Release of SpeA from Streptococcus pyogenes after exposure to penicillin: Dependency on dose and inhibition by clindamycin

Recent development and fighting strategies for lincosamide antibiotic resistance

SUMMARYLincosamides constitute an important class of antibiotics used against a wide range of pathogens, including methicillin-resistant Staphylococcus aureus. However, due to the misuse of lincosamide and co-selection pressure, the resistance to lincosamide has become a serious concern. It is urgently needed to carefully understand the phenomenon and mechanism of lincosamide resistance to effectively prevent and control lincosamide resistance. To date, six mobile lincosamide resistance classes, including lnu, cfr, erm, vga, lsa, and sal, have been identified. These lincosamide resistance genes are frequently found on mobile genetic elements (MGEs), such as plasmids, transposons, integrative and conjugative elements, genomic islands, and prophages. Additionally, MGEs harbor the genes that confer resistance not only to antimicrobial agents of other classes but also to metals and biocides. The ultimate purpose of discovering and summarizing bacterial resistance is to prevent, control, and combat resistance effectively. This review highlights four promising strategies, including chemical modification of antibiotics, the development of antimicrobial peptides, the initiation of bacterial self-destruct program, and antimicrobial stewardship, to fight against resistance and safeguard global health.

Should Linezolid Replace Clindamycin as the Adjunctive Antimicrobial of Choice in Group A Streptococcal Necrotizing Soft Tissue Infection and Toxic Shock Syndrome? A Focused Debate

Group A Streptococcus (GAS) necrotizing soft tissue infections and toxic shock syndrome remain high-mortality conditions. In vitro and animal model data, as well as multiple observational studies, suggest adjunctive clindamycin (ie, given with a beta-lactam) reduces invasive GAS infection mortality by inhibiting exotoxin production. Unfortunately, clindamycin resistance in GAS has been rapidly increasing in the United States since the mid-2010s, although the clinical significance of this remains unclear. Linezolid is a promising alternative adjunctive agent to which US GAS isolates remain near-universally susceptible, with a similar mechanism of action and similar in vitro evidence of GAS virulence factor attenuation. However, the clinical data supporting linezolid's value in severe GAS infections are far more limited. Here the authors review the data and reasoning behind a general preference for clindamycin or linezolid in a focused, pro-con debate format.

Playing With Fire: Proinflammatory Virulence Mechanisms of Group A Streptococcus

Group A Streptococcus is an obligate human pathogen that is a major cause of infectious morbidity and mortality. It has a natural tropism for the oropharynx and skin, where it causes infections with excessive inflammation due to its expression of proinflammatory toxins and other virulence factors. Inflammation directly contributes to the severity of invasive infections, toxic shock syndrome, and the induction of severe post-infection autoimmune disease caused by autoreactive antibodies. This review discusses what is known about how the virulence factors of Group A Streptococcus induce inflammation and how this inflammation can promote disease. Understanding of streptococcal pathogenesis and the role of hyper-immune activation during infection may provide new therapeutic targets to treat the often-fatal outcome of severe disease.

Interventions for the prevention of recurrent erysipelas and cellulitis

BACKGROUND

Erysipelas and cellulitis (hereafter referred to as 'cellulitis') are common bacterial skin infections usually affecting the lower extremities. Despite their burden of morbidity, the evidence for different prevention strategies is unclear.

OBJECTIVES

To assess the beneficial and adverse effects of antibiotic prophylaxis or other prophylactic interventions for the prevention of recurrent episodes of cellulitis in adults aged over 16.

SEARCH METHODS

We searched the following databases up to June 2016: the Cochrane Skin Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and LILACS. We also searched five trials registry databases, and checked reference lists of included studies and reviews for further references to relevant randomised controlled trials (RCTs). We searched two sets of dermatology conference proceedings, and BIOSIS Previews.

SELECTION CRITERIA

Randomised controlled trials evaluating any therapy for the prevention of recurrent cellulitis.

DATA COLLECTION AND ANALYSIS

Two authors independently carried out study selection, data extraction, assessment of risks of bias, and analyses. Our primary prespecified outcome was recurrence of cellulitis when on treatment and after treatment. Our secondary outcomes included incidence rate, time to next episode, hospitalisation, quality of life, development of resistance to antibiotics, adverse reactions and mortality.

