Fastidious bacteria require very specific conditions such as specialized media composition, temperature and concentration of carbon dioxide or oxygen for growth.
Bacteria that are difficult to maintain in the laboratory conditions as they have very specific and complex requirements are called fastidious bacteria. This is due to their highly specific habitat conditions and the difficulty to mimic those conditions, in-vitro.
Fastidious bacteria are naturally present in the environment as well but they are not as widely spread as the non-fastidious ones. Some examples of fastidious bacteria are mentioned below.
- Bordetella SP.
- Francisella tularensis
- Helicobacter pylori
- Legionella pneumophila
- Leuconostoc mesenteroides
- Neisseria gonorrhoeae
- Paenibacillus popilliae
- Streptococcus pneumoniae
- Treponema pallidum
- Ureaplasma urealyticum
In laboratories, growth of Bordetella henselae gets restricted not only by the several usual constituents of media but also by their own metabolic products. Supplementing, Bordet-Gengou media with activated charcoal or starch allows the bacterium to grow by absorbing suh components from the media.
Francisella tularensis are soönotiese bacteria. It is capable of surviving in phagocytic cells and convert it into phagolysosome. It grows better in liquid media and has a long incubation time. It is generally grown on blood containing media of which cysteine and histone is an important component.
Helicobactor pylori has some special properties that allow them to persist in low pH environment. It contains urease enzyme which maintains a pH neutral microenvironment for the bacteria in stomach where the pH is low.
In laboratories, they are generally grown on agar plates of 7 to 10% blood or lysed blood containing media such Brucella agar or Columbia agar. They show optimum growth at 35°C–37°C and in a carbon dioxide enriched (around 5 to 10%) atmosphere.
Lactobacillus are fermentative acidophiles. They are found in carbohydrate rich environments, that produce lactic acid, acetic acid, ethanol and carbon dioxide by fermenting hexose sugar. They are also found in spoiled food, milk and other beverages.
In laboratories, they grow best in MRS (deMan, Rogosa and Sharpe media) broth media.
Leginonella penumophila are obligate aerobes that are generally found in all kinds of aquatic bodies. They are found in water bodies containing algae, rust, sludge and other organic compounds, where they form biofilms.
They are grown on buffered charcoal yeast extract media at an optimal pH of 6.3 and temperature of 25°C-50°C. Cysteine and iron are crucial to its growth. Presence of charcoal and starch in the media can improve the growth by absorbing the toxic substances such as fatty acids.
Leuconostoc mesenteroides are heterofermentative lactic acid bacteria that grow in specific conditions. They undergo fermentasie to produce dextran. They require low temperature of 10°C to 30°C, high salinity and hyperglycemic conditions for growth.
They can spoil preserved food as well and pose a huge concern in the food industry. They can be cultured in MRS, skim milk and tomato juice agar media, supplemented with sucrose.
Mycoplasma are cell wall lacking bacteria of which the hemotropic mycoplasma are extremely difficult to culture in in-vitro conditions. Mycoplasma live as commensals in the mucosal membranes.
Lack of cell wall infers to them resistant to anti-microbial agents. They grow on cellular media for optimal growth.
Neisseria gonorrhoeae are obligate pathogens of Homo sapiens. In laboratories, they are cultured on the petri-plates of chocolate agar media containing hemoglobin, as it is difficult to cultivate in liquid medium.
Paenibacillus popilliae are another fastidious bacteria found in the insect host of family Scarabaeidae, such as Japanese beetle. They grow well in MYPGP agar supplemented with vankomisien, brain heart infusion growth media, Columbia blood agar media.
Vitamins such are thiamine and barbituric acid are important for in vitro growth. Trehalose sugar is critical for their growth as it is also found in the insect hemolymph and helps mimic the original growth environment.
Streptococcus pneumoniae are pre-dominantly found in the mucosal layer of the respiratory system. They show optimum growth at 35°C-37°C temperature and 5% carbon dioxide. They can be cultured on both blood agar medium and chocolate agar medium.
Streptococcus pyogenes is a facultative anaerobe. Streptococcus pyogenes grow well on blood agar media. Media containing 5% sheep blood agar and trypticase soy base that has been incubated in air is one of the most preferred culture media for these bacterium.
They show optimum growth at 35°C to 37°C and 5% carbon dioxide concentration as well.
Treponema pallidum is a spirochete and their only known source are Homo sapiens. The pathogenic strains of the bacterium are recalcitrant to normal culture media used in laboratories and are usually maintained in the testes of rabbits.
To reduce the damage to the testicular tissues by lipid peroxidation, media is generally supplemented with free radical traps such as sulfhydryl compounds.
Ureaplasma urealyticum belong to a group of cell wall lacking bacteria called mycoplasma. They possess urease enzyme which allows it to undertake urea hydrolysis and produce adenosientrifosfaat or ATP. Hence, it requires either broth or agar medium containing urea to grow on, in vitro.
Fastidious bacteria need very specific media composition, temperature, pH, carbon dioxide and oxygen concentrations as they exist in very few and very specific natural habitats. Thus many bacteria, specially those that are pathogenic, are difficult to grow in laboratory conditions.