Association of penicillin tolerance with failure to eradicate group A streptococci from patients with pharyngitis

Integrative Reverse Genetic Analysis Identifies Polymorphisms Contributing to Decreased Antimicrobial Agent Susceptibility in Streptococcus pyogenes

Identification of genetic polymorphisms causing increased antibiotic resistance in bacterial pathogens traditionally has proceeded from observed phenotype to defined mutant genotype. The availability of large collections of microbial genome sequences that lack antibiotic susceptibility metadata provides an important resource and opportunity to obtain new information about increased antimicrobial resistance by a reverse genotype-to-phenotype bioinformatic and experimental workflow. We analyzed 26,465 genome sequences of Streptococcus pyogenes, a human pathogen causing 700 million infections annually. The population genomic data identified amino acid changes in penicillin-binding proteins 1A, 1B, 2A, and 2X with signatures of evolution under positive selection as potential candidates for causing decreased susceptibility to β-lactam antibiotics. Construction and analysis of isogenic mutant strains containing individual amino acid replacements in penicillin-binding protein 2X (PBP2X) confirmed that the identified residues produced decreased susceptibility to penicillin. We also discovered the first chimeric PBP2X in S. pyogenes and show that strains containing it have significantly decreased β-lactam susceptibility. The novel integrative reverse genotype-to-phenotype strategy presented is broadly applicable to other pathogens and likely will lead to new knowledge about antimicrobial agent resistance, a massive public health problem worldwide. IMPORTANCE The recent demonstration that naturally occurring amino acid substitutions in Streptococcus pyogenes PBP2X are sufficient to cause severalfold reduced susceptibility to multiple β-lactam antibiotics in vitro raises the concern that these therapeutic agents may become compromised. Substitutions in PBP2X are common first-step mutations that, with the incremental accumulation of additional adaptive mutations within the PBPs, can result in high-level resistance. Because β-lactam susceptibility testing is not routinely performed, the nature and extent of such substitutions within the PBPs of S. pyogenes are poorly characterized. To address this knowledge deficit, polymorphisms in the PBPs were identified among the most comprehensive cohort of S. pyogenes genome sequences investigated to date. The mutational processes and selective forces acting on the PBPs were assessed to identify specific substitutions likely to influence β-lactam susceptibility and to evaluate factors posited to be impediments to resistance emergence.

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.

Reduced In Vitro Susceptibility of Streptococcus pyogenes to β-Lactam Antibiotics Associated with Mutations in the pbp2x Gene Is Geographically Widespread

Recently, two related Streptococcus pyogenes strains with reduced susceptibility to ampicillin, amoxicillin, and cefotaxime, antibiotics commonly used to treat S. pyogenes infections, were reported. The two strains had the same nonsynonymous (amino acid-substituting) mutation in the pbp2x gene, encoding penicillin-binding protein 2X (PBP2X). This concerning report led us to investigate our library of 7,025 genome sequences of type emm1, emm28, and emm89 S. pyogenes clinical strains recovered from intercontinental sources for mutations in pbp2x We identified 137 strains that, combined, had 37 nonsynonymous mutations in 36 codons in pbp2x Although to a lesser magnitude than the two previously published isolates, many of our strains had decreased susceptibility in vitro to multiple beta-lactam antibiotics. Many pbp2x mutations were found only in single strains, but 16 groups of two or more isolates of the same emm type had an identical amino acid replacement. Phylogenetic analysis showed that, with one exception, strains of the same emm type with the same amino acid replacement were clonally related by descent. This finding indicates that strains with some amino acid changes in PBP2X can successfully spread to new human hosts and cause invasive infections. Mapping of the amino acid changes onto a three-dimensional structure of the related Streptococcus pneumoniae PBP2X suggests that some substitutions are located in regions functionally important in related pathogenic bacterial species. Decreased beta-lactam susceptibility is geographically widespread in strains of numerically common emm gene subtypes. Enhanced surveillance and further epidemiological and molecular genetic study of this potential emergent antimicrobial problem are warranted.

Biological Characterization and Inhibition of Streptococcus pyogenes ZUH1 Causing Chronic Cystitis by Crocus sativus Methanol Extract, Bee Honey Alone or in Combination with Antibiotics: An In Vitro Study

Streptococcus pyogenes (S. pyogenes) ZUH1 was isolated and characterized using morphological, cultural and biochemical methods. The results showed that the marker genes (namely spyCEP, ssa, sic, sdaB and speG) indicating group A streptococci (GAS) were detected in the S. pyogenes genome. The results showed that the S. pyogenes strain was inhibited by Crocus sativus methanol extract (CSME), bee honey (BH) and catfish glycoprotein (CFG). The inhibitory activity of these natural agents were compared with standard antibiotics such as Ceftazidime (30 μg/mL), Cefoperazone (75 μg/mL), Cefoxitin (30 μg/mL) and Imipenem (10 μg/mL). There was a synergistic effect between certain antibiotics and CSME. GC-MS and IR analysis of CSME showed different cyclic ketones, aldehydes, esters, alcohols and acids. The main compounds were tetradecanoic acid, safranal and isophorone. Transmission electron microscopy (TEM) images of S. pyogenes cells treated with CSME showed signs of an irregular wrinkled outer surface, fragmentation, adhesion and aggregation of damaged bacterial cells or cellular debris. The marker genes (spyCEP, ssa, sic, sdaB and speG) could be used as a rapid diagnostic tool for GAS. CSME, BH and CFG showed distinctive anti-streptococcal activity either alone or in combinations with antibiotics; their action on S. pyogenes cells was studied by TEM. There was a synergistic effect between antibiotics and Crocus sativus, bee honey, and glycoprotein against S. pyogenes ZUH1. The action of natural agents on the pathogenic cells was shown using TEM.