MAIN RESULTS

We included six trials, with a total of 573 evaluable participants, who were aged on average between 50 and 70. There were few previous episodes of cellulitis in those recruited to the trials, ranging between one and four episodes per study.Five of the six included trials assessed prevention with antibiotics in participants with cellulitis of the legs, and one assessed selenium in participants with cellulitis of the arms. Among the studies assessing antibiotics, one study evaluated oral erythromycin (n = 32) and four studies assessed penicillin (n = 481). Treatment duration varied from six to 18 months, and two studies continued to follow up participants after discontinuation of prophylaxis, with a follow-up period of up to one and a half to two years. Four studies were single-centre, and two were multicentre; they were conducted in five countries: the UK, Sweden, Tunisia, Israel, and Austria.Based on five trials, antibiotic prophylaxis (at the end of the treatment phase ('on prophylaxis')) decreased the risk of cellulitis recurrence by 69%, compared to no treatment or placebo (risk ratio (RR) 0.31, 95% confidence interval (CI) 0.13 to 0.72; n = 513; P = 0.007), number needed to treat for an additional beneficial outcome (NNTB) six, (95% CI 5 to 15), and we rated the certainty of evidence for this outcome as moderate.Under prophylactic treatment and compared to no treatment or placebo, antibiotic prophylaxis reduced the incidence rate of cellulitis by 56% (RR 0.44, 95% CI 0.22 to 0.89; four studies; n = 473; P value = 0.02; moderate-certainty evidence) and significantly decreased the rate until the next episode of cellulitis (hazard ratio (HR) 0.51, 95% CI 0.34 to 0.78; three studies; n = 437; P = 0.002; moderate-certainty evidence).The protective effects of antibiotic did not last after prophylaxis had been stopped ('post-prophylaxis') for risk of cellulitis recurrence (RR 0.88, 95% CI 0.59 to 1.31; two studies; n = 287; P = 0.52), incidence rate of cellulitis (RR 0.94, 95% CI 0.65 to 1.36; two studies; n = 287; P = 0.74), and rate until next episode of cellulitis (HR 0.78, 95% CI 0.39 to 1.56; two studies; n = 287). Evidence was of low certainty.Effects are relevant mainly for people after at least two episodes of leg cellulitis occurring within a period up to three years.We found no significant differences in adverse effects or hospitalisation between antibiotic and no treatment or placebo; for adverse effects: RR 0.87, 95% CI 0.58 to 1.30; four studies; n = 469; P = 0.48; for hospitalisation: RR 0.77, 95% CI 0.37 to 1.57; three studies; n = 429; P = 0.47, with certainty of evidence rated low for these outcomes. The existing data did not allow us to fully explore its impact on length of hospital stay.The common adverse reactions were gastrointestinal symptoms, mainly nausea and diarrhoea; rash (severe cutaneous adverse reactions were not reported); and thrush. Three studies reported adverse effects that led to discontinuation of the assigned therapy. In one study (erythromycin), three participants reported abdominal pain and nausea, so their treatment was changed to penicillin. In another study, two participants treated with penicillin withdrew from treatment due to diarrhoea or nausea. In one study, around 10% of participants stopped treatment due to pain at the injection site (the active treatment group was given intramuscular injections of benzathine penicillin).None of the included studies assessed the development of antimicrobial resistance or quality-of-life measures.With regard to the risks of bias, two included studies were at low risk of bias and we judged three others as being at high risk of bias, mainly due to lack of blinding.

AUTHORS' CONCLUSIONS

In terms of recurrence, incidence, and time to next episode, antibiotic is probably an effective preventive treatment for recurrent cellulitis of the lower limbs in those under prophylactic treatment, compared with placebo or no treatment (moderate-certainty evidence). However, these preventive effects of antibiotics appear to diminish after they are discontinued (low-certainty evidence). Treatment with antibiotic does not trigger any serious adverse events, and those associated are minor, such as nausea and rash (low-certainty evidence). The evidence is limited to people with at least two past episodes of leg cellulitis within a time frame of up to three years, and none of the studies investigated other common interventions such as lymphoedema reduction methods or proper skin care. Larger, high-quality studies are warranted, including long-term follow-up and other prophylactic measures.

