Gram-negative coccobacilli
Haemophilus influenzae:
Haemophilus influenzae is a bacterial cause of pneumonia, and it can also cause bacterial meningitis and epiglottitis. It is Gram-negative, non-motile, a tiny pleomorphic coccobacillus, a facultative anaerobe, pathogenic, and a capnophile, meaning that it loves CO2. It is a member of the Pasteurellaceae family. This mesophilic bacterium thrives at temperatures ranging between 35-37 degrees Celsius. It contains pili, or hairlike fimbriae over its surface, which enable it to "stick" to mucosal surfaces, colonizing the human nasopharynx. They possess the ability to form biofilms, enabling them to cause middle ear and lower respiratory infections. Most strains are part of the normal human microflora of the upper and lower respiratory tract, urogenital tract, and conjunctivae.
This bacterium can cause local and systemic infections, and in addition to pneumonia and meningitis, can get into the bloodstream, causing bacteremia and sepsis. Occasionally, it is associated with cellulitis, osteomyelitis, infectious arthritis, and neonatal infection. Penicillin or augmentin are the treatments of choice in mild cases. Beginning in the 1980's, a vaccine was developed, known as the Hib vaccination, given to infants to help prevent meningitis caused by this organism and its consequences, including hearing loss, brain damage, and even death. It was the very first organism whose entire genome was sequenced.
This bacterium can cause local and systemic infections, and in addition to pneumonia and meningitis, can get into the bloodstream, causing bacteremia and sepsis. Occasionally, it is associated with cellulitis, osteomyelitis, infectious arthritis, and neonatal infection. Penicillin or augmentin are the treatments of choice in mild cases. Beginning in the 1980's, a vaccine was developed, known as the Hib vaccination, given to infants to help prevent meningitis caused by this organism and its consequences, including hearing loss, brain damage, and even death. It was the very first organism whose entire genome was sequenced.
Haemophilus influenzae is a facultative anaerobic, oxidase positive, Gram-negative coccobacillus that produces glistening, umbonate orange-tan colonies with raised centers on chocolate agar(8)(9)(10). It grows at 35-37 degrees Celsius, and is a fastidious organism, requiring CO2, factor X (hemin) and factor V (NAD) for growth.
Haemophilus influenzae can cause respiratory tract infections including pneumonia, otitis media (middle ear infection), epiglottitis (swelling of the epiglottis in the back of the throat), eye infections (conjunctivitis), bloodstream infections (bacteremia and sepsis), and bacterial meningitis. Other infections it has been linked to include cellulitis (skin infection) and infectious arthritis (inflammation of the joint).
Treatment is typically with Ceftriaxone or Cefotaxime.
Haemophilus influenzae can cause respiratory tract infections including pneumonia, otitis media (middle ear infection), epiglottitis (swelling of the epiglottis in the back of the throat), eye infections (conjunctivitis), bloodstream infections (bacteremia and sepsis), and bacterial meningitis. Other infections it has been linked to include cellulitis (skin infection) and infectious arthritis (inflammation of the joint).
Treatment is typically with Ceftriaxone or Cefotaxime.
Pasteurella multocida:
Pasteurella multocida is a facultative anaerobic, Gram-negative, pleomorphic coccobacillus/rod that exhibits bipolar staining at times, and can resemble a safety pin(1). It is catalase +, oxidase +, indole +, and nonmotile(5). It is susceptible to Penicillin, Nalidixic Acid and Tetracycline. It grows well on blood or chocolate agar at 37 degrees Celsius, but does not grow on MacConkey agar. Colonies are white, cream or translucent, mucoid, and glistening. They sometimes produce a "mousy" odor as well as it metabolizes nutrients and breaks molecules down, resulting in waste products. The best and most accurate means of identifying this bacterium is PCR (polymerase chain reaction)(7). Mass spectrophotometry and ID cards are also very accurate.
Because it can be carried by domestic dogs and cats and poultry, it can causes zoonosis infections in humans who have received bite or scratch wounds from infected animals. Wound infections are the most common infection produced by this bacteria, and can progress to cellulitis and lymphadenopathy(3). Inflammation of the soft tissue typically reveals itself within 24 hours following a bite. On the CBC, you can expect to see elevated levels of neutrophils and lymphocytes. Severe cases can lead to bacteremia and can spread further into the bone, resulting in osteomyelitis. If the bacteria travel to the heart, it can cause bacterial endocarditis. In addition to these infections, it has also been linked to pneumonia in patients, especially if they are immunocompromised. This bacteria can also cross the blood-brain barrier and cause meningitis, resulting in confusion, headache, nausea, vomiting, fatigue and stiff neck(5). B-lactams, fluoroquinolones, tetracycline are all excellent treatments, but the most effective antibiotic is amoxicillin-clavulanate(6).