Systematic review of factors contributing to penicillin treatment failure in Streptococcus pyogenes pharyngitis

Objective

Review the evidence for various explanations for microbiologic treatment failure following use of penicillin in group A streptococcal (GAS) tonsillopharyngitis.

DATA SOURCE

Systematic review of the literature based on Medline and EMBASE searches, and review of reference lists of included studies.

RESULTS

The explanations for penicillin treatment failure in GAS tonsillopharyngitis include 1) carrier state, 2) lack of compliance, 3) recurrent exposure, 4) in vivo copathogenicity of β-lactamase–producing normal pharyngeal flora, 5) in vivo bacterial coaggregation, 6) poor antibiotic penetration to tonsillopharyngeal tissue, 7) in vivo eradication of normal protective flora, 8) early initiation of antibiotic therapy resulting in suppression of an adequate host immune response, 9) intracellular localization of GAS, 10) GAS tolerance to penicillin, 11) contaminated toothbrushes or orthodontic appliances, and 12) transmission from the family pet. There is very little type I or II evidence to support any of the above-cited explanations for treatment failure in GAS tonsillopharyngitis; available studies are mostly observational (in patients) or laboratory-based without clinical confirmation.

CONCLUSION

Multiple explanations have been offered by investigators to explain penicillin treatment failures in GAS tonsillopharyngitis, but the evidence base to support the proposed explanations is generally weak by current standards. Further research is needed to better understand the mechanism(s) of penicillin treatment failure in GAS tonsillopharyngitis.

The Group A Streptococcal Carrier State Reviewed: Still an Enigma

Despite the common nature of group A streptococcal (GAS) infections, the carrier state of this organism is not well understood. In this article, we review the historical and recent research on the definition, epidemiology, and pathogenesis of the GAS carrier state. In addition, we outline trials of antimicrobial agents in the eradication of the carrier state and discuss indications for providing treatment to patients in the clinical setting.

Susceptibility and emm type of Streptococcus pyogenes isolated from children with severe infection

Minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of various antimicrobial agents were measured against 12 strains of Streptococcus pyogenes isolated from children with invasive infections between 2003 and 2012. The patients ranged in age from 1 day to 15 years, with patients younger than 5 years, including three neonates, accounting for a half of the patients. The disease was sepsis in four patients, skin and soft tissue infection in three patients, retropharyngeal abscess in two patients, pneumonia plus sepsis in one patient, empyema in one patient, and pyogenic arthritis in one patient. One patient with sepsis died, while cure without sequelae was achieved in all the remaining patients. When classified by type, emm1 (six strains) was the most prevalent type, followed by emm12 (two strains). The MIC₉₀/MBC₉₀ values were 0.015/0.015 μg/mL for penicillin G, 0.03/0.03 μg/mL for ampicillin, 0.015/0.03 μg/mL for cefotaxime, 0.03/0.03 μg/mL for ceftriaxone, 0.008/0.008 μg/mL for panipenem, 0.008/0.008 μg/mL for meropenem, and ≤0.004/≤0.004 μg/mL for doripenem, indicating the superior antimicrobial activities of carbapenem.

The association between vitamin D levels and recurrent group A streptococcal tonsillopharyngitis in adults

OBJECTIVES

To determine the association between recurrent group A streptococcal (GAS) tonsillopharyngitis and serum 25-hydroxy (25(OH)) vitamin D among adult subjects.

METHODS

Adult patients with tonsillopharyngitis between January 2007 and December 2009 were reviewed and identified retrospectively. Cases with a medical history of recurrent GAS tonsillopharyngitis were compared to age- and gender-matched individuals without a medical history of GAS tonsillopharyngitis. Recurrent tonsillopharyngitis was defined as three or more episodes of GAS tonsillopharyngitis per year for a period of two consecutive years.

RESULTS

Fifty-four cases with recurrent GAS tonsillopharyngitis and 50 controls were enrolled. There were no significant differences between cases and controls with regard to mean age (41 ± 13 vs. 42 ± 12 years; p=0.7) and male gender (55% vs. 54%; p=0.6). Mean serum levels of 25(OH) vitamin D among subjects with recurrent GAS tonsillopharyngitis were significantly lower from the controls (11.5 ng/ml ± 4.7 vs. 26 ng/ml ± 7; p=0.001). Multiple regression analysis showed that a serum 25(OH) vitamin D level <20 ng/ml was associated with recurrent GAS tonsillopharyngitis (odds ratio 1.62, 95% confidence interval 1.51-1.76; p < 0.001).

CONCLUSIONS

Our findings indicate a link between vitamin D deficiency and the recurrence of GAS tonsillopharyngitis.

Evaluation of potential factors contributing to microbiological treatment failure in Streptococcus pyogenes pharyngitis

BACKGROUND

A cohort study of children with pharyngitis aged two to 16 years was conducted to assess the role of microbial and host factors in group A beta-hemolytic streptococcus (GABHS) microbiological treatment failure.

METHODS

GABHS-infected children had pharyngeal swabs repeated two to five days after completing a 10-day course of penicillin V. M and T typing, and pulsed field gel electrophoresis were performed on the isolates, and the isolates were evaluated for tolerance. Patient characteristics and clinical features were noted and nasopharyngeal swabs for respiratory viruses were taken at enrolment.

RESULTS AND CONCLUSIONS

Of 286 patients enrolled, 248 (87%) could be evaluated. GABHS was cultured from 104 patients (41.9%), of whom 33 (33.7%) had microbiological treatment failures on follow-up. Although there was a trend toward failure for younger children (mean 6.5+/-2.4 years versus 7.3+/-2.4 years, P=0.07) and M type 12 (24% versus 10%, P=0.08), no factors were associated with treatment failure.

