Gram-negative bacteria
Introduction:-
Gram-negative bacteria are used in the method of gram staining of bacterial differentiation. These bacteria don’t retain the crystal violet stain. These bacteria’s cell envelopes are made of thin peptidoglycan cell walls and are present in between the cytoplasmic cell membrane and bacterial outer membrane (Nordmann et al,2019). This outer membrane protects it from many antibodies. These antibodies include aminopenicillins, ureidopenicillins, carbapenems, quinolones, cephalosporins, etc. When these bacteria are lysed by the immune cells, it can cause adverse effects such as fever, low blood pressure, and respiratory problem.
Background:-
- The bacteria are constituted of a cell membrane, which is cytoplasmic.
- In gram-negative bacteria, a thin peptidoglycan layer is present (Tulum et al,2019). In gram-positive bacteria, this layer is thinner.
- In the inner leaflet, phospholipids are present, and in the outer leaflet, an outer membrane is present, which includes lipopolysaccharides.
- Polysaccharide backbone is attached to lipoproteins.
- If there is a presence of flagella, then they are four supporting rings instead of two.
- There are no traces of teichoic acids and lipoteichoic acids.
- Usually, the S-layer is attached to peptidoglycan, but it is attached to these bacteria’s outer membrane.
- Spores are not formed though in an exceptional case.
- Some of the bacteria contain Braun’s lipoprotein, the bridge between the outer membrane and peptidoglycan.
- In the outer membrane, it consists of porins, which act as pores for certain molecules.
Classification:-
In 1987, the kingdom of Monera was divided into four groups based on gram staining. These are:-
- Firmacutes
- Gracillicutes
- Mollicutes
- Mendocutes
However, after much research, it has been found that gram-negative bacteria belong to the family of Negibacteria and can be treated as a monophyletic taxon.
The genetic basis of antimicrobial resistance of gram-negative bacteria:-
The resistance of gram-negative bacteria are as follows:-
ü Enterobacteriaceae
ü Acinetobacter baumannii
ü Pseudomonas aeruginosa
ü Helicobacter pylorus
ü Campylobacter fluoroquinolone
Aims:-
- This research aims to detect whether the antimicrobial resistance in gram-negative bacteria is directly proportional to a gene or not.
Objectives:-
- To determine the side effects of gram-negative bacteria
- To determine the genetic basis of antimicrobial resistance in gram-negative bacteria.
- To evaluate the impact of gram-negative bacteria on the genes.
Methods:-
- Enterobacteriaceae:-
The main reason for urinary tract infections and blood infections is Escherichia coli and Klebsiell spp, which belong to Enterobacteriaceae’s family. Enterobacteriaceae resists cephalosporins and stimulates the production of β-lactamases. Ampicillin and amoxicillin are restricted by TEM-1, TEM-2, and SGV-1, which are the enzymes of β-lactamases. During the mutation of genes, these resist cephalosporins and produce β-lactamases to hydrolyze them. Carbapenem results in loss of outer membrane protein (Cui et al,2019). The genes of carbapenemase are present on mobile genetic elements.
- Acinetobacter baumannii:-
Acinetobacter baumanni is an aerobic gram-negative bacterium that can surpass the effect of drugs as declared by WHO. It is involved in developing an instant resistance to antimicrobials in the following mechanism:-
- baumannii results in the incorporation of DNA into genomes and is also responsible for identifying a huge amount of β-lactamases. Some β-lactamases are responsible for hydrolyzing ESBL, while CTX-M is responsible for reducing the chances of carbapenems.
- In A. baumannii, efflux pumps should be drugged against various antibiotics such as tigecycline.
- Acetyltransferases and phosphotransferase mediate the resistance of A. baumannii to aminoglycoside. Aminoglycoside is modified by these enzymes chemically. With the help of plasmids and integrons, the coding genes are transferred (Trebosc et al,2019).
- Integrons are used for clustering and restricting genes. It is located on the bacterial chromosomes. It is useful for epidemic strains.
- Pseudomonas aeruginosa:-
Pseudomonas aeruginosa is again an aerobic gram-negative bacterium and is situated in the intestinal flora. P. aeruginosa decreases the permeability of the outer membrane and expresses efflux pumps (Pang et al,2019). Benzylpenicillin and imipenem induce AmpC β-lactamases. Overexpression of AmpC β-lactamase in gene mutation whose resistance is acquired by P. aeruginosa. Colistin is used to treat MDR Pseudomonas, which is more efficient than β-lactum drugs.
