Common Bacterial Infections in Children

Epiglottitis is a serious infection of the epiglottis that can be life-threatening. It is usually caused by Haemophilus influenzae type B (HiB) and is characterized by symptoms such as sepsis, stridor, and airway obstruction. Early and controlled intubation is crucial in managing this condition. Fortunately, the introduction of HiB vaccination in the UK has significantly reduced the incidence of epiglottitis, making it a rare condition.

Botulism is another bacterial infection that affects children. It is caused by the anaerobic C. botulinum, which produces a toxin that causes paralysis. Unlike HiB, there is no vaccine available for botulism.

Diphtheria, a severe pharyngitis that causes massive swelling of the neck, is now rare in the UK. The vaccination schedule includes C. diphtheriae, which is the bacteria that causes this condition.

Moraxella is a bacterial infection that causes respiratory tract and ear infections. Children are not vaccinated against it.

Staph. aureus is another bacterial infection that affects children. It causes cellulitis and wound infections, among others. However, there is no vaccine available for this condition.

In summary, while some bacterial infections such as epiglottitis and diphtheria have become rare in the UK due to vaccination, others such as botulism, Moraxella, and Staph. aureus still pose a risk to children. It is important to be aware of the symptoms and seek medical attention promptly if necessary.

Differences in Cell Wall Composition between Fungi and Bacteria

Fungi and bacteria both have cell walls, but the composition of their cell walls differs. While bacterial cell walls contain lipopolysaccharide in Gram negative bacteria and lipoteichoic acid in Gram positive bacteria, fungal cell walls contain chitin and glucans. These polysaccharides are not found in bacterial cell walls, which do not contain cellulose like plant cell walls do.

Peptidoglycan is a major structural component of Gram positive cell walls and a minor component of Gram negative cell walls. This compound is responsible for the ability of Gram positive cells to stain dark purple and Gram negative cells to stain pink. Peptidoglycan binds crystal violet, which is used in the Gram staining process. Overall, the differences in cell wall composition between fungi and bacteria contribute to their distinct characteristics and functions.

The Eclipse Phase of Viral Life-Cycle

The initial entry of viruses into cells is known as the eclipse phase of the viral life-cycle. When a person is infected with a virus, they receive an inoculating dose, some of which enters the bloodstream, causing viraemia. The inoculating viruses then enter cells to undergo replication, causing the viral load in venous blood to fall. This is because the virions are now intracellular.

After replication, the virions bud-off cells or cause host cell lysis, spilling into the blood and causing the viral count to rise again. In some viral infections, such as hepatitis B, there may be a phase of immune tolerance where the immune system does not respond to the virus. This allows for very high levels of viraemia without almost any host cell damage. However, the immune system will eventually recognize the presence of the virus and enter an immune responsive phase, leading to viral clearance and a decrease in viraemia.

Blood Cell Types and Their Presence in Various Disorders

Lymphocytes are a type of blood cell that can be found in higher numbers during viral infections. Eosinophils, on the other hand, are present in response to allergies, drug reactions, or infections caused by flatworms and strongyloides. Monocytes are another type of blood cell that can be found in disorders such as EBV infection, CMML, and other atypical infections. Neutrophils are present in bacterial infections or in disorders such as CML or AML where their more immature blastoid form is seen. Lastly, platelets can be increased in infections, iron deficiency, or myeloproliferative disorders.

In summary, different types of blood cells can indicate various disorders or infections. By analyzing the presence of these cells in the blood, doctors can better diagnose and treat patients. It is important to note that the presence of these cells alone is not enough to make a diagnosis, and further testing may be necessary.

Antibiotic-Associated Diarrhoea and Clostridium Difficile Infection

The majority of cases of antibiotic-associated diarrhoea are non-infective and are caused by changes in the normal gut flora. However, in certain patients, the use of broad-spectrum antibiotics can lead to the development of Clostridium difficile infection. This Gram-positive bacillus causes a colitis that results in profuse watery diarrhoea. In severe cases, the entire colonic mucosa is affected, leading to the formation of a pseudomembrane and severe dilatation of the colon, which can be life-threatening.

C. difficile is first-line treated with metronidazole, but if this is ineffective, oral vancomycin is used as a second-line treatment. Vancomycin is a glycopeptide antibiotic that has zero oral bioavailability, meaning that if it is given orally, none of it will enter the bloodstream. This makes it an ideal treatment for infections that are limited to the gastrointestinal tract, but it would not be useful for treating a systemic infection.

The Structure of Viruses

Viral structure can differ greatly, but all viruses contain some form of genetic material (either DNA or RNA, single or double-stranded) enclosed in a protein coat called the capsid. The capsid is responsible for packaging the replicated genome inside and can theoretically transcribe only two or three proteins to make it.

Some viruses have a lipid coating, known as an envelope, which aids in evading the immune system and entering cells. The envelope can also have surface glycoproteins that are involved in attachment, but these glycoproteins are different from and external to the capsid.

Certain RNA viruses have reverse transcriptase, which allows for the formation of DNA from RNA, such as HIV. However, not all viruses have RNA or reverse transcriptase.

Overall, the structure of viruses can vary, but they all contain genetic material enclosed in a protein coat, with some having an additional lipid coating and surface glycoproteins.

