is strep part of normal flora

Is Streptococcus pneumoniae a pathogen?

Streptococcus pneumoniae is part of the normal upper respiratory tract flora. As with many natural flora, it can become pathogenic under the right conditions, typically when the immune system of the host is suppressed.

Why is the genus Streptococcus important?

The genus Streptococcus , a heterogeneous group of Gram-positive bacteria, has broad significance in medicine and industry. Various streptococci are important ecologically as part of the normal microbial flora of animals and humans; some can also cause diseases that range from subacute to acute or even chronic.

What is normal flora?

Normal Flora - Medical Microbiology - NCBI Bookshelf A diverse microbial flora is associated with the skin and mucous membranes of every human being from shortly after birth until death. The human body, which contains about 1013 cells, routinely harbors about 1014 bacteria (Fig. 6-1).

Where are Streptococcus found in mouth?

A varied microbial flora is found in the oral cavity, and streptococcal anaerobes inhabit the gingival crevice. The pharynx can be a point of entry and initial colonization for Neisseria, Bordetella, Corynebacterium, and Streptococcus spp.

Is strep pyogenes normal flora?

S. pyogenes is a frequent pathogen in humans of all ages. Approximately 5–15% of normal individuals carry the organism, usually in the upper respiratory tract, without disease signs or symptoms. As part of the normal flora (now often referred to as the “microbiome”), S.

Is strep pneumoniae part of normal flora?

Streptococcus pneumoniae is part of the normal bacterial flora of the narsopharynx, but is also associated with several invasive and non-invasive diseases.

Where is strep normally found?

Group A streptococci are bacteria commonly found in the throat and on the skin. The vast majority of GAS infections are relatively mild illnesses, such as strep throat and impetigo.

Is strep A flora skin?

Bacterial Disease. Nonhuman primates have a resident skin flora. Staphylococcus and Streptococcus are frequently found on the skin during non-disease states and appear important in maintaining skin pH and for inhibiting nonresident pathogens from becoming established.

What is the most abundant normal flora in throat cultures?

The normal basic throat flora includes Gram-negative cocci, non-hemolytic streptococci, and for certain individuals "large Gram-positive cocci," B. influenzae, Bacillus "X," and diphtheroids. Transient organisms are Staphylococcus albus, hemolytic streptococci,Staphylococcus aureus and citreus, and pneumococci.

Where is normal flora not found in the body?

Normal flora is found in all areas of the human body exposed to the environment (one exception is the lungs), but internal organs and body fluids are considered sterile in a healthy individual.

Where does strep A bacteria come from?

These bacteria are spread by direct contact with discharges from the nose and throat of infected people or by contact with infected wounds or sores on the skin. The risk of spreading the infection is highest when a person is ill, such as when people have "strep throat" or an infected wound.

What is strep throat caused by?

Bacteria cause strep throat Viruses are the most common cause of a sore throat. However, strep throat is an infection in the throat and tonsils caused by bacteria called group A Streptococcus (group A strep).

Where did strep throat originate?

According to most scholars, Johann Weyer of the Netherlands was the first to describe a sore throat occurring during epidemics of scarlatina anginosa, which he did in 1565.

What are the two types of normal flora?

There are two types of flora, normal flora and transient flora.

Is strep throat caused by bacteria or virus?

Strep throat is a bacterial infection caused by group A Streptococcus or “group A strep.” People who are sick with strep throat are very contagious.

What is normal oral flora?

Normal Flora of the Oral Cavity The presence of nutrients, epithelial debris, and secretions makes the mouth a favorable habitat for a great variety of bacteria. Oral bacteria include streptococci, lactobacilli, staphylococci and corynebacteria, with a great number of anaerobes, especially bacteroides.

Is Haemophilus influenzae normal flora?

Haemophilus influenzae is a Gram-negative, opportunistic pathogen that remains a significant human pathogen. It is commonly found as a member of the normal flora of the nasopharynx. H. influenzae strains are distinguished by the presence of a capsule.

What is the normal flora in the lungs?

Normal respiratory flora include Neisseria catarrhalis, Candida albicans, diphtheroids, alpha-hemolytic streptococci, and some staphylococci.

How does resident flora cause pneumonia?

Bacterial pneumonia follows aspiration of recognized bacterial pathogens (RBPs) such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus after they have colonize the nasopharynx. We hypothesized that aspiration of normal respiratory flora (NRF) might also cause CAP.

Where is Streptococcus pneumoniae found in the environment?

Streptococcus pneumoniae is found predominantly in the mucus layer overlying the epithelial surface of the upper respiratory tract.

How many bacteria are in the human body?

The human body, which contains about 1013 cells, routinely harbors about 1014 bacteria (Fig. 6-1).

Is microbial flora harmful to humans?

Even though most elements of the normal microbial flora inhabiting the human skin, nails, eyes, oropharynx, genitalia, and gastrointestinal tract are harmless in healthy individuals, these organisms frequently cause disease in compromised hosts.

What are the other medically important streptococci?

