I have a problem with antibiotic guidelines. Okay, I know that’s a controversial statement for a microbiologist to make given all the efforts that have been put in over the last 15-20 years to try and make antibiotic prescribing better, but let me explain.
 
Or better yet, let me ask you a question. How do you choose an antibiotic?
 
Nowadays, when I ask this question, I get a really irritating answer, “I look at the guidelines”.

So basically, people check their brains at the door and just follow what is written down on a piece of paper or on a computer screen, without even thinking about whether it’s the right thing to do. I also suspect that many people think Microbiologists just pluck the names of antibiotics out of the air when giving advice… the ECIC thinks that stat Gentamicin is the answer to every question!
 
But in reality, Gentamicin is not the ONLY answer and guidelines may be the WRONG choice; this leads to mistakes being made every day in the choice of antibiotics to treat patients, and most of these are avoidable.
 
Let me give you some daily scenarios where following a local antibiotic guideline would be the wrong thing to do:

• Patient has frequent urinary tract infections with a Gentamicin resistant E. coli but is treated with Gentamicin because that’s what the antibiotic guidelines say to use for pyelonephritis (Hint, those previous urine results would also have said what the E. coli would actually be sensitive to!) The guideline is NOT applicable in this scenario
• Patient has cellulitis following a dog bite but is treated for cellulitis with Flucloxacillin using the generic cellulitis guidelines, but the prescriber should have looked at the infected bites guideline (Hint, bites often involve Gram-negative bacteria and the generic cellulitis guidelines target Gram-positives) The guideline is NOT applicable in the scenario
• Patient has Clostridium difficile and should be receiving oral Vancomycin, but because someone has decided to make them “nil by mouth” the person has prescribed IV Vancomycin instead even though this will NOT cross into the gut to treat the infection (Hint, making a patient “nil by mouth” doesn’t usually stop them receiving their oral medications)

 
So, how do you avoid making mistakes when choosing what antibiotic to use?
 
First considerations for prescribing
Before deciding whether to prescribe an antibiotic there are a number of things to consider and questions to ask:

• Make sure you know normal flora and the causes of common infections
• Know your speciality’s serious and common infections, the microorganisms that cause these, and the usual treatments for them
• Use the British National Formulary (BNF) for interactions, cautions and contraindications as well as dosing information

Where do "guidelines" come from? 
Empirical antibiotic guidelines are established by answering many of the questions below. It is essential to understand the relevance of these questions and the effect of the answers. Relying on empirical antibiotic guidelines without knowing why or how these guidelines are produced can be dangerous and is poor practice.
 
Important questions to ask when choosing an antibiotic
I have a specific process I follow when choosing what to prescribe. I have been doing this for so long now that much of this is instinctive or I am able to quickly skip the less relevant questions for a given scenario. BUT when you first start prescribing though it is important to be more careful and consider each question IN TURN, all 15 of them!

1. Does the patient have an infection?

There are many non-infectious reasons for “signs of infections”

• Fever caused by drugs, malignancy, connective tissue disorders
• Increased CRP caused by inflammation, malignancy, connective tissue disorders
• Chest crackles caused by heart failure, pulmonary embolus, fibrosis
• Pyuria (white blood cells in urine) caused by appendicitis, connective tissue disorders, malignancy

 
2. If the patient has an infection what is the likely source?

• Urine, respiratory tract, skin, bone, joint, heart, CNS etc.…

 
3. What are the likely causative microorganisms?

• Viruses, bacteria, fungi, parasites

 
4. Does the patient need an antibiotic or is the infection self-limiting?

• Viral infections are usually self-limiting
• Urethral syndrome and gastroenteritis do not usually require antibiotics

 
5. Does the patient need urgent treatment or is there time to make a diagnosis?

There is often time to make a diagnosis before starting treatment HOWEVER certain infections require immediate management without waiting for investigations as delays can lead to serious and permanent harm to the patient:

• Sepsis
• Neutropaenic sepsis
• Meningitis
• Meningococcal sepsis
• Encephalitis
• Epiglottitis
• Spinal epidural abscess
• Necrotising fasciitis
• Toxic shock syndrome

 
6. Is the antibiotic active against the microorganisms?

• See Table of Antibiotic Spectrum of Activity (content from Microbiology N&B)

 
7. Does the antibiotic get into the site of infection?

• See Table of Penetration, content in Microbiology N&B)

 
8. Does the patient need a bactericidal antibiotic or is bacteriostatic adequate?

• Immunodeficient patients require bactericidal antibiotics because they are unable to fight infections themselves

 
9. What route of administration should be used?

• DO NOT use oral antibiotics to treat systemic infections if patients are unable to absorb from the gastrointestinal tract
• Antibiotics with good oral bioavailability rarely need to be given intravenously

 
10. How much antibiotic should be prescribed?

• Patients in renal failure may need doses of antibiotics reducing
• Patients over 60-70kg may need increased doses of antibiotics as normal doses are calculated for previously normal body size (male of 65kg back in the 1950s!)

