Neisseria, Moraxella, Haemophilus, Acinetobacter baumannii Flashcards
What are the common clinical syndromes caused by Neisseria meningitidis?
Meningitis and meningococcemia (septicemia). High-risk presentations include purpura fulminans and Waterhouse-Friderichsen syndrome.
The classic triad of meningitis includes:
fever, neck stiffness, and altered mental status.
Look for petechial rash in meningococcemia.
What complement deficiency increases the risk of meningitis due to infection with Neisseria?
Terminal complement factors
(C5 to C9)
What type of bacteria is Neisseria?
gram-negative diplococci
Metabolically, what differentiates Neisseria gonorrhoeae and meningitidis?
- Neisseria meningitidis is capable of metabolizing glucose and maltose.
- Neisseria gonorrhoeae can metabolize glucose.
What enzyme is present in both Neisseria gonorrhoeae and meningitidis?
oxidase.
What agar is used for Neisseria?
chocolate agar and Thayer-Martin agar, which contains vancomycin, polymyxin, nystatin, and trimethoprim.
What key virulence factor exists with Neisseria spp. that allows for surface attachment?
Pili.
Promotes nasopharyngeal colonization (attachment and movement). Both Neisseria meningitidis and Neisseria gonorrhoeae have pili, but they serve different functions. N gonorrhoeae binds to host epithelial cells using pili, proteinaceous projections on the outer surface of the bacteria. Gonococcal pili undergo both phase variation (ie, on-off expression) and antigenic variation, which rapidly alter the antigenic profile of the pilus and limit the development of long-lasting immunity against the organism. Species of N gonorrhoeae that do not express pili are unable to bind host cells and are therefore unable to cause infection. Pili for Neisseria meningitidis is less crucial for immune evasion compared to N. gonorrhoeae. Pili in Neisseria meningitidis is used for adhesion to nasopharyngeal epithelium and allows for bloodstream invasion, yet the pili in Neisseria meningitidis is not as antigenically variable as N. gonorrhoeae, so immunity can develop after infection or vaccination.
What enables Neisseria to colonize mucosal surfaces more easily that aids in mucosal adherence.
IgA protease.
Which species of Neisseria are encapsulated?
Neisseria meningitidis.
Neisseria gonorrhoeae is NOT encapsulated and instead uses lipooligosaccharides (LOS), which allows for blebbing (spreading).
What key virulence factor exists with Neisseria that prevents phagocytosis?
capsule (only Neisseria meningitidis).
What highly-inflammatory compound is possessed by Neisseria that is similar to endotoxins?
These proinflammatory agents lead to DIC (capillary leakage, fluid extravasation, hypovolemia, thrombocytopenia, and thrombosis):
- Lipooligosaccharides (LOS)
- OPA (opacity proteins)
How is Neisseria meningitidis spread?
respiratory droplets
**Use a face mask in the hospital setting for PPE. **
Where is Neisseria most commonly found?
Places that commonly experience outbreaks are college dormitories and military barracks.
What endocrine organ is commonly implicated with Neisseria meningitidis?
Adrenal glands
Adrenal involvement in meningococcemia can lead to a syndrome of adrenal insufficiency known as Waterhouse-Friderichsen syndrome.
Adrenal insufficiency → metabolic derangements → hypoglycemia, hyponatremia, HYPERkalemia.
What sequelae is commonly seen with an infection with Neisseria meningitidis?
Sequelae of Neisseria meningitidis infection include immune-complex mediated complications (e.g., pericarditis, arthritis).
What prodrome is seen with Neisseria meningitidis?
Febrile, flu-like illness with myalgias.
What can Neisseria meningitidis mimic?
Neisseria meningitidis infection can resemble strep throat by manifesting as pharyngitis.
What skin symptom suggests DIC secondary to Neisseria meningitidis?
Neisseria meningitidis infection can manifest as a petechial rash due to DIC.
Neisseria meningitidis is the _____ most common cause of bacterial meningitis.
2nd.
Streptococcus pneumoniae is usually the most common in patients older than 1 month and in neonates, Group B Streptococcus (Streptococcus agalactiae) is the most common cause.
What is an effective antibiotic against Neisseria meningitidis?
Ceftriaxone
What antibiotic is used for Neisseria meningitidis in penicillin and beta-lactam allergic patients?
Chloramphenicol
What antibiotics are used for post-exposure prophylaxis against Neisseria meningitidis?
Rifampin, ciprofloxacin, or ceftriaxone.
Ideally given within 24 hours of exposure.
Children can be given ceftriaxone or Rifampin.
Adults can receive rifampin (600 mg twice daily for two days), ciprofloxacin (single oral 500 mg dose), or ceftriaxone (single IM dose). Ciprofloxacin is not recommended for children or pregnant women due to risks of cartilage toxicity.
