An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection.
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 severity of the condition is variable.
Sputum is mucus that is coughed up from the lower airways. In medicine, sputum samples are usually used for naked eye exam, microbiological investigations of respiratory infections and cytological investigations of respiratory systems. It is critical that the patient not give a specimen that includes any mucoid material from the interior of the nose.
Atypical pneumonia, also known as walking pneumonia, is any type of pneumonia not caused by one of the pathogens most commonly associated with the disease. Its clinical presentation contrasts to that of "typical" pneumonia. A variety of microorganisms can cause it. When it develops independently from another disease, it is called primary atypical pneumonia (PAP).
Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose-fermenting, facultative anaerobic, rod-shaped bacterium. It appears as a mucoid lactose fermenter on MacConkey agar.
Bacterial pneumonia is a type of pneumonia caused by bacterial infection.
A blood culture is a medical laboratory test used to detect bacteria or fungi in a person's blood. Under normal conditions, the blood does not contain microorganisms: their presence can indicate a bloodstream infection such as bacteremia or fungemia, which in severe cases may result in sepsis. By culturing the blood, microbes can be identified and tested for resistance to antimicrobial drugs, which allows clinicians to provide an effective treatment.
Community-acquired pneumonia (CAP) refers to pneumonia contracted by a person outside of the healthcare system. In contrast, hospital-acquired pneumonia (HAP) is seen in patients who have recently visited a hospital or who live in long-term care facilities. CAP is common, affecting people of all ages, and its symptoms occur as a result of oxygen-absorbing areas of the lung (alveoli) filling with fluid. This inhibits lung function, causing dyspnea, fever, chest pains and cough.
Ventilator-associated pneumonia (VAP) is a type of lung infection that occurs in people who are on mechanical ventilation breathing machines in hospitals. As such, VAP typically affects critically ill persons that are in an intensive care unit (ICU) and have been on a mechanical ventilator for at least 48 hours. VAP is a major source of increased illness and death. Persons with VAP have increased lengths of ICU hospitalization and have up to a 20–30% death rate. The diagnosis of VAP varies among hospitals and providers but usually requires a new infiltrate on chest x-ray plus two or more other factors. These factors include temperatures of >38 °C or <36 °C, a white blood cell count of >12 × 109/ml, purulent secretions from the airways in the lung, and/or reduction in gas exchange.
Lobular pneumonia is a form of pneumonia characterized by inflammatory exudate within the intra-alveolar space resulting in consolidation that affects a large and continuous area of the lobe of a lung.
Chlamydia felis is a Gram-negative, obligate intracellular bacterial pathogen that infects cats. It is endemic among domestic cats worldwide, primarily causing inflammation of feline conjunctiva, rhinitis and respiratory problems. C. felis can be recovered from the stomach and reproductive tract. Zoonotic infection of humans with C. felis has been reported. Strains FP Pring and FP Cello have an extrachromosomal plasmid, whereas the FP Baker strain does not. FP Cello produces lethal disease in mice, whereas the FP Baker does not. An attenuated FP Baker strain, and an attenuated 905 strain, are used as live vaccines for cats.
Hospital-acquired pneumonia (HAP) or nosocomial pneumonia refers to any pneumonia contracted by a patient in a hospital at least 48–72 hours after being admitted. It is thus distinguished from community-acquired pneumonia. It is usually caused by a bacterial infection, rather than a virus.
Medical microbiology, the large subset of microbiology that is applied to medicine, is a branch of medical science concerned with the prevention, diagnosis and treatment of infectious diseases. In addition, this field of science studies various clinical applications of microbes for the improvement of health. There are four kinds of microorganisms that cause infectious disease: bacteria, fungi, parasites and viruses, and one type of infectious protein called prion.
Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of these pathogenic species in humans is estimated to be fewer than a hundred. By contrast, several thousand species are part of the gut flora present in the digestive tract.
Pathogenic fungi are fungi that cause disease in humans or other organisms. Approximately 300 fungi are known to be pathogenic to humans. Markedly more fungi are known to be pathogenic to plant life than those of the animal kingdom. The study of fungi pathogenic to humans is called "medical mycology". Although fungi are eukaryotic, many pathogenic fungi are microorganisms. The study of fungi and other organisms pathogenic to plants is called plant pathology.
Pseudallescheria boydii is a species of fungus classified in the Ascomycota. It is associated with some forms of eumycetoma/maduromycosis and is the causative agent of pseudallescheriasis. Typically found in stagnant and polluted water, it has been implicated in the infection of immunocompromised and near-drowned pneumonia patients. Treatment of infections with P. boydii is complicated by resistance to many of the standard antifungal agents normally used to treat infections by filamentous fungi.
Pneumonia can be classified in several ways, most commonly by where it was acquired, but may also by the area of lung affected or by the causative organism. There is also a combined clinical classification, which combines factors such as age, risk factors for certain microorganisms, the presence of underlying lung disease or systemic disease and whether the person has recently been hospitalized.
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, and the sampling tool or sampler is the person or material to collect the sample.
In biology, a pathogen in the oldest and broadest sense, is any organism that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ.
Clinical metagenomic next-generation sequencing (mNGS) is the comprehensive analysis of microbial and host genetic material in samples from patients. It uses the techniques of metagenomics for the identification and genomic characterization of bacteria, fungi, parasites, and viruses without the need for a prior knowledge of a specific pathogen directly from clinical specimens. The capacity to detect all the potential pathogens in a sample makes metagenomic next generation sequencing a potent tool in the diagnosis of infectious disease especially when other more directed assays, such as PCR, fail. Current limitations include clinical utility, laboratory validity, sense and sensitivity, cost and regulatory considerations.
