eMedicine Specialties > Infectious Diseases > Bacterial Infections

Haemophilus Influenzae Infections: Differential Diagnoses & Workup

Author: Vidya R Devarajan, MD,
Contributor Information and Disclosures

Updated: Aug 12, 2008

Differential Diagnoses

Bronchitis

Other Problems to Be Considered

Otitis media
Epiglottitis

Workup

Laboratory Studies

  • Gram stain: Test results on body fluids from various sites of infection that reveal small, gram-negative, pleomorphic coccobacilli with polymorphonuclear cells are strong evidence of infection.
  • Bacterial culture  
    • Detection of the organism in a blood culture or any other body fluid is the most confirmatory method of establishing the diagnosis.
    • Slide agglutination with type-specific antisera is used for serotyping H influenzae. In one study, molecular typing with PCR was found to be more accurate than slide agglutination serotyping.6
    • Seventy to 90% of patients with epiglottitis have positive blood culture results. However, to avoid laryngospasm, perform venipuncture and cultures of the inflamed epiglottitis only after the airway has been secured.
  • Immunologic studies  
    • Detection of the PRP polysaccharide capsule via countercurrent immunoelectrophoresis, latex particle agglutination, co-agglutination, and enzyme-linked immunosorbent assay is an important adjunct to culturing in establishing a rapid diagnosis.
    • Even if antibiotics were previously administered, the diagnosis can be confirmed based on the detection of the polysaccharide capsule in body fluids, including serum, CSF, urine, and pleural, pericardial, and articular fluid. False-positive results in CSF are rare but occur with serum or urine because of nonspecific agglutination and antigenic cross-reactivity with other bacteria.
  • CSF features  
    • In meningitis, the CSF examination demonstrates pleocytosis (mean, 4000-5000 WBCs/µL) with a predominance of neutrophils.
    • Decreased CSF glucose levels are encountered in 75% of patients, increased CSF protein levels and detectable capsular antigen in 90%, and a positive CSF Gram stain result in 80%.
    • Prior antibiotic treatment significantly decreases the H influenzae type b (Hib) concentration in the CSF and decreases the sensitivity of the Gram stain; however, antibiotics do not substantially affect the total CSF blood cell count, differential, chemistries, and presence of the PRP capsule in pretreated patients.
  • Blood cell counts: Perform blood cell counts for anemia, leukocytosis, and thrombocytosis or thrombocytopenia.
  • Acute phase reactants: Elevated erythrocyte sedimentation rates (ESRs) and C-reactive protein levels are characteristically observed in patients with septic arthritis.

Imaging Studies

  • CT scanning  
    • In meningitis, a CT scan of the head is not required routinely unless focal neurologic findings are present or clinical response is lacking after 3 days' administration of appropriate antibiotics. In these situations, a head CT scan helps identify subdural effusion.
    • In patients with orbital cellulitis, a CT scan of the head is useful in delineating the extent of the lesion.
  • Chest radiography  
    • Patients with Hib pneumonias tend to have more pleural and pericardial involvement (50% of patients) than those with other bacterial pneumonias.
    • Community-acquired pneumonias due to NTHi are characterized by alveolar infiltrates in patchy or lobar distributions.
  • Lateral neck radiography  
    • In epiglottitis, a lateral neck radiograph reveals dilatation of the hypopharynx and a swollen epiglottis (termed the thumbprint sign). In addition, the cervical spine is usually straightened.
    • If epiglottitis is clinically suspected, obtain radiography only if a functional airway is guaranteed.
  • Echocardiography: Obtain this when pericarditis is suspected.

Other Tests

  • In patients with cellulitis, direct aspiration of the soft tissue or aspiration after injecting the subcutaneous tissue with sterile nonbacteriostatic solution can be used to detect the organisms via Gram stain and culture.

Procedures

  • Perform a lumbar puncture when meningitis is suspected.
  • The following invasive procedures can be used to obtain appropriate fluid and to establish an etiologic diagnosis:  
    • Bronchoscopy
    • Joint, lung, sinus, and soft-tissue aspiration
    • Transtracheal aspiration
    • Tympanocentesis
    • Pericardiocentesis
  • In women, obtain tubal cultures via laparoscopy and peritoneal fluid cultures by culdocentesis for NTHi.
  • In patients with epiglottitis, use endotracheal intubation or tracheostomy to secure an airway.

More on Haemophilus Influenzae Infections

Overview: Haemophilus Influenzae Infections
Differential Diagnoses & Workup: Haemophilus Influenzae Infections
Treatment & Medication: Haemophilus Influenzae Infections
Follow-up: Haemophilus Influenzae Infections
References
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Further Reading

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Keywords

Haemophilus influenzae infection , Hib infection, H influenzae, Haemophilus influenzae type b , H influenzae type b, Haemophilus flu, Weeks bacillus, influenza bacillus, bacteremia, Hib occult bacteremia, Hib meningitis, Hib cellulitis, Hib pericarditis, Hib epiglottitis, Hib septic arthritis, Hib pneumonia, Hib empyema, Hib otitis media, Hib conjunctivitis, Hib bronchitis, Hib pneumonia, Hib neonatal sepsis, Hib maternal sepsis, Hib endophthalmitis, Hib urinary tract infection, Hib cervical adenitis, Hib glossitis, Hib osteomyelitis, Hib endocarditis, mucosal infections, Haemophilus aegyptius, H aegyptius, Hib conjugate vaccine, nonencapsulated H influenzae infections, nontypeable H influenzae, NTHi , Haemophilus influenzae type a, Hia

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Contributor Information and Disclosures

Author

Vidya R Devarajan, MD, 
Disclosure: Nothing to disclose.

Medical Editor

Wesley W Emmons, MD, FACP, Assistant Professor, Department of Medicine, Thomas Jefferson University; Consulting Staff, Infectious Diseases Section, Department of Internal Medicine, Christiana Care, Newark, DE
Wesley W Emmons, MD, FACP is a member of the following medical societies: American College of Physicians, American Medical Association, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, and International AIDS Society
Disclosure: Nothing to disclose.

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Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
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Managing Editor

Charles V Sanders, MD, Edgar Hull Professor and Chairman, Department of Internal Medicine, Professor of Microbiology, Immunology and Parasitology, Louisiana State University School of Medicine at New Orleans; Medical Director, Medicine Hospital Center, Charity Hospital and Medical Center of Louisiana at New Orleans; Consulting Staff, Ochsner Medical Center
Charles V Sanders, MD is a member of the following medical societies: Alliance for the Prudent Use of Antibiotics, Alpha Omega Alpha, American Association for the Advancement of Science, American Association of University Professors, American Clinical and Climatological Association, American College of Physician Executives, American College of Physicians, American Federation for Medical Research, American Foundation for AIDS Research, American Geriatrics Society, American Lung Association, American Medical Association, American Society for Microbiology, American Thoracic Society, American Venereal Disease Association, Association for Professionals in Infection Control and Epidemiology, Association of American Medical Colleges, Association of American Physicians, Association of Professors of Medicine, Infectious Disease Society for Obstetrics and Gynecology, Infectious Diseases Society of America, Louisiana State Medical Society, Orleans Parish Medical Society, Royal Society of Medicine, Sigma Xi, Society of General Internal Medicine, Southeastern Clinical Club, Southern Medical Association, Southern Society for Clinical Investigation, and Southwestern Association of Clinical Microbiology
Disclosure: Nothing to disclose.

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

 
 
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