What antibiotics should be used for post-exposure prophylaxis against Neisseria meningitidis in children?
Drug of Choice for children:
Rifampin alternative is ceftriaxone).
Dose for older children:
10 mg/kg twice daily for two days.
Dose for infants:
5 mg/kg for infants <1 month.
What antibiotics should be used for post-exposure prophylaxis against Neisseria meningitidis in pregnancy?
Pregnant patients should be given ceftriaxone.
Azithromycin: A secondary option if ceftriaxone is contraindicated.
what are the common medications that increase susceptibility of getting meningitis by Neisseria?
Eculizumab (Soliris): Inhibits C5, blocking MAC formation; used in PNH and aHUS.
Ravulizumab: Similar mechanism to eculizumab but with longer duration of action.
Corticosteroids: High doses can transiently impair complement function.
Immunosuppressive Drugs: Rituximab, mycophenolate mofetil, and cyclophosphamide may indirectly impair complement activity.
What are the countermeasures for preventing Neisseria meningitidis when taking immunpsuppressing medications?
Vaccination: Meningococcal vaccines (MenACWY and MenB) prior to starting therapy.
How is the vaccination for Neisseria formulated?
A vaccine with capsular polysaccharides of four serotypes of meningococcus with capsular antigens linked to a carrier protein (e.g., diphtheria toxoid).
By conjugating the bacterial polysaccharides to a protein carrier, it elicits a robust T-cell-dependent response, leading to longer-lasting immunity. Conjugate vaccines also reduce nasopharyngeal carriage, contributing to herd immunity.
What serogroups does the meningococcal conjugate vaccine (MenACWY) protect against?
Serogroups A, C, W, and Y.
Administer at age 11-12 years, with a booster at 16 years. It is mandatory for military recruits and travelers to the meningitis belt of sub-Saharan Africa.
Who should receive the MenB vaccine?
Adolescents aged 16-18 years (clinical discretion) and high-risk groups (e.g., during outbreaks, individuals with complement deficiencies, or asplenia).
Serogroup B is responsible for outbreaks in developed countries, especially in close-living settings like dormitories.
What is a mnemonic to remember the Neisseria meningitidis vaccine schedule?
“11-16-Boost”:
11 years: First MenACWY dose. 16 years: Booster dose. Boost every 5 years if high-risk.
Who requires booster doses of the MenACWY vaccine?
Individuals at persistent high risk (e.g., asplenia, complement deficiencies, microbiologists exposed to N. meningitidis). Boosters are given every 5 years.
College freshmen living in dormitories are at increased risk and may also need vaccination.
What vaccination is recommended for travelers to sub-Saharan Africa?
MenACWY vaccine, as serogroup A outbreaks are common in the meningitis belt. The vaccine is required for Hajj and Umrah pilgrims in Saudi Arabia.
What is the public health strategy for managing meningococcal outbreaks?
Targeted vaccination campaigns with MenACWY or MenB vaccines based on the serogroup causing the outbreak.
Prophylactic antibiotics (e.g., rifampin, ciprofloxacin) are also used for close contacts of infected individuals.
What are the contraindications for meningococcal vaccines?
Severe allergic reaction (e.g., anaphylaxis) to a prior dose or vaccine component. Minor illnesses (e.g., cold) are not contraindications; vaccination should proceed in these cases.
What is the gram staining and morphology of Neisseria gonorrhoeae?
Gram-negative diplococci.
What type of intracellular presence does Neisseria gonorrhoeae exhibit?
Facultative intracellular within polymorphonuclear cells (PMNs).
Is Neisseria gonorrhoeae encapsulated?
No, Neisseria gonorrhoeae is not encapsulated.
How is Neisseria gonorrhoeae transmitted?
Sexually transmitted infection (STI).
What is the significance of asymptomatic carriers in Neisseria gonorrhoeae infection?
They can transmit the infection without showing symptoms.
How can Neisseria gonorrhoeae affect newborns?
It can be transmitted during birth, causing neonatal eye infections (ophthalmia neonatorum).
What are common manifestations of Neisseria gonorrhoeae in men?
Urethritis, prostatitis, and epididymitis.
What are common manifestations of Neisseria gonorrhoeae in women?
Cervicitis, pelvic inflammatory disease (PID), and salpingitis.
Intermenstrual bleeding, such as post-coital spotting, is an alarming symptom of gonococcal cervicitis
What is the name of the syndrome associated with liver capsule inflammation due to Neisseria gonorrhoeae?
Fitz-Hugh-Curtis syndrome.
What are symptoms of disseminated gonococcal infection?
Purulent arthritis, tenosynovitis, and dermatitis.
