Deepthi Nair

Minimum inhibitory concentration of carbapenems and tigecycline against Salmonella spp.

Antimicrobial resistance in Salmonella spp. is of grave concern, more so in quinolone-resistant and extended-spectrum beta-lactamase (ESBL)-producing isolates that cause complicated infections. The MIC of azithromycin, ciprofloxacin, cefixime, cefepime, ceftriaxone, gatifloxacin, imipenem, levofloxacin, meropenem and ofloxacin (E-test strip) and tigecycline and faropenem (agar dilution) against 210 Salmonella spp. was determined. MIC(90) (defined as the antimicrobial concentration that inhibited growth of 90 % of the strains) of the carbapenems (imipenem and meropenem) for Salmonella Typhi and Salmonella Paratyphi A was 0.064 microg ml(-1). MIC(90) of faropenem was 0.25 microg ml(-1) for S. Typhi, S. Paratyphi A and Salmonella Typhimurium. The MIC(90) of azithromycin for all Salmonella spp. ranged from 8 to 16 microg ml(-1). Tigecycline showed an MIC(90) of 2 microg ml(-1) for S. Typhi, 1 microg ml(-1) for S. Paratyphi A and 4 microg ml(-1) for S. Typhimurium. We concluded that tigecycline and the carbapenems are likely to have roles in the final stage of treatment of quinolone-resistant and ESBL-producing multidrug-resistant salmonellae.

Evaluation of gidB alterations responsible for streptomycin resistance in Mycobacterium tuberculosis

OBJECTIVES To evaluate gidB alterations for possible impact on the cumulative mechanism underlying the acquisition of high-level streptomycin resistance in Mycobacterium tuberculosis. METHODS Fifty-two isolates with high streptomycin resistance and 23 isolates with low streptomycin resistance were sequenced for mutational analysis in the rpsL, rrs and gidB region. As the gidB protein has a complex substrate and no activity assay has yet been formulated, mutants of interest were subjected to in silico modelling and were structurally mapped together with active-site amino acid residues for assessment of the relevance to activity of the mutations found. RESULTS Eight novel sense mutations and four novel mis-sense mutations in gidB were identified. Findings showed that active-site morphology is not only greatly affected by mutants lying in close proximity to the active-site pocket, but also by other mutations altering secondary-structure motifs and having an overall effect on protein structure. CONCLUSIONS We conclude that gidB mutations address many unanswered questions and explain the whole story behind phenotypic streptomycin-resistant strains exhibiting no mutation in rpsL or rrs. They also validate the hypothesis of sequential progression of resistance from low to high due to the existence of gidB alterations in the genetic background.

Concomitant TB and cryptococcosis in HIV-infected patients

Four cases of concomitant tuberculosis and cryptococcosis infection in HIV-positive patients are described. As the HIV pandemic progresses and the proportion of patients with end-stage disease increases, a high suspicion of incidence and unusual forms of infections must always be kept in mind.

“Caught by the Eye of Sound” – Epigastric Swelling due to Xiphisternal Tuberculosis

Summary Background Common causes of an epigastric mass include hepatomegaly, pancreatic pseudocyst and epigastric hernia, less common causes being carcinoma of the stomach or pancreas, whereas diseases of the sternum presenting as an epigastric swelling is extremely uncommon. We report a case of tubercular infection of the sternum located in the xiphoid process resulting in its presentation as an epigastric swelling. Case Report A 30-year-old immunocompetent woman with complaints of an epigastric swelling and undocumented pyrexia for four months was referred for sonographic evaluation with a clinical suspicion of an incompletely treated liver abscess. The patient was examined with ultrasound, sternal radiographs, CT and MRI. Ultrasound revealed a heterogeneous epigastric collection with linear echogenic components suggestive of bone fragments. These appearances suggested chronic infective osteomyelitis of the xiphoid process of the sternum. Lateral chest radiograph demonstrated lytic destruction of the xiphisternum. Tubercular etiology was considered and further evaluation with Multidetector Computed tomography (MDCT) and Magnetic Resonance Imaging (MRI) demonstrated erosive osteomyelitis of the xiphoid process with enhancing inflammation and collection in the adjoining soft tissue. Ultrasound-guided aspiration, PCR and Amplified Mycobacterium tuberculosis DNA test confirmed tubercular infection. Conclusions We report a new case of osteo-articular tuberculosis localized to the xiphisternum, a rare clinical entity with an extremely unusual clinical presentation as an epigastric mass. The role of ultrasound in primary diagnosis and as an interventional diagnostic modality for guided aspiration is highlighted.