Penicillin V, loracarbef and clindamycin in tonsillar surface fluid during acute group A streptococcal pharyngotonsillitis

A previously healthy 37-y-old male presented with community-acquired pneumonia and extensive upper limb deep vein thrombosis. The diagnosis of Legionella pneumonia was made based on a positive direct immunofluorescence of the bronchial wash. An extensive investigation for hypercoagulable states was negative. The possible association between Legionella infection and deep vein thrombosis is highlighted.

Streptococcus pyogenes pharyngeal colonization resulting in recurrent, prepubertal vulvovaginitis

BACKGROUND

Recurrent, prepubertal, vaginal infections are an uncommon, troublesome problem for the patient and her family. Failure of initial therapy to alleviate vulvovaginitis may be related to vulvar skin disease, foreign body, sexual abuse, pinworms, reactions to medications, anatomic anomalies, or allergies. This report describes a case of recurrent Streptococcus pyogenes vulvovaginitis secondary to presumed vaginal re-inoculation from pharyngeal colonization.

CASE

A 4-yr-old presented with one year of culture proven, recurrent Streptococcus pyogenes vulvovaginitis. Her symptoms repeatedly resolved with penicillin therapy, but continued to recur following cessation of antibiotic therapy. Evaluation included physical examination, trans-abdominal pelvic ultrasound, and vaginoscopy which all revealed normal upper and lower genital tract anatomy. Both the patient and her mother demonstrated culture proven, Group A Streptococcus pharyngeal colonization. Because of the possibility of repeated inoculations of the vaginal area from the colonized pharynx, they were both treated for decolonization with a regimen of amoxicillin and rifampin for ten days. Following this therapy there was resolution of vaginal symptoms with no further recurrence. Follow-up pharyngeal culture done on both mother and child on their last visit were negative for Group A Streptococcus.

CONCLUSION

This case demonstrated an unusual specific cause of recurrent vaginitis resulting from presumed self or maternal re-inoculation with group A beta-hemolytic streptococcus from pharyngeal colonization. Group A beta-hemolytic streptococcus are consistently sensitive to penicillin, but up to 25% of acute pharyngitis cases treated with penicillin having continued asymptomatic, bacterial carriage within the nasopharynx. Thus initial alleviation of symptoms in a patient with Group A beta-hemolytic vulvovaginitis treated with penicillin, can have continued asymptomatic pharyngeal colonization which can result in recurrence of the vulvovaginitis. This case stresses the importance of considering re-infection through this route in the patient with recurrent Group A beta-hemolytic streptococcus vulvovaginitis.

Comparison of European and U.S. results for cephalosporin versus penicillin treatment of group A streptococcal tonsillopharyngitis

The outcome of cephalosporin versus penicillin treatment of group A streptococcal tonsillopharyngitis may differ between Europe and the USA. In the present study, Medline, Embase, reference lists, and abstract searches were used to identify randomized, controlled trials of cephalosporin versus penicillin treatment of group A streptococcal (GAS) tonsillopharyngitis. The outcomes of interest were bacteriologic and clinical cure rates from investigations conducted in Europe versus those conducted in the USA. Forty-seven trials involving 11,426 patients were included in the meta-analyses. For the comparison of 10 days of treatment with cephalosporins versus 10 days of treatment with penicillin, there were ten European and 25 U.S. trials, all involving pediatric subjects. The overall odds ratio (OR) favored cephalosporins more strongly in bacteriologic cure rate in Europe (OR=4.27, p<0.00001) than in the USA (OR=2.70, p<0.00001). Studies of 4-5 days of cephalosporin treatment versus 10 days of penicillin treatment were also analyzed. For nine European trials, the OR significantly favored cephalosporins (OR=1.30, p=0.03) in bacteriologic cure rates, but not as strongly as in the USA, (OR=2.41, p<0.00001). When results for 4-5 days of cephalosporin treatment were divided into pediatric versus adult populations, the differences in bacteriologic eradication rates obtained with cephalosporins were more pronounced in children. The likelihood of bacteriologic and clinical failure of GAS tonsillopharyngitis treatment in both European and U.S. patients is significantly less if a 10-day course of oral cephalosporin is prescribed, and is at least similar, if not significantly less, with a 4- to 5-day course of oral cephalosporin compared with a 10-day course of oral penicillin.

Explaining the poor bacteriologic eradication rate of single-dose ceftriaxone in group a streptococcal tonsillopharyngitis: a reverse engineering solution using pharmacodynamic modeling

OBJECTIVE

To explore pharmacokinetic factors underlying the poor bacteriologic eradication rate with a single 500-mg dose of ceftriaxone for streptococcal tonsillopharyngitis and to identify the minimum ceftriaxone dose required for effective treatment.

METHODS

Population modeling techniques were applied to pharmacokinetic data derived from paired plasma and tonsil samples from 153 children to assess the contribution of pharmacokinetic variability to patients' responses to ceftriaxone. In addition, a Monte Carlo simulation was performed to determine (1) the amount of time that free ceftriaxone concentrations must exceed the minimum inhibitory concentration (MIC) of group A Streptococcus to achieve bacteriologic eradication and (2) the ceftriaxone dose required to maintain free drug concentrations above the target MIC for the requisite amount of time. Ceftriaxone MICs for group A Streptococcus were obtained from a previous trial, in which all MICs (n = 115) were < or = 0.064 mg/L; 33.9% were susceptible at < or = 0.016 mg/L, 66.4% were susceptible at 0.032 mg/L, and 1.7% were susceptible at 0.064 mg/L.

