Non-interchangeable functions of efflux transporters of Pseudomonas aeruginosa in survival under infection-associated stress.

Pseudomonas aeruginosa is a challenging opportunistic pathogen due to its intrinsic and acquired mechanisms of antibiotic resistance. A large repertoire of efflux transporters actively expels antibiotics, toxins, and metabolites from cells and enables growth of P. aeruginosa in diverse environments. In this study, we analyzed the roles of representative efflux pumps from the Resistance-Nodulation-Division (RND), Major Facilitator Superfamily (MFS), and Small Multidrug Resistance (SMR) families of proteins in the susceptibility of P. aeruginosa to antibiotics and bacterial growth under stresses imposed by human hosts during bacterial infections: an elevated temperature, osmotic stress, low iron, bile salts, and acidic pH. We selected five RND pumps MexAB-OprM, MexEF-OprN, MexCD-OprJ, MuxABC-OpmB, and TriABC-OpmH that differ in their substrate specificities and expression profiles, two MFS efflux pumps PA3136-3137 and PA5158-5160 renamed here into MfsAB and MfsCD-OpmG, respectively, and an SMR efflux transporter PA1540-1541 (MdtJI). We found that the most promiscuous RND pumps such as MexEF-OprN and MexAB-OprM are integrated into diverse survival mechanisms and enable P. aeruginosa growth under various stresses. MuxABC-OpmB and TriABC-OpmH pumps with narrower substrate spectra are beneficial only in the presence of the iron chelator 2,2'-dipyridyl and bile salts, respectively. MFS pumps do not contribute to antibiotic efflux but play orthogonal roles in acidic pH, low iron, and in the presence of bile salts. In contrast, MdtJI protects against polycationic antibiotics but does not contribute to survival under stress. Thus, efflux pumps play specific, non-interchangeable functions in P. aeruginosa cell physiology and bacterial survival under stresses. IMPORTANCE: The role of multidrug efflux pumps in the intrinsic and clinical levels of antibiotic resistance in Pseudomonas aeruginosa and other gram-negative bacteria is well-established. Their functions in bacterial physiology, however, remain unclear. The P. aeruginosa genome comprises an arsenal of efflux pumps from different protein families, the substrate specificities of which are typically assessed by measuring their impact on susceptibility to antibiotics. In this study, we analyzed how deletions and overproductions of efflux pumps affect P. aeruginosa growth under human-infection-induced stresses. Our results show that the physiological functions of multidrug efflux pumps are non-redundant and essential for the survival of this important human pathogen under stress.

Organ Regeneration Through Stem Cells and Tissue Engineering.

Loss of organ and tissue due to injuries or diseases led to the development of regenerative therapies to decrease reliance on organ transplantations. It deals with employing the self-renewal ability of stem cells to differentiate into numerous lineages to assist in providing effective treatment for a range of various injuries and diseases. Regenerative engineering of organs or tissues represents an ever-expanding field that is aimed at developing biological replacements for dysfunctional organs or injured tissues. The critical issue, however, with the engineering of organs outside the human body is the insufficient availability of human cells, the absence of a suitable matrix with the same architecture and composition as the target tissue, and the maintenance of organ viability in the absence of the blood supply. The issue regarding the maintenance of the engineered organ viability can be solved using bioreactors consisting of mediums with defined chemical composition, i.e., nutrients, cofactors, and growth factors that can successively sustain the target cell's viability. Engineered extracellular matrices and stem cells to regenerate organs outside the human body are also being used. Clinically, various adult stem cell therapies are readily under practice. This review will focus on the regeneration of organs through various types of stem cells and tissue engineering techniques.

Association of Malnutrition With Weaning Practices Among Infants in Pakistan.

Background An appropriate diet is critical for the growth and development of infants, especially in the first two years of life. Despite considerable efforts made by government and local authorities to raise awareness, mothers still lack basic knowledge of weaning practices; as a result, infants face a growing number of health problems in their later years of life. This research aims to investigate the association between malnutrition and knowledge of different weaning practices among mothers and to study the factors influencing it. Methodology The current study was a cross-sectional study conducted at Mayo Hospital, Services Hospital, and Jinnah Hospital, Lahore, Pakistan between November 2019 and May 2020. A total of 200 infants of both genders aged between one and 12 months were included in the study. Knowledge and practices of complementary feeding by the mothers were assessed using a close-ended, pre-tested questionnaire. Results Mothers of 200 infants were interviewed and it was found that 79.5% of the infants were being breastfed while 24% never received breast milk. Among those who never received breast milk were given liquids (25%) and semi-solid foods (64.5%). Of the mothers, 8% started weaning at an early age (less than six months old) while the remaining started weaning at the age of six months or later and reported that their infants were either underweight or had reduced heights for that age. Based on the medical reports obtained from the hospital after getting parental consent, it was also found that the infants had distinct signs of deficiency of vitamins A and D, iron, and folate. Conclusions The majority of infants were breastfed, and, in most cases, weaning started at an age of less than six months. Most of the infants were fed semi-solid food as their first complementary food. Two-thirds of the infants were underweight for that age, and one-fifth had reduced heights. Based on deficiency statistics, mothers should be encouraged to start weaning at six months to have minimized malnourishment instances in infants.

Interplay of immune components and their association with recurrent pregnancy loss.

Maintenance and progression of pregnancy is an intricate process governed by a variety of developmental cues. Recurrent pregnancy loss (RPL) is a complication experienced by expecting mothers that is defined as three or more consecutive pregnancy losses. This review focuses on the dysfunctions of the immune system as one of the key contributors towards RPL. The current data suggests that the alloimmune and autoimmune factors contribute to the loss of fetus. Such causes despite being recognized as a definitive reason for recurrent pregnancy loss, are still under extensive investigation with new parameters being discovered and scrutinized for their association with RPLs. More in-depth and high throughput studies are required for devising better diagnostic tools and management strategies for the affected female so that they can carry their pregnancy to term.