Phenotypic characterization of non-typhi Salmonella species associated with severe malaria in children admitted toKilifi district hospital
Oundo, Joseph Owiti
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Infections caused by both typhoid salmonella and non-typhoid Salmonellae (NTS) species cause major health problems such as acute gastroenteritis, typhoid fever, severe bacteraemia and septicaemia that result in high morbidity and mortality. Non-typhoid Salmonellae species are amongst the most common causes of invasive bacterial childhood disease in sub-Saharan Africa. Malaria is a major cause of global morbidity and mortality and may be responsible for between one to two million-childhood deaths each year in sub-Saharan Africa alone. A study to determine the association between severe malaria and non-typhi salmonella in children was carried out during a 54-month period between January 1997 and June 2001 at the Kilifi district hospital on the coast of Kenya. The ages of the children varied between 3 months and 123 months (median 21 months, Inter Quartile Range 10-35 months). During this period 9147 children with severe malaria were admitted at this hospital. A total of 19, 118 blood cultures obtained from all admissions and 1820 stool cultures were performed which yielded positive growth of 7.3% and 10% respectively. Non-typhi salmonella were isolated from 18.6% of the positive blood cultures and 28.4% of the stool cultures out of which a total of 101 NTS occurred in children with severe malaria. Out of the 9147 malaria cases admitted during this period of time 1.10% had concomitant NTS infection. Non-typhi Salmonella with severe malaria as a ratio of all malaria admissions for the period varied between 0.8% and 1.5%. The NTS isolates occurring with severe malaria showed varying levels of antibiotic resistance. They were resistant to ampicillin (35%), chloramphenicol (18%), gentamicin (22%), Cefuroxime (29%), co-trimoxazole (39%), ciprofloxacin (3%), cefotaxine (14%), amoxycillin-clavulanic acid (26%) and tobramycin (18%). Multidrug resistance (MDR) was seen in 34% of the isolates. Some of this resistance was transferable. There was a significant association between clinical outcome and male sex of the patient. It can be concluded from this study that NTS and severe malaria occurring together are a major problem in this area and that a large number of the isolates are MDR. A high mortality has also been associated with these diseases in this area with a significant association with the male patients. Two major salmonella serotypes are responsible for this infection namely S. typhimurium and S. enteritidis. It is proposed that during the sequestion of plasmodium parasites, they make these vessels porous and hence open them up to invasion by salmonella from the gut. The salmonellae find a medium rich in iron, which it needs both for growth and virulence. This may explain why an occurrence of both NTS and plasmodium leads to a severe illness, which has high mortality. A more controlled study is required to elucidate the chain of events of both NTS and malaria parasite co-existence.