Purulent arthritis of the knee (cloudy fluid with a leukocyte count of more that 20,000/mm^3 with 75% neutrophils), oligoarticular joint pain (monoarthritis or asymmetric polyarthritis) or tenosynovitis, and vesiculopustular skin lesions on the extremities, raises suspicion for disseminated gonococcal infection, which is one of the most common causes of septic arthritis in young, sexually active individuals. It is due to the spread of Neisseria gonorrhea from a (usually asymptomatic) genitourinary infection into the systemic circulation. Patients typically present with either purulent arthritis or the triad of polyarthralgia, dermatitis, and tenosynovitis; however, some overlap in these 2 syndromes can occur. Perform an arthrocentesis and gram stain sample with microscopy (can be of blood, urine, or joint fluid sample), which usually reveals gram-negative intracellular diplococci. Treatment is with IV ceftriaxone plus azithromycin or doxycycline (covers concomitant Chlamydia).
What diagnostic test is preferred for Neisseria gonorrhoeae?
Nucleic acid amplification testing (NAAT).
What is the drug of choice for treating Neisseria gonorrhoeae?
Ceftriaxone.
Why is doxycycline or a macrolide added to Neisseria gonorrhoeae treatment?
To cover potential Chlamydia co-infection.
If Chlamydia is negative following lab results, only treat Neisseria.
What preventive method is emphasized for Neisseria gonorrhoeae?
Consistent condom use.
What area is commonly implicated by disseminated gonococcal infection?
Achilles tendon.
What is the morphology and Gram-staining of Moraxella catarrhalis?
Moraxella catarrhalis is a Gram-negative diplococcus.
Where does Moraxella catarrhalis commonly colonize?
M. catarrhalis commonly colonizes the nasopharynx.
What test results are characteristic of Moraxella catarrhalis?
M. catarrhalis is an aerobic bacteria that is catalase-positive, oxidase-positive, and forms biofilms.
The “hockey puck sign” refers to the smooth sliding of colonies across agar when nudged with a loop.
What enzyme does Moraxella catarrhalis produce that enhances antibiotic resistance?
M. catarrhalis produces beta-lactamase, which breaks down beta-lactam antibiotics.
What are common infections caused by Moraxella catarrhalis?
Otitis media (especially in children)
Bacterial sinusitis
COPD exacerbations (bronchopneumonia in adults)
What are the treatments of choice for Moraxella catarrhalis infections?
Cephalosporins
Amoxicillin-clavulanate
Trimethoprim-sulfamethoxazole (TMP-SMX)
Fluoroquinolones
Which 2 bacteria are the most common causes of pelvic inflammatory disease (PID)?
Chlamydia trachomatis (subacute; often undiagnosed)
Neisseria gonorrhoeae (acute)
If gonorrhea/chlamydia is suspected, then treat _________ .
empirically
Standard STI screening panel for common infections in both men & women includes:
Neisseria gonorrhea
Chlamydia trachomatis
HIV
Treponema pallidum
What is the outpatient treatment regimen for pelvic inflammatory disease (PID)?
IM ceftriaxone (or other cephalosporin)
Oral doxycycline
Oral metronidazole
What type of bacteria is Haemophilus influenzae?
Haemophilus influenzae is a gram-negative coccobacillus.
What are the growth requirements for Haemophilus influenzae?
It requires chocolate agar enriched with factor V (NAD) and factor X (hemin).
How is Haemophilus influenzae transmitted?
It is transmitted via respiratory droplets (aerosol transmission).
What gives Haemophilus influenzae its pathogenicity?
Haemophilus influenzae is a gram-negative coccobacillus that can be either encapsulated (serotypes a-f) or unencapsulated (nontypeable). H influenzae type b (Hib) is the most invasive strain due to its polyribosy|ribitol phosphate (PRP) capsule, which inhibits complement-mediated phagocytosis and allows it to invade tissues and survive in the bloodstream.
What are the TOP TWO diseases caused by Haemophilus influenzae type B?
- Diseases caused by the encapsulated (type B) Haemophilus influenzae bacteria can range from meningitis, epiglottitis, otitis media, pneumonia, septic arthritis.
- The top two diseases caused by Haemophilus influenzae type B are meningitis and epiglottitis. Common symptoms of meningitis caused by Haemophilus influenzae include headache, neck stiffness, photophobia, nausea, and vomiting. Symptoms for epiglottitis include rapidly progressive high fever, toxic appearance, dysphagia, dysphonia, drooling, and a cherry red epiglottis. These patients tend to position themselves in a sniffing or tripod position. These patients tend to have stridor (high-pitch on inspiration).
- These diseases and their considerations are important when children are not vaccinated. The Nontypeable Haemophilus influenzae illnesses are acute otitis media, conjunctivitis, sinusitis, pneumonia and the Hib vaccine does do not help prevent these injections. Also, the most common pathogens that cause conjunctivitis, acute otitis media, and sinusitis are Streptococcus pneumonia, Moraxella catarrhalis, and Nontypeable Haemophilus influenzae.
