Zobia Noreen

Antibacterial, Structural and Optical Characterization of Mechano-Chemically Prepared ZnO Nanoparticles.

Structural investigations, optical properties and antibacterial performance of the pure Zinc Oxide (ZnO) nanoparticles (NPs) synthesized by mechano-chemical method are presented. The morphology, dimensions and crystallinity of the ZnO NPs were controlled by tweaking the mechanical agitation of the mixture and subsequent thermal treatment. ZnO nanoparticles in small (< 20 nm) dimensions with spherical morphology and narrow size distribution were successfully obtained after treating the mechano-chemically prepared samples at 250°C. However, higher temperature treatments produced larger particles. TEM, XRD and UV-Vis spectroscopy results suggested crystalline and phase pure ZnO. The NPs demonstrated promising antibacterial activity against Gram negative foodborne and waterborne bacterial pathogens i.e. Enteropathogenic E. coli (EPEC), Campylobacter jejuni and Vibrio cholerae as well as Gram positive methicillin resistant Staphylococcus aureus (MRSA), thus potential for medical applications. Scanning electron microscopy and survival assay indicated that most probably ZnO nanoparticles cause changes in cellular morphology which eventually causes bacterial cell death.

Antibiotic susceptibility profiling and virulence potential of Campylobacter jejuni isolates from different sources in Pakistan

OBJECTIVE To determine antibiotic resistance patterns and virulence potential of Campylobacter jejuni (C. jejuni) isolates from clinical human diarrheal infections, cattle and healthy broilers. METHODS Antibiotic sensitivity patterns of C. jejuni isolates were determined by Kirby Bauer Disc Diffusion assay. These isolates were then subjected to virulence profiling for the detection of mapA (membrane-associated protein), cadF (fibronectin binding protein), wlaN (beta-l,3-galactosyltransferase) and neuAB (sialic acid biosynthesis gene). Further C. jejuni isolates were grouped by random amplification of polymorphic DNA (RAPD) profiling. RESULTS A total of 436 samples from poultry (n=88), cattle (n=216) and humans (n=132) from different locations were collected. Results revealed percentage of C. jejuni isolates were 35.2% (31/88), 25.0% (54/216) and 11.3% (15/132) among poultry, cattle and clinical human samples respectively. Antibiotic susceptibility results showed that similar resistance patterns to cephalothin was ie. 87.0%, 87.1% and 89%among humans, poultry and cattle respectively, followed by sulfamethoxazole+trimethoprim 40.0%, 38.7% and 31.0% in humans, poultry and cattle and Ampicillin 40%, 32% and 20% in humans, poultry and cattle respectively. Beta-lactamase activity was detected in 40.00% humans, 20.37% cattle and 32.25% in poultry C. jejuni isolates. CadF and mapA were present in all poultry, cattle and human C. jejuni isolates, wlaN was not detected in any isolate and neuAB was found in 9/31 (36%) poultry isolates. RAPD profiling results suggested high diversity of C. jejuni isolates. CONCLUSIONS Detection of multidrug resistant C. jejuni strains from poultry and cattle is alarming as they can be potential hazard to humans. Moreover, predominant association of virulence factors, cadF and mapA (100% each) in C. jejuni isolates from all sources and neuAB (36%) with poultry isolates suggest the potential source of transmission of diverse types of C. jejuni to humans.

Comparative Analysis of Biosorption Potential for Chromium Removal by Live and Dead Biomass of Aspergillus niger ZH2

Tannery led chromium toxicity is one of the major threats to public health in developing countries, where most of the hides are treated at local cottage industry level and chromium liquor is released without detoxification. In this connection, the present study was conducted to develop a reliable cost effective fungal-based biosorbent for chromium removal. Six strains of Aspergillus niger were isolated from various environmental conditions and assessed for chromium tolerance. Biosorption potentials of two different biomass, i.e., live and dead, of selected Aspergillus niger ZH2 was investigated as a function of appropriate equilibrium time, pH, temperature, concentration of biosorbent and adsorbate in batch system. The chromium uptake by these biomasses was quantitatively evaluated using Langmuir and Freundlich isotherms. In order to determine the best fit isotherm, three error analysis methods were used to evaluate the data: correlation coefficient, residual root mean square error and chi-square test. Maximum adsorption capacity (qmax) was calculated to be 322.60 and 12.00 mg/g for live and dead biomass respectively. Application of Langmuir isotherm showed that live biomass was more favorable (95% CI, 1.053-8.718) than dead biomass in removing chromium and thus can serve as better biosorbent.