Some of the other medically important streptococci are S agalactiae(group B), an etiologic agent of neonatal disease; E faecalis(group D), a major cause of endocarditis, and the viridans streptococci. Particularly for the viridans streptococci, taxonomy and nomenclature are not yet fully reliable or consistent.

What are the diseases caused by streptococci?

Among the significant human diseases attributable to streptococci are scarlet fever, rheumatic heart disease, glomerulonephritis, and pneumococcal pneumonia. Streptococci are essential in industrial and dairy processes and as indicators of pollution.

What is the significance of streptococci?

The genus Streptococcus, a heterogeneous group of Gram-positive bacteria, has broad significance in medicine and industry . Various streptococci are important ecologically as part of the normal microbial flora of animals and humans; some can also cause diseases that range from subacute to acute or even chronic.

What are the members of the Viridans streptococci?

Important members of the viridans streptococci, normal commensals, include S mutansand S sanguis (involved in dental caries), S mitis(associated with bacteremia, meningitis, periodontal disease and pneumonia), and “S milleri” (associated with suppurative infections in children and adults).

Is streptococcus a Gram positive organism?

Streptococcus. The genus <i>Streptococcus</i> , a heterogeneous group of Gram-positive bacteria, has broad significance in medicine and industry. Various streptococci are important ecologically as part of the normal microbial flora of animals and humans; some can also cause diseases that range from subacute to acu ….

What are the pathogenic factors of flora?

As with many natural flora, it can become pathogenic under the right conditions, typically when the immune system of the host is suppressed. Invasins, such as pneumolysin, an anti phagocytic capsule, various adhesins, and immunogenic cell wall components are all major virul ence factors.

What is the role of Streptococcus pneumoniae?

Streptococcus pneumoniae played a central role in demonstrating that genetic material consist s of DNA. In 1928, Frederick Griffith demonstrated transformation of life turning harmless pneumococcus into a lethal form by co-inoculating the live pneumococci into a mouse along with heat-killed virulent pneumococci.

Why was Streptococcus pneumoniae renamed?

It was renamed Streptococcus pneumoniae in 1974 because it was very similar to streptococci. Streptococcus pneumoniae played a central role in demonstrating that genetic material consists of DNA.

How many genes are in the genome of S. pneumoniae?

pneumoniae is a closed, circular DNA structure that contains between 2.0 and 2.1 million base pairs depending on the strain. It has a core set of 1553 genes, plus 154 genes in its virulome, which contribute to virulence and 176 genes that maintain a noninvasive phenotype.

What is the effect of S pneumoniae on the host?

The ability of S. pneumoniae to repair the oxidative DNA damages in its genome, caused by this host defense, likely contributes to this pathogen's virulence.

When was the pneumococcus first isolated?

History. In 1881, the organism, known later in 1886 as the pneumococcus for its role as a cause of pneumonia, was first isolated simultaneously and independently by the U.S. Army physician George Sternberg and the French chemist Louis Pasteur. The organism was termed Diplococcus pneumoniae from 1920 because of its characteristic appearance in ...

Is Streptococcus pneumoniae a Gram positive or negative?

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 are usually found in pairs ( diplococci) and do not form spores and are non motile. As a significant human pathogenic bacterium S. pneumoniae was recognized as a major cause of pneumonia in the late 19th century, and is the subject of many humoral immunity studies.

What is a group B streptococcal?

Group B Streptococcus was first reported as a veterinary pathogen causing bovine mastitis long before its human clinical importance was recognized. The first description of Group B streptococcal human disease was in three cases of fatal puerperal sepsis over 60 years ago ( 23 ). Since the early 1970s, Group B ß-haemolytic streptococcus (GBS) ( Streptococcus agalactiae) has been the leading pathogen causing serious perinatal infection in the USA as well as most developed countries. Control of this infection has therefore become a major priority in pediatrics. Significant advances have been achieved in the areas of diagnosis and management leading to a reduction in mortality from 35-50% in the 1970s to less than half of this initial rate. The incidence of invasive early-onset GBS diseasedecreased by more than 80% from 1.8 cases/1000 live births in the early 1990s to 0.26 cases/1000 live births in 2010; from 1994 to 2010 it is estimated that over 70,000 cases of early onset GBS invasive disease were prevented in the United States ( 40 ). The decline stemmed from the increased use of penicillin during labor in women at high risk for transmitting the infection to their newborns.

How to diagnose invasive group B streptococci?

The diagnosis of invasive group B streptococcal infection is established by routine culture techniques and isolation of the organism from normally sterile sites such as blood, urine, cerebrospinal fluid, bone, joint, or from an abscess. Isolation of the organism on surface areas, the genital tract or the gastrointestinal tract only indicates colonization which may or may not be associated with invasive disease. Rapid antigen detection methodology is readily available primarily employing latex particle agglutination methodology. Group B streptococcal antigen can be detected in approximately 90% of CSF specimens and 95% of concentrated urine specimens from patients with meningitis. However, urine assays may be positive in otherwise healthy infants who are heavily colonized with group B streptococci. False positive reactions in CSF are also well reported. Colonization with group B streptococcus can be identified rapidly and reliably by a polymerase chain reaction assay in pregnant women in labor both before and after the rupture of membranes and this test can also be employed for the diagnosis of invasive disease.