RESULTS

Mean population pharmacokinetic parameters and their variances reflected substantial variability of clearance and half-life in the target population. Tonsillar ceftriaxone protein binding was 89.1%. The proportions of 1000 simulated patients with free ceftriaxone concentrations that exceeded MICs of 0.016 mg/L, 0.032 mg/L, and 0.064 mg/L at 24 hours were 71.7%, 65.4%, and 57.2%, respectively, and at 48 hours were 41.8%, 35.8%, and 28.6%, respectively. The amount of time that free ceftriaxone concentrations need to exceed MIC to achieve bacteriologic success was estimated to be 36 hours. Using this time criterion, two 500-mg doses of ceftriaxone separated by 18 hours should achieve a bacteriologic cure rate of approximately 95%.

CONCLUSIONS

Pharmacokinetic variability and high ceftriaxone tonsillar protein binding explain the high microbiologic failure rate for a single 500-mg dose of ceftriaxone in group A streptococcal tonsillopharyngitis. Monte Carlo simulation suggests that a second dose administered 18 hours after the first will be required to achieve an acceptable bacteriologic cure rate.

Diagnosis and treatment of pharyngitis in children

Acute pharyngitis is one of the most common illnesses for which children visit primary care physicians. Most cases of acute pharyngitis in children are caused by viruses and are benign and self-limited. Group A beta-hemolytic streptococcus is the most important of the bacterial causes of acute pharyngitis. Strategies for diagnosis and treatment of acute pharyngitis are directed at distinguishing children with viral pharyngitis, who would not benefit from antimicrobial therapy, from children with group A beta-hemolytic streptococcal pharyngitis, for whom antimicrobial therapy would be beneficial. Making this distinction is crucial in attempting to minimize the unnecessary use of antimicrobial agents in children.

Defining the optimum treatment regimen for azithromycin in acute tonsillopharyngitis

Pharyngitis is one of the most common infectious diseases affecting children. Group A streptococci are the leading bacterial cause of pharyngitis in children and adults. Because inappropriate antibiotic treatment for pharyngitis is becoming a major issue, only true group A beta-hemolytic streptococcus (GABHS) infections, proven by rapid antigen test or culture, should be treated with antibiotics. GABHS pharyngitis is often a mild and self-limiting infection in the absence of antimicrobial therapy. However, antimicrobial treatment must be administered to eradicate the pathogen from the throat, limit the spread of the infection and prevent possible progression to rheumatic fever, suppurative disease or toxin-mediated complications. Penicillin V for 10 days is the standard therapy and is effective in the management of GABHS pharyngitis. However, there are drawbacks to penicillin V therapy, including the length of the dosing regimen, which are leading to decreasing penicillin prescription rates in many countries. In addition bacteriologic treatment failures have been documented in up to 35% of GABHS patients treated with penicillin V, particularly in children <6 years old. A number of mechanisms may be responsible for these failures, but poor compliance with the standard 10-day penicillin treatment is likely to be a major factor. There is growing evidence to suggest that children with GABHS pharyngitis can be effectively treated with non-penicillin V antibiotics, which have the advantage of simpler and shorter dosing regimens compared with penicillin V. Among the antibiotics that have been tested clinically, azithromycin is the most widely studied. A total dose of 60 mg/kg azithromycin, given either as 12 mg/kg once daily for 5 days or 20 mg/kg once daily for 3 days, provides the best rate of GABHS eradication. Thus a total dose of 60 mg/kg azithromycin given during 3 or 5 days constitutes an alternative treatment to standard penicillin therapy in cases of penicillin hypersensitivity, when patient nonadherence to a 10-day penicillin regimen is suspected or for patients who fail therapy with a beta-lactam.

Group A Streptococcal Sepsis

The fulminant nature of group A streptococcal sepsis poses impressive challenges from diagnostic and therapeutic perspectives. Most patients are seen early in the course of infection by primary care providers or emergency department physicians and sent home, only to return in 12 to 24 hours with fully developed group A streptococcal sepsis. Early diagnosis is imperative, but the clinician must have a high index of suspicion. Often, the diagnosis is established only after aggressive interventional management has begun. This review emphasizes salient clinical features and provides general recommendations for critical care management.

Antimicrobial susceptibility patterns and genomic diversity in strains of Streptococcus pyogenes isolated in 1978-1997 in different Brazilian cities

Penicillin has been the antimicrobial of choice for the treatment of Streptococcus pyogenes infections for almost six decades. Although penicillin-resistant isolates have not been described to date, clinical failures have been reported after treatment with beta-lactams. In this study, we analysed the antimicrobial susceptibility and genetic diversity of S. pyogenes isolates obtained from healthy carriers or patients in different cities in the south and south east of Brazil. The MICs were determined for penicillin and seven other antimicrobials. Penicillin tolerance was also investigated. Genetic diversity was analysed by PFGE after SmaI fragmentation of the genomic DNA. All 211 isolates tested were susceptible to penicillin (MIC 0.0025-0.02 mg l(-1)). Four isolates were moderately penicillin-tolerant (MBC/MIC = 16 mg l(-1)). Most of the other drugs tested were very active against the strains examined, except for tetracycline, to which 50 % of strains were resistant. We also found extensive genetic diversity, in that 60 different patterns were recognized in the 96 strains studied. Indeed, we found no correlation between tetracycline resistance and clonality. Despite this diversity, some PFGE patterns persisted for up to 18 years and specific clone types were spread over different geographical locations

Short-course therapy with cefaclor for treatment of streptococcal pharyngotonsillitis

Short-course treatments for streptococcal pharyngotonsillitis with oral cephalosporins or macrolides have resulted in a similar bacteriological and clinical cure rate and better compliance compared with the conventional 10-day course. One hundred and thirty eight of 420 recruited patients had a positive culture for Streptococcus pyogenes and were randomly assigned to receive cefaclor (25 mg/kg/bid) for a 5-day (70 patients) or 10-day (68 patients) course. Patients were assessed clinically and bacteriologically 2-3 days after completing the course and followed up after 20-30 days. All 420 recruited patients belonged to a population of 2800 children who had been previously screened for a streptococcal carrier state to exclude carriers from final evaluation. Clinical cure and bacterial eradication was recorded in 92.8 and 92.6% of patients in groups A and B, respectively. Therefore, short-course therapy with cefaclor may offer an effective alternative treatment to conventional regimens, with potential for better compliance.

