Episode Transcript
Hi and Welcome to Clerkship Ready - Pediatrics - A podcast aimed at helping you excel during your clinical clerkship in Pediatrics.
I’m Dr. Rachel Moon, and I am a Professor of Pediatrics at the University of Virginia School of Medicine. Today we’re going to talk about what you need to know before you choose antibiotics. If you haven’t already, we would also recommend that you listen to the episode “Before You Prescribe Medicines”, which provides some general tips for prescribing medications for the pediatric population. In this episode, we’ll specifically talk about how you should approach choosing the appropriate antibiotic for your pediatric patient.
It seems basic, but you need to know what organisms you want to treat before you prescribe antibiotics. You may know that amoxicillin is the first choice to treat a child with pneumonia in the outpatient setting. But it is important for you to know why amoxicillin is the first choice. And spoiler alert: these are favorite questions that attendings and residents will ask you: Why do you want to use Amoxicillin? What organisms are you worried about? In the case of pneumonia in a healthy child, you will want to say: “The most common bacteria is Strep pneumoniae.”
As a side note here, one common response that I hear from students when I ask about organisms is “Strep.” As you’ll see, just from this podcast episode, there are multiple different species of Streptococcus that we worry about in pediatrics. So in this case, I just mentioned Strep pneumoniae – which is often known as Pneumococcus or Strep pneumo. But in pediatrics, in different scenarios, we may be worried about other species of Strep, such as Group A strep or Group B strep. These are all very different organisms.
When you think about which organisms you are concerned about – and what antibiotic you want, you need to think about anatomy, immunization status, drug allergies, and specific circumstances. We will try to get cultures if at all possible. However, because we often do not have the results of cultures or diagnostic testing when we need to start antibiotics, we need to treat empirically – based on what organisms are typically found in this particular situation. We also want to treat with as narrow-spectrum antibiotics as we can get away with, so that we don’t encourage antibiotic resistance. Many of the clinical practice guidelines for antibiotic choices take these factors – what organisms are typically found, and antibiotic spectrum – into account. Sometimes we end up using more than 1 antibiotic to cover all of the organisms we’re worried about. Sometimes more than one antibiotic can also provide some synergistic effects. The classic example of antibiotic synergy is a beta-lactam with an aminoglycoside. The beta-lactam damages the bacterial cell membrane, which allows more aminoglycoside to be taken up into the cell to cause cell damage by inhibiting protein synthesis.
One exception to trying to use narrow-spectrum antibiotics is when a child has fever and neutropenia, particularly after receiving chemotherapy for cancer. In this case, because the child has virtually no immune defenses and because fever can be the only sign of a life-threatening infection, we use a range of antibiotics that collectively have a broad spectrum against multiple bacteria.
Here are few examples of how to think about how to match the antibiotic to the organism or organisms that you are worried about.
With regards to anatomy, if an infant in the first 4-6 weeks of life has fever, we are worried about organisms that the infant might have been exposed to during pregnancy or during delivery. The delivery canal is very close to the GI tract, so you have to be worried about organisms that live in the genital and GI tracts, such as E. coli and Group B strep. You also want to worry about Listeria monocytogenes. This is a bacterium that is most commonly found in contaminated foods, particularly not-well-refrigerated deli foods and unpasteurized dairy products. For some reason, pregnant women – and their newborns – are susceptible to Listeria infections. Here is another question that medical students are frequently asked: What are the most common bacterial organisms that can cause fever in neonates? That would be E. coli, Group B strep, and Listeria. In the past, Group B strep (GBS) was the most common of these 3, but now pregnant people are tested for GBS at 36-37 weeks gestation. If they are positive, they will receive antibiotics, usually penicillin or ampicillin, during labor. Now, E. coli is becoming more common as a cause of neonatal fever. A typical combination of antibiotics for a neonate with fever would be Ampicillin and Gentamicin. Ampicillin covers Group B strep and Listeria, and Gentamicin is for gram negatives, including E.coli, that are commonly seen in the GI and genital tracts. And remember, this combination also provides antibiotic synergy.
Another example of how anatomy is important is otitis media. Because the Eustacian tube is connected to the upper respiratory tract, you want to think about upper respiratory pathogens. The most common pathogens for otitis media are Hemophilus influenza (or H flu), Strep pneumoniae, and Moraxella catarrhalis. Particularly in children older than 2 years of age who are afebrile and otherwise healthy, we may do watchful waiting, where just treat the symptoms with acetaminophen or ibuprofen and don’t treat with antibiotics unless it’s been 3 days without improvement. This is because the majority of these infections will resolve without antibiotics. We’ll talk more about when watchful waiting is appropriate or not in another episode. However, when antibiotics are used for ear infection, Amoxicillin is the first line treatment, because it covers these organisms if they are not beta-lactamase positive, has an excellent safety profile, is inexpensive, and is easily tolerated by children. For children who have recurrent ear infections or are in day care, they are more likely to have bacteria that are beta-lactamase positive, particularly nontypeable H flu and Moraxella catarrhalis – so these organisms will be resistant to Amoxicillin and other beta-lactams. For these children, we usually use amoxicillin-clavulanate. The clavulanate is a beta-lactamase inhibitor, so adding it allows for better coverage on these organisms. If you are seeing a child who has recurrent ear infections, a question that you may be asked is “When do you need to worry about amoxicillin resistance in a child who has recurrent ear infections?” The answer is 30 days. If the child has been on amoxicillin within the last 30 days, you would want to use an antibiotic that has beta-lactamase coverage.