Galleria mellonella is low cost and suitable surrogate host for studying virulence of human pathogenic Vibrio cholerae.

Vibrio cholerae causes a severe diarrheal disease affecting millions of people worldwide, particularly in low income countries. V. cholerae successfully persist in aquatic environment and its pathogenic strains results in sever enteric disease in humans. This dual life style contributes towards its better survival and persistence inside host gut and in the environment. Alternative animal replacement models are of great value in studying host-pathogen interaction and for quick screening of various pathogenic strains. One such model is Galleria mellonella, a wax moth which has a complex innate immune system and here we investigate its suitability as a model for clinical human isolates of O1 El TOR, Ogawa serotype belonging to two genetically distinct subclades found in Pakistan (PSC-1 and PSC-2). We demonstrate that the PSC-2 strain D59 frequently isolated from inland areas, was more virulent than PSC-1 strain K7 mainly isolated from coastal areas (p=0.0001). In addition, we compared the relative biofilm capability of the representative strains as indicators of their survival and persistence in the environment and K7 showed enhanced biofilm forming capabilities (p=0.004). Finally we present the annotated genomes of the strains D59 and K7, and compared them with the reference strain N16961.

Resistance patterns of diversified phylogroups of Escherichia coli associated with mothers having history of preterm births in Pakistan.

Abstract Objective: Urinary tract infections (UTIs) are caused by extraintestinal pathogenic Escherichia coli (ExPEC), and are one of the key predictors of preterm births. In the light of this fact, present study was conducted to determine the predominant Escherichia coli (E. coli) phylotypes and their associated antibiotic susceptibility patterns, isolated from pregnant mothers with the history of preterm births. Methods: Forty seven E. coli strains were isolated out of a total of 80 urine samples of pregnant women. The isolates were phylotyped and further screened for the presence of Clonal group A. Moreover, Antimicrobial susceptibility testing and screening for Extended Spectrum Beta Lactamase (ESBL) producing strains were also performed. Results: Among the 47 isolates, phylogroup B2 was found to be highly prevalent (45%), followed by group D (23%), B1 (10.64%), A (6.38%), E (6.38%), cryptic clade I (4.25%) and F (2.13%). Two isolates belonged to CgA and 41 (87.23%) isolates were found to be multidrug-resistant. Out of nine antibiotics tested in the study, the isolates displayed high resistance to Ampicillin (82.6%), Sulphamethoxazole (65.22%), Nalidixic acid (60.87%), Sulphamethoxazole-Trimethoprim, Doxycycline and Erythromycin (56.52% each). In total, 8 (17.02%) of the isolates were found to be ESBL positive. Conclusions: The prevalence of infections caused by virulent and highly drug resistant E. coli isolates constitute a risk of developing preterm birth complications in pregnant women and requires the selection of appropriate antibiotics for the treatment of infections caused during pregnancy.

Characterization of enteropathogenic Escherichia coli of clinical origin from the pediatric population in Pakistan.

BACKGROUND Enteropathogenic Escherichia coli (EPEC) is one of the leading causes of watery diarrhea among children. METHODS In this study EPEC isolates from the pediatric population of Pakistan (2010-2012) were subjected to phylotyping, antibiotic susceptibility, extended-spectrum beta-lactamase (ESBL) profiling and evaluation of one representative strain from each panel of phylotypesin Galleria mellonella, infection model. RESULTS A total of 46/225 (20.4%) stool samples were positive for EPEC. Isolates mainly belong to D phylogroup (18, 39%) followed by nontypeable (10, 22%), B1 (9, 20%), B2 (8, 17%) and A (1, 2%). High resistance was observed for ampicillin (42, 91%), erythromycin (41, 89%), cefaclor (37, 80%), trimethoprim/sulfamethoxazole (36, 78%), tetracycline (36, 78%). Among nalidixic acid resistant isolates 13 (28%) showed presence of single nucleotide polymorphism (SNP) in parC (C330-T330) whereas 1 (2%) isolate showed gyrB (A660-T660) SNP. Furthermore, 27 (59%) isolates were ESBL producers. Representative isolates of phlyotypes A and B2 showed enhance killing of G. mellonella compared to ones belonging to phylotypes B1 and D. CONCLUSIONS Non-typeable EPEC strains were frequently observed. ESBL production in ESBL producers was found to be plasmid mediated. No significant association of antibiotic resistance profile with specific phylogroup of EPEC was found, however G. mellonella infection model differentiated representative phylotypes.