Penicillin treatment failure in group A streptococcal tonsillopharyngitis: no genetic difference found between strains isolated from failures and nonfailures

Despite penicillin (pcV) treatment, tonsillopharyngitis caused by group A streptococci (GAS) is associated with bacterial failure rates as high as 25%. The reason for this rate of failure is not fully understood. One explanation might be that certain DNA profiles of GAS strains are responsible for treatment failures. Using arbitrarily primed polymerase chain reaction (AP-PCR), we compared the DNA profiles of GAS strains from 4 patients with several treatment failures following pcV treatment of tonsillopharyngitis with the profiles of strains of the same T type from patients who were clinically and bacteriologically cured after a single course of pcV. The isolates were obtained during the same time period and from the same geographic area. Thirty-seven strains of T types 4, 12, and R28 were investigated. Eleven different DNA profiles could be detected with the AP-PCR technique. Five DNA profiles were identified as T type 12, 3 as T type 4, and 3 as T type R28. The DNA profiles of the strains from the 4 patients with several treatment failures differed, but all isolates from each one of these patients exhibited the same or a very similar profile. The DNA profiles of the failure strains were also represented in nonfailure strains. Treatment failure in these 4 patients therefore seems to be due to insufficient eradication of GAS, rather than to reinfection with a new strain. The finding that the same DNA profile can be present in both failure and nonfailure strains suggests that the treatment failure may be to some extent host-related and not only due to bacterial factors.

Failure of rifampin to eradicate group B streptococcal colonization in infants

BACKGROUND

Mucous membrane colonization with group B streptococci (GBS) frequently persists in infants after treatment of invasive infection and may be associated with recurrent disease.

OBJECTIVE

To determine the frequency with which GBS colonization persists at mucous membrane sites after treatment of invasive early or late onset infection and to determine the efficacy of oral rifampin in eradicating colonization in these infants and their mothers.

METHODS

Cultures for isolation of GBS were obtained from infants and their mothers after completion of the infant's parenteral therapy, 1 week later when rifampin therapy was initiated and at approximately 1 and 4 weeks after completion of rifampin therapy. Rifampin was administered (10-mg/kg dose; maximum, 600 mg) twice daily for 4 days.

RESULTS

Ten of 21 infants (48%) and 13 (65%) of their 20 mothers were colonized with GBS at throat or rectal (infant) or vaginal, rectal or breast milk (mother) sites before rifampin was initiated. One week or less after rifampin treatment, 7 (70%) infants and 4 (31%) mothers remained colonized with GBS. At study completion 6 infants and 7 mothers had GBS colonization. Persistent colonization was not related to GBS serotype, to initial rifampin minimal inhibitory concentration or to the development of rifampin resistant strains.

CONCLUSIONS

Rifampin treatment for four days utilized as a single agent after completion of parenteral therapy failed to reliably eradicate GBS colonization in infants.

Persistence of Lactobacillus plantarum DSM 9843 on human tonsillar surface after oral administration in fermented oatmeal gruel. A pilot study

The occurrence of Lactobacillus plantarum DSM 9843 on tonsillar scrapings was studied after single-dose administration. Six healthy volunteers gargled 100 ml of fermented oatmeal gruel containing 2 x 10(11) colony forming units (cfu) of Lb. plantarum DSM 9843 for 2 min and then swallowed it. Two healthy volunteers drank 50 ml fermented oatmeal gruel (containing 1 x 10(11) cfu of Lb. plantarum DSM 9843) mixed with 50 ml fruit juice, and in another experiment, 5 ml fermented oatmeal gruel (containing 1 x 10(10) cfu of Lb. plantarum DSM 9843) mixed with 95 ml fruit juice. Lb. plantarum DSM 9843 were found in tonsillar scrapings 4-8 h after intake of 2 x 10(11) cfu, for 5-8 h after intake of 1 x 10(11) cfu, and finally up to 4 h after intake of 1 x 10(10) cfu. On electron microscopy micrographs, short rod-shaped bacteria were visible 1 h after intake of the fermented oatmeal gruel, but not 2 h after intake. The results suggest that Lb. plantarum DSM 9843 possess an ability to adhere to tonsillar cells.

Deregulation of the arginine deiminase (arc) operon in penicillin-tolerant mutants of Streptococcus gordonii

Penicillin tolerance is an incompletely understood phenomenon that allows bacteria to resist drug-induced killing. Tolerance was studied with independent Streptococcus gordonii mutants generated by cyclic exposure to 500 times the MIC of penicillin. Parent cultures lost 4 to 5 log(10) CFU/ml of viable counts/24 h. In contrast, each of four independent mutant cultures lost < or =2 log(10) CFU/ml/24 h. The mutants had unchanged penicillin-binding proteins but contained increased amounts of two proteins with respective masses of ca. 50 and 45 kDa. One mutant (Tol1) was further characterized. The two proteins showing increased levels were homologous to the arginine deiminase and ornithine carbamoyl transferase of other gram-positive bacteria and were encoded by an operon that was >80% similar to the arginine-deiminase (arc) operon of these organisms. Partial nucleotide sequencing and insertion inactivation of the S. gordonii arc locus indicated that tolerance was not a direct consequence of arc alteration. On the other hand, genetic transformation of tolerance by Tol1 DNA always conferred arc deregulation. In nontolerant recipients, arc was repressed during exponential growth and up-regulated during postexponential growth. In tolerant transformants, arc was constitutively expressed. Tol1 DNA transformed tolerance at the same rate as transformation of a point mutation (10(-2) to 10(-3)). The tolerance mutation mapped on a specific chromosomal fragment but was physically distant from arc. Importantly, arc deregulation was observed in most (6 of 10) of additional independent penicillin-tolerant mutants. Thus, although not exclusive, the association between arc deregulation and tolerance was not fortuitous. Since penicillin selection mimicked the antibiotic pressure operating in the clinical environment, arc deregulation might be an important correlate of naturally occurring tolerance and help in understanding the mechanism(s) underlying this clinically problematic phenotype.

