Trends in antimicrobial resistance in Shigella species in Karachi, Pakistan.

Background: Shigellosis is a common cause of morbidity, especially in the very young and old, in developing countries. The disease is treated with antibiotics. Surveillance of antimicrobial resistance trends is essential owing to the global emergence of antimicrobial resistance. Methodology: The study involved 1,573 isolates of Shigella species (1996-2007) that were analyzed for trends in antimicrobial resistance. Results: The majority of the specimens (1046, 66.5%) were from the pediatric population, and of these 887 (84.8%) were under 5 years of age (p = 0.001). S. flexineri was the most frequent species (54.5%) isolated. Isolation of S. sonnei increased from 15.4 % (1996) to 39% (2007) (p = 0.001). Although none of the isolates was found sensitive to all the antibiotics tested, 58% (n =9 07) were resistant to ampicillin and 85% (n = 1,338) were resistant to trimethoprim-sulfamethoxazole (TMP-SMX). Out of a total of 198 (12.6%) nalidixic acid resistant isolates, 6 (3.0%) were also resistant to ofloxacin. Overall 1.7 % of isolates were resistant to ofloxacin, 2.4% to ceftriaxone and 2.3% were resistant to combination of ampicillin, nalidixic acid and TMP-SMX. Conclusion: Ofloxacin is still an effective drug for treatment of acute shigellosis in Pakistan. Emergence of resistance to ceftriaxone in Shigella may have grave implications in treatment of severe shigellosis in very young Patients

The Plasmodium falciparum CCCH Zinc Finger Protein ZNF4 Plays an Important Role in Gametocyte Exflagellation through the Regulation of Male Enriched Transcripts

CCCH zinc finger proteins (ZFPs) function mainly as RNA-binding proteins (RBPs) and play a central role in the mRNA metabolism. Over twenty seven CCCH-ZFPs are encoded in the genome of the human malaria parasite Plasmodium falciparum, the causative agent of malaria tropica. However, little is known about their functions. In this study, we characterize one member of the PfCCCH-ZFP named ZNF4. We show that ZNF4 is highly expressed in mature gametocytes, where it predominantly localizes to the cytoplasm. Targeted gene disruption of ZNF4 showed no significant effect in asexual blood stage replication and gametocyte development while male gametocyte exflagellation was significantly impaired, leading to reduced malaria transmission in the mosquito. Comparative transcriptomics between wildtype (WT) and the ZNF4-deficient line (ZNF4-KO) demonstrated the deregulation of about 473 genes (274 upregulated and 199 downregulated) in mature gametocytes. Most of the downregulated genes show peak expression in mature gametocyte with male enriched genes associated to the axonemal dynein complex formation, and cell projection organization is highly affected, pointing to the phenotype in male gametocyte exflagellation. Upregulated genes are associated to ATP synthesis. Our combined data therefore indicate that ZNF4 is a CCCH zinc finger protein which plays an important role in male gametocyte exflagellation through the regulation of male gametocyte-enriched genes

Brief Original Articles Trends in antimicrobial resistance in Shigella species in Karachi, Pakistan

Background: Shigellosis is a common cause of morbidity, especially in the very young and old, in developing countries. The disease is treated with antibiotics. Surveillance of antimicrobial resistance trends is essential owing to the global emergence of antimicrobial resistance. Methodology: The study involved 1,573 isolates of Shigella species (1996-2007) that were analyzed for trends in antimicrobial resistance. Results: The majority of the specimens (1046; 66.5%) were from the pediatric population, and of these 887 (84.8%) were under 5 years of age (p = 0.001). S. flexineri was the most frequent species (54.5%) isolated. Isolation of S. sonnei increased from 15.4 % (1996) to 39% (2007) (p = 0.001). Although none of the isolates was found sensitive to all the antibiotics tested, 58 % (n =9 07) were resistant to ampicillin and 85 % (n = 1,338) were resistant to trimethoprim-sulfamethoxazole (TMP-SMX). Out of a total of 198 (12.6%) nalidixic acid resistant isolates, 6 (3.0%) were also resistant to ofloxacin. Overall 1.7 % of isolates were resistant to ofloxacin, 2.4 % to ceftriaxone and 2.3 % were resistant to combination of ampicillin, nalidixic acid and TMP-SMX. Conclusion: Ofloxacin is still an effective drug for treatment of acute shigellosis in Pakistan. Emergence of resistance to ceftriaxone in Shigella may have grave implications in treatment of severe shigellosis in very young patients

The G9a Histone Methyltransferase Inhibitor BIX-01294 Modulates Gene Expression during Plasmodium falciparum Gametocyte Development and Transmission

Transmission of the malaria parasite Plasmodium falciparum from the human to the mosquito is initiated by specialized sexual cells, the gametocytes. In the human, gametocytes are formed in response to stress signals and following uptake by a blood-feeding Anopheles mosquito initiate sexual reproduction. Gametocytes need to fine-tune their gene expression in order to develop inside the mosquito to continue life-cycle progression. Previously, we showed that post-translational histone acetylation controls gene expression during gametocyte development and transmission. However, the role of histone methylation remains poorly understood. We here use the histone G9a methyltransferase inhibitor BIX-01294 to investigate the role of histone methylation in regulating gene expression in gametocytes. In vitro assays demonstrated that BIX-01294 inhibits intraerythrocytic replication with a half maximal inhibitory concentration (IC50) of 13.0 nM. Furthermore, BIX-01294 significantly impairs gametocyte maturation and reduces the formation of gametes and zygotes. Comparative transcriptomics between BIX-01294-treated and untreated immature, mature and activated gametocytes demonstrated greater than 1.5-fold deregulation of approximately 359 genes. The majority of these genes are transcriptionally downregulated in the activated gametocytes and could be assigned to transcription, translation, and signaling, indicating a contribution of histone methylations in mediating gametogenesis. Our combined data show that inhibitors of histone methylation may serve as a multi-stage antimalarial