 
11. Are there any contraindications or cautions for prescribing this antibiotic?

• DO NOT use any Beta-lactam antibiotics if the patient has a history of severe penicillin allergy
• Many antibiotics interact with Methotrexate e.g. Trimethoprim, Ciprofloxacin, Doxycycline
• Many antibiotics are contraindicated in myasthenia gravis e.g. macrolides, quinolones, aminoglycosides, Colistin
• Always check the BNF for interactions, cautions and contraindications as well as dosing information

 
12. What are the side effects of this antibiotic?

• See section Antibiotics, in Microbiology N&B for individual antibiotic agents
• Always check the BNF for side effects

 
13. When should the patient be reviewed?

• Septic patients should be reviewed within 1 hour of starting treatment
• Daily review of ALL patients on antibiotics
• Don’t forget “stop and review” dates as these help prevent over-treatment and CDAD

 
14. When can I switch from IV to oral, and how long should I treat the patient for?
 
15. Do the results of the microbiology investigations identify a specific causative microorganism?

• Once the cause is known, antibiotics should be narrowed down to cover the specific microorganisms identified e.g. CAP caused by Streptococcus pneumoniae can be treated with Penicillin rather than Co-amoxiclav and Clarithromycin

 
So, there it is. When choosing an antibiotic, I run through 15 questions in this order to choose what the right treatment is. It isn’t easy when you start out with prescribing. Like everything it takes time to learn how to do it properly, but it’s worth it. Patients don’t get better on the wrong antibiotic, and prescribers get in trouble when they mess it up, so it’s in everyone’s interest to get it right first time… so give this method a try… it works for me!
 
Don’t forget to order your copy of Microbiology Nuts and Bolts; it’s the perfect size for a stocking filler! Yep that’s a desperate plug for Xmas sales to cover the cost of ECIC’s stocking fillers: a tube of orange smarties, drumstick sweets and refreshers :-)

The Duty Microbiologist had just got to the duty desk when the phone rang, 09:02 no time to even pour a cup of coffee… this was going to be a bad day!
 
The ward doctor from Phlegming Ward was treating an unknown illness in a patient who had just returned from a holiday from the Indian Subcontinent.
 
It sounded bad… they were septic, with low blood pressure and a very high lactate. The Critical Care Outreach Team were on their way but the team were worried the normal IV Amoxicillin, Gentamicin and Metronidazole for sepsis wasn’t working!
 
“Change to Meropenem, give a dose of Amikacin stat and isolate the patient ASAP. Also send us a blood culture, sputum and urine and we’ll see what we can grow. As there is a risk of enteric fever, make sure you write High Risk on the request form please!”
 
However, at the same time the Sister from Phlegming Ward was calling the Infection Control Nurses to say she thought they might have an outbreak as they had a number of patients that had all been in the same bay who were now all suddenly septic!
 
The Infection Control Nurses told the Sister they’d drop everything and hurry along to assess the situation; so they brought forward elevenses to a 10am cake break and then off they went… which is pretty speedy for IC! (…I am going to be in so much trouble for writing that!!!)
                                                     
When they arrived on Phlegming Ward the corridor looked dark and gloomy. The overhead strip lights flickered on and off like a broken strobe light at an 80s disco. A trail of bright pink slime oozed its way across the broken floor tiles disappearing off into the distance. Nothing moved; everything was silent. The ICNs looked through the doors to see carnage. To be fair it was often a chaotic place where no one ever washed up their coffee cups, so mould outbreaks were common. They entered the ward. This seemed different; the patients looked terrible, emaciated and sunken eyed which, although food was being cut back to make hospital savings, shouldn’t be noticeable quiet yet. There was also blood and vomit everywhere, as well as some funny looking bright pink stains no one quite knew what to make of, and the over-worked staff looked like they had finally lost the plot! 

I grew up in the 1980s. I know I’m getting old, not far off 50 now, but I still remember the impact of the discovery of Human Immunodeficiency Virus (HIV) and the effect it had on society.
 
