Stringent Response-Mediated Control of GTP Homeostasis Is Required for Long-Term Viability of Staphylococcus aureus.

Staphylococcus aureus is an opportunistic bacterial pathogen that often results in difficult-to-treat infections. One mechanism used by S. aureus to enhance survival during infection is the stringent response. This is a stress survival pathway that utilizes the nucleotides (p)ppGpp to reallocate bacterial resources, shutting down growth until conditions improve. Small colony variants (SCVs) of S. aureus are frequently associated with chronic infections, and this phenotype has previously been linked to a hyperactive stringent response. Here, we examine the role of (p)ppGpp in the long-term survival of S. aureus under nutrient-restricted conditions. When starved, a (p)ppGpp-null S. aureus mutant strain ((p)ppGpp0) initially had decreased viability. However, after 3 days we observed the presence and dominance of a population of small colonies. Similar to SCVs, these small colony isolates (p0-SCIs) had reduced growth but remained hemolytic and sensitive to gentamicin, phenotypes that have been tied to SCVs previously. Genomic analysis of the p0-SCIs revealed mutations arising within gmk, encoding an enzyme in the GTP synthesis pathway. We show that a (p)ppGpp0 strain has elevated levels of GTP, and that the mutations in the p0-SCIs all lower Gmk enzyme activity and consequently cellular GTP levels. We further show that in the absence of (p)ppGpp, cell viability can be rescued using the GuaA inhibitor decoyinine, which artificially lowers the intracellular GTP concentration. Our study highlights the role of (p)ppGpp in GTP homeostasis and underscores the importance of nucleotide signaling for long-term survival of S. aureus in nutrient-limiting conditions, such as those encountered during infections. IMPORTANCE Staphylococcus aureus is a human pathogen that upon invasion of a host encounters stresses, such as nutritional restriction. The bacteria respond by switching on a signaling cascade controlled by the nucleotides (p)ppGpp. These nucleotides function to shut down bacterial growth until conditions improve. Therefore, (p)ppGpp are important for bacterial survival and have been implicated in promoting chronic infections. Here, we investigate the importance of (p)ppGpp for long-term survival of bacteria in nutrient-limiting conditions similar to those in a human host. We discovered that in the absence of (p)ppGpp, bacterial viability decreases due to dysregulation of GTP homeostasis. However, the (p)ppGpp-null bacteria were able to compensate by introducing mutations in the GTP synthesis pathway that led to a reduction in GTP build-up and a rescue of viability. This study therefore highlights the importance of (p)ppGpp for the regulation of GTP levels and for long-term survival of S. aureus in restricted environments.

Study on Serum Total Cholesterol in Patient with Chronic Kidney Disease.

In the present study serum total cholesterol were estimated in chronic kidney diseased patient to observe the frequency of high serum total cholesterol in chronic kidney diseased patient (CKD) and to assess the incidence of hyper-cholesterolemia. This cross-sectional study was carried out in the department of Physiology of Mymensingh Medical College, Mymensingh from July 2014 to June 2015. For this purpose, total 200 subjects with age ranged from 25 to 60 years were selected and divided into 100 healthy persons as control group and 100 CKD patients as study group. Serum total cholesterol (TC) was evaluated by the Enzymatic, Liquid, Colorimetric test - CHOD/PAP method. Statistical analysis of data was done by unpaired student's t test. The results showed that serum total cholesterol the Mean±SE of control group male and study group male were 164±3.20mg/dl and 220±5.96mg/dl respectively. In study group male, mean±SE serum TC was increased. Result was statistically highly significant (p<0.0001). The Mean±SE serum TC of control group female and study group female were 158±3.13mg/dl and 213±5.49mg/dl respectively. In study group female, Mean±SE serum TC was increased & result was highly significant (p<0.0001). The mean serum total cholesterol level was increased in study group than in control group. The results were statistically significant. From this study, it may be concluded that the increasing frequency of Serum total cholesterol level in CKD may predispose the patients to hypercholesterolemia accelerates development of atherosclerosis, increases risk of cardiovascular disease (CVD) and the other complications.

The stringent response and physiological roles of (pp)pGpp in bacteria.

The stringent response is a stress signalling system mediated by the alarmones guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp) in response to nutrient deprivation. Recent research highlights the complexity and broad range of functions that these alarmones control. This Review provides an update on our current understanding of the enzymes involved in ppGpp, pppGpp and guanosine 5'-monophosphate 3'-diphosphate (pGpp) (collectively (pp)pGpp) turnover, including those shown to produce pGpp and its analogue (pp)pApp. We describe the well-known interactions with RNA polymerase as well as a broader range of cellular target pathways controlled by (pp)pGpp, including DNA replication, transcription, nucleotide synthesis, ribosome biogenesis and function, as well as lipid metabolism. Finally, we review the role of ppGpp and pppGpp in bacterial pathogenesis, providing examples of how these nucleotides are involved in regulating many aspects of virulence and chronic infection.

Study of Diameter of Lymphoid Follicle of Vermiform Appendix in Bangladeshi People of Different Age and Sex.

