Any local lesion, e.g. an abscess, should be drained. Systemic infection is treated with antibiotics. Hospitalacquired infections are usually penicillin resistant and therefore treatment is with flucloxacillin often together with fusidic acid. Of infections acquired outside the hospital 75% are penicillin sensitive and a penicillin is the drug of choice. Increasing antibiotic resistance is still a problem and most hospitals have restrictions on the use of single antibiotics. The control of staphylococcal crossinfection as discussed below is important.
Methicillin-resistant Staph. aureus (MRSA) were detected in 1961 soon after methicillin was introduced. Such strains were only resistant to ,B-lactam antibiotics and never caused serious problems. The MRSA strains that emerged first in Australia in the late 1970s and have spread worldwide are resistant to many other antibiotics, including aminoglycosides. These are now referred to as MARSA (methicillin-aminoglycoside-resistant Staph. aureus). There have been many outbreaks of infection, particularly in patients in tertiary referral centres, in the seriously ill and in those with surgical wounds and venous access sites. Origin of infection is often ‘another hospital’ e or from healthy staff carriers. Control is essential and involves:
• Close and constant microbiological surveillance both r _,before and during attacks
• Immediate isolation of infected individuals
• Appropriate management of the carrier state
Although topical antibiotics have been used to eradicate nasal colonization their efficacy is now in doubt. Careful C handwashing with chlorhexidine solution is still widely recommended. MARSA can be treated with vancomycin but teichoplanin and the quinolones are effective.
Streptococci are round or ovoid Gram-positive bacteria. Virulence is attributed to the cell-wall M protein and the production by some streptococci of hyaluronidase, DNAses or streptokinase. The spread of streptococci is mediated by direct contact, fomites or airborne droplet infection. Group A ,B-haemolytic streptococci (Strep pyogenes) are responsible for over 95% of human infections (Table 1.13). Group B streptococci frequently produce neonatal sepsis and meningitis, group C, F and G organisms occasionally cause pharyngitis and group D endocarditis and septicaemia. o-Haernolytic streptococci (known collectively as Strep. viridans) found commonly in the mouth, e.g. Strep. sanguis and Strep. mitior as well as Strep. mutans, a non-haemolytic streptococcus, cause three-quarters of all streptococcal endocarditis. Strep. pneumoniae is the commonest cause of pneumonia .
Scarlet fever Scarlet fever occurs when the infectious organism (usually a group A streptococcus) produces erythrogenic toxin in an individual who does not possess neutralizing antitoxin antibodies. This is a notifiable disease in the UK.
The incubation period of this relatively mild disease of childhood is 2-4 days following a streptococcal infection, usually in the pharynx. Regional lymphadenopathy, fever, rigors, headache and vomiting are present. The rash, which usually appears on the second day of illness, initially occurs on the neck but rapidly becomes punctate, erythematous and generalized. It is typically absent from the face, palms and soles, and is prominent in the flexures. The rash usually lasts about 5 days and is followed by extensive desquamation of the skin. The face is flushed with characteristic circumoral pallor. Early in the disease the tongue has a white coating through which prominent bright red papillae can be seen (,strawberry tongue’). Later the white coating disappears, leaving a raw-looking,bright red colour (‘raspberry tongue’). Scarlet fever may be complicated by the development of peritonsillar or retropharyngeal abscesses and otitis media.
The diagnosis is established by the typical clinical features and culture of throat swabs, where the organisms are usuallyfound in abundance, or more rapidly by latex agglutination of throat swab extracts. Elevated antistreptolysin o and anti-DNAse B levels in the serum are indicative of streptococcal infection.
TREATMENT OF STREPTOCOCCAL INFECTIONS
Treatment is directed at preventing the non-suppurative complications of streptococcal infections. Penicillin is the drug of choice and may be given orally as phenoxyrnethylpenicillin 125 mg four times daily for 10 days or as a single intramuscular injection of benzathine penicillin 916 mg in adults. Individuals allergic to penicillin can be treated effectively with erythromycin 250 mg four times daily for 10 days. The role of tonsillectomy in preventing further attacksof pharyngitis remains controversial.
Chemoprophylaxis with penicillin or erythromycin should be given in epidemics.
Erysipelas is an acute, rapidly progressive infection of the skin that is almost always due to group A streptococci. It usually occurs in the very young, the elderly, the debilitated or the immunosuppressed. The onset is abrupt; fever, headache and vomiting are common. The erythematous skin lesion, which is usually on the face, enlarges rapidly and has a sharply demarcated raised edge. Vesicles and bullae appear within this lesion, which then rupture, leaving crusts on the surface. Regionallymphadenopathy is common. Bacteraemia, when present, is associated with a high mortality rate. Treatment with penicillin is rapidly effective.