Epidemic levels of drug resistant tuberculosis (MDR and XDR-TB) in a high HIV prevalence setting in Khayelitsha, South Africa

Background

Although multidrug-resistant tuberculosis (MDR-TB) is emerging as a significant threat to tuberculosis control in high HIV prevalence countries such as South Africa, limited data is available on the burden of drug resistant tuberculosis and any association with HIV in such settings. We conducted a community-based representative survey to assess the MDR-TB burden in Khayelitsha, an urban township in South Africa with high HIV and TB prevalence.

Methodology/Principal Findings

A cross-sectional survey was conducted among adult clinic attendees suspected for pulmonary tuberculosis in two large primary care clinics, together constituting 50% of the tuberculosis burden in Khayelitsha. Drug susceptibility testing (DST) for isoniazid and rifampicin was conducted using a line probe assay on positive sputum cultures, and with culture-based DST for first and second-line drugs. Between May and November 2008, culture positive pulmonary tuberculosis was diagnosed in 271 new and 264 previously treated tuberculosis suspects (sample enriched with previously treated cases). Among those with known HIV status, 55% and 71% were HIV infected respectively. MDR-TB was diagnosed in 3.3% and 7.7% of new and previously treated cases. These figures equate to an estimated case notification rate for MDR-TB of 51/100,000/year, with new cases constituting 55% of the estimated MDR-TB burden. HIV infection was not significantly associated with rifampicin resistance in multivariate analyses.

Conclusions/Significance

There is an extremely high burden of MDR-TB in this setting, most likely representing ongoing transmission. These data highlight the need to diagnose drug resistance among all TB cases, and for innovative models of case detection and treatment for MDR-TB, in order to interrupt transmission and control this emerging epidemic.     

Phage pilH alpha: a phage which adsorbs to IncHI and IncHII plasmid-coded pili

Phage pilH alpha was specific for bacterial strains, of various genera, harbouring plasmids of the HI and HII incompatibility groups. Plaque formation was temperature sensitive in that plaques formed at 26 degrees C but not at 37 degrees C. Plaques were fairly clear, irregular in outline and varied from pin point to about 2 mm in diameter on all hosts where plaques were detected. The phage had an isometric hexagonal outline with a diameter of 25 nm. It contained RNA but differed from all but one other plasmid-dependent RNA phage by being sensitive to chloroform. It adsorbed along the length of the shafts of IncHI and HII plasmid-coded pili.     

Two mutant low-density-lipoprotein receptors in Afrikaners slowly processed to surface forms exhibiting rapid degradation or functional heterogeneity.

Two distinct mutant low-density-lipoprotein receptors in South African Afrikaners exhibit retarded posttranslational processing to mature forms. One mutation gives rise to cell-surface receptors that are subject to abnormally rapid degradation, whereas the other is associated with a functionally heterogeneous surface population degraded at a normal rate.     

Bacteriophage X-2: a filamentous phage lysing IncX-plasmid-harbouring bacterial strains

Phage X-2, a filamentous rod about 950 nm in length, was isolated from sewage as plating on strains of Escherichia coli, Salmonella typhimurium or Serratia marcescens carrying either the IncX plasmid R6K, or the unique plasmid R775. Phage X-2 differs morphologically from a previously described very broad host range filamentous phage X which also lyses plasmid R6K-carrying strains and the phages differ in their resistance to inactivation by diethyl ether. Phage X-2 is serologically unrelated to phage X and the X-like phages IKe and I2-2. The adsorption site of the phage on the plasmid-bearing strains could not be determined but evidence implicating conjugative pili is presented.     