Streptococcal toxic shock syndrome associated with necrotizing fasciitis

Streptococcal toxic shock syndrome (strep TSS) with associated necrotizing fasciitis is a rapidly progressive process that kills 30-60% of patients in 72-96 h. Violaceous bullae, hypotension, fever, and evidence of organ failure are late clinical manifestations. Thus, the challenge to clinicians is to make an early diagnosis and to intervene with aggressive fluid replacement, emergent surgical debridement, and general supportive measures. Superantigens such as pyrogenic exotoxin A interact with monocytes and T lymphocytes in unique ways, resulting in T-cell proliferation and watershed production of monokines (e.g. tumor necrosis factor alpha, interleukin 1, interleukin 6), and lymphokines (e.g. tumor necrosis factor beta, interleukin 2, and gamma-interferon). Penicillin, though efficacious in mild Streptococcus pyogenes infection, is less effective in severe infections because of its short postantibiotic effect, inoculum effect, and reduced activity against stationary-phase organisms. Emerging treatments for strep TSS include clindamycin and intravenous gamma-globulin.

Prophylactic efficiency of 3-weekly benzathine penicillin G in rheumatic fever

Benzathine penicillin G (BPG) is effective for secondary prophylaxis of rheumatic fever (RF). However, interval between injections a remains a controversial matter. In a study population of 74 patients, following the initial diagnosis of RF, 3-weekly BPG (1.2 million units) regimen was started. During the first three-week period, serum penicillin concentrations were examined on the 7th, 14th and 21st days and throat culture done for group-A b hemolytic streptococcal (GABHS) infection. Ten patients (13.5%) at 21st day of injection had low serum penicillin concentration after the first BPG. GABHS was isolated in 5 patients during this period. Although two of these 5 patients had symptoms of respiratory tract infection, according to laboratory data, the other three were accepted as carriers. All 74 patients were then followed-up for rheumatic recurrence (RR) during long-term period (6 to 60 months, mean 25 +/- 5 months). There was no RR among regular (missing no more than one injection a year) group. We concluded that 3-weekly BPG regimen was satisfactory for secondary prophylaxis in RF, even though serum penicillin level was inadequate during the third week in some of the patients.

Potential mechanisms for failure to eradicate group A streptococci from the pharynx

OBJECTIVE

To investigate the relative efficacy of orally administered cefadroxil and penicillin V in the treatment of group A streptococcal (GABHS) pharyngitis and the mechanism(s) responsible for failure of antimicrobial therapy to eradicate GABHS from the pharynx.

STUDY DESIGN

A prospective, randomized clinical trial was conducted in four pediatric offices in which 462 patients with acute pharyngitis and positive culture for GABHS were randomly assigned to receive cefadroxil (n = 232) or penicillin V (n = 230).

RESULTS

Bacteriologic treatment success rates for patients in cefadroxil and penicillin groups were 94% and 86%, respectively. However, among patients classified clinically as likely to have bona fide GABHS pharyngitis, there was no difference in bacteriologic treatment success rates in cefadroxil and penicillin groups (95% and 94%, respectively). Among patients classified clinically as likely to be streptococcal carriers, bacteriologic treatment success rates in cefadroxil and penicillin groups were 92% and 73%, respectively. The presence of beta-lactamase and/or bacteriocin-producing pharyngeal flora had no consistent effect on bacteriologic eradication rates among patients in either penicillin or cefadroxil treatment groups or among patients classified as having either GABHS pharyngitis or streptococcal carriage.

CONCLUSIONS

Neither beta-lactamase nor bacteriocin produced by normal pharyngeal flora are related to bacteriologic treatment failures in GABHS pharyngitis. Cefadroxil seems to be more effective than penicillin V in eradicating GABHS from patients classified as more likely to be streptococcal carriers. However, among patients we classified as more likely to have bona fide GABHS pharyngitis, the effectiveness of cefadroxil and penicillin V seems to be comparable.

Tonsillar microbial flora: comparison of recurrent tonsillitis and normal tonsils

Tonsillar microbial flora was studied in cultures of tonsillar core specimens from 34 patients tonsillectomized due to recurrent group A streptococcal pharyngotonsillitis (n = 17) or sleep apnoea (n = 17). Patients in the sleep apnoea subgroup, who had no history of recurrent tonsillitis and manifested no tonsillar hypertrophy at ENT examination, served as controls. Tonsillar core specimens were cultured for semi-quantitative estimation of growth of aerobic, anaerobic and facultative organisms. The recurrent tonsillitis and apnoea subgroups did not differ significantly in the mean number of isolates per patient, either of aerobic spp. (3.8 vs. 4.3) or anaerobic spp. (5.2 vs. 4.7). Nor did the two subgroups differ significantly in the proportion of patients whose specimens manifested beta-lactamase producers (71% vs. 59%), in the isolation frequency of viridans (alpha) streptococci, or in the occurrence of semi-quantitative growth estimates of 3-4+ for aerobic, anaerobic or beta-lactamase-producing spp. Thus, the study provided no support for the hypothesis that inactivation of penicillin V by beta-lactamase-producing bacteria in oral or throat flora, or the eradication of viridans streptococci with their GAS-inhibitory capacity, is an important factor with regard to recurrent group A streptococcal tonsillitis. Other possible explanations, such as poor antibiotic penetration at the site of infection, are discussed.