I remember the prejudice. I remember the offensive term Gay Related Immune Deficiency (GRID) and the unhelpful public health campaigns. I also remember the movie Philadelphia with Tom Hanks and Denzel Washington which showed how many people felt about HIV. I remember being in a class at school called “Personal and Social Vocational Education” where we were discussing what we would do if we came across a person with HIV bleeding to death… and I remember being shocked and surprised that I was the only person in the room who would try to help the person… 

What do you do when the proverbial stool sample hits the rotary ventilation device and ALL your IT stops working, yep all of it, all at once!? What happens when the laboratory computer system locks everyone out and you can’t put results in or look results up? What can you do when the fancy piece of automation that moves agar plates around the lab like some kind of daemonic sushi bar fails because of a power cut?
 
What would you do? Burst into tears? Swear profusely? Run screaming to the nearest pub? Sing a jolly pop song?

Over the past few weeks I have seen a lot of patients being admitted with infections due to the bacterium Staphylococcus aureus, which we have grown from their blood cultures. S. aureus is a common pathogen, but the number of positive blood cultures has been above our normal baseline, and I have found myself giving the same advice over and over again to the ward doctors looking after these patients.
 
S. aureus bacteraemia is a serious infection with a mortality of at least 20%; that is on average 20 in 100 people with S. aureus in their blood will die despite what we do to try and help. That’s a lot! And it gets even worse if you can’t find the cause of the bacteraemia, up to 60%. The mortality for S. aureus from an unknown source is so high for lots of reasons; patients are often frail or have underlying immunodeficiencies, but also because if you can’t find the “focus” you can’t easily undertake “source control”. If you can’t control the source, then the infection will persist…! Your patient might not!!!!
 
So, one of the key parts to dealing with S. aureus bacteraemia is finding the source or focus of infection so you can deal with it.

​NOTE: Don’t forget to treat the patient whilst looking for the source. S. aureus is a serious pathogen, so don’t wait for your investigations or results… treat first and then ask the questions!

This may seem like a strange question for a Microbiologist to ask but it’s not as straight forward as many people think. I have blogged about this kind of thing before, but recent conversations with other healthcare workers have shown me that many still do not understand the effect that antimicrobial resistance is going to have on the wider scope of medicine. Well, it’s my blog so I’m going to blog about it again… 😊
 
Most people, including healthcare workers, think that antimicrobial resistance’s biggest threat is related to our ability to treat common infections such as pneumonia, urinary tract infections or cellulitis, but I think that is incorrect. Don’t get me wrong, it’s still important, but for me it’s not the most important threat from antimicrobial resistance.
 
Before I tell you what I think the biggest threats are, let me tell why treating common infections isn’t the biggest threat…

Things go wrong in medicine, people make mistakes, sometimes patients come to harm. I know that sounds obvious, but I think it is something that the healthcare profession and the public often forget. No one is infallible. No one is right all the time.
 
The microbiology laboratory I work in is one of the biggest in the country and it processes about 1.5 million samples per year. That’s 1.5 million results. Do I think we get every one of those results correct… no. That would be unrealistic and I’m not that gullible (or fabulous!). Even if we were only wrong once in every 10,000 samples (0.01%) that would still be 150 errors a year. Which seems a high number, I think you’d agree? I suspect mistakes occur daily in the NHS.
 
The key to errors in medicine is to reduce them to as low as possible by recognising that they occur and learning from them when they do.
 
In order to do this, we use tools like incident reporting, root cause analysis (RCA) and serious incident investigations. The aim is to make sure the same mistakes don’t keep happening. 

In 1988 the World Health Organisation announced its intention to eradicate polio by 2000. It was a lofty goal but one that was achievable as polio only infects humans, and so if they can stop polio spreading between people then it can be eradicated, and the way to stop spreading polio is to vaccinate against it.

Haemophilia is back in the news with the UK government being advised most strongly by Sir Brian Langstaff, in the Infected Blood Inquiry Interim Report, to issue immediate £100,000 compensation to the men, women and children treated by the National Health Service for conditions like haemophilia, who were given infected blood and infected blood products since 1970.

“Hello, is that the Duty Microbiologist? I’m a local GP, could I please discuss a patient with you?”
 
The Microbiologist put down his cup of coffee, yep, coffee, it may be the hottest day of the year out there, but here in the lab it’s air-conditioned to the point of refrigeration!!!!
 
“Go on then” said the Microbiologist being his normal cheery self.