Streptococci are Gram-positive, coccal-shaped bacteria, usually appearing in chains of various lengths. The bacteria have been divided into eighteen major groups according to the Lancefield system, designated A through R. Group A can be further subdivided into some eighty types based on differences in the antigen called the M protein, important because it is responsible for virulence. Group B streptococci generally cause such diseases as neonatal meningitis and sepsis. Groups C and G are responsible for the occasional wound infection and pharyngitis; group D (enterococci), for urinary tract infections, bacteremia, and endocarditis. Streptococci are often found as normal flora of healthy people.
Group A Strep infection is the cause of the previously known “childbed fever,” where the bacteria spread rapidly from the inflammed uterus into the blood. The most important streptococcal infections are caused by S. pyogenes of the Lancefield group A. In 1989, Jim Henson, of Muppet fame, felt as if he was fighting a cold through a weekend, but, by Monday, he was coughing up blood and was admitted to hospital. Despite multiple antibiotics, his lungs, kidneys, heart, and blood-clotting systems failed, and, in less than twenty-four hours, he was dead. Following that, reports of similar illnesses were coming in from around the world. The cause was soon dubbed the “flesh-eating strep”. Particularly disturbing was that all contracted the disease by various means – sometimes only through the smallest of scratches or cuts. All the germ needs is a break in the skin in order to gain entrance to the bloodstream. Besides massive doses of antibiotics, the only other solution is to surgically remove any and all of the tissue involved. After surgery, however, the wounds can leak nutrients, and massive amounts of nutrients are needed to replace what group A strep destroys.
Various strains of S. pyogenes are widespread in humans, but most are asymptomatic carriers. The highest rates of infection are in children between the ages of one and fifteen. Streptococci are readily transmitted when large numbers of people share common environments. S. pyogenes, like S. aureus, are able to cause lesions on the skin where such prior injuries as insect bites, wounds, and burns have occurred. Impetigo can be caused by streptococci, as can erysipelas since both diseases begin with lesions. Impetigo can occur anywhere on the body, while erysipelas occurs mainly on the face. Cellulitis can also be a serious streptococcal infection. Fournier’s gangrene, caused by this organism, is an anaerobic cellulitis of the groin and scrotum found in immunocompromised individuals.
Rheumatic fever has returned after being under control for many years by penicillin. Strains of the bacterium ‘group A beta-hemolytic Streptococcus’ (also called Streptococcus pyogenes or simply group A strep). Of the various strains of group A strep, only a few are capable of causing rheumatic fever and are referred to as rheumatogenic. The strains called M types 1,3,5,6, and 18 cause the current cases of rheumatic fever. Rheumatic fever is a delayed secondary complication of such other group A infections as strep throat or scarlet fever. There also appears to be a genetic tendency toward the disease. A diagnosis will generally include one or two, of the following five symptoms:
- arthritic-type symptoms;
- chorea or Sydenham’s chorea, a temporary disease of the nervous system causing poor coordination.
- Carditis, which is an inflammation of the heart muscle which can leave permanent damage.
- Painless nodules which appear under the skin and on the outer surfaces of the large joints.
- A brief, flat, painless rash that may appear for a day or so.
Group B Strep is a circular bacterium grouped in chains. S. agalactiae is a member of this group, and is responsible for UTIs (urinary tract infections) and wound infections. Group B tends to infect pregnant women and newborns more often. Infants can contract the infection either before birth or as it makes its way through the birth canal. Early onset is the most dangerous form of the disease. The baby usually becomes ill within forty-eight hours of life, but may not show worrisome symptoms for another four days. Initial symptoms vary from difficulty in breathing, with grunting and apnea, paleness, lethargy, fever, poor feeding, and a low body temperature. Mothers usually do not have any symptoms during pregnancy unless it is with a UTI or a bladder infection. Symptoms in the mother usually occur within twelve hours after delivery, beginning with fevers, an increased pulse, chills, and tenderness in the uterus or cesarean sites.
Group C Strep has been implicated as the cause of impetigo, abscesses, pneumonia, and pharyngitis.
Group D Strep is known to be the cause of endocarditis, sepsis, and UTIs. Three species of this group, S. durans, S. faecalis, and S. faecium are disignated as enterococci and separated from other group D organisms, mainly because of their ability to grow in a sodium chloride medium. This group is now in a class of its own, called Enterococcus.