Clindamycin Affects Group A Streptococcus Virulence Factors and Improves Clinical Outcome

Group A Streptococcus (GAS) has acquired an arsenal of virulence factors, promoting life-threatening invasive infections such as necrotizing fasciitis. Current therapeutic regimens for necrotizing fasciitis include surgical debridement and treatment with cell wall-active antibiotics. Addition of clindamycin (CLI) is recommended, although clinical evidence is lacking. Reflecting the current clinical dilemma, an observational study showed that only 63% of the patients with severe invasive GAS infection received CLI. This work thus aimed to address whether CLI improves necrotizing fasciitis outcome by modulating virulence factors of CLI-susceptible and CLI-resistant GAS in vitro and in vivo. Treatment with CLI reduced extracellular DNase Sda1 and streptolysin O (SLO) activity in vivo, whereas subinhibitory CLI concentrations induced expression and activity of SLO, DNase, and Streptococcus pyogenes cell envelope protease in vitro. Our in vivo results suggest that CLI should be administered as soon as possible to patients with necrotizing fasciitis, while our in vitro studies emphasize that a high dosage of CLI is essential.

Intrauterine device infection causing concomitant streptococcal toxic shock syndrome and pelvic abscess with Actinomyces odontolyticus bacteraemia

Intrauterine devices (IUDs) are rarely associated with serious infections. We report an unusual concomitant infection of group A Streptococcus (GAS) causing toxic shock syndrome and pelvic abscess with Actinomyces odontolyticus associated with an IUD in a healthy 50-year-old patient. The IUD was subsequently removed and the patient recovered on the appropriate antibiotics. This case highlights the importance of clinicians' high index of suspicion of an IUD infection and prompt removal of the infected foreign body to obtain source control.

Management of invasive group A streptococcal infections

Invasive group A streptococcal (GAS) disease in children includes deep soft tissue infection, bacteraemia, bacteraemic pneumonia, meningitis and osteomyelitis. The expression of toxins and super antigens by GAS can complicate infection by triggering an overwhelming systemic inflammatory response, referred to as streptococcal toxic shock syndrome (STSS). The onset and progression of GAS disease can be rapid, and the associated mortality high. Prompt antibiotics therapy and early surgical debridement of infected tissue are essential. Adjunctive therapy with intravenous immunoglobulin and hyperbaric therapy may improve outcomes in severe disease. Nosocomial outbreaks and secondary cases in close personal contacts are not uncommon; infection control measures and consideration of prophylactic antibiotics to those at high risk are important aspects of disease control. To reduce a substantial part of the global burden of GAS disease, an affordable GAS vaccine with efficacy against a broad number of strains is needed.

Serious group a streptococcal infections

The spectrum of illnesses caused by group A streptococcus (GAS) includes invasive infections, noninvasive infections, and noninfectious complications. Increasingly virulent infections associated with high morbidity and mortality have been observed since the late 1980s and continue to be prevalent in North America and worldwide. Penicillin remains the therapy of choice, with the addition of clindamycin recommended in high risk cases. Early recognition of GAS as the cause of these serious clinical syndromes is critical for timely administration of appropriate therapy. In this review, the pathophysiology, clinical manifestations, and treatment of invasive GAS infections are discussed.

Streptococcus pyogenes and re-emergence of scarlet fever as a public health problem

Explosive outbreaks of infectious diseases occasionally occur without immediately obvious epidemiological or microbiological explanations. Plague, cholera and Streptococcus pyogenes infection are some of the epidemic-prone bacterial infections. Besides epidemiological and conventional microbiological methods, the next-generation gene sequencing technology permits prompt detection of genomic and transcriptomic profiles associated with invasive phenotypes. Horizontal gene transfer due to mobile genetic elements carrying virulence factors and antimicrobial resistance, or mutations associated with the two component CovRS operon are important bacterial factors conferring survival advantage or invasiveness. The high incidence of scarlet fever in children less than 10 years old suggests that the lack of protective immunity is an important host factor. A high population density, overcrowded living environment and a low yearly rainfall are environmental factors contributing to outbreak development. Inappropriate antibiotic use is not only ineffective for treatment, but may actually drive an epidemic caused by drug-resistant strains and worsen patient outcomes by increasing the bacterial density at the site of infection and inducing toxin production. Surveillance of severe S. pyogenes infection is important because it can complicate concurrent chickenpox and influenza. Concomitant outbreaks of these two latter infections with a highly virulent and drug-resistant S. pyogenes strain can be disastrous.