Differences in Cell Wall Thickness between Resistant and Nonresistant Strains of <i>Mycobacterium tuberculosis</i>: Using Transmission Electron Microscopy

Abstract

The ultrastructure of the cell wall of extensively drug-resistant (XDR), multidrug-resistant (MDR) and susceptible tuberculosis (TB) bacilli was viewed under transmission electron microscopy (TEM). Under the TEM, marked differences were observed in the thickness of their cell wall: 20.2 ±1.5 and 17.1 ±1.03 nm for the XDR and MDR TB bacilli, respectively, and 15.6 ± 1.3 nm for the susceptible isolates (p < 0.05). In MDR bacilli, thickening of the cell wall was observed in the intermediate electron-transparent layer (ETL) and outer electron-opaque layer, whereas in XDR TB cells the basal peptidoglycan layer was denser and almost fused with the ETL. Five to seven percent of XDR TB bacilli had the appearance of the stationary phase with cell wall thickness ranging from 21 to 26 nm (p < 0.001). Information provided in this study is of significant importance in terms of drug selection for effective treatment of resistant strains.

Morphologic characterization of Mycobacterium tuberculosis circulating strains in a Lisbon hospital.

“…The XDR strain is shorter (p=0.009) and has a ticker cell envelope (p=0.004) than the pan-susceptible strain. These results are in agreement with those published in the literature [5,6].…”

“…The XDR strain is shorter (p=0.009) and has a ticker cell envelope (p=0.004) than the pan-susceptible strain. These results are in agreement with those published in the literature [5,6].Altogether our data clearly shows the existence of a link between mycobacteria ultrastructure and drug susceptibility. In order to better evaluate these differences a larger number of isolates must be studied.…”

Totally drug-resistant tuberculosis strains: evidence of adaptation at the cellular level

“…Each of anti-TB drugs has a major role in dealing with one of these populations [9]. However, there are still persistent bacterial populations that are not killed by any available TB drugs [10]. Clinically, we have experienced such cases in our TB wards.…”

Broadening Our View About the Role of Mycobacterium tuberculosis Cell Envelope Components During Infection: A Battle for Survival

“…The development of new technologies and/or the use of known technologies already successfully applied in other fields (such as cancer research) are moving fast into the field of TB. Thus, studies using scanning electron and atomic force microscopy revealed that the M.tb cell wall from MDRand XDR-strains differs from susceptible strains (Velayati et al, 2009a(Velayati et al, , 2009b(Velayati et al, , 2010. Experiments analyzing infected granulomas by using high-resolution magic angle spinning nuclear magnetic resonance (HR-MAS-NMR) showed that we are capable of analyzing the cell wall of M.tb w h e n i n s i d e o f t h e g r a n u l o m a w i t h o u t f u r t h e r manipulation (Somashekar et al, 2011).…”

“…What is the cell wall constitution of these strains? Studies performed using transmission electron and atomic force microscopy techniques started to dig into this question showing that MDR-, XDR-, XXDR-and TDR-strains have thicker cell wall and rougher cell surface (supposedly produced by the progressive erosion of their cell wall by the action of the drugs) with tubular extensions than susceptible strains (Velayati et al, 2009a(Velayati et al, , 2010. Because some XDRand TDR-M.tb strains are related to the Beijing family (Velayati et al, 2009b), which are shown to have their cell wall overpopulated with triglycerides, it is plausible to question any relationship between the abundance of a specific hydrophobic lipid on the M.tb cell wall and drug resistance.…”