Antibiotic Susceptibility and Molecular Characterization of Campylobacter jejuni Strain Isolated from a Guillain Barré Syndrome Child

To the Editor : Campylobacter jejuni is among the leading etiological agents associated with bacterial diarrhea worldwide. In rare occasions,Campylobacter jejuni infectionmay trigger the human immune system to attack self-gangliosides resulting in Guillain-Barré syndrome [1]. We here, present case of a 7-yold girl suffering from acute flaccid paralysis of lower limbs after an episode of bloody diarrhea. The child was wheel chair bounded but did not have any difficulty in breathing or swallowing and did not receive any antibiotic treatment. The patient showed elevated levels of cerebrospinal fluid (CSF) (261 csf mg/dl). Shewas treatedwith – 5d course of intravenous immunoglobulin (IVIG) at standard dose of 0.4 g/kg/d. No ventilation support was needed. On day 25th, she walked – 5m distance with aid. C. jejuni was isolated from the patient’s stool sample and identification was confirmed by using species specific (hipO) PCR [2]. The strain was found to be resistant to three antibiotics i.e., erythromycin, sulfamethoxazole + trimethoporim, cephalothin. PCR analysis for the detection of genes (sul1, sul2 and sul3) showed that the isolate was positive for all the three resistivity genes [3, 4]. Virulence genes i.e., cadF (fibronectin binding protein) and wlaN (putative beta-1,3-galactosyl transferase) were present whereas NeuAB (sialic acid biosynthesis gene) was absent [2]. ThewlaN gene inC. jejuni is proposed to encode an enzyme β-1,3-galactosyl transferase that converts GM2-like LOS structure to a GM1-like structure. These GM1-like structures trigger the human host to produce the anti-GM1 antibodies which binds to GM1 expressed on the motor nerves of the limbs, resulting in Guillain–Barré syndrome [5]. The presence of wlaN gene in the present isolate further confirms the role of the gene in triggering AMAN, a variant of GBS. To our knowledge this is the first case of GBS following infection with C. jejuni, reported from Pakistan. Further investigations on prevalence and molecular characterization of C. jejuni associated GBS may contribute to a better understanding of the disease.

Draft Genome Sequence of the Enteropathogenic Bacterium Campylobacter jejuni Strain cj255

ABSTRACT The enteropathogen Campylobacter jejuni is a global health disaster, being one of the leading causes of bacterial gastroenteritis. Here, we present the draft genome sequence of C. jejuni strain cj255, isolated from a chicken source in Islamabad, Pakistan. The draft genome sequence will aid in epidemiological studies and quarantine of this broad-host-range pathogen.

Structural basis for the pathogenesis of Campylobacter jejuni Hcp1, a structural and effector protein of the Type VI Secretion System

The Type VI Secretion System (T6SS) provides enhanced virulence to Campylobacter jejuni and has been associated with a high incidence of bloody diarrhea. The hemolysin‐coregulated protein (Hcp)—the hallmark of the T6SS—can act as a structural and effector protein. Unlike other T6SS‐harboring bacteria, which possess multiple Hcp proteins each performing different functions, C. jejuni possesses only one Hcp protein, and its structural and functional role has not been elucidated previously. Here, we report the structure and functional studies of Hcp from C. jejuni. We found similarities between the hexameric ring structure of Hcp‐Cj and that of Hcp3 from Pseudomonas aeruginosa. Through functional studies, we showed two roles for Hcp‐Cj that is, in cytotoxicity toward HepG2 cells and in biofilm formation in C. jejuni. In structure‐based mutational analyses, we showed that an Arg‐to‐Ala mutation at position 30 within the extended loop results in a significant decrease in cytotoxicity, suggesting a role for this loop in binding to the host cell. However, this mutation does not affect its biofilm formation function. Collectively, this study supports the dual role of Hcp‐Cj as a structural and effector protein in C. jejuni.