Hospital Acquired - Noscomial - Infections

At the beginning of the 20th century infectious diseases, caused by microbial pathogens, were the major cause of death. Large numbers of children and the elderly succumbed to diseases such as tuberculosis, diphtheria and pneumonia. At this time microbiologists had little idea about how diseases were spread, or how they could be controlled, so epidemics flourished. The Spanish influenza pandemic of 1918–1919, caused c.50 million deaths worldwide - more than the total number of deaths recorded in World War One. Diarrhoeal disease was also common since people regularly ate contaminated food and drank contaminated water.

Microbiology research has been concerned with developing antibiotics and vaccines to protect the population from infectious disease. The discovery of penicillin by Alexander Fleming saved the lives of many millions of people. The development of vaccines which protect against, diphtheria and pneumonia dramatically reduced the number of childhood deaths caused by these diseases. Children in developed countries are also routinely vaccinated against common viral infections such as measles, mumps, rubella and polio. As a direct result of the efforts of microbiologists, smallpox, once a dreadful scourge, is now officially extinct on the planet. However a vaccine against HIV, which in 2009 was reported to infect approximately 33.3 million people around the world, still eludes us.

Babies are colonised by bacteria immediately after birth. It has been estimated that the average person is colonised by 200 trillion bacteria, comprising at least 1,000 different species. The bacteria that call the human body home are often essential for our health and well being. Our intestines contain about 100 trillion bacteria and collectively they make up 60% of the dry weight of faeces. These intestinal bacteria play an essential role in helping us to digest food, they provide us with essential vitamins such as vitamin K and biotin and they help to prevent the growth of harmful pathogenic bacteria. The surface of our skin is also home to millions of friendly bacteria which crowd out potential pathogens and prevent them from growing. One bacterium which is abundant on the skin is Staphylococcus epidermidis which produces chemicals called bacteriocins that kill pathogenic bacteria. Friendly bacteria can also be found in our noses but many of these bacteria also carry a health warning. Neisseria meningnitidis which causes meningitis, lives in the noses of millions of people without causing disease, but if the immune system becomes weakened through ill-health then this bacteria can, almost by accident, cause disease which may result in the death of the human that has become its home.

At least 1.3 million people died worldwide from infections by bacteria resistant to antibiotics in 2019, greater than deaths from malaria and AIDS. Most AMR (antimicrobial resistance) deaths are caused by lower respiratory infections such as pneumonia and bloodstream infections leading to sepsis. MRSA was particularly lethal. Antibiotics transform and extend lives, new antibiotics must be brought to market. Very few countries have a national action plan todeal with the growing problem of AMR, leading to 5 million infections annually.

Health Service Executive, Ireland data imply AMR infections are increasing since the pandemic. Not all infections in Irish hospitals are caused by superbug MRSA, methicillin resistant staphylococcus aureus, most infections are caused by MSSA, methicillin sensitive Staphylococcus aureus which is more readily treated, there is a risk of death. Carbapenemase producing Enterobacteralase (CPE) is higher now than three years ago. This rise since 2020 is due to more people presenting to hospital, delayed by Covid-19 they were unable to present at hospitals and are now returning to normal hospital attendance, however, bed and staff shortages are prevalent.

The threat posed by MRSA some two decades ago has not receded, CPE has overtaken MRSA in terms of numbers and is regarded as the most dangerous superbug because it is resistant to most antibiotics. Since the Sars virus has receded CPE has become more prevalent. There are persistent environmental reservoirs of superbug CPE in several hospitals including sinks, drains and other areas of standing water that can become infected with CPE. Some superbugs are receding VRE, vancomycin resistant enterococcus, an antibiotic resistant infection which may be linked to agriculture. Patients may be infected yet not feel unwell. The spread of superbugs is costly by delaying recovery or even causing death rivalling the burden of certain cancers and rheumatoid arthritis.

Clostridium difficile, if severe can be fatal in older people. Clostridium difficile infections are lower than pre-pandemic levels. MRSA, should MRSA or MSSA enter the bloodstream it can be fatal to elderly people.CPE, live in the intestine, it is the most concerning for the health service as it resists most antibiotics. Vancomycin, found in faeces of most humans and animals, most common urinary tract and wound infections. ESBL, Extended-Spectrum Betalactamase or ESBL can cause serious infection on entering the blood or body tissues. SRSV, the small round structured virus, winter vomiting bug, spread through the air and by personal contact, most symptoms vanish within 72 hours.

Source:- PLOS 2022; Irish Times, Sunday Times