Interpretation of Direct Gram stain versus culture isolates of Pyogenic infections

Abstract

INTRODUCTION: Pyogenic infections are characterized by the inflammation with
the collection of pus at the site due to bacterial infections. To know the type of
organism and its antimicrobial susceptibility pattern it is important to utilize the
microbiology services like staining, culture and sensitivity. In the present study we
are trying to enlighten the importance of gram stain and culture testing in pyogenic
infections.
MATERIALS AND METHODS: A 3 months (March 2024 to May 2024)
prospective observational study conducted with a total of 150 pus samples were
collected from outpatient and inpatient clinical departments under aseptic precautions
using a sterile syringe aspiration or sterile swabs by following standard protocols.
The entire quantitative variables were expressed as number, frequency and
percentage. The tests accuracy was measured by sensitivity (Sn), specificity (Sp),
positive predictive value (PPV), negative predictive value (NPV).
RESULTS: Out of 150 pus samples studied, direct Gram stain examination was
matched with culture isolates in nearly 70% (105 out of 150) of the samples. 30 out
of 150 (20%) were Gram stain negative and culture showed pathogens and 5 out of
150 (3.33%) were gram positive and culture negative. Gram staining was evaluated
with pus culture by calculating sensitivity, specificity, positive predictive value and
negative predictive values with percentages of 77.7%, 66.6%, 95.4%, and 25%
respectively.
CONCLUSION: Though the culture is a gold standard and confirmatory test for the
diagnosis of infection, the gram stain with a good positive predictive value will help
the physicians in the appropriate antibiotic selection, however the physician should
focus on hospital antibiogram and microbiotia of the community.