- Helicobacter pylorus:-
Helicobacter pylorus is the most impactful pathogen responsible for gastric cancer and peptic ulcers (He et al,2019). Clarithromycin develops resistance because of various mutations in the domain V of the 23S RNA genes. A2142G, A2143G present in the bacteria are responsible for decreasing the effectiveness of the drug. According to WHO, clarithromycin is the most popular antibiotic research.
- Campylobacter fluoroquinolone:-
With the consumption of contaminated food and water, infections are caused by Campylobacter fluoroquinolone, which is also a gram-negative bacterium (Khademi et al,2019). No antibiotics are required for the treatment, but in exceptional cases, ciproflaxin is given. C257T mutation in the gyrA gene in ciproflaxin has been noticed due to the transfer of resistance DNA among strains.
Ethical considerations:-
- AMR results in complications in treating this infectious disease. The impacts of AMR are an ethical issue.
- AMR results in a reduction of population by causing injury or death. So the resources should be divided accurately, and a proper balance should be made between the benefits and the hazards.
Health and safety consideration:-
- Gram-negative bacteria are resistant and can resist multiple drugs.
- It can pass the resistant feature along with the genetic material and ensures other bacteria are resistant.
- Polymyxins are used to stop the spread of gram-negative bacteria causing various infections in the human body.
- Also, colistimethate sodium in the series of 118 was used to get rid of these bacteria. It was induced with TBSA of +64- -64 at 19%. It was previously used at Galveston Shriners hospital in 2000.
- Antimicrobial photodynamic therapy can also be used to treat gram-negative bacteria. It is considered to be the most effective measure to stop resistance caused by the gram-negative bacteria ( et al,2019).
Scientific importance to society:-
Gram-negative bacteria are the most impactful bacteria, which can give rise to many public health problems. It is mainly because of the high resisting power of the antibodies. It caused various infections such as pneumonia, wound infections, blood infections, etc.
Conclusion:-
The outer membrane of the bacteria protects it—there is association of components of their membrane with the pathogenic capability of the gram negative bacteria. The term gram-negative was derived from Hans Christian Gram and was named after his surname.
According to a report in 2014, around 80 species of bacteria were found to inherit the ability to transfer. This transformation is carried from the gene to the intervening medium. The gram-positive bacteria and gram-negative bacteria are evenly divided into the human body.
References:-
Nordmann, P. and Poirel, L., 2019. Epidemiology and diagnostics of carbapenem resistance in gram-negative bacteria. Clinical Infectious Diseases, 69(Supplement_7), pp.S521-S528.
Bassetti, M., Peghin, M., Vena, A. and Giacobbe, D.R., 2019. Treatment of infections due to MDR Gram-negative bacteria. Frontiers in medicine, 6, p.74.
Cui, X., Zhang, H. and Du, H., 2019. Carbapenemases in Enterobacteriaceae: detection and antimicrobial therapy. Frontiers in microbiology, 10, p.1823.
Trebosc, V., Gartenmann, S., Tötzl, M., Lucchini, V., Schellhorn, B., Pieren, M., Lociuro, S., Gitzinger, M., Tigges, M., Bumann, D. and Kemmer, C., 2019. Dissecting colistin resistance mechanisms in extensively drug-resistant Acinetobacter baumannii clinical isolates. MBio, 10(4), pp.e01083-19.
Pang, Z., Raudonis, R., Glick, B.R., Lin, T.J. and Cheng, Z., 2019. Antibiotic resistance in Pseudomonas aeruginosa: mechanisms and alternative therapeutic strategies. Biotechnology advances, 37(1), pp.177-192.
He, C., Peng, C., Wang, H., Ouyang, Y., Zhu, Z., Shu, X., Zhu, Y. and Lu, N., 2019. The eradication of Helicobacter pylori restores rather than disturbs the gastrointestinal microbiota in asymptomatic young adults. Helicobacter, 24(4), p.e12590.
Khademi, F. and Sahebkar, A., 2020. Prevalence of Fluoroquinolone-Resistant Campylobacter Species in Iran: A Systematic Review and Meta-Analysis. International Journal of Microbiology, 2020.
Tulum, I., Tahara, Y.O. and Miyata, M., 2019. Peptidoglycan layer and disruption processes in Bacillus subtilis cells visualized using quick-freeze, deep-etch electron microscopy. Microscopy, 68(6), pp.441-449.