Sputum Gram stain at 1000x magnification. The sputum is from a person with<unk>  pneumonia, and the Gram negative coccobacilli are visible with a background of neutrophils. X and V factors for growth. In this culture,<unk>  has only grown around the paper disc that has been impregnated with X and V factors. No bacterial growth is seen around the discs that only contain either X or V factor. Chest X-ray of a case of<unk> , presumably as a secondary infection from<unk>  It shows patchy consolidations, mainly in the right upper lobe (arrow). Chest X-ray in a case of COPD exacerbation where a nasopharyngeal swab detected<unk> : Opacities (on the patient's right side) can be seen in other types of pneumonia, as well. Clinical features may include initial symptoms of an upper respiratory tract infection mimicking a viral infection, usually associated with fevers, often low-grade. This may progress to the lower respiratory tract in a few days, with features often resembling those of wheezy bronchitis. Sputum may be difficult to expectorate and is often grey or creamy in color. The cough may persist for weeks without appropriate treatment. Many cases are diagnosed after presenting chest infections that do not respond to penicillins or first-generation cephalosporins. A chest X-ray can identify alveolar consolidation. Clinical diagnosis of H.<unk>  is typically performed by bacterial culture or latex particle agglutinations. Diagnosis is considered confirmed when the organism is isolated from a sterile body site. In this respect, H.<unk>  cultured from the nasopharyngeal cavity or sputum would not indicate H.<unk>  disease, because these sites are colonized in disease-free individuals. However, H.<unk>  isolated from cerebrospinal fluid or blood would indicate H.<unk>  infection. Culture Bacterial culture of H.<unk>  is performed on agar plates, the preferable one being chocolate agar, with added X (hemin) and V (nicotinamide adenine dinucleotide) factors at 37 °C in a CO2-enriched incubator. Blood agar growth is only achieved as a satellite phenomenon around other bacteria. Colonies of H.<unk>  appear as convex, smooth, pale, grey, or transparent colonies. Gram stained and microscopic observation of a specimen of H.<unk>  will show Gram-negative coccobacillus. The cultured organism can be further characterized using catalase and oxidase tests, both of which should be positive. Further serological testing is necessary to distinguish the capsular polysaccharide and differentiate between H.<unk>  b and nonencapsulated species. Although highly specific, bacterial culture of H.<unk>  lacks sensitivity. Use of antibiotics prior to sample collection greatly reduces the isolation rate by killing the bacteria before identification is possible. Beyond this, H.<unk>  is a finicky bacterium to culture, and any modification of culture procedures can greatly reduce isolation rates. Poor quality of laboratories in developing countries has resulted in poor isolation rates of H.<unk> .. Recent work has shown that H.influenzae uses a highly specialised spectrum of nutrients where lactate is a preferred carbon source. H.<unk>  will grow in the hemolytic zone of Staphylococcus aureus on blood agar plates; the hemolysis of cells by S. aureus releases factor V which is needed for its growth. H.<unk>  will not grow outside the hemolytic zone of S. aureus due to the lack of nutrients such as factor V in these areas. Fildes agar is best for isolation. In Levinthal medium, capsulated strains show distinctive iridescence. Latex particle agglutination The latex particle agglutination test (LAT) is a more sensitive method to detect H.<unk>  than is culture. Because the method relies on antigen rather than viable bacteria, the results are not disrupted by prior antibiotic use. It also has the added benefit of being much quicker than culture methods. However, antibiotic sensitivity testing is not possible with LAT alone, so a parallel culture is necessary. Molecular methods Polymerase chain reaction (PCR) assays have been proven to be more sensitive than either LAT or culture tests, and highly specific. However, PCR assays have not yet become routine in clinical settings. Countercurrent immunoelectrophoresis has been shown to be an effective research diagnostic method but has been largely supplanted by PCR.
Haemophilus influenzae
Bordetella pertussis
Streptococcus bovis
Neisseria meningitidis
Bacillus anthracis
Rhodococcus equi
Bordetella bronchiseptica
Streptococcus pyogenes