Lactose Fermenting Salmonella Paratyphi A: A case report

Abstract

Mahwish Latif, Mehreen Gilani, Javaid Usman, Tehmina Munir, Maria Mushtaq, Nazish Babar There are more than 2500 antigenic types of the genus Salmonella. Typhoid fever is caused by Salmonella typhi, Salmonella paratyphi A, B and C. Characteristically all four of these is non-fermenters of lactose. We report a case of lactose fermenting Salmonella paratyphi A isolated from the blood sample of a 27 years old male with 12 days history of fever. Lactose fermenting colonies were isolated on Crystal Mac Conkey agar plate after 24 hours incubation at 35°C. It was identified using colony morphology, Gram staining, Oxidase test, sugar sets (Indole, Urea, Citrate, Triple sugar iron tests) and API 20E. It was confirmed as Salmonella paratyphi A after positive agglutination reaction with Salmonella antisera polyvalent A-S and antiserum O2. The emergence of lactose fermenting strain of Salmonella paratyphi A is important because it is likely to be missed or misdiagnosed. As Salmonella paratyphi A is taking over Salmonella typhi as cause of typhoid and is exhibiting high levels of drug resistance too. So in order to avoid incorrect identification it should be kept in mind that S. paratyphi A can very rarely yield lactose fermenting colonies on Crystal MacConkey agar after 24 hours incubation.

Keywords

• Antibiotic resistance, Lactose fermentation, Salmonella, Salmonella Paratyphi A

Lactose Fermenting Salmonella Paratyphi A: A case report

Öz

Salmonella genusunda 2500’den fazla antijenik tipleri bulunmaktadır. Salmonella Typhi ve Salmonella Paratyphi A, B ve C tifo etkenidirler. Karakteristik olarak bu dört tür de laktozu fermente etmezler. Burada, 12 günlük ateş hikâyesi olan 27 yaşında bir erkek hastanın kanından izole edilen ve laktozu fermente eden bir S. Paratyphi A olgusu sunuldu. Laktozu fermente eden koloniler Crystal Mac Conkey agar besiyerinde 35°C’de 24 saatlik inkübasyon sonunda izole edildi. Bakteri, koloni morfolojisi, Gram boyama, Oksidaz testi, şeker testleri (indol, üre, sitrat, üç-şeker-demir) ve API 20E ile adlandırıldı. İzole edilen bakteri Salmonella polivalan A-S ve antiserum O2 antiserumları ile pozitif aglütinasyon reaksiyonu vermesi ile teyit edildi.Laktozu fermente eden S. Paratyphi A suşunun tanınması, atlanması veya yanlış tanı konması açısından önemlidir. S. Paratyphi A, tifo etkeni olarak S. Typhi’nin yerini almaktadır ve yüksek ilaç direncine sahiptir. Bu nedenle yanlış tanıdan kaçınmak için, S. Paratyphi A’nın nadiren 24 saatlik Crystal MacConkey agar üzerindeki inkübasyonunda laktozu fermente eden koloniler şeklinde üreyebileceği unutulmamalıdır

Anahtar Kelimeler

• Antibiyotik direnci, Laktoz fermantasyonu, Salmonella, Salmonella Paratyphi A

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