Viridans streptococci contains about ten species and are responsible for about 70% of all cases of bacterial endocarditis. They are also sometimes isolated from deep wound infections, abdominal abscesses, and septicemia. These organisms are normally present in the human mouth and are thought to be a major contributor to tooth decay. Streptococcus mutans plays a central role in the initiation of cavities. With a diet high in milk and sugar, the bacteria are able to stick to the surface of the tooth enamel easier and, thereby, multiply faster.
Streptococcus pneumoniae (also called pneumococcus) are slightly elongated Gram-positive cells that appear in pairs (diplococci) or short chains. It was previously known as Diplococcus pneumoniae, but has since been reclassified as a streptococcus. Its antigens have been used to subdivide the pneumococci into more than eighty types, and protection against infection is type-specific. S. pneumoniae produces alpha-type hemolysis which may cause it to be mistakenly identified as a viridans streptococcus. They can remain alive for weeks once expelled from the body, but readily succumb to various common disinfectants and numerous antibiotics. It is often difficult to distinguish clearly between many of the streptococcal species which has made precise classification difficult.
Streptococcus pneumoniae was the leading cause of death before the age of antibiotics. Even in 1991, it was still listed as number six among the top ten causes of death in the US. It remains the most common form of pneumonia and is responsible for at least half of all ear infections. More than 50% of the healthy population can carry this organism in their respiratory tract, with the numbers of carriers increasing in winter. This bacterium does not possess any apparent enzymes or toxins associated with invasiveness, but it does have a capsule which plays an important role in pathogenic disease and antibiotic resistance. twenty-three of the most commonly encountered serotypes that are responsible for about 88% of serious pneumococcal disease. Data regarding its effectiveness is varied.
Streptococcal pharyngitis is an infection of the pharynx (the upper portion of the throat), and is a relatively common condition in children. The problem with it really begins when the bacteria spreads to the lungs, causing pneumonia or pleurisy. Onset is from one to four weeks after an acute strep infection. The disease is most commonly induced by type 12 of group A. About 80-90% of the cases undergo spontaneous healing, while the rest develop into a chronic condition. Poststreptococcal diseases include glomerulonephritis (involves the glomeruli, the filtering membrane of the kidneys) and rheumatic fever.
Before the days of penicillin, a disease known as toxic scarlet fever caused a high mortality rate. The modern-day ‘Streptococcal toxic shock’ is clinically similar to that disease, with mortality rates of about 50%. The bacterium isolated from streptococci toxic shock produces an abundance of type A toxins, as did isolates from toxic scarlet fever (also known as septic or fulminating scarlet fever). Scarlet Fever is spread by coming into contact with an asymptomatic, but infectious, person’s respiratory secretions. In the beginning, symptoms are the same as for strep throat, but, about two days later, a pinpoint rash will appear on the body and possibly inside the mouth. After one bout of scarlet fever, immunity develops, but not to repeated bouts of strep throat. Scarletina is the mildest and most common form of scarlet fever.
The first recorded epidemic of scarlet fever, then known as rossalia, happened in Sicily in 1543. It was often confused with measles and came as a result of drinking infected milk. With the advent of pasteurization, the disease diminished. Interestingly, in order to obtain the harmless sour milk and the creamy texture of yogurt, a strain of Streptococcus is needed. Rheumatic fever is another result of strep bacteria. In WWI, strep infection was the main complication of influenza, leading to fatal pneumonia. Unlike the ever-mutating Staphylococcal germ, Strep did not show any signs of doing the same until the 1970s when penicillin-resistant strains began to appear. With Strep-A virtually disappearing, Strep-B began to appear in infants. Then, Strep-A reemerged in the late 1980s, stronger than ever. By the 1990s, the dose of penicillin required to kill the bacteria had increased by a factor of 2,400. Strep-A is known to increase the rate of gangrene by an inch an hour. These sensational headlines cause panic until the public is educated to the fact that such infections are very rare. Still, you do not want to be that one rare person.
Enterococcus bacterium are streptococcus-like. Since they were found to differ slightly from the strep bacteria, they now have their own classification. Two forms, E. faecium and E. faecalis, are proving troublesome as they display a super-resistance to antibiotics. They first appeared in NYC in the late 1980s, causing some deaths. Strains soon began emerging worldwide. By 1994, 8% of all reported Enterococcus-causing illnesses were caused by drug-resistant bacteria. The greatest fear is that the bacteria will transfer their resistance to such other intestinal bugs as streptococci and staphylococci. This is another example of bugs on the move.
