Listeriosis – A retrospective study of 5 years on risk factors and clinical outcomes at a tertiary care hospital in Islamabad, Pakistan

Background: Listeria monocytogenes is a common foodborne organism identified as a causative agent of multiple clinical conditions in unique circumstances such as pregnancy and immunocompromise. It is a Gram-positive rod and a facultative anaerobic organism. This paper presents a study over a timeline of 5 years in retrospect and explores the incidence of listeriosis amongst patients of different age groups, along with its associated risk factors and clinical outcomes. Materials and methods: This study was conducted in retrospect from June 2019 to June 2024 at Shifa International Hospital, Islamabad. Ninety-seven cases of listeriosis were identified. These cases were culture-positive listeriosis where the pathogen was isolated from various samples such as blood and cerebrospinal fluid (CSF). Important risk factors associated with the clinical presentations were also documented, which included diabetes mellitus (DM), Chronic Kidney disease (CKD) and malignancy. The mean ± SD was calculated for the continuous variable. Frequency and percentage were calculated for categorical variables. Chi-square tests was performed to assess associations with mortality and fetal outcomes. Results: A total of 97 culture-confirmed listeriosis cases, comprising 44 (45.5%) males and 53 (54.6%) females, were obtained. 15 of the females were pregnant. Fever was the most common presenting symptom across all groups, with pregnant patients also reporting abdominal pain, vomiting, and fetal complications, while non-pregnant patients showed a wider range, including neurological, respiratory, and gastrointestinal complaints. Of the 97 patients, 86 had co-morbidities—most commonly hypertension and diabetes—while 15 total adult deaths occurred. Eight pregnancies resulted in fetal losses. Descriptive trends in pregnant patients suggested worse fetal outcomes with higher CRP, TLC and maternal comorbidities. Ampicillin-based regimens were the most frequently used treatments, and all isolates were sensitive to the tested antibiotics. Conclusion: This study highlights how listeriosis poses substantial morbidity and mortality risk, especially in pregnant cases. There is also a critical data gap, emphasizing the need for better diagnostic strategies, timely and targeted interventions, awareness of the clinical team, and public health surveillance to reduce the burden of this often-overlooked infection in Pakistan.