How long does it take for streptococcus to kill?

As compared to group A streptoccoccus, Group B Streptococcus grows more rapidly and requires a longer period of time for killing by beta-lactam antibiotics. In the presence of 1 µg/ml of ampicillin, elimination of group A strains is complete at four hours while sterilization of group B strains does not occur until 20-24 hours even at concentrations of 10 µg/ ml ( 39 ). In studies using 50 times the minimal bactericidal concentration (MBC) of ampicillin, killing of Group A strains occurred within 4 hours. In contrast, virtually no killing of group B strains was observed over this time. The relatively slow bactericidal action of ampicillin on this organism may explain the difficulty in treating immunosuppressed hosts.

Does penicillin help with streptococcal disease?

Early administration of penicillin to prevent Group B streptococcal disease in neonates has been investigated in a number of clinical studies, but results were variable. Two encouraging reports demonstrated efficacy of penicillin prophylaxis although neither focused on high risk populations of neonates ( 18 , 42 , 44 ). In the latter study, the incidence of severe infection caused by non Group B streptococcal pathogens was increased, thereby negating clinical benefits of intervention.

Does streptococcal carriage occur during pregnancy?

Pregnant women probably vary in extent and duration of Group B streptococcal carriage. Only a small number appear to be heavily and continually colonized during pregnancy but heavy colonization greatly increases the likelihood of vertical transmission and infection in the neonate ( 48 ).

Does ampicillin prevent streptococcal infection?

The best designed and most convincing prospective, randomized, controlled clinical trial focused on pregnant women colonized with Group B Streptococcus and showed that intrapartum prophylaxis with intravenous ampicillin resulted in preventing at least 50% of the early onset Group B streptococcal infections in their patient population ( 10 ). A metaanalysis of seven additional trials which included studies of carriers with and without risk factors estimated a 30-fold reduction in early onset Group B streptococcal disease with similar chemoprophylaxis ( 45 ).

How many serotypes are there in Streptococcus pneumoniae?

There are 100 known serotypes of Streptococcus pneumoniae, the bacteria that cause pneumococcal disease. Streptococcus pneumoniae are lancet-shaped, gram-positive, facultative anaerobic bacteria with 100 known serotypes. Most S. pneumoniae serotypes can cause disease, but only a minority of serotypes produce the majority of pneumococcal infections.

How many people are carriers of pneumococci?

The bacteria may be isolated from the nasopharynx of 5–90% of healthy persons, depending on the population and setting: 5–10% of adults without children are carriers. 20–60% of school-aged children may be carriers.

Where is Streptococcus constellatus found?

Streptococcus constellatus is a species of Streptococcus part of the normal flora in the oral cavity, urogenital region, and intestinal tract. However, it can frequently cause purulent infections in other parts of the body.

Is Streptococcus constellatus a purulent infection?

However, it can frequently cause purulent infections in other parts of the body. DNA homology studies and 16S rRNA sequence analysis demonstrate S. constellatus belongs to the Streptococcus anginosus group (milleri group) along with Streptococcus intermedius and Streptococcus anginosus.

How many species are there in Streptococcus?

The species of the genus Streptococcus have been classified on the basis of their DNA-DNA hybridization and rRNA sequences into about 60 different species and 12 subspecies.

What is the name of the group of streptococci?

S. anginosus belongs to the anginosus subgroup of viridans streptococci which was traditionally called the ‘milleri group’. However, the name is now pseudotaxonomic as the idea that all the members in the group belonged to the Streptococcus milleri species was discarded.

What is Streptococcus anginosus?

Streptococcus anginosus is a Gram-positive bacterium that is present in the mouth, upper respiratory tract, gastrointestinal tract, and vagina as a normal inhabitant.

Where does Streptococcus anginosus colonize?

The primary site of colonization of the organism is the oral cavity, gastrointestinal tract, and vaginal tract.

Which bacteria are closely related to lactic acid?

Streptococcus species are closely related to the group of lactic acid bacteria as they produce lactic acid as their primary end product during carbon metabolism.

Does Streptococcus anginosus grow on agar?

Streptococcus anginosus does not show profuse growth on traditional media like Nutrient Agar and might require supplements like carbohydrates and other nutrients.

Overview

Infection

Streptococcus pneumoniae is part of the normal upper respiratory tract flora. As with many natural flora, it can become pathogenic under the right conditions, typically when the immune system of the host is suppressed. Invasins, such as pneumolysin, an antiphagocytic capsule, various adhesins, and immunogenic cell wall components are all major virulence factors. After S. pneumoniae colonizes the air sacs of the lungs, the body responds by stimulating the inflammatory response, …

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Interaction with Haemophilus influenzae