3. Coccal infections

Bacteria can be classified in several ways, In­cluding by their shape. Bacteria that have a spher­ical shape are called cocci. A cocci that can cause infection in humans include staphylococci, strep­tococci, pneumococci, and meningococci.

Text A Staphylococcal Infections

Staphylococcal infections are those caused by staphylococci, which are common gram-positive bacteria.

Normally found in the nose and on the skin of 20 to 30 percent of healthy adults (and less com­monly in the mouth, mammary glands, and genitourinary, intestinal, and upper respiratory tracts), staphylococci do no harm most of the time. However, a break in the skin or another injury may allow the bacteria to penetrate the body’s defenses and cause infection.

People prone to Staphylococcal infections include newborns, breastfeeding women, people with chronic diseases (especially lung disease, diabetes, and cancer), those with skin conditions and surgical incisions, and those whose immune 'systems are suppressed by corticosteroids, ra­diation therapy, immunosuppressive drugs, or anticancer medications.

Symptoms

Staphylococci can infect any site in the body, and the symptoms depend on the location of the infection. The infection may be mild or life threat­ening. Commonly, Staphylococcal infections pro­duce pus-filled pockets, such as abscesses and boils (furuncles and carbuncles). Staphylococci can travel through the blood and cause abscesses in internal organs, such as the lungs, as well as infections of bones (osteomyelitis) and the inner lining of the heart and its valves (endocarditis).

Staphylococci tend to infect the skin. Staphy­lococcal abscesses on the skin appear as warm, pus-filled pockets below the surface. They usually rupture like a large pimple and ooze pus onto the skin, where further infection can occur if the pus isn't cleaned off. Staphylococci can also cause cellulitis, a spreading infection under the skin. Usually boils also are caused by staphylococci. Two particularly serious staphylococcal skin in­fections are toxic epidermal necrolysis and the scalded skin syndrome, both of which lead to large-scale peeling of skin.

Newborns may develop staphylococcal skin in­fections, usually within 6 weeks after birth. The most common symptom is large blisters filled with clear fluid or pus that appear in the armpit, groin, or neck skin-folds. More severe staphylo­coccal infections can cause many skin abscesses, sloughing of the skin in large patches, blood in­fection, infection of the membranes covering the brain and spinal cord (meningitis), and pneumonia.

Breastfeeding mothers may develop staphylo­coccal breast infections (mastitis) and abscesses 1 to 4 weeks after delivery. Such infections often are contracted by the infant in the hospital nurs­ery and transferred to the mother's breast during feeding.

Staphylococcal pneumonia is a severe infection. People with chronic lung diseases (such as chronic bronchitis and emphysema) and those with influenza are particularly at risk. Staphylo­coccal pneumonia often causes a high fever and severe lung symptoms, such as shortness of breath, rapid breathing, and cough productive of sputum that may be tinged with blood. In newborns—and sometimes adults—staphylococcal pneumonia may cause lung abscesses and an infection of the pleura (the membrane layers sur­rounding the lungs). The infection, called thoracic empyema, worsens the difficulties in breathing caused by the pneumonia.

Although a staphylococcal infection of the blood (staphylococcal bacteremia) often devel­ops from a staphylococcal infection elsewhere in the body, it usually comes from an infected intra­venous device, such as a catheter, which gives staphylococci direct access to the bloodstream. Staphylococcal bacteremia is a common cause of death in severely burned people. Typically, the bacteremia causes a persistent, high fever and sometimes shock.

Staphylococci in the bloodstream can lead to an infection of the inner lining of the heart and its valves (endocarditis), especially in injecting drug users. The infection can quickly damage the valves, leading to heart failure and death.

Bone infections (osteomyelitis) predominantly affect children, although they also affect the el­derly, especially those with deep skin ulcers (bedsores). Bone infections cause chills, fever, and bone pain. Redness and swelling appear over the infected bone, and fluid may build up in joints near the areas invaded by the bacteria. The site of infection may be painful, and the person usu­ally has a fever. Sometimes x-rays and other radiologic scans can identify an area of infection, but they generally don't help the doctor make an early diagnosis.

A staphylococcal infection of the intestine of­ten causes a fever, abdominal bloating and distention, a temporary halting of the intestine's normal contractile movements (ileus), and diarrhea. The infection is most common in hospitalized pa­tients, especially those who have undergone ab­dominal surgery or received antibiotic treatment.

Surgery increases the risk of staphylococcal in­fection. The infection may produce abscesses at the stitches or may cause extensive destruction of the incision site. Such infections usually appear a few days to several weeks after an operation but may develop more slowly if the person received antibiotics at the time of surgery. A postoperative staphylococcal infection may worsen and pro­gress to toxic shock syndrome.

Treatment

For most skin infections, oral antibiotics, such as cloxacillin, dicloxacillin, and erythromycin, are adequate. More severe infections, especially blood infections, require intravenous antibiotic therapy, often for up to 6 weeks.