Also something to think about with regards to anatomy is whether the anatomy is normal or abnormal. For instance, children with cardiac structural anomalies may be at higher risk for endocarditis with organisms such as Staph aureus, Strep viridans, or enterococcus. Or children who have hardware that has been surgically implanted, such central venous catheters are at higher risk for specific infections, particularly from skin flora, such as Staphylococcus epidermidis or other coagulase-negative Staph and Staph aureus.
With regards to immunization status, if the child is not fully immunized, you will need to also think about vaccine-preventable infections. For instance, if the child has meningitis, you will need to think about strep pneumo, H flu, and Neisseria meningitides, or meningococcus. Not being fully vaccinated may also change your differential. For instance, if you are seeing a young child with stridor, in addition to viral croup, you may need to think about epiglottitis from H flu.
Remember to ask about drug allergies. If the child has an allergy to a particular medicine, you’ll need to find an alternative. Up to date and the AAP’s Red Book both have excellent algorithms to help with alternative antibiotics in the case of allergy. However, you will first want to know what type of reaction the patient had. This can help to differentiate a type 1 hypersensitivity reaction that is IgE-mediated – such as urticarial, angioedema, anaphylaxis, or anaphylactic shock – from other reactions, such as a non-urticarial rash. If the reaction is consistent with a type 1 hypersensitivity reaction, you definitely don’t want to prescribe that medicine. In addition, you need to think about related antibiotics that may have cross-reactivity. For instance, if a patient has a history of an anaphylactic reaction to penicillin or amoxicillin, you would avoid other beta-lactams, such as 1st and 2nd generation cephalosporins. Some parents will be reluctant to have their child take a certain antibiotic because someone in the family had a reaction to that antibiotic. A parent or sibling having a drug allergy does not mean that your patient will also have that allergy and is not a contraindication to using that antibiotic.
OK, now let’s think about specific circumstances. There are circumstances based on location and the child’s individual circumstances.
Location is important because there are local resistance patterns. For instance, if there is a lot of MRSA in your community, you need to consider that if you have a patient with a possible Staph infection. Many hospitals will publish their antibiotic resistance patterns, also known as antibiograms, which can be helpful. This is particularly helpful if you know what bacteria you want to treat. For instance, if you know that 60% of the Staph aureus cultures in your hospital are resistant to cefalexin, then you would likely choose an antibiotic that had a better sensitivity profile.
With regards to the child’s individual circumstances, do they have a chronic disease that may contribute? For instance, if they have sickle cell disease, you may need to worry about encapsulated organisms – S pneumo, H flu, and N meningitidis- because of the functional asplenia that these patients have.
What might the patient have been exposed to in their environment? For instance, if a child has a skin and soft tissue infection, such as a cellulitis of the leg, you would typically think about Staph aureus (including methicillin-resistant staph) and strep species. However, if the child has a recent history of swimming in the ocean, you may need to add Vibrio to your list of possible organisms to cover, and you may need to think about the possibility of necrotizing fasciitis. If the patient is a wrestler or has recurrent skin and soft tissue infections, you may need to cover for methicillin-resistant Staph aureus (MRSA). Antibiotics that are commonly used to treat MRSA in children include trimethoprim-sulfamethoxazole (brand name Bactrim) and clindamycin. If the child needs to get IV medication, then Vancomycin is usually used. Remember that PO Vancomycin is not absorbed from the GI tract, so cannot be used to treat infections outside of the GI tract. So if you are asked, PO Vancomycin is not a good option for MRSA skin and soft tissue infections.
Again, thinking about skin and soft tissue infections, infections after puncture wounds are fairly common. You have to think about staph and strep. In addition, Pseudomonas aeruginosa is common in very specific circumstances. One is after ear cartilage piercings. The other extremely specific circumstance when you have to think about Pseudomonas is if someone steps on a nail while wearing sneakers. There’s something about the inner sole of the shoe that creates a good environment for Pseudomonas. Aminoglycosides in combination with a beta-lactam, and 4th generation cephalosporins, such as ceftazidime and cefepime, are appropriate options. The only class of antibiotics that comes IV and PO and can treat Pseudomonas is fluoroquinolones – so ciprofloxacin or levofloxacin.
You often will not know about what the patient has been exposed to unless you ask. This means that you need to get a good history of the present illness, and a good social and travel history.
Today, we talked a lot about how to choose an antibiotic. The next time your attending asks you, “What antibiotic do you want to choose and why?” talk through your thinking process about the anatomy and the specific circumstances pertaining to the child and the child’s environment to explain your rationale, and your attending will be impressed!
OUTRO:
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