Fuchsin fluorescence in Mycobacterium tuberculosis: the Ziehl-Neelsen stain in a new light

Tuberculosis (TB) is often diagnosed by observation of reddish pink fuchsin-stained Mycobacterium tuberculosis (MTB) in Ziehl-Neelsen (Z-N) stained smears by transmitted light microscopy. MTB too faintly stained with fuchsin to be seen by transmitted light may be detected by their green-excited orange-red fluorescence; this finding may be clinically relevant.     

Non‐Tuberculosis mycobacterium speciation using HPLC under Revised National TB Control Programme (RNTCP) in India

Aims

Non‐Tuberculous Mycobacteria (NTM) are ubiquitous in nature. The data on prevalence of NTM under the RNTCP is scarce. Many NTM species have clinical significance, and hence their identification and speciation are important.

Methods and Results

It is a cross‐sectional study conducted at the five RNTCP accredited culture and drug susceptibility testing (CDST) laboratory. The culture isolates from AFB positive but Immunochromatographic test negative samples were taken for identification and speciation using HPLC. Of the total 266 isolates only 164 isolates had a second sample received at the laboratory. The speciation was done using HPLC for those isolates. The type of species identified are: 26·8% (44) were Mycobacterium chelonae, 12·8% (21) were Mycobacterium fortuitum, 9% (15) were Mycobacterium gordonae, 9% (15) were Mycobacterium tuberculosis complex, 6·1% (10) were Mycobacterium kansasii, 4·9% (8) were Mycobacterium simiae, 2·4% (4) were Mycobacterium thermophile, 1·2% (2) were Mycobacterium gastri, 0·6% (1) were Mycobacterium scrofulaceum, 0·6% (1) were Mycobacterium avium and 4·9% (8) isolates had chromatogram which was un‐interpretable.

Conclusion

Identification and its speciation of NTM are not routinely done under TB control programme. Since HPLC could identify 95% of isolates belonging to 10 species, the speciation of NTM using HPLC should gain importance in the diagnosis of disease caused by NTM.

Significance and Impact of Study

NTM are emerging as important causative agents of pulmonary and extra pulmonary disease, the ability to recognize disease caused by NTM and subsequently treat such disease has become increasingly important. The identification of NTM up to its species level should gain importance in all TB reference Laboratories.