Because it can be carried by domestic dogs and cats and poultry, it can causes zoonosis infections in humans who have received bite or scratch wounds from infected animals. Wound infections are the most common infection produced by this bacteria, and can progress to cellulitis and lymphadenopathy(3). Inflammation of the soft tissue typically reveals itself within 24 hours following a bite. On the CBC, you can expect to see elevated levels of neutrophils and lymphocytes. Severe cases can lead to bacteremia and can spread further into the bone, resulting in osteomyelitis. If the bacteria travel to the heart, it can cause bacterial endocarditis. In addition to these infections, it has also been linked to pneumonia in patients, especially if they are immunocompromised. This bacteria can also cross the blood-brain barrier and cause meningitis, resulting in confusion, headache, nausea, vomiting, fatigue and stiff neck(5). B-lactams, fluoroquinolones, tetracycline are all excellent treatments, but the most effective antibiotic is amoxicillin-clavulanate(6).
References:
1. Kuhnert P; Christensen H, eds. (2008). Pasteurellaceae: Biology, Genomics and Molecular Aspects. Caister Academic Press. ISBN 978-1-904455-34-9.
2. Casolari C, Fabio U. Isolation of Pasteurella multocida from Human Clinical Specimens: First Report in Italy. European Journal of Epidemiology. Sept 1988; 4(3):389-90
3. Ryan KJ; Ray CG, eds. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9.
4. Boyce JD, Adler B: The capsule is a virulence determinant in the pathogenesis of Pasteurella multocida M1404 (B:2). Infect Immun 2000, 68(6):3463-3468.
5. Casolari C, Fabio U. Isolation of Pasteurella multocida from Human Clinical Specimens: First Report in Italy. European Journal of Epidemiology. Sept 1988; 4(3):389-90
6. Red Book: 2006 Report of the Committee on Infectious Diseases - 27th Ed.
7. Miflin, J.K. and Balckall, P.J. (2001) Development of a 23 SrRNA-based PCR assay for the identification of Pasteurella multocida. Lett. Appl. Microbiol. 33: 216-221
8. https://www.cdc.gov/meningitis/lab-manual/chpt09-id-characterization-hi.pdf
9. Clinical Microbiology Procedures Handbook, 3rd edition. 2010. ASM. Washington, D.C. 2,540 pages
10. Murray, P. R., E. J. Baron, J. H. Jorgensen, M. L. Landry, and M. A. Pfaller (ed.). 2007. Manual of Clinical Microbiology, 9th ed, vol. ASM Press, Washington, D. C
2. Casolari C, Fabio U. Isolation of Pasteurella multocida from Human Clinical Specimens: First Report in Italy. European Journal of Epidemiology. Sept 1988; 4(3):389-90
3. Ryan KJ; Ray CG, eds. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9.
4. Boyce JD, Adler B: The capsule is a virulence determinant in the pathogenesis of Pasteurella multocida M1404 (B:2). Infect Immun 2000, 68(6):3463-3468.
5. Casolari C, Fabio U. Isolation of Pasteurella multocida from Human Clinical Specimens: First Report in Italy. European Journal of Epidemiology. Sept 1988; 4(3):389-90
6. Red Book: 2006 Report of the Committee on Infectious Diseases - 27th Ed.
7. Miflin, J.K. and Balckall, P.J. (2001) Development of a 23 SrRNA-based PCR assay for the identification of Pasteurella multocida. Lett. Appl. Microbiol. 33: 216-221
8. https://www.cdc.gov/meningitis/lab-manual/chpt09-id-characterization-hi.pdf
9. Clinical Microbiology Procedures Handbook, 3rd edition. 2010. ASM. Washington, D.C. 2,540 pages
10. Murray, P. R., E. J. Baron, J. H. Jorgensen, M. L. Landry, and M. A. Pfaller (ed.). 2007. Manual of Clinical Microbiology, 9th ed, vol. ASM Press, Washington, D. C