The choice of an antibiotic depends on the site of infection, the severity of the illness, and which; of the antibiotics most effectively kills the particular bacteria. Methicillin-resistant staphylococcus aureus is resistant to most commonly used anti­biotics and is a major concern because the bac­terium is increasingly common in big city and university hospitals. Among the few antibiotics that are usually effective against methicillin-resistant; Staphylococcus aureus are vancomycin and trimethoprim-sulfamethoxazole.Vancomycin kills the bacteria, whereas trimethoprim-sulfamethoxazole acts by inhibiting their ability to multiple an abscess that develops must be drained. Draining an abscess on the skin is relatively sim­ple. A doctor makes a small cut in the area and applies pressure to clean out the infected mate­rial. Abscesses deeper in the body may require surgery.

Notes:

suppress подавлять

delivery родоразрешение

empyema скопление гноя в полости, эмпиема

newborn новорожденный

fill with заполнять

slough сходить(о коже), шелушиться

be tinged with иметь примесь чего-л

distention вздутие живота

Text B Streptococcal Infections

Streptococcal infections are caused by gram-posi­tive bacteria called streptococci.

The various disease-causing strains of strep­tococci are grouped by their behavior, chemistry, and appearance. Each group tends to produce specific types of infections and symptoms.

• Group A streptococci are the most virulent spe­cies for humans, who are their natural host. These streptococci can cause strep throat (a Strepto­coccal infection of the throat), tonsillitis, wound and skin infections, blood infections (septicemia), scarlet fever, pneumonia, rheumatic fever, Sydenham's chorea (St. Vitus' dance), A and kid­ney inflammation (glomerulonephritis).

• Group B streptococci most commonly cause dangerous infections in newborns (neonatal sepsis) and infections in the joints (septic arthritis) and heart (endocarditis).

• Groups C and G streptococci often are carried by animals but also grow in the human throat intestine, vagina, and skin. These streptococci can cause severe infections, including strep throat, pneumonia, skin infections, wound infec­tions, postpartum and neonatal sepsis, endocar­ditis, and septic arthritis. After an infection with one of these bacteria, kidney inflammation may develop.

• Group D streptococci and enterococci grow nor­mally in the lower digestive tract, vagina, and sur­rounding skin. They can also cause infections in wounds and in the heart valves, bladder, abdo­men, and blood.

Infections with certain types of streptococci can cause an autoimmune reaction in which the body attacks its own tissues. Such reactions may occur after an infection such as strep throat and may lead to rheumatic fever, chorea, and kid­ney damage (glomerulonephritis).

Symptoms

Streptococci may live in the respiratory tract, intestine, vagina, or elsewhere in the body with­out causing problems. Occasionally, such bacte­ria are found in an inflamed area (such as the throat or vagina) of a person who is a carrier, and the streptococci are incorrectly identified as the cause of the infection.

The most common type of streptococcal infec­tion is a throat infection (strep throat). Typically, symptoms appear suddenly and include sore throat, a general feeling of illness (malaise), chills, fever, headache, nausea, vomiting, and a rapid heartbeat. The throat is beefy red, the tonsils are swollen, and lymph nodes in the neck may be enlarged and tender. Children may have convul­sions. In children under age 4, the only symptom may be a runny nose. A cough, an inflammation of the larynx (laryngitis), and a stuffy nose are uncommon in streptococcal infections; these symptoms suggest another cause, such as a cold or allergy.

Scarlet fever is caused by streptococcal toxins that lead to a widespread, pink-red rash. The rash is most obvious on the abdomen, on the sides of the chest, and in the skinfolds. Other symptoms include a pale area around the mouth, a flushed face, an inflamed red tongue, and dark red lines in the skinfolds. The outer layer of reddened skin often peels after the fever subsides.

Streptococci also cause several types of skin infection but rarely produce abscesses. Rather, the infections tend to spread in the deep layers under the skin, producing cellulitis and some­times hot, red eruptions called erysipelas (St. An­thony's fire). Streptococci, alone or with staphylococci, also can spread along the top layers of the skin, producing scabby, crusted eruptions (impetigo).

Certain strains of streptococci may cause a rap­idly spreading and destructive infection under the skin (necrotizing fasciitis). For unknown reasons, outbreaks of this infection have become more common recently.

Diagnosis

Although symptoms may suggest a streptococ­cal infection, the diagnosis must be confirmed by tests. The best way to be certain of a streptococ­cal infection is to culture a sample from the in­fected area. After overnight growth, a culture shows characteristic bacterial colonies.

To diagnose strep throat, a culture is taken by rubbing a sterile swab over the back of the throat. The sample then is placed in a Petri dish and allowed to grow overnight. Alternatively, Group A streptococci may be detected by special, rapid tests that can produce results within a few hour's. If the result of a rapid test is positive, the slower overnight culture is not needed. Because both methods can detect streptococci in people who do not need treatment, examination by a doctor is necessary. .