A cross sectional descriptive study was performed on 40 postmortem vermiform appendix (male 24 and female 16) to find out the diameter of lymphoid follicle of vermiform appendix of Bangladeshi people. The specimens were collected from autopsy laboratory of the Department of Forensic Medicine, Mymensingh Medical College, Mymensingh, Bangladesh by purposive sampling technique and were divided into four age groups. They were Group A (upto 20 years), Group B (21 to 40 years), Group C (41 to 60 years) and Group D (above 60 years). For this purpose, about 3mm long of whole thickness transverse section was taken from the middle of the vermiform appendix and thus the permanent slides were made for microscopic examination. To measure the diameter of the lymphoid follicle two measurements were taken. One was taken at the maximum diameter and another was perpendicular to it by ocular micrometer. Diameter of one largest and one smallest lymphoid follicles were measured and find out the mean diameter of lymphoid follicle between them. Diameter of lymphoid follicle = (Maximum transverse diameter + perpendicular diameter) /2. All data were recorded in the predesigned data sheet, analyzed by SPSS program (version 21, 2012) and compared with the findings of other national and international studies and standard text books. It was observed that diameter of lymphoid follicle of vermiform appendix gradually decreased as age advanced. The mean±SD diameter of lymphoid follicle was 580.31±37.07, 545.58±38.37, 485.68±40.20 and 428.12±68.41µm in Group A, B, C and D respectively. Statistical analysis shows that the mean differences of diameter of lymphoid follicle between A&B, C&D were statistically non significant at p= or >0.05 level, difference between Group B&C was statistically moderately significant at p<0.01 level and differences between Group A&C, B&D, A&D were statistically highly significant at p<0.001 level. Mean diameter of lymphoid follicle of vermiform appendix in male was higher (584.30±12.65µm in Group A, 549.42±38.36µm in Group B, 487.38±39.91µm in Group C, 430.68±70.30µm in Group D) than in female (576.31±53.77µm in Group A, 536.61±45.14µm in Group B, 483.14±46.68µm in Group C, 424.28±75.95µm in Group D) but mean difference between sexes in the different groups was statistically non significant at p=or >0.05 level. The present study will help to increase the information pool on the diameter of lymphoid follicle of vermiform appendix of Bangladeshi people.

Study on Hemoglobin Concentration in Patient with Chronic Kidney Disease.

In the present study hemoglobin concentration were estimated in chronic kidney diseased patient to observe the frequency of low hemoglobin level in chronic kidney diseased (CKD) patient and to assess the incidence of anaemia. This cross sectional study was carried out in the department of Physiology of Mymensingh Medical College, Mymensingh, Bangladesh from July 2014 to June 2015. For this purpose, total 200 subjects with age ranged from 25 to 60 years were selected and divided into100 healthy persons as control group and 100 CKD patients as study group. Both control and study group were further divided into 50 male and 50 female. Hemoglobin concentration was evaluated by the Cyanmethemoglobin (CMG) method. Statistical analysis of data was done by unpaired student's 't' test. The results showed that hemoglobin levels decreased significantly in chronic kidney diseased patients than the normal healthy persons. The decreasing frequency of hemoglobin level in CKD may predispose the patients to anemia and increasing the other complications.

Interaction between Hypertension and Asthma in Adult.

Asthma has been defined as a chronic inflammatory disorder of the airways that is associated with recruitment of inflammatory cells and the clinical development of wheezing, shortness of breath, chest tightness, and cough. The prevalence of asthma increased steadily over the latter part of the last century, first in the developed and then in the developing world. Current estimates suggest that asthma affects 300 million people worldwide, with a predicted additional 100 million people affected by 2025. This cross sectional study was conducted from January 1999 to August 1999 on 5642 Bangladeshi people and another same study carried out from November 2009 to April 2010 on 8088 subjects. In 1999 the prevalence of asthma was 6.9% whereas in 2010 it is 6.96%. Both asthma and hypertension are spastic disorders of smooth muscle, there is the similarities between these two diseases may predispose the individuals with one disease to the other. This descriptive type of cross-sectional study was done to find the Interaction between hypertension and asthma in adult and carried out in the Department of Physiology, Mymensingh Medical College, Mymensingh, Bangladesh from July 2014 to January 2016. Fifty (50) male and fifty (50) female adult asthmatic patients aged 18-60 years were included in the study group. They are enrolled from the Department of Medicine, Mymensingh Medical College, Mymensingh and also from locality. For comparison age matched 50 male and 50 female apparently healthy persons were also studied as control. Blood pressure was estimated by auscultatory method by sphygmomanometer. For statistical analysis unpaired student's 't' test was used. Mean blood pressure were significantly increased in study group in comparison to control group and the result was statistically significant (p<0.001). The study findings showed a high prevalence of hypertension among asthmatic patients than non asthmatic healthy persons. From this study, it may be concluded that hypertension and asthma are closely connected.

Fasting Serum Glucose Level in Postmenopausal Bangladeshi Women.

The study was done to find out the causes that changes the fasting serum glucose level in postmenopausal women. This was descriptive type of cross sectional study carried out over a period of one year from July 2014 to June 2015 in the department of physiology, Mymensingh Medical College, Mymensingh. Women of reproductive age (25-45 years) and clinically diagnosed 100 menopausal women (45-70 years) were included for this study. Convenience type of sampling technique was used for selecting the study subjects. Measurement of fasting serum glucose was done by GOD-PAP method. Data were expressed as mean±SD and statistical significance of difference among the groups were calculated by unpaired student's 't' test. The mean±SD of serum glucose in menopausal women were significant at 1% level of probability than women of reproductive age. This study revealed that postmenopausal women showed higher levels of fasting serum glucose level. Fasting blood sugar level between the study & control group were 7.69±2.37 and 4.59±0.73 and the difference was statistically significant.