Structural characteristics, cation distribution, and elastic properties of Cr3+ substituted stoichiometric and non-stoichiometric cobalt ferrites

Structural, elastic and cation distribution properties have been investigated on stoichiometric and non-stoichiometric cobalt ferrites. Crystal structure, formation of spinel type ferrite, chemical bonding, cation distribution, and thermal properties of two series of Cr³⁺ substituted stoichiometric and non-stoichiometric various cobalt ferrites with general formula Co_1−xCr_xFe₂O₄ (S1), and Co_1+xCr_xFe_2−xO₄ (S2) were reported. Samples are synthesized by the solid-state reaction technique via planetary ball milling. X-ray diffraction (XRD) analysis confirms the formation of a single phase cubic spinel structure with the space group Fd3̄m. Rietveld refinement results show that Cr occupies both the tetrahedral (A-site) and octahedral sites (B-site). The experimental lattice parameters show increasing trends for both the series with increase of Cr content. The cation–anion vacancies, chemical bonding, and the displacement of oxygen have been evaluated to understand the effect of Cr substitution and how the non-stoichiometry affects the physical and chemical properties of the material. The crystallite size is found to be the decreasing value with an increase of Cr concentration for both series of samples. Specific vibrational modes from the FTIR spectra suggest a gradual change of inversion of the ferrite lattice with the increase of Cr concentration which is also evident from Rietveld refinement data. The elastic properties analysis reveals that the synthesized samples for both series are ductile in nature. The non-stoichiometric structure with excess Co²⁺ may pave a new way to realize the lowering of Curie temperature of ferrite that is expected to improve the magnetocaloric properties.

Structural, elastic and cation distribution properties have been investigated on stoichiometric and non-stoichiometric cobalt ferrites.

Culture of pathogenic campylobacter species at Mymensingh Medical College

Childhood diarrhea represents a major public health problem in developing countries, where campylobacteriosis is widespread and causes significant morbidity and mortality in infants and children. Despite the increasing importance of campylobacteriosis, most developing countries and even many developed countries do not have surveillance systems to measure the health and economic burden of human campylobacteriosis, nor detect trends in outbreaks. The present study was carried out to diagnose etiology of diarrhea caused by Campylobacter species. A total of 150 clinically diagnosed diarrheal pediatric patients were included in this study, of which 98(65.3%) were male and 52(34.6%) female from the Department of Pediatrics, Mymensingh Medical College Hospital, Mymensingh, Bangladesh from July 2011 to April 2012. Stool specimens were collected from each of the cases. The specimens were cultured in appropriate media and Campylobacters were isolated and identified by recommended tests. Among 150 cases, 17(11.3%) were culture positive for Campylobacter species, of which 15(88.2%) were C. jejuni and 02(11.7%) were C. coli. Of the cases, below 1 year of age group were 106(70.6%) cases showing 12(70.5%) positive for Campylobacters and 44(29.33%) cases were above 1 year of age group showing 05(29.41%) positive. The prevalence of Campylobacter infection found in the present study was higher below 1 year age group and was very much close to other countries of this subcontinent.

Methicillin-resistant coagulase-negative staphylococci (MRCoNS) by disk diffusion method

The antimicrobial susceptibility of 80 coagulase-negative staphylococci (CoNS) isolates from surgical wound, pus from infected skin lesions, burn exudates and diabetic ulcer exudates of patients in Mymensingh Medical College Hospital, Bangladesh, was evaluated in order to see their pattern of antimicrobial resistance. The study was carried out in the department of Microbiology, Mymensingh Medical College during the period from July 2009 to May 2011. The 80 CoNS isolates were subjected to antimicrobial susceptibility to relevant antibiotics including oxacillin by disk diffusion method. Out of 80 CoNS isolates, the highest number were resistant to oxacillin 36(45%), followed by gentamicin 32(40%), cefuroxime 25(31%), ceftriaxone 24(30%) and ciprofloxacin 18(22%). All isolates of CoNS were sensitive to imipenem and vancomycin. As MRCoNS were found multidrug resistant, therefore, antibiotic sensitivity must be done prior to treatment in infections caused by these species.

Comparative study of immunochromatographic assay (IgM) and widal test for early diagnosis of typhoid fever

Typhoid fever is a severe systemic infection endemic in many developing countries, including Bangladesh. Present study evaluated immunochromatographic test (ICT) and Widal test in the early diagnosis of typhoid fever cases. The study was carried out in the department of Microbiology, Mymensingh Medical College, Mymensingh between July, 2010 and June, 2011, including 200 individuals of different age and sex. Of them, 150 were clinically suspected cases of typhoid fever and 50 age-sex matched controls. Among 150 blood samples from the suspected cases 106(70.7%) were positive for IgM of Salmonella typhi by ICT and 67(44.7%) were positive by Widal test. Whereas, among the 50 controls 4(8%) were positive by ICT and 6(12%) were positive by Widal test. The sensitivity, specificity, positive and negative predictive value of the ICT was found as 83.3%, 92.00%, 91.9% and 83.6% respectively. On the other hand corresponding values for Widal test were of 44.4%, 88%, 80% and 59.5% respectively. Thus, The ICT (IgM) is better alternative to Widal test for early and accurate diagnosis of typhoid fever. The ICT (IgM) is rapid, easy to perform, applicable for field use and highly sensitive and specific for detection of antibodies in patients with typhoid fever.

Enteropathogens associated with acute diarrhea in a tertiary hospital of Bangladesh

Acute diarrheal diseases are great concern throughout the world, as they are responsible for considerable morbidity and mortality, especially in developing countries. The present study was carried out during the period from January' 2011 to December' 2011 in the Department of Microbiology, Mymensingh Medical College. A total of 300 stool specimens were examined by standard laboratory methods for identification of enteropathogens. Rotavirus was detected by Polyacrylamide Gel electrophoresis (PAGE). Different diarrheagenic E. coli (DEC) were detected by Multiplex PCR following standard methods. Of the 300 stool specimens examined, Enteropathpgens were detected in 160(53.5%) cases. Rota virus was detected in 82(27.5%) cases, followed by DEC in 54(18%), Shigella spp. in 8(2.4%), Salmonella spp. in 5(1.6%), Entameoba histolytica in 4(1.5%) and Giardia lamblia in 3(1.0%) cases. Among the DEC, the Enterotoxigenic E. coli (ETEC) was most prevalent (72%, 39/54). The present study revealed a high prevalence of rotavirus and DEC as the predominant causes of diarrhea in this region.

An overview of Brucellosis

Brucellosis is the most important zoonotic disease caused by Brucella species comprising Gram negative, facultative, intracellular pathogens. The true incidence of human brucellosis is unknown for most countries of the world including Bangladesh. But brucellosis is not uncommon in our country. Due to its increasing incidence in many countries of the world it is an important issue now days. Domestic animals such as cattle, goats, sheep, pigs, camel, buffalo and dogs serve as a reservoir hosts. Transmission of brucellosis to humans occurs through the consumption of infected, unpasteurized animal milk and milk products, through direct contact with infected animal parts, through ruptures of skin and mucous membranes and through the inhalation of infected aerosolized particles. Due to variability of clinical features and limited availability of laboratory facilities, the disease remains largely under-reported. Early and specific diagnosis is important to ensure a favourable outcome regarding this zoonotic disease.