Treatment

People with strep throat and scarlet fever gen­erally get better in 2 weeks, even without treat­ment. Nonetheless, antibiotics can shorten the duration of symptoms in young children and pre­vent serious complications, such as rheumatic fever. They also help prevent the spread of the infection to the middle ear, sinuses, and mastoid bone as well as to other people. An antibiotic, usually oral penicillin, should be started promptly after the appearance of symptoms.

Other streptococcal infections, such as cellulitis, necrotizing fasciitis, and endocarditis, are very serious and require intravenous penicillin, sometimes together with other antibiotics. Group A streptococci are usually eliminated by penicil­lin. Some Group D streptococci, and especially enterococci, are resistant to penicillin and most antibiotics; there is no reliable antibiotic therapy available for many enterococcal strains.

Symptoms such as a fever, headache, and sore throat can be treated with drugs that reduce pain (analgesics) and fever (antipyretics), such as acetaminophen. Neither bed rest nor isolation is necessary; however, family members or friends who have similar symptoms or who have had complications from a streptococcal infection may be at risk for infection.

Notes:

Sydenham’s chorea Сиденгама хорея

malaise усталость

necrotizing fasciitis некротизирующий фасциит

convulsion судорога

flushed face покрасневшее лицо

scabby покрытый корками

strep throat стрептококовое воспаление

горла

swab тампон на палочке

Text C Pneumococcal Infections

Pneumococcal infections are caused by Streptococcus pneumoniae (pneumococcus), a gram-positive coccus that usually infects the lungs.

Pneumococci commonly inhabit the upper respiratory tract of people, their natural host, particularly during the winter and early spring. Despite their presence, pneumococci only occasionally cause illness. The most common serious pneumococcal disease is pneumonia, an infection of the tissues of the lungs. Pneumococci may also cause infections in the ear (otitis media), paranasal sinuses (sinusitis), the tissues covering the brain and spinal cord (meningitis), and, less often, the heart valves, joints, and abdominal cavity. Sometimes these areas become infected because the pneumococci have spread through the bloodstream from another site of infection. People at particular risk of developing pneumococcal infection include those with chronic illnesses and a weakened immune system—for example, people with Hodgkin's disease, lymphoma, multiple myeloma, malnutrition, and sickle cell disease. Older people also often develop pneumococcal infections. Because antibodies produced in the spleen normally help prevent pneumococcal infection, people who have had their spleen removed or who have a nonfunctioning spleen are also at risk. Pneumococcal pneumonia also may develop after chronic bronchitis or if a common respiratory virus, notably the influenza virus, damages the lining of the respiratory tract.

Symptoms and Diagnosis

Symptoms begin suddenly with sharp chest pains and shaking chills. Sometimes, these symptoms follow the symptoms of a viral upper respiratory tract infection (sore throat, stuffed nasal passages, runny nose, and nonproductive cough). Fever and cough develop, and the cough produces sputum, which may have a rusty color. The person feels generally sick and is often short of breath. Sometimes, doctors can recognize pneumococci when examining a sample of sputum under a microscope. Usually, however, a sample of sputum, pus, or blood is sent for culture. Chest x-rays are taken to look for pneumonia.

People with pneumococcal meningitis have fever, headache, and a general feeling of illness (malaise). The neck becomes stiff and painful to move, although this is not always obvious early in the disease. As soon as doctors suspect meningitis, they perform a spinal tap (lumbar puncture) to look for signs of infection, such as white blood cells and bacteria, in the cerebrospinal fluid. Pneumococcal ear infections are common in children. These infections cause ear pain and a red, bulging eardrum. Cultures and other diagnostic tests are usually not done. The use of a vaccine against pneumococci in children very significantly lowers the rate of serious infection.

Two types of pneumococcal vaccines are available. One (conjugate vaccine) can be given to children as young as 2 months of age. The other (nonconjugate vaccine) is for older children and adults; this vaccine protects against the most common strains of pneumococci, substantially reducing the chance of developing pneumococcal pneumonia and bacteremia. Pneumococcal vaccine is recommended for people 55 and older, infants, and some older children, and should also be given to people with chronic heart and lung diseases, diabetes, sickle cell disease, Hodgkin's disease, HIV infection, and metabolic disorders. People who have had their spleen removed or who have a nonfunctioning spleen also should be given pneumococcal vaccine. Penicillin is the preferred antibiotic for most pneumococcal infections. It is taken by mouth for ear and sinus infections and given intravenously for more severe infections. Pneumococci that are resistant to penicillin are becoming increasingly common, so newer quinolone antibiotics are often used.

Notes:

gram-positive bacterium грамм позитивная бактерия

rusty color рыживатый оттенок

be short of breath задыхаться