Muhammad Ali Syed

Hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) from Pakistan: molecular characterisation by microarray technology

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in Pakistan is known to be high, but very few studies have described the molecular epidemiology of the different MRSA clones circulating in the country. Forty-four MRSA isolates were collected from two tertiary care hospitals of the Rawalpindi district of Pakistan. All strains were identified by a conventional phenotypic method and then subjected to genotyping by microarray hybridisation. Six clonal complexes (CCs) and 19 strains were identified. The most commonly identified strains were: (i) Panton–Valentine leucocidin (PVL)-positive CC772-MRSA-V, “Bengal Bay Clone” (ten isolates; 22.3%), (ii) ST239-MRSA [III + ccrC] (five isolates) and (iii) a CC8-MRSA-IV strain, as well as CC6-MRSA-IV (both with four isolates; 9.1% each). Several of the strains detected indicated epidemiological links to the Middle Eastern/Arabian Gulf region. Further studies are needed to type MRSA from countries with less known epidemiology and to monitor the distribution and spread of strains, as well as possible links to global travel, migration and commerce.

Prevalence of carbapenemase-producing organisms at the Kidney Center of Rawalpindi (Pakistan) and evaluation of an advanced molecular microarray-based carbapenemase assay

AIM A DNA microarray-based assay for the detection of antimicrobial resistance (AMR) genes was used to study carbapenemase-producing organisms at the Kidney Center of Rawalpindi, Pakistan. METHODS The evaluation of this assay was performed using 97 reference strains with confirmed AMR genes. Testing of 7857 clinical samples identified 425 Gram-negative bacteria out of which 82 appeared carbapenem resistant. These isolates were analyzed using VITEK-2 for phenotyping and the described AMR assay for genotyping. RESULTS The most prevalent carbapenemase gene was blaNDM and in 12 isolates we detected two carbapenemase genes (e.g., blaNDM/blaOXA-48). CONCLUSION Our prevalence data from Pakistan show that - as in other parts of the world - carbapenemase-producing organisms with different underlying resistance mechanisms are emerging, and this warrants intensified and constant surveillance.

Molecular typing of ST239-MRSA-III from diverse geographic locations and the evolution of the SCCmec III element during its intercontinental spread

ST239-MRSA-III is probably the oldest truly pandemic MRSA strain, circulating in many countries since the 1970s. It is still frequently isolated in some parts of the world although it has been replaced by other MRSA strains in, e.g., most of Europe. Previous genotyping work (Harris et al., 2010; Castillo-Ramírez et al., 2012) suggested a split in geographically defined clades. In the present study, a collection of 184 ST239-MRSA-III isolates, mainly from countries not covered by the previous studies were characterized using two DNA microarrays (i) targeting an extensive range of typing markers, virulence and resistance genes and (ii) a SCCmec subtyping array. Thirty additional isolates underwent whole-genome sequencing (WGS) and, together with published WGS data for 215 ST239-MRSA-III isolates, were analyzed using in-silico analysis for comparison with the microarray data and with special regard to variation within SCCmec elements. This permitted the assignment of isolates and sequences to 39 different SCCmec III subtypes, and to three major and several minor clades. One clade, characterized by the integration of a transposon into nsaB and by the loss of fnbB and splE was detected among isolates from Turkey, Romania and other Eastern European countries, Russia, Pakistan, and (mainly Northern) China. Another clade, harboring sasX/sesI is widespread in South-East Asia including China/Hong Kong, and surprisingly also in Trinidad & Tobago. A third, related, but sasX/sesI-negative clade occurs not only in Latin America but also in Russia and in the Middle East from where it apparently originated and from where it also was transferred to Ireland. Minor clades exist or existed in Western Europe and Greece, in Portugal, in Australia and New Zealand as well as in the Middle East. Isolates from countries where this strain is not epidemic (such as Germany) frequently are associated with foreign travel and/or hospitalization abroad. The wide dissemination of this strain and the fact that it was able to cause a hospital-borne pandemic that lasted nearly 50 years emphasizes the need for stringent infection prevention and control and admission screening.

Aptamers and Aptasensors as Novel Approach for Microbial Detection and Identification: An Appraisal

BACKGROUND Tremendous efforts through dedicated research have been made for the development of robust, point of care, portable, cost effective, sensitive and specific assays of microbial detection. Biosensing and nanotechnology offer novel strategies of designing state of the art devices and assay formats with enhanced sensitivity and all other desired features. Monoclonal antibodies have been in use as biorecognition elements for decades. However, recent studies have demonstrated superiority of aptamers to monoclonal antibodies in a number of applications. Many of the research groups have successfully utilized aptamers as capture probes in developing biosensors for microbial detection. OBJECTIVES The main objective of this review article is to present the reader with an overview of the recent advances made in the field of aptamers and aptasensors for the detection and identification of microbial agents. RESULTS Our search for relevant information on current advances on aptamers and aptasensors has revealed that a number of successful attempts have been made in the last two decades for the selection of aptamers as well as their applications in aptasensors for microbial detection. CONCLUSION Aptamers and aptasensors, although in their infancy, may find promising application in rapid, sensitive, point of care and cost effective microbial detection.

Nano-antimicrobials: A Viable Approach to Tackle Multidrug-Resistant Pathogens

Escalating resistance to almost every class of antibiotics is reducing the utility of currently available antimicrobial drugs. A part of this menace is attributed to poor pharmacokinetics and pharmacodynamics of the drug. Improvement in drug delivery is the most challenging task encountered by the pharmaceutical industries; however, nanotechnology can bring a revolution in drug design and delivery. Nano-antimicrobials have their own intrinsic antimicrobial activity (nanoparticles) or augment overall efficacy of enclosed antibiotics (nano-carriers), thus contribute in mitigating or reversing the resistance phenomenon. Nanoparticles (NP) having their own intrinsic antimicrobial activity kill microbes by mimicking natural course of killing by phagocytic cells, i.e., by producing large quantity of reactive oxygen species (ROS) and reactive nitrogen species (RNS). It is believed that NPs kill microbes by simultaneously acting on many essential life processes or metabolic routes of microbes; that as many genetic mutations to develop resistance against them seems to be impossible. Nano-carriers improve the pharmacokinetics of the enclosed drug. Moreover, one of the major techniques by which NAMs can overcome resistance is targeted drug delivery to the site of disease. In this chapter, a comprehensive detail about the mechanism of action of NAMs is presented in context to multidrug-resistance phenomenon.