Is Haemophilus influenzae the most common cause of epiglottitis or otitis media?
No, infection of the ear canal (otitis media) or the aryepiglottic area (epiglottitis) is most commonly secondary to Streptococcus pneumoniae due to increased vaccination compliance against Haemophilus influenzae type b. Children who get epiglottitis secondary to Haemophilus influenzae infection are likely unvaccinated and might have other missing vaccines. The most common causes of epiglottitis and otitis media is pneumococcus. The other causes are from Staphylococcus aureus and Group A Streptococcus.
How is epiglottitis managed?
Manage airway and intubate (endotracheal intubation) if needed.
Antibiotics:
Augmentin (Amox-Clav) –> covers Haemophilus influenzae
Vancomycin or Ceftriaxone –> covers most other bacteria (including Haemophilus influenzae)
Is Racemic Epinephrine Used in Epiglottitis?
No, racemic epinephrine is NOT effective for epiglottitis and is NOT part of standard management. Racemic epinephrine works by reducing subglottic swelling (e.g., in croup), but epiglottitis is a supraglottic disease caused by a swollen, inflamed epiglottis. Instead, after securing the airway, initiate antibiotic therapy, such as, IV Ceftriaxone or Cefotaxime (3rd-gen cephalosporins), which covers H. influenzae type B (Hib) and other bacterial causes. Give IV Vancomycin (if MRSA is suspected, though rarely needed). IV fluids is usually initiated if the patient is dehydrated from drooling. Finally provide humidified oxygen the patient remains hypoxia and dexamethasone can be given as optional treatment to reduce airway swelling, but is only used in some cases.
What prophylactic treatment is recommended for close contacts of patients diagnosed with What prophylaxis is recommended for close contacts of Haemophilus influenzae type b infections (epiglottitis, otitis media, or meningitis, secondary to Haemophilus influenzae type b)?
Rifampin prophylaxis.
When is the first vaccination for Hib given?
The Hib vaccine is administered beginning at age 2 months to provide continued immunity. The immunization is composed of PRP conjugated with a protein toxoid (eg, tetanus, diphtheria), which induces a T cell-dependent immune response. The production of opsonizing anticapsular antibodies by B-lymphocytes allows for efficient phagocytosis of the bacterium. Without the protection from the vaccine, children are at risk for invasive disease caused by Hib, such as meningitis, bacteremia, pneumonia, and epiglottitis.
How are neonates protected from Haemophilus influenzae?
Passive immunity
During the first months of life, transient immunity to Hib is accomplished by IgG antibodies acquired transplacentally from the mother while in utero.
Acinetobacter baumannii most commonly affects … ?
hospitalized patients
patients usually develop pneumonia or bacteremia
Why is Acinetobacter baumannii hard to treat?
often this bacteria multidrug resistant
How is Acinetobacter baumannii treated?
carbapenem
polymyxin
cefepime
What is Acinetobacter baumannii?
- Gram-negative opportunistic pathogen causing nosocomial infections
- Non-lactose fermenting
- Oxidase-negative coccobacillus
How does Acinetobacter baumannii appear on Gram stain?
It appears as short, gram-negative coccobacilli, often in pairs or clusters.
What types of infections does Acinetobacter baumannii commonly cause?
Pneumonia (especially ventilator-associated pneumonia), bloodstream infections, urinary tract infections, wound infections, and meningitis (especially in post-neurosurgical patients).
Why is Acinetobacter baumannii significant in hospital settings?
It is highly resistant to multiple antibiotics and can survive on surfaces for long periods, leading to outbreaks in ICUs.
What is the primary mode of transmission for Acinetobacter baumannii?
It spreads via contaminated hospital equipment, hands of healthcare workers, and environmental surfaces.
What is the preferred treatment for Acinetobacter baumannii infections?
- Carbapenems (e.g., meropenem) are often used, but resistance is common.
- Colistin, polymyxins, or tigecycline may be needed for multidrug-resistant strains.
What are the risk factors for Acinetobacter baumannii infection?
Mechanical ventilation, prolonged hospital stay, prior antibiotic use, immunosuppression, trauma, and invasive devices (e.g., catheters, endotracheal tubes).
How does Acinetobacter baumannii develop antibiotic resistance?
Through beta-lactamase production, efflux pumps, porin mutations, and enzymatic modification of antibiotics.
What infection control measures are necessary to prevent Acinetobacter outbreaks?
Strict hand hygiene, contact precautions, environmental disinfection, and antimicrobial stewardship programs.
Why is Acinetobacter baumannii a major concern in combat and disaster medicine?
It has been associated with infections in military personnel and disaster victims due to its ability to survive harsh environments and resist multiple antibiotics.
