What is that
Streptococcus agalactiae - or, more correctly, Streptococcus agalactiae - is a Gram-positive bacterium, part of the human microbiota. In fact, streptococcus agalactiae is a harmless colonizer commonly found in the gastrointestinal and urogenital areas.
Most likely, streptococcus agalactiae is better known as the beta-hemolytic streptococcus of group B and represents one of the potentially pathogenic microorganisms most feared by pregnant women.
Did you know that ...
When we talk about streptococcus agalactiae, beta-hemolytic streptococcus of group B and beta-hemolytic streptococci of group B, more and more often, much confusion is generated.
In reality, all the aforementioned nomenclatures indicate the same bacterial species: Streptococcus agalactiae . This species, in turn, can be classified into as many as ten serotypes that differ in the type of antigens present on the bacterial capsule.
The presence of these different serotypes - although belonging to the same bacterial species - explains the existence of the plural form "beta-hemolytic streptococci of group B".
Features
General characteristics
Streptococcus agalactiae is a diplococcus (that is, it is arranged in Gram-positive pairs), optional aerobic but with a predilection for the condition of anaerobiosis.
Based on the Lancefield classification, streptococcus agalactiae is identified as a beta-hemolytic streptococcus in group B, named for its ability to cause complete destruction of red blood cells in blood agar media (the culture method used, precisely, for Lancefield's classification of streptococci).
As mentioned, there are ten different serotypes of this species, which are so named: Ia, Ib, Ia / c, II, III, IV, V, Vi, VII, VIII.
Normally harmless, it is estimated that the streptococcus agalactiae is present in the gastrointestinal, rectal and uro-genital tract of about 30% of healthy individuals, both female and male. However, as happens with many of the microorganisms present in the human bacterial flora, in some cases, it can proliferate excessively leading to the onset of even very serious infections. Serotype III, in particular, appears to be the main cause of neonatal infections that cause meningitis.
The infection
Streptococcus Agalactiae Infection and Associated Pathologies
Infections given by streptococcus agalactiae can occur in different districts of the body giving rise to diseases such as pneumonia, endometritis, amnionitis (inflammatory process that develops in the amniotic cavity following an infection), bacteremia, infectious diseases of the urinary tract and meningitis .
Although strep agalactiae infections can occur at any age and in patients of any sex, they are particularly relevant when they occur in pregnant women and newborns.
Indeed, neonatal streptococcal agalactiae infections can cause serious - and potentially lethal - diseases in the newborn, such as meningitis, pneumonia and bacteremia. Similarly, if the infection affects a pregnant woman and is not properly and promptly treated, the consequences for the fetus - and sometimes even for the mother - could be tragic.
Infection transmission
As for neonatal infection, it is usually transmitted from mother to baby during birth.
With regard to the transmission of infection among adult individuals, on the other hand, the mechanism by which it occurs is not yet fully understood. However, since streptococcus agalactiae is commonly present in the male and female genitourinary tract, it is believed that transmission can take place through unprotected sexual intercourse.
Curiosity
Streptococcus agalactiae infections do not only affect humans. This beat, in fact, is one of the main responsible for the onset of mastitis in dairy cows. A streptococcal infection of this type in cattle can trigger an acute febrile illness that leads to a reduced synthesis of milk by the animal.
In addition to this, Streptococcus agalactiae can also infect other animal species, such as dogs, cats, camels, seals, dolphins and even crocodiles. Similarly, this microorganism is capable of triggering real epidemics in farmed fish, causing bacteremia and bleeding.
Treatment
Treatment and Prophylaxis of Streptococcus Agalactiae infections
Of course, the treatment of streptococcal infections agalactiae involves the administration of antibiotic drugs. The most employed are:
- Penicillins such as benzylpenicillin and ampicillin . In particular, the latter is used in the treatment of neonatal infections.
- Cephalosporins such as cefotaxime .
- Macrolides such as azithromycin, clarithromycin and erythromycin . In addition to being used as first choice drugs in the treatment of streptococcal agalactiae infections, macrolides are the drugs of choice used in patients with allergies to beta-lactam antibiotics, such as penicillins and cephalosporins.
As for pregnant women, in case of a positive test for streptococcus agalactiae, in order to avoid - or at least reduce - the possibility of transmission of the pathogen to the child, it is necessary to intervene by intravenous antibiotic prophylaxis during labor .
To learn more, read: Streptococcus in Pregnancy
