The Menace of Typhoid / Paratyphoid Fever – The Abuja Experience: A 5 Year Retrospective Study

Typhoid / paratyphoid fever is caused by Salmonella typhi and Salmonella paratyphi A, B and C respectively. A 5 year retrospective study on blood (Oxoid signal blood culture system) and faecal cultures at the Medical Microbiology Laboratory of National Hospital, Abuja was carried out. Of the 2,818 blood cultures, only 90 (3.2%) had positive cultures for Salmonella species while the 10,007 faecal samples cultured, only 159 (1.58%) were positive for Salmonella species. Identification was by biochemical and serological methods. The sensitivity pattern in both blood and faecal isolates show Ceftazidime (97.9% and 98.1%), Ceftriaxone (98.0% and 95.4%), Cefotaxime (97.6% and 93.7%), Gentamicin (80.9% and 78.5%), Augmentin (76.1% and 69.5%), Amoxycillin (45.5% and 56.4%), Chloramphenicol (40.6% and 75.2%), Tetracycline (100% and 51.1%), Ampicillin (35.3% and 32.6%) and Cotrimoxazole (34.4% and 76.6%). Our results indicate a very low rate of typhoid / paratyphoid fever and the need for isolation and proper sensitivity testing before the commencement of therapy. Appropriate specimens (faeces, urine, or blood) from suspected patients should be cultured for the presence of salmonellae. INTRODUCTION Typhoid / paratyphoid fever is caused by Salmonella typhi and Salmonella paratyphi A, B and C respectively. It is customary in our society that any feverish condition is first treated for malaria. If this fails, then treatment for typhoid automatically follows and if the patient at this stage fails to respond, it is only then that laboratory investigations are remembered. Salmonellosis is responsible for a variety of clinical syndromes, including gastroenteritis, enteric (typhoid) fever and extraintestinal manifestations. Typhoid fever remains one of the most prevalent acute infectious diseases in the developing world including Nigeria. It continues to exist as an endemic disease due to poor (improper) sanitation and low socio-economic status of the people. The Widal test (Widal’s agglutination reaction) is routinely employed for the serodiagnosis of typhoid fever by most Medical Laboratories in Nigeria. However, several workers within the Medical community have expressed doubt regarding the reliability of the test. There are several contributing factors for this uncertainty. Some have started calling for the discontinuance of Widal test as a diagnostic test for typhoid fever. Their argument is based on; 1. The difficulty of interpreting Widal test result in areas where typhoid fever is endemic and where the baseline titre of the normal population are not known. 2. The typhoid febrile agglutination test (Widal test) is often positive (raised O and H titres) in patients with infections caused by other bacteria, because of cross-reacting antibodies or previous vaccination with TAB or typhoid vaccine; chronic liver disease associated with raised globulin levels, and disorders such as rheumatoid arthritis, rheumatic The Menace of Typhoid / Paratyphoid Fever – The Abuja Experience: A 5 Year Retrospective Study 2 of 5 fever, multiple myeloma, nephrotic syndrome, and ulcerative colitis. 3. The differential behavioural pattern of isolates of Salmonella species to various antibiotics as seen from our susceptibility test results. The aim of this work therefore is to re-emphasize the importance of using appropriate specimens (faeces, urine and blood) in the laboratory diagnosis of Salmonella species and its antimicrobial susceptibility pattern prior to treatment for typhoid / paratyphoid fever. MATERIALS AND METHODS A 5-year retrospective study on blood (Oxoid Signal blood culture system) and faecal cultures at the Medical Microbiology Laboratory of National Hospital, Abuja was carried out. BLOOD CULTURE The Oxoid Signal Blood Culture System (produced by Oxoid Limited, Wade Road, Basingstoke, Hampshire, RG24 8PW, England) was used to culture samples of blood collected from patients where the condition of bacteriaemia is suspected. Figure 1 Figure i: Picture of Oxoid Signal Blood Culture System PROCEDURE FOR BLOOD CULTURE ml of blood is inoculated into Oxoid Signal Blood Culture System. This is a semi-automated system that recognizes bacterial growth in the blood culture by gas production. The inoculated bottle is placed at 36C (+/-) 1C for 1 hour before inserting the Signal device. It is continuously shaken for 24 hours. Incubate at 36C (+/-) 1C for at least 7 days. A positive bottle is indicated by upward movement of fluid into the signal device while a negative bottle is indicated by absence of fluid in the signal device. All positive bottles are sub cultured onto Chocolate agar, 3 Blood agar and MacConkey agar plates and incubated for 24 hours at 36 (+/-) 1C. When applicable, it is re-incubated for a further 18 – 24 hours. The second Blood agar plate is incubated at 10% CO2 while the third Blood agar plate is incubated anaerobically (AnO2) for 48 hours. Isolates are identified by gram stain, biochemical reactions (Kliegar Iron Agar – KIA, Urea, Citrate, MRVP) as well as sero-typing using Salmonella Polyvalent O sera and Monovalent A, B, C, and D sera. vi sera is also available for typing. Antibiotic susceptibility test (disc diffusion technique) is carried out on isolates. PROCEDURE FOR FAECAL CULTURES Faecal samples were cultured on Salmonella /Shigella Agar (SSA) or Deoxycholate Citrate Agar (DCA) and Selanite Fluid (SF) and incubated at 37C for 18 – 24 hours. The Selanite fluid preparation is sub cultured on SSA or DCA and further incubated at 37C for 18 – 24 hours. Non Lactose Fermenting Colonies (NLFs) isolated are subjected to identification as stated above under the blood culture methodology. RESULTS BLOOD CULTURE Of the 2,818 blood cultures, only 90 (3.2 %) had positive cultures for Salmonella species. Figure 2 Table i : Occurence rate of Blood species The Menace of Typhoid / Paratyphoid Fever – The Abuja Experience: A 5 Year Retrospective Study 3 of 5 ANTIBIOTIC SUSCEPTIBILITY TESTING OF BLOOD AND FAECAL ISOLATES Ten (10) antibiotic discs were used for the susceptibility testing. Viz; Amoxycillin, Ampicillin, Augmentin, Cefotaxime, Ceftazidime, Ceftriaxone, Chloramphenicol, Cotrimoxazole, Gentamicin, and Tetracycline. Note:Only six (6) antibiotic discs are used for testing at any given time! Figure 3 Table ii: Susceptibility Pattern of Blood isolates Figure 4 Figure ii – Graphical representation of susceptibility pattern of blood Salmonellae isolates FAECAL CULTURES Of the 10,007 faecal samples cultured, only 159 (1.58%) had positive cultures for Salmonella species. Figure 7 Figure iii – Graphical representation of susceptibility pattern of faecal Salmonellae isolates Figure 6 Table iv : Susceptibility Pattern of Faecal isolates Figure 8 Table v : Comparism of Antibiotic Susceptibility Pattern of Blood and Faecal isolates The Menace of Typhoid / Paratyphoid Fever – The Abuja Experience: A 5 Year Retrospective Study 4 of 5 Figure 9 Figure iv: Graphical representation of the comparism of antibiotic susceptibility pattern of blood and faecal isolates