Question

During the golden age of antibiotic discovery, many new antibiotics were isolated from the soil. Recent studies have found that soil bacteria are naturally resistant to most antibotics. Some of the soil bacteria may even use antibiotics as a nutrient source. Antibiotics must kill a broad spectrum of bacteria while being absorbed harmlessly by the body. Most antibiotics were developed based on Ehrlich "magic bullet" paradigm which is suited to testing antibiotic efficacy in a lab. However, infections are more complex than a pure culture on media in a petri plate. Antibiotic resistance conjures up the pre-antibiotic era of medicine in the early 20th century. The emergence of a plasmid mediated resistance to carbopenems, a last-line drug against a variety of bacteria was alarming to public health workers. Antibiotics may cause collateral damage like a C. diff infection that leads to colitis.

5. Why is a bacterial infection that involves a biofilm harder to control with antibiotics than an infection which does not involve a biofilm?

6. Explain how taking antibiotics would cause the bacteria Clostridium difficle, which is part of the healthy colon microbiome, to become pathogenic?

7. How do bacteria resist antibiotics?

Bacteria also develop resistance to biocides. Traditional cleaning methods for equipment may have limitations. For example, patients who recieve a bed used by a prior patient with a bacterial infection are at an increased risk for being colonized and infected by that same bacteria. In addition, bacteria in a healthcare setting are exposed to disinfection which selects for the resistant members of that bacterial population. No-touch methods of disinfection, i.e. uv light or hydrogen peroxide vapor, of equipment may be an improvement. https://www.ncbi.nlm.nih.gov/pubmed/29214175# (Links to an external site.)Links to an external site..

8. Are biofilms a concern when disinfecting equipment? Why?

During the Flint, MI water crises as levels of chlorine fell in the drinking water cases of Legionnaires' disease increased. Legionnaires' disease is a water borne infectious disease caused by Legionella. One study reported that for every drop in cholorine concentration of mg/L of river water the odds of a reported case of Legionnaire's disease increased by 80%, thus establishing not causation but association. Some argued that Legionella is tolerant of chlorine, espceillay when it grows in biofilms and that the temperature difference between lake and river water accounts for the increase in Legionella infections. The recommended level of chlorine to treat water for drinking is 0.2-0.5 mg/L.

doi:10.1126/science.aat2210 Was Flint’s deadly Legionnaires’ epidemic caused by low chlorine levels in the water supply? David Shult (Links to an external site.)Links to an external site.z

Was Flint’s deadly Legionnaires’ epidemic caused by low chlorine levels in the water supply?

9. What effect would increasing the concentration of chlorine to 1.4 mg/L have had on the people who drink Flint water?

10. What happens to the water pipes when chlorine levels are increased to control bacteria? Could these uninteded consequences increase bacterial growth?

Answer 1

Ans 5. Bacteria associated with Biofilm are less sensitive to antibiotics than free-living cells, as bacterial cells in biofilms have their own growth conditions and their survival depends on mutation and exchange in genetic information. Antibiotics Resistance in cells can being observed with the phenotypic shift in nature when bacterial cells becomes immobile. Other reason is the change in physiology and which leads to oxygen and nutrition deprivation in the deep layers of the biofilm which makes them more tolerant to the antibiotic. pH changes in the layers of biofilm leads to accumulation of organic acids which is followed by deactivation of penetrating compounds.

Ans 6. Pathogenesis of Clostridium. difficile is depends on the action of two major toxins, A and B which are encoded by TcdA and TcdB genes (family of Clostridium glycosylating toxins) . C. difficile glycosylating toxins releases a cytotoxic effector domain to the target cells which mediates the membrane insertion during translocation process.

Ans 7.Bacteria develop resistance to antibiotics mainly by two ways:

1. Genetic mutation: mutations enables bacteria to produce potent enzymes which inactivates antibiotics, and other mutations eliminates the cell target where the antibiotic attacks
2. Acquiring resistance from other bacteria by undergoing a simple mating process known as "conjugation," where, bacteria transfer’s genetic material, including genes encoding resistance to antibiotics from one bacteria to other.
   

Ans 8.

Biofilm “matrix-enclosed microbial populations” adhered to each other or to surfaces. biofilms are formed from the growth of attached microorganisms by the production of extracellular polysaccharides, which are able to form micro or macro colonies on surfaces. Some nonspecific factors such as adverse pH, change in nutrient properties of the medium due to oxidative reactions, and certain level of cell damage and cell survival in biofilm layers affects the viability which is released from biofilms and growth of the bacterial cells.

Ans 9. Flint water is high in corrosive chloride which leads to the iron (released from pipes) reacts with residual chlorine which kills microorganisms, and does not allow to function as a disinfectant and the because of this bacteria level increases and the coliform bacteria are mainly screened in such type of water. So, the high level of chlorine or particular concentration will reduce the growth of coliform bacteria and leads to the formation of trihalomethanes.

Ans 10. The higher level of residual chlorine in the water supply pipes, give water smell and bad taste which discourage people from drinking it. For domestic use, residual chlorine levels should be between 0.2 and 0.5 mg/l.