Randomized, single-blinded comparative study of the efficacy of amoxicillin (40 mg/kg/day) versus standard-dose penicillin V in the treatment of group A streptococcal pharyngitis in children

A 10-day course of amoxicillin at a dosage of 40 mg per kilogram per day was compared with conventional (lower dosage) penicillin V therapy in the treatment of culture-proven Group A streptococcal pharyngitis in children 3 to 18 years of age in a prospective, randomized, and single-blinded study. Children had to have signs and symptoms compatible with the diagnosis of streptococcal pharyngitis and to have a throat swab positive for Group A streptococci. A second throat culture was obtained 10 to 14 days after the completion of therapy. Serotyping was performed to help differentiate carrier states from reinfections. Of 161 children enrolled, 113 were evaluable; 55 received penicillin and 58 received amoxicillin. At the completion of therapy 70.9% (39/55) of patients in the penicillin group vs 87.9% (51/58) of patients in the amoxicillin group were asymptomatic (clinical cure, P = 0.025). At the completion of therapy, 54.5% (30/55) of patients in the penicillin group vs 79.3% (46/58) of patients in the amoxicillin group had negative throat cultures (bacteriologic cure, P = 0.005). The carrier rate (children who were well but who were still carrying the same serotype of Group A streptococcus) also differed between the groups: 13 (23.6%) in the penicillin group compared with six (10.3%) in the amoxicillin group. Amoxicillin at 40 mg/kg/day was significantly more effective than lower dosages of penicillin V for clinical and bacteriologic cure in the treatment of Group A streptococcal pharyngitis in children. The current perception that penicillin is declining in effectiveness may be due to inadequate dosing.

Studies of the continuing susceptibility of group A streptococcal strains to penicillin during eight decades

BACKGROUND

In view of the widespread use of penicillin for >50 years for the treatment of group A streptococcal infections, we examined the question of whether there has been a change in susceptibility to penicillin in group A streptococcal strains collected during a span of 80 years (1917 to 1997).

METHODS

One hundred thirty-three group A streptococcal strains collected during 80 years were tested for changes in penicillin susceptibility. Three tests were used: (1) the microtiter broth minimal inhibitory concentration (MIC); (2) the minimal bactericidal concentration (MBC); and (3) the penicillin E strip MIC.

RESULTS

The results indicate there has been no change in the susceptibility to penicillin in these group A streptococci during the past 80 years. The microtiter broth MIC90 for the oldest strains (0.032 microg/ml) was not significantly different from those collected most recently (0.032 microg/ml); there is no statistical difference between the raw MIC data for the four collection periods (P=0.468, analysis of variance on ranks).

CONCLUSIONS

There has been no change in the susceptibility of group A streptococci during this time in spite of well-documented cases of penicillin resistance in other Gram-positive organisms and despite recognized resistance of group A streptococci to other antibiotics.

In vitro antimicrobial effects of various combinations of penicillin and clindamycin against four strains of Streptococcus pyogenes

Previous studies using mouse models of Streptococcus pyogenes necrotizing fasciitis demonstrated that clindamycin had greater efficacy than penicillin. Frequently both agents are used concurrently in the treatment of severe S. pyogenes infections. This study investigated interactions between penicillin and clindamycin. E-test and broth microdilution assays suggested additivity or indifference, while timed-killing assays demonstrated concentration-dependent variable effects. Timed-kill studies utilizing clinical concentrations suggest that there is no antagonism with the combination of drugs but that the combination does not have a bactericidal advantage over either penicillin or clindamycin alone.

Clinical comparison of cefaclor twice daily versus amoxicillin-clavulanate or erythromycin three times daily in the treatment of patients with streptococcal pharyngitis

The present study was undertaken to compare the efficacy and safety of a new regimen of cefaclor (25 mg/kg BID) with amoxicillin-clavulanate and erythromycin TID at standard doses for the treatment of pediatric patients with acute pharyngotonsillitis (APT). A total of 673 children (age range, 2 to 12 years) with signs and symptoms of APT were enrolled; 245 of these children who had a positive throat culture for group A beta-hemolytic streptococci (GABHS) entered the study and were randomly assigned to receive cefaclor 25 mg/kg BID, amoxicillin-clavulanate 15 mg/kg TID, or erythromycin 15 mg/kg TID. A 10-day antibiotic course was prescribed for each patient. Clinical and bacteriologic responses were assessed at the end of treatment (day 10) and at the follow-up visit (day 30). All GABHS strains isolated from throat cultures were tested for in vitro sensitivity to the antibiotics used in the study. Side effects (mainly nausea) were rare and mild in each group and did not require discontinuation of therapy. No GABHS strain was resistant to cefaclor or to amoxicillin-clavulanate; 37.9% of the strains were resistant to erythromycin. The results indicated that cefaclor given BID seems to be as effective as amoxicillin-clavulanate given TID (cure rate, 91.9% and 90.5%, respectively) and more effective than erythromycin given TID (cure rate, 76.8%) for the treatment of patients with APT. Erythromycin resistance among GABHS is an emerging problem in many geographic areas.

Clindamycin in recurrent group A streptococcal pharyngotonsillitis--an alternative to tonsillectomy?

