Upper respiratory tract infections (URTIs) account for substantial attendances at emergency departments (EDs). There is a need to elucidate determinants of antibiotic prescribing in time-strapped EDs – popular choices for primary care despite highly accessible primary care clinics. Semi-structured in-depth interviews were conducted with purposively sampled physicians (n = 9) in an adult ED in Singapore. All interviews were analysed using thematic analysis and further interpreted using the Social Ecological Model to explain prescribing determinants. Themes included: (1) reliance on clinical knowledge and judgement, (2) patient-related factors, (3) patient–physician relationship factors, (4) perceived practice norms, (5) policies and treatment guidelines and (6) patient education and awareness. The physicians relied strongly on their clinical knowledge and judgement in managing URTI cases and seldom interfered with their peers’ clinical decisions. Despite departmental norms of not prescribing antibiotics for URTIs, physicians would prescribe antibiotics when faced with uncertainty in patients’ diagnoses, treating immunocompromised or older patients with comorbidities, and for patients demanding antibiotics, especially under time constraints. Participants had a preference for antibiotic prescribing guidelines based on local epidemiology, but viewed hospital policies on prescribing as a hindrance to clinical judgement. Participants highlighted the need for more public education and awareness on the appropriate use of antibiotics and management of URTIs. Organisational practice norms strongly influenced antibiotic prescribing decisions by physicians, who can be swayed by time pressures and patient demands. Clinical decision support tools, hospital guidelines and patient education targeting at individual, interpersonal and community levels could reduce unnecessary antibiotic use.

The immunomodulatory effects of live or non-viable lactic acid bacteria have been extensively investigated. We reported that oral intake of heat-killed Lactobacillus plantarum L-137 (HK L-137) augmented innate and acquired immunity in mice and human subjects. To examine the effects of HK L-137 intake on upper respiratory tract infection (URTI) symptoms and immune functions in human subjects, a randomised, double-blind, placebo-controlled, parallel study was conducted in subjects with high psychological stress levels. A total of seventy-eight healthy subjects (thirty-three men and forty-five women; mean age 50·6 years) with scores of >41 on eighteen-item subscales of psychological distress in the Brief Job Stress Questionnaire were randomly assigned to receive a tablet containing HK L-137 (10 mg) or a placebo tablet daily for 12 weeks. The URTI symptoms were rated once daily on the validated twenty-one-item Wisconsin Upper Respiratory Symptom Survey-21. Immune functions, such as concanavalin A-induced proliferation and percentages of interferon (IFN)-γ- and IL-4-producing CD4 T cells of peripheral blood mononuclear cells (PBMC), and serum IFN-β concentrations were measured every 4 weeks. URTI incidence was significantly lower in the HK L-137 group than in the control group. URTI incidence, duration and severity, and duration of medication showed significant negative correlations with duration of HK L-137 intake. The percentage change from baseline of concanavalin A-induced proliferation of PBMC was significantly greater in the HK L-137 group than in the control group. These findings suggest that daily HK L-137 intake can decrease URTI incidence in healthy subjects, possibly through augmentation of immune functions.

Zn supplementation has shown inconsistent effects on respiratory morbidity in young children in developing countries. Few studies have focused on upper respiratory tract infection (URTI), a frequent cause of morbidity in this group, and potential benefit from Zn supplementation or factors that influence its efficacy. We investigated the effects of Zn supplementation on URTI before and after vitamin A supplementation. This randomised double-blinded controlled Zn supplementation study was conducted on 826 children aged 2–5 years. Placebo or Zn (10 mg/d) was given in syrup daily for 4 months, with 200 000 IU vitamin A (60 mg retinol) given to all children at 2 months. Health workers visited children every 3 d for compliance and morbidity information. We found that 84 % of children experienced URTI during the study. Zn supplementation reduced the percentage of days with URTI (12 % reduction; P = 0·09), with greater impact following vitamin A supplementation (20 % reduction; P = 0·01). Vitamin A supplementation was associated with a decreased number but an increased duration of URTI episodes. We conclude that Zn combined with vitamin A supplementation significantly reduced the percentage of days with URTI in a population of preschool Indonesian children with marginal nutritional status. The results suggest that vitamin A status modifies the efficacy of Zn supplementation on URTI.