:Cawthorn et al.,2004).