Malaria Transmission and Life Cycle

Malaria is a disease caused by a protozoan called Plasmodium falciparum. The most likely diagnosis for someone who has recently travelled to a high-risk malaria region and has not been taking any antimalarial prophylaxis is malaria. However, leishmaniasis should also be considered if blood tests are negative for malaria.

Mosquitoes are the carriers of malaria. They inject the disease in the form of schizonts from their salivary glands into the human bloodstream. These schizonts then migrate to the liver where they invade hepatocytes and multiply as merozoites. After a while, the hepatocytes rupture and the merozoites invade red blood cells in the bloodstream. In these cells, they undergo replication as trophozoites.

At this stage, gametocytes can also be produced, which are taken up by feeding mosquitoes. In the mosquito midgut, gametocytes fuse to form an oocyst. Schizonts bud off from the oocyst to reside in the mosquito salivary glands. This completes the life cycle of malaria.

Mechanisms of Antibiotic Action

Antibiotics work by targeting specific components of bacterial cells to inhibit their growth and replication. Penicillins, for example, target the bacterial cell wall by binding to penicillin-binding proteins, preventing cross-linking, and stimulating breakdown by activating autolytic enzymes. While penicillins have a relatively narrow range of coverage, they have been modified to give wider action, but the same mechanism of action is used by more advanced penicillins such as amoxicillin and piperacillin.

Other antibiotics target different components of bacterial cells. Rifampicin inhibits DNA synthesis, while trimethoprim inhibits folate production. Colistin inhibits membrane production, and chloramphenicol inhibits protein synthesis. Each antibiotic has a specific mechanism of action that makes it effective against certain types of bacteria.

the mechanisms of antibiotic action is important for developing new antibiotics and for using existing antibiotics effectively. By targeting specific components of bacterial cells, antibiotics can effectively kill or inhibit the growth of harmful bacteria, helping to prevent and treat infections.

Antibiotics and their Mechanisms of Action

Amoxicillin is an antibiotic that belongs to the penicillin family. It has some resistance against penicillinase enzymes, but it is susceptible to beta-lactamase enzymes, which is a common bacterial resistance mechanism. To increase its resistance to breakdown and broaden its spectrum of activity, clavulanic acid is given in combination with amoxicillin, particularly against Gram-negative organisms. Compared to penicillin V, amoxicillin has better oral bioavailability. However, it has relatively poor bone penetration, which requires long courses of IV antibiotics for bone infections. Some oral antibiotics, such as linezolid and clindamycin, have slightly better bone penetration.

DNA gyrase, also known as topoisomerase II, is an enzyme that helps to hold DNA in place during replication. Fluoroquinolones, such as ciprofloxacin, target DNA gyrase as their mechanism of action. There are several antibiotics that target cell wall synthesis, including penicillins, cephalosporins, and carbapenems.

Bacterial Causes of Food Poisoning

Food poisoning can be caused by various bacteria, including Bacillus cereus, Staphylococcus aureus, Campylobacter, Yersinia, and E. coli. Bacillus cereus is known for secreting an exotoxin into rice, particularly rice that has been kept warm for a long time, causing vomiting within 1-6 hours of ingestion. Staphylococcus aureus, on the other hand, tends to infect meat and eggs and causes similar symptoms.

Campylobacter, Yersinia, and E. coli, on the other hand, cause diarrhea (with or without vomiting) after an incubation period of 1-4 days. While all three can cause bloody diarrhea, it is less common with Campylobacter and does not occur with all strains of E. coli. In most cases, these infections resolve on their own without the need for antibiotics. However, if the diarrhea persists, Campylobacter may be treated with a macrolide.

Overall, it is important to be aware of the various bacterial causes of food poisoning and take necessary precautions to prevent contamination and ensure safe food consumption.

Hepatitis B Virus Transmission and Chronicity

Worldwide, the most common way of acquiring Hepatitis B virus (HBV) is through vertical transmission during the perinatal period. Infants who acquire the virus are usually asymptomatic, but 95% of them develop a chronic asymptomatic infection that does not clear spontaneously. This is because they enter a state of immune tolerance where the virus multiplies without immune-mediated hepatocyte death. However, between 20-50 years later, the immune system recognizes the virus, leading to a greatly raised ALT and potential clearance of the viral infection.

In contrast, adults who acquire HBV have a higher chance of developing symptomatic infection, with about 40-60% experiencing acute hepatitis and rarely liver failure. However, less than 5% of them will develop chronic infection, regardless of whether the acute infection was symptomatic or not. It is important to note that the degree of chronicity is unaffected by the patient’s age for the other hepatitis viruses. Hepatitis A and E always result in acute infections with no chronicity, while Hepatitis C is chronic only, with 90% of infected individuals developing chronicity. Lastly, Hepatitis D is only present if Hepatitis B is present. the transmission and chronicity of HBV is crucial in preventing its spread and managing its long-term effects.

The obligate intracellular pathogen that can cause respiratory and genital tract infections is Chlamydia trachomatis.

Chlamydia trachomatis is a bacterium that can cause a variety of infections in humans, including respiratory infections such as pneumonia and genital tract infections such as urethritis, cervicitis, and pelvic inflammatory disease (PID). It is transmitted through sexual contact and can also be transmitted from mother to newborn during childbirth, leading to neonatal conjunctivitis and pneumonia.