Bad Bugs – preventing gram-negative infections
Hospital acquired infections remain a considerable challenge to patient safety. Bloodstream infections are a significant cause of morbidity and mortality in hospitalised patients despite advances in antimicrobial therapy and supportive care.
Although there has been a reduction in MRSA and C difficile cases by 57 per cent and 45 per cent respectively since 2010, there has been an increase in reported blood stream infections. Of concern is the increase in the number of Escherichi coli (E. coli) bloodstream infections, which are up by 20% per cent in the past five years³.
A total of 38,132 cases of E. coli bacteraemia were reported by NHS Trusts in England between 1 April 2015 and 31 March 2016³. This led to the Secretary of State for Health launching a public health initiative this year to reduce healthcare associated gram-negative bloodstream infections by 50 per cent by 2021, as well as reducing inappropriate antimicrobial prescribing by 50 per cent during the same time frame. E. coli infection rates will be displayed on wards, making them visible to patients and visitors in the same way that MRSA and C. difficile are currently³.
The term gram-negative bacteria is derived from a test designed by the Danish scientist Hans Christian Gram to differentiate two types of bacteria based on the structural differences in their cell walls. In a staining test, bacteria that retain a crystal violet dye do so because of a thick layer of peptidoglycan and are called gram-positive bacteria.
Whereas gram-negative bacteria do not retain the violet dye and are coloured red or pink. Compared to gram-positive bacteria, gram-negative bacteria are more resistant to antimicrobials because of their impenetrable cell wall. Gram-positive bacteria do not have the outer cell membrane found in gram-negative bacteria.
Gram-negative bacteria cause infections including pneumonia, bloodstream infections, wound or surgical site infections, and meningitis in healthcare settings. Gram-negative bacteria are resistant to multiple drugs and are increasingly resistant to many available antibiotics. They have a plethora of resistance mechanisms and may use multiple mechanisms against the same antibiotic or use a single mechanism to affect multiple antibiotics.
Gram-negative infections include those caused by Klebsiella, Acinetobacter, Pseudomonas aeruginosa and E. coli as well as other less common bacteria. Gram-negative bacteraemia is a frequent cause of sepsis and gram negative bacillary sepsis with shock has a mortality rate of 30-50 per cent¹.
Gram negative bacteria are the key sources of ventilator-associated pneumonia and urinary tract infections – 47 per cent and 45 per cent respectively, with rates of about 70% for both in intensive care². About 30 per cent of bloodstream infections in intensive care units are caused by a species of klebsiella, E. coli, Enterobacter species and P. aeruginosa². Although given an adequate portal of entry, almost any gram-negative organism can cause bloodstream infection².
E. coli infections represent 65 per cent of gram-negative infections and contributed to around 5,500 NHS patient deaths in 2015³. They have increased by a fifth in the past five years and infection with E. coli could cost the NHS £2.3 billion by 2018³.
Hospital infection rates show considerable variation, with the poorest performing hospitals having rates of infection five times greater than the best performing hospitals. It is estimated that potentially between £900-£2,400 per patient could be saved for every E. coli bloodstream infection that is prevented³.
E. coli bacteraemia England 2015/16
• 70 people out of every 100,000 will acquire and E. coli bacteraemia (up from 60 per 100,000 in 2011/12)
• The risk is greatest among older people, with 824 out of 100,000 men aged 85 or over acquiring an E. coli bacteraemia
• Urinary Tract Infections (UTIs) are the most common cause of infection accounting for 45 per cent of cases.³
According to Public Health England 2017, ‘Infection rates can be cut with better hygiene and improved patient care in hospitals.’ One of the 10 defined core elements of PHE’s Infection Prevention and Control strategy is to ‘provide a safe, clean environment’ for patient care.
The careful selection of appropriate disinfectants for hospital use will help create a cleaner and safer environment for both patients and staff alike.
¹ Kalam K, Qamar F et al 2014, Risk factors for carbapenem resistant bacteraemia and mortality due to gram negative bacteraemia in a developing country, J Pak Med Assoc
NHS England, 2016, DH UK 5 Year Antimicrobial Resistance (AMR) Strategy 2013-2018, Annual progress report
² Peleg YA, Hooper DC, 2010, Hospital-Acquired Infections Due to Gram-Negative Bacteria
N Engl J Med 362:1804-1813
³ Public Health England, 2016, E. coli Bacteraemia England 2015/16
Public Health England, NHS Improvement, 2017, Preventing healthcare associated Gram-negative bloodstream infections: an improvement resource