A sputum culture is a

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

to detect and identify

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

that infect the

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of ...

s or breathing passages.

Sputum Sputum is mucus that is coughed up from the lower airways (the trachea and bronchi). In medicine, sputum samples are usually used for a naked eye examination, microbiological investigation of respiratory infections and cytological investigatio ...

is a thick fluid produced in the lungs and in the adjacent airways. Normally, fresh morning sample is preferred for the bacteriological examination of sputum. A sample of sputum is collected in a sterile, wide-mouthed, dry, leak-proof and break-resistant plastic-container and sent to the laboratory for testing. Sampling may be performed by sputum being expectorated (produced by coughing), induced (saline is sprayed in the lungs to induce sputum production), or taken via an endotracheal tube with a

protected specimen brush In medicine, sampling is gathering of matter from the body to aid in the process of a medical diagnosis and/or evaluation of an indication for treatment, further medical tests or other procedures. In this sense, the sample is the gathered matter ...

(commonly used on patients on respirators) in an intensive care setting. For selected organisms such as Cytomegalovirus or " Pneumocystis jiroveci" in specific clinical settings (immunocompromised patients) a bronchoalveolar lavage might be taken by an experienced pneumologist. If no bacteria or fungi grow, the

culture Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups ...

is negative. If organisms that can cause the

infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...

(

Pathogenicity In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a ge ...

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...

s) grow, the culture is positive. The type of bacterium or fungus is identified by

microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...

colony morphology In microbiology, colonial morphology refers to the visual appearance of bacterial or fungal colonies on an agar plate. Examining colonial morphology is the first step in the identification of an unknown microbe. The systematic assessment of the c ...

and biochemical tests of bacterial growth. If bacteria or fungi that can cause infection grow in the culture, other tests can determine which

antimicrobial agent An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ...

will most effectively treat the infection. This is called susceptibility or sensitivity testing. In a hospital setting, a sputum culture is most commonly ordered if a patient has a

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severit ...

. The

Infectious Diseases Society of America The Infectious Diseases Society of America (IDSA) is a medical association representing physicians, scientists and other health care professionals who specialize in infectious diseases. It was founded in 1963 and is based in Arlington, Virginia. ...

recommends that sputum cultures be done in pneumonia requiring hospitalization, while the

American College of Chest Physicians The American College of Chest Physicians (CHEST) is a medical association in the United States consisting of physician A physician (American English), medical practitioner (Commonwealth English), medical doctor, or simply doctor, is a ...

does not. One reason for such a discrepancy is that normal, healthy lungs have bacteria, and sputum cultures collect both normal and pathogenic bacteria. However, pure cultures of common respiratory pathogens in the absence of upper respiratory flora combined with symptoms of respiratory distress provides strong evidence of the infectious agent, and its significance. Such pathogens include ''

Streptococcus pneumoniae ''Streptococcus pneumoniae'', or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic (under aerobic conditions) or beta-hemolytic (under anaerobic conditions), aerotolerant anaerobic member of the genus Streptococcus. They ar ...

'', ''

Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bact ...

'' and the highly infectious ''

M tuberculosis ''Mycobacterium tuberculosis'' (M. tb) is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. First discovered in 1882 by Robert Koch, ''M. tuberculosis'' has an unusual, waxy coating on its c ...

'', which are transmitted by inhaling aerosols. For this reason, laboratory processing of sputum for respiratory pathogens are performed with the aid of a

biological safety cabinet A biosafety cabinet (BSC)—also called a biological safety cabinet or microbiological safety cabinet—is an enclosed, ventilated laboratory workspace for safely working with materials contaminated with (or potentially contaminated with) pathog ...

References

{{DEFAULTSORT:Sputum Culture Medical tests Bacteriology