Genotypic detection of rifampicin and isoniazid resistant Mycobacterium tuberculosis strains by DNA sequencing: a randomized trial

BACKGROUND

Tuberculosis is a growing international health concern. It is the biggest killer among the infectious diseases in the world today. Early detection of drug resistance allows starting of an appropriate treatment. Resistance to drugs is due to particular genomic mutations in specific genes of Mycobacterium tuberculosis(MTB). The aim of this study was to identify the presence of Isoniazid (INH) and Rifampicin(RIF) drug resistance in new and previously treated tuberculosis (TB) cases using DNA sequencing.

METHODS

This study was carried out on 153 tuberculous patients with positive Bactec 460 culture for acid fast bacilli.

RESULTS

Of the 153 patients, 105 (68.6%) were new cases and 48 (31.4%) were previously treated cases. Drug susceptibility testing on Bactec revealed 50 resistant cases for one or more of the first line antituberculous. Genotypic analysis was done only for rifampicin resistant specimens (23 cases) and INH resistant specimens (26 cases) to detect mutations responsible for drug resistance by PCR amplification of rpoB gene for rifampicin resistant cases and KatG gene for isoniazid resistant cases. Finally, DNA sequencing was done for detection of mutation within rpoB and KatG genes. Genotypic analysis of RIF resistant cases revealed that 20/23 cases (86.9%) of RIF resistance were having rpoB gene mutation versus 3 cases (13.1%) having no mutation with a high statistical significant difference between them (P < 0.001). Direct sequencing of Kat G gene revealed point mutation in 24/26 (92.3%) and the remaining 2/26 (7.7%) had wild type KatG i.e. no evidence of mutation with a high statistical significant difference between them (P < 0.001).

CONCLUSION

We can conclude that rifampicin resistance could be used as a useful surrogate marker for estimation of multidrug resistance. In addition, Genotypic method was superior to that of the traditional phenotypic method which is time-consuming taking several weeks or longer.

Parvovirus B19 infection in pediatric oncology patients: diagnostic value of clinical and serologic parameters compared with nested PCR

BACKGROUND

Oncology patients are at particular risk for parvovirus B19 infection, which may cause severe, persistent, usually nonspecific illness in this group.

AIM

This study was designed to assess the prevalence and impact of parvovirus B19 in pediatric oncology patients receiving chemotherapy, and to define the optimal diagnostic tests in such patients.

SUBJECTS AND METHODS

Fifty-nine children under chemotherapy (39 with acute lymphocytic leukemia and 20 with solid tumors) with mean age of 4.96+/-1.94 years, in addition to 30 healthy children of matched age and sex, were enrolled in this study. Clinical and laboratory data were collected by examination and from patients' records. Specific parvovirus B19 immunoglobulin (Ig) M and IgG antibodies were assessed by enzyme-linked immunosorbent assay, and parvovirus DNA was detected by nested polymerase chain reaction (PCR) for all patients and controls.

RESULTS

Parvovirus DNA was detected in 16 (27.1%), IgM in 3 (5.1%), and IgG in 36 (61%) patients. IgM had sensitivity, specificity, and accuracy of 18.75%, 100%, and 77.9%, respectively, whereas those of IgG were 81.25%, 53.4%, and 61%, respectively. PCR-positive patients had significantly higher frequency of unexplained anemia, red blood cell transfusions, and longer hospital stay than PCR-negative patients (P<0.001). Multiple linear regression analysis showed that unexplained anemia and multiple red blood cell transfusions were the most important variables that can predict PCR positivity.

CONCLUSIONS

Parvovirus B19 is not an uncommon problem in pediatric oncology patients who exhibited weak antibody response and nonspecific clinical features. Screening of these patients with PCR rather than serology is recommended when infection is suspected.

ErratumTo: Genotypic detection of rifampicin and isoniazid resistant Mycobacterium tuberculosis strains by DNA sequencing: a randomized trial

Correction to Genotypic detection of rifampicin and isoniazid resistant Mycobacterium tuberculosis strains by DNA sequencing: a randomized trial Amina Abdelaal, Hassan Abd El-Ghaffar, Mohammad Hosam Eldeen Zaghloul, Noha El mashad, Ehab Badran, Amal Fathy Annals of Clinical Microbiology and Antimicrobials 2009, 8:4 (30 January 2009)