Isolation of an autocrine growth factor from hepatoma HTC-SR cells

A growth factor has been isolated from HTC-SR rat hepatoma tissue culture cells which specifically stimulates DNA synthesis and cell proliferation of the HTC cells that produce it. The factor can be isolated from HTC cell conditioned medium or from an HTC cell extract. This autocrine factor has been purified 640-fold from a postmicrosomal supernatant by successive steps, involving ethanol precipitation, heating at 80 degrees C for 10 min, chromatography on a DEAE Bio-Gel A column, and chromatography on a heparin-sepharose affinity column. The major peak of activity eluted from the heparin column migrates as a single band on SDS-PAGE with an apparent Mr of 60,000. The factor is resistant to acid, heat, and neuraminidase but sensitive to trypsin, papain, and protease. The autocrine nature of the factor is indicated by the finding that several other types of cells do not respond with increased DNA synthesis. Mouse L-cells, BHK cells, Novikoff hepatoma cells, hepatocytes in primary culture, and an epithelial-like rat liver-derived cell line (Clone 9) were tested, and none of the cells could be stimulated. Small amounts of the factor could be extracted from the Clone 9 cells, however. This material had the same physical and purification properties as the factor extracted from HTC cells, but it did not stimulate DNA synthesis in Clone 9 cells, only in HTC cells. Addition of the factor resulted in an almost immediate stimulation of DNA synthesis in a proliferating HTC cell population. When the factor was added together with [3H]thymidine for 2 h, a significant stimulation of DNA synthesis was observed, provided the addition was made between 18 and 48 h after the cells had been plated. Autoradiographic studies indicated that the factor both accelerates DNA synthesis in cells already making DNA and increases the number of cells entering the S period. The stimulation of DNA synthesis was completely inhibited by 10 mM hydroxyurea, whether the factor was present for 2, 24, or 48 h in the culture. A significant increase in cell number due to addition of the factor was also observed. This accelerated proliferation was detectable only after the cells had been in culture for at least 48 h with the factor present.     

Bacteriophages F0lac h, SR, SF: phages which adsorb to pili encoded by plasmids of the S-complex

Phage F0lac is an RNA-containing phage which plates only on strains carrying the plasmid EDP208, a pilus derepressed derivative of the unique incompatibility plasmid F0lac. A host range mutant, phage F0lac h, was selected which plated on strains carrying the ungrouped plasmid pPLS::Tn5 and lysed strains carrying another ungrouped plasmid TP224::Tn10 or the Com9 plasmid R71. An RNA-containing phage, SR, was isolated from sewage on bacteria harbouring plasmid pPLS::Tn5. It was antigenically distinct from the above two phages but had the same host range as phage F0lac h. Phages F0lac h and SR adsorbed unevenly to the shafts of the conjugative pili. Another phage, SF, was filamentous and plated or propagated on strains carrying any of the above plasmids as well as on strains harbouring IncD or F-complex plasmids. Plasmids TP224::Tn10 and pPLS::Tn5 were compatible with representative plasmids of all Inc groups also encoding thick flexible pili. The four plasmids EDP208, R71, TP224::Tn10 and pPLS::Tn5 were compatible with one another except for the reaction of TP224::Tn10 in the presence of pPLS::Tn5 which was slightly ambiguous. The host ranges of the bacteriophages, together with the serological relatedness of the thick flexible pili determined by these four compatible plasmids, suggested that they constitute a new complex, here designated S.     

IncI2 plasmids specify sensitivity to filamentous bacteriophage IKe.

Bacterial strains carrying the derepressed incompatibility group IncI2 plasmids TP114drp-l or R721pilc were lysed by the filamentous bacteriophages IKe, I2-2, and X. Phage I2-2 was serologically related to IKe, but phage X was not. Phage IKe adsorbed to the tips of thick pili determined by the IncI2 plasmids, but not to the well-known thin I2 pili.     

Ecology of Proteus flagellar phages

Summary Phages identical to X ₇ in host range and serological properties are liberated by several Proteus strains. Another Proteus flagellar phage, X ₈, differs from X ₇ antigenically and in host range.     

The covalent binding of 3-methylindole metabolites to bovine tissue

Tritiated 3-methylindole (3MI) was administered intravenously to calves. Total and covalent bound radioactivity were measured in different tissues. Pulmonary tissue showed the highest concentration of covalent bound radioactivity. (G-³H) or (methyl-¹⁴C) 3MI became covalently bound to microsomal protein when incubated with bovine lung microsomes. This covalent binding was dependent on time, temperature, oxygen and NADPH and was inhibited by SKF-525A, cytochrome c, a carbon monoxide enriched atmosphere and cysteine. The microsomal enzyme system catalysing covalent binding of 3MI has the classical characteristics of a cytochrome P-450 dependent mixed function oxidase. Metabolic activation of 3MI to a highly electrophilic intermediate, may be fundamental in the pathogenesis of 3MI induced pulmonary damage.