ABSTRACT
BACKGROUND: Acid-fast bacilli microscopy is the first step in the diagnosis and screening of pulmonary tuberculosis (PTB) in developing countries. It remains a rapid and inexpensive diagnostic tool for diagnosing a large number of PTB cases with limited resources. OBJECTIVE: To evaluate three different staining techniques used in the detection of acid-fast bacilli. The conventional Ziehl-Neelsen (ZN) stain and two cold stains, Gabbett's cold stain and modified cold stain (MCS), were compared with sputum culture. MATERIALS AND METHODS: A total of 300 sputum samples from 100 clinically suspected PTB patients referred to Maamorah Chest Hospital in Alexandria, Egypt, were tested. For staining and culture, three sputum samples from each patient were collected (one 'on spot' and two early morning samples) and pooled together. Smears were prepared using three different staining methods (ZN, Gabbett's cold stain, and MCS) and were inoculated in the Lowenstein-Jensen media. RESULTS: Comparison of sputum staining results using three different staining techniques versus culture proved that the highest sensitivity and specificity were seen for Gabbett's stain (76.6 and 98.5%, respectively). ZN stain had a sensitivity and specificity of 70 and 97.1%, whereas MCS had a sensitivity and specificity of 60 and 95.7%, respectively. CONCLUSION: Gabbett's stain was more accurate in the diagnosis of PTB compared with both ZN and MCS, even though the results were not statistically significant. It can replace ZN for initial diagnosis and follow up of cases. It is also easier, faster, and does not require a heating step.
Subject(s)
Mycobacterium tuberculosis/isolation & purification , Sputum/microbiology , Staining and Labeling/methods , Tuberculosis, Pulmonary/diagnosis , Cells, Cultured , Coloring Agents , Egypt , Humans , Microscopy, Fluorescence/methods , Tuberculosis, Pulmonary/microbiologyABSTRACT
BACKGROUND: Salmonella is a significant microbial hazard in seafood. Salmonella-contaminated seafood usually looks and smells normal; it is therefore essential that every effort is made toward the rapid detection of Salmonella as an important criterion in quality control of seafood. AIMS: This study aims to determine the percentage of Salmonella in some Egyptian seafood sold in Alexandria markets and to study the validity of Chromagar Salmonella Plus (CASP) agar versus xylose lysine desoxycholate and Salmonella-Shigella agar for the isolation and identification of Salmonella in seafood. MATERIALS AND METHODS: Two hundred and twenty-five samples of three seafood types, shrimp, gandofli, and river mussel (om-elkhloul) were studied. Samples were selectively enriched in Rappaport-Vassiliadis and tetrathionate broth, and then plated onto the aforementioned plating media for the detection of Salmonella. RESULTS: In total, Salmonella was detected in 9.8% of the samples. The sensitivity and specificity of the media used varied according to the media and enrichment broth combinations used. The CASP and Rappaport-Vassiliadis combination yielded the best sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 95.45, 100, 100, 99.5, and 99.5%, respectively. CONCLUSION AND RECOMMENDATION: CASP was more accurate than xylose lysine desoxycholate and Salmonella-Shigella in the detection of Salmonella from seafood samples. We recommend that CASP medium should be tested against more Salmonella-positive samples before it is used as a screening plating medium for Salmonella in seafood.
