Beta-lactam antibiotics and viridans group streptococci.

The aim of this review is to present an update on the susceptibility of viridans group streptococci (VGS) to β-lactam antimicrobials, with emphasis on the Argentinean scenario. VGS are a heterogeneous group including five groups of species, each one exhibiting peculiar susceptibility patterns to penicillin (PEN). Species of the Streptococcus mitis group are frequently nonsusceptible to PEN.

Ceftaroline as salvage therapy for methicillin susceptible Staphylococcus aureus complicated bacteremia.

Infections caused by methicillin-susceptible Staphylococcus aureus (MSSA) are still associated with significant morbidity and mortality. Treatment failures of cefazolin (CFZ) have been reported and probably related to the inoculum effect. New treatments for severe MSSA infections are needed and ceftaroline fosamil (CPT) could be an option.

Resistance to β-lactams in Streptococcus pneumoniae.

Streptococcus pneumoniae is an important causal agent of pneumonia, meningitis, sepsis, bacteremia, and otitis media. Penicillin resistance rates in S. pneumoniae have remained stable in Argentina in the last years.

Resistance to β-lactams in enterococci.

Enterococci are intrinsically resistant to several antimicrobial classes and show a great ability to acquire new mechanisms of resistance. Resistance to β-lactam antibiotics is a major concern because these drugs either alone or in combination are commonly used for the treatment of enterococcal infections. Ampicillin resistance, which is rare in Enterococcus faecalis, occurs in most of the hospital-associated Enterococcus faecium isolates.

Susceptibility to β-lactams in β-hemolytic streptococci.

Group A (GAS), B (GBS), C (GCS) and G (GGS) β-hemolytic streptococci are important human pathogens. They cause infections of different severity and frequency. Nowadays, after 70 years of use, penicillin is still universally active against GAS, GCS and GGS.