Necrotising fasciitis and Group B streptococcal infections

This type of infection usually arises within the first two days of delivering a baby. Mothers may have infection of the womb (endometritis) or a wound infection at, for example, the site of a caesarean section. Occasionally, all that is found, are bacteria in the bloodstream, associated with a high fever. Although easily treated with antibiotics, doctors must ensure that the womb has been fully emptied following delivery, in case any left over tissue is acting as a focus for the infection; this sometimes means that a special scan is necessary, or a small operation to empty the womb. Occasionally, the condition is complicated by an abscess (pus collection) in the abdomen which would require drainage, or by septic shock.

This type of infection must be treated with antibiotics; some doctors will try tablet antibiotics first, but usually if there is fever or other signs of severe illness, it is sensible to give antibiotics in the form where they can act quickly, that is, intravenously, which normally requires hospital. It is very difficult to grow bacteria from cases of cellultis, so often the exact bug is not identified. The group A strep is believed to be the commonest cause of cellulitis (except where there had been a boil or insect bite recently). Other bacteria can cause cellulitis, and antibiotics will be tailored to fit the likely infections in any given patient. Sometimes, cellulitis in the leg can mimic a deep vein thrombosis (blocked vein), so doctors may perform scans to check for that.

Once antibiotics are started, doctors will look for signs of improvement (reduction in size of the red area, reduction in fever or pain, improvement in blood tests). If any of these worsen, or if the skin begins to blacken or blister on treatment, the doctors may increase the antibiotic treatment and consider whether the infection could have spread to deeper tissues, or whether there are dead tissues which need to be removed, and whether the antibiotics are targeted at the correct bugs.

Sometimes surgery is needed to explore these possibilities; tissue taken by the surgeons can be tested in the labs for bacteria, and can be examined for evidence of dead tissue. Any dead tissue (‘necrotic”) must be removed surgically, otherwise it will continue to generate a destructive inflammatory response in the body and proved a good ‘culture medium’ for the bacteria to thrive in. Cellulitis can occasionally be complicated by bacteremia (bacteria spreading into the bloodstream) and septic or toxic shock.

Group B strep can cause infection of the lung tissue; whether the bugs reach the lung directly from the throat, or whether they reach the lung via the bloodstream is unknown (and may vary from case to case). Pneumonia due to these types of streptococci is rare but can be associated with bacteremia (bacteria spreading into the bloodstream) and septic or toxic shock.

GBS can spread from the blood (or skin) into joints , often those that are previously damaged by injury or arthritis and especially in diabetics. This may cause swelling, redness, and pain over the joint. Sometimes, the joint infection (arthritis) spreads into the bone, causing ‘osteomyelitis’. This type of infection requires prolonged antibiotic treatment, alongside drainage of any pus around the joint or bone.

GBS is a common cause of cystitis in women, and can also cause a more serious infection of the upper urinary tract, to include the kidney. This normally only occurs in people with poor immunity e.g. diabetics, or in pregnant women.

This is a particularly risky but rare infection that involves the heart valves. People who have previously damaged heart valves through, for example, rheumatic fever, are most at risk. The bacteria form clumps on the valves which can ‘fly off’ to cause serious problems such as a stroke or damage to other organs, Treatment will involve several weeks of intravenous antibiotics and sometimes surgery is essential to cure the condition.

Sometimes, doctors may guess that the group A strep is a likely cause of an illness, for example, in necrotising fasciitis, and antibiotics and surgery are planned accordingly. Often, however, the first indication that an infection is caused by group A strep in will be, that the blood culture shows a group A strep. Doctors may have started antibiotics using a ‘best guess’ approach. Fortunately, group A strep is killed by most of the antibiotics commonly used in a wide range of conditions.

It is widely believed that group A strep bacteremia can itself cause a focus of infection in the body by “seeding” abnormal areas, such as a bruised muscle, or faulty heart valve. Seeding appears to be the way in which cases of meningitis arise, although these conditions are exceedingly rare.

Occasionally, GBS can cause infections like meningitis (infection of the lining of the brain), infection of the abdominal cavity (peritonitis), or eye (ophthalmitis). Sometimes, if pus (abscess) or dead tissue has collected, needle aspiration or surgery is needed alongside antibiotics. All of these infections can be associated with bacteremia (bacteria spreading into the bloodstream; “blood poisoning”) and septic or toxic shock.

The appearance of bacteria in the blood stream is a serious indicator of deep-seated streptococcal infection. Bacteremia is more commonly known as “blood poisoning” and of course can be used to describe the appearance of any bug in the bloodstream. Doctors have to take special blood samples (blood cultures) to detect bacteria in the blood; because the bacteria have to grow in the lab in order to be detected and identified, doctors often do not know the result for a day or two. Sometimes, doctors may guess which bug is a likely cause of an illness, for example, in necrotising fasciitis, and antibiotics and surgery are planned accordingly. Often, however, the first indication that an infection is due to strep will be, that the blood culture is positive and grows a strep, usually the following day or two days later. Special tests will be done to check which group the strep belongs to (i.e. group A, B, C, F, or G) Doctors may have started antibiotics using a ‘best guess’ approach. Fortunately, streps are killed by most of the antibiotics commonly used in a wide range of conditions.

Bacteremia is usually seen only in cases of invasive or deep infection. Occasionally, doctors cannot work out the site of a strep infection in the body, but will try and investigate using blood tests and scans. This is important because a patient might need surgery in addition to antibiotics.