Haemophilus Influenzae Type B

00:01 So how does Haemophilus influenzae cause disease and what diseases does it cause? There are several different manifestations depending on whether the Haemophilus is encapsulated or unencapsulated.

00:15 The unencapsulated are the most common.

00:18 These are the nasal mucosal colonizers which pretty much every human being has at some point or frequent points in their life.

00:27 They colonize the upper respiratory tract and when they break down normal mucosal barriers, they can cause infections such as otitis media, conjunctivitis, bronchitis, pneumonia.

00:40 The encapsulated Haemophilus influenzae in general, are more often associated with more severe infections.

00:48 Type B Haemophilus influenza, also known as Hib.

00:52 Haemophilus influenza type B is historically the most virulent, and it does so by being quite good at invading mucosa through an Ig A protease.

01:04 Because it is so invasive, it can enter bloodstream quite readily causing systemic infections, sepsis, pneumonia, meningitis, you name it.

01:14 In addition to being able to invade its mucosal barriers so easily, it also produces endotoxins which further trigger an inflammatory response and contribute to the symptoms.

01:27 Because historically, Haemophilus influenza type B was so robust, so evil at causing invasive disease, it became a target for one of the most successful vaccination practices in the history of the medical world.

01:43 The Hib vaccine was so successful that it largely eradicated disease caused by Haemophilus influenza type B.

01:52 Unfortunately, nature abhors a vacuum, and so other encapsulated types of Haemophilus; type A, type C that have emerged or grown into the ecological niche left by Haemophilus influenza type B.

02:08 So let's now look a little bit more closely at the types of infection caused by Haemophilus influenza type B even though we are able to vaccine prevent it, it's a good indicator of other types of disease from the other encapsulated bacteria.

02:24 So meningitis. The feared word which everybody everywhere knows about.

02:29 Infants especially before their second or third birthday are most at risk for disease caused by Haemophilus influenza type B.

02:38 Even though it is vaccine preventable and even though the infants are growing their own humoral antibody immune response, they are still at high risk because their overall immune system is still largely infantile.

02:52 It's still learning how to address encapsulated antigens or encapsulated bacteria.

02:58 Therefore infants in that age group are most likely to suffer from invasive disease.

03:02 The clinical manifestations: typically a brief, mild upper respiratory infection which may be some runny nose, some low-grade fever, some headaches.

03:12 But then, invasion occurs followed by bacteremia, followed by delivery to the central nervous system and then the classic signs and symptoms of meningitis: severe headache, extreme fuzziness and nuchal rigidity or neck stiffness if the patient is able to manifest that.

03:30 Otitis media, the most common disease associated with Haemophilus influenza of any type; encapsulated, unencapsulated, you name it.

03:39 All ages are at risk for this although again, children are most at risk.

03:44 As anybody who has suffered from otitis media as an adult knows, the ear pain can be quite extreme and it can be associated with nausea, malaise and sometimes even emesis.

03:55 In this case, most patients will have, again that mild upper respiratory infection followed by localization to one or sometimes both of the ears with severe pain, higher fever, and the irritability due to the pain. Epiglottitis.

04:12 This is the classic illness associated with Haemophilus influenza type B.

04:17 And in fact, it was relatively quite common prior to the days of the Hib vaccine.

04:24 Children at risk for epiglottitis were under age - four years of age, again prior to immunologic maturity.

04:31 And they would typically develop that same upper respiratory tract infection followed by a progressive pain in their pharynx; very much like a pharyngitis.

04:41 However, the epiglottis itself was specifically targeted by both the bacteria and immunolidre - excuse me, immunologic reaction to the bacteria.

04:52 And as that reaction occurred, further engorged and further swelling occurred at the - of the epiglottis until it would actually occlude or block the complete airway.

05:03 You can see an x-ray picture of that projected on the screen with the green arrow showing what's called the thumb sign.

05:10 That dense structure projecting from the left side of the screen across the airway is the edematous swollen epiglottitis looking very much like a thumb which has been smudged across the screen.

05:24 That is simply is showing that there's no way airway is open and no air can pass through.

05:30 That constitutes a surgical emergency and the patients have to be managed very carefully.

05:35 Fortunately, many of them will present prior to complete occlusion of the airway with inspiratory stridor, that high-pitched sound of air whistling as it tries to get past that swollen epiglottis.

05:48 And so those patients could be anesthetized, intubated with a breathing tube quite easily and then allowed to be treated for their underlying infection. Pneumonia.

05:59 The next most common after otitis media, is typically seen in all ages.

06:04 Although now, we're looking at older patients who now - may have waning immunity.

06:10 Also those who are asplenic. The spleen; a part of the immune system which is largely responsible for responding to encapsulated organisms such as some pneumococci and Haemophilus species.

06:23 Patients who have compliment deficiencies, patients who have other immuno deficiencies all are at risk for getting invasive progressive disease due to Haemophilus influenza type B and all the others.

06:36 Typical manifestation; may or may not be preceded by that mild upper respiratory infection depending on whether the patient aspirated infected secretions or developed a mild upper respiratory tract infection first.

06:50 Regardless, the onset of the pneumonia is associated with abrupt onset of fever, high fever with rigor, shaking chills, a productive cough which can become blood-tinged and also chest pain overlying the focal or the locus of the infection itself.

07:06 Chest x-ray or chest radiograph will show you white out or a complete occlusion of that particular lobe and it's quite striking when seen.

07:15 Cellulitis. Although one - doesn't commonly associate Haemophilus influenzae as a cause of skin infection it indeed can cause cellulitis especially in young children.

07:27 And when it typically occurs, it is over the buccal mucosa, right overlying the cheek and it can spread downwards to the neck or across the entire face.

07:37 The cellulitis itself is striking because it looks not just bright red, but almost purplish.

07:43 In fact, many describe a blue or blue purple hue or color to the cellulitis.

07:50 That appearance alone and the location over the cheeks is enough to strongly suggest Haemophilus influenza as the source.

07:58 And then arthritis. Again, not commonly associated with musculoskeletal infections, but Haemophilus influenza can be a source of septic arthritis and when so, it usually affects a single large joint, especially the hip.

08:13 So, treatment. Another important thing to remember about Haemophilus influenzae; all types, is that many express or carry a beta-lactamase.

08:24 This would mean that the typical infection such as an otitis media which you might initially treat with simply amoxicillin alone may not be an adequate effective treatment for Haemophilus influenza.

08:38 Instead, one would start with a beta-lactamase stabilized beta-lactam, like amoxicillin.

08:41 And especially amoxicillin clavulanate.

08:42 which would be very effective against Haemophilus influenzae.

08:46 For patients with more invasive diseases especially meningitis or pneumonia, epiglottitis, mastoiditis, a use of a cephalosporin such as ceftriaxone is always indicated to get excellent tissue penetration and to avoid any chance that the penicillin focused beta-lactamase might if - inactivate the antibiotic.

09:09 And then those patients who have a severe invasive disease, especially including meningitis are very contagious, and the thoughts are that they may be contagious with the strain of Haemophilus which itself might be quite invasive or virulent.

09:25 If so, people who are exposed to such patients require prophylaxis with a drug like rifampin.

09:31 Prevention is always the better treatment of course.

09:35 And in this case, the Haemophilus influenza type B vaccine as noted has been highly effective.

09:41 It is part of the primary vaccine series for all infants and typically conveys a lasting protection without need for boosters after the age of 15 months or so.