Fifty-three patients with bacterial treatment failure after a 10-day course of treatment with phenoxymethyl penicillin (pcV) for group A streptococcal (GAS) pharyngotonsillitis were randomly assigned to continued treatment with pcV, or to treatment with clindamycin instead. The patients were then followed for 1 year with throat cultures and clinical examination every third month and in the event of symptoms of sore throat. In the first 3-month period, 15/22 patients in the pcV group yielded one or more positive cultures for GAS, all of the same T-type as in the original throat culture, as compared to 3/26 in the clindamycin group (p < 0.001). All three cases in the clindamycin group were due to a new T-type and thus were re-infections. In the pcV group, owing to repeated treatment failure, 12/22 patients were switched to treatment with clindamycin within the 3-month period following the second treatment. During the remainder of the 1-year follow-up period, sporadic cases of GAS-positive throat cultures occurred in both groups, but there was no significant difference in frequency between the two groups. It is concluded that, in patients with GAS pharyngotonsillitis and failure after pcV treatment, a 10-day course of clindamycin can protect the patient from recurrence for at least 3 months and might be an alternative to tonsillectomy.

Intracellular reservoir of Streptococcus pyogenes in vivo: a possible explanation for recurrent pharyngotonsillitis

Numerous theories have been presented that attempt to explain the frequent recurrences of pharyngotonsillitis caused by Streptococcus pyogenes; these recurrences occur after seemingly adequate antibiotic treatment. We previously have demonstrated that Spyogenes can survive for up to 7 days intracellularly in immortalized human respiratory epithelial cells grown in an antibiotic supplemented medium. Viable S pyogenes were externalized and established an extracellular infection, whenever the extracellular antibiotic was removed. We have investigated the presence of intracellular S pyogenes in two in vivo studies using respiratory epithelial cells collected from patients with tonsillitis and the tonsils of asymptomatic carriers. Electron microscopy and immunohistochemistry demonstrated intracellular S pyogenes in pharyngeal epithelial cells in 13 of 14 patients with tonsillitis (93%). Furthermore, intracellular S pyogenes were found in macrophage-like cells in eight (73%) and in epithelial cells in four (36%) tonsils from 11 asymptomatic S pyogenes carriers. These in vivo data strongly support the hypothesis that intracellular S pyogenes can constitute a reservoir of bacteria with the potential to cause reinfections.

Molecular DNA analysis for differentiation of persistence or relapse from recurrence in treatment failure of Streptococcus pyogenes pharyngitis

In the evaluation of treatment failure in group A streptococcal pharyngitis, it is essential to distinguish persistence or relapse with homologous streptococcal strains from the acquisition of new, unrelated strains. Randomly amplified polymorphic DNA analysis and restriction fragment length polymorphism analysis of total DNA were used as epidemiological tools to compare 122 pre- and post-treatment Streptococcus pyogenes isolates obtained from 61 patients. The results obtained by molecular typing showed that bacteriological failures were due to the original strains in 43 cases (70%) and to new strains in 18 cases (30%). In the present study, restriction fragment length polymorphism analysis of total DNA appeared to be more discriminative than randomly amplified polymorphic DNA analysis. Thus, molecular analysis of DNA is an effective way to distinguish recurrence from persistence or relapse and will be useful in assessing the efficacy of new antibiotic treatments.

The toxic shock syndromes

Because of the frequency with which Staphylococcus aureus and Streptococcus pyogenes infections occur, physicians are quite familiar with the diversity of their clinical presentations. In the 1970s, however, shock associated with multiorgan failure was described in menstruating female patients as well as in male patients following a variety of surgical procedures, such as rhinoplasty. This previously undescribed presentation of S. aureus infection, termed staphylococcal toxic shock syndrome, was associated with unique strains of S. aureus. In the mid-1980s, the emergence of streptococcal toxic shock syndrome was heralded by several case reports describing patients with group A streptococcal infections associated with shock and organ failure. This article compares the differences in the epidemiologic, clinical, and pathophysiologic features of the toxic shock syndromes.

Streptococcal toxic shock syndrome from a puncture wound to the foot

Puncture wounds to the foot are a common occurrence. If treated properly, the majority will be resolved without major complications. Toxic shock syndrome and streptococcal toxic shock-like syndrome are devastating complications of some staphylococcal and streptococcal infections. This paper discusses the similarities and differences between the two toxic states, reviews the pathophysiology, and presents a case report of near-fatal streptococcal toxic shock-like syndrome secondary to a puncture wound of the foot.

Azithromycin versus penicillin V in the treatment of paediatric patients with acute streptococcal pharyngitis/tonsillitis. Paediatric Azithromycin Study Group

The efficacy and safety of azithromycin and penicillin V in the treatment of acute streptococcal pharyngitis/tonsillitis in paediatric patients were compared in a double-blind, double-dummy prospective study. A total of 489 children (age range, 2-13 years) were randomized to receive treatment with penicillin V (125-250 mg 4 x daily for 10 days) or azithromycin in an oral suspension (10 or 20 mg/kg 1 x daily for 3 days). Only patients with baseline cultures positive for Streptococcus pyogenes and complete clinical and microbiological assessments at the end of the therapy and follow-up one month later were included in the efficacy analysis. A satisfactory clinical response (cure or improvement) was recorded in 99% of the 10 mg/kg azithromycin group, 100% of the 20 mg/kg azithromycin group, and 97% of the penicillin V group at the end of therapy (day 12-14). At the follow-up evaluation (day 28-30), relapse rates in patients cured or improved at the end of therapy were 6%, 5%, and 2%, respectively. Bacteriological eradication rates at the end of therapy were 98% in both azithromycin groups and 92% in patients who received penicillin V (p = 0.011); pathogen recurrence was recorded at follow-up in 4% of the 20 mg/kg azithromycin group and in 6% of both the 10 mg/kg azithromycin and penicillin V groups. Treatment-related adverse events, the majority of mild to moderate severity, occurred in 13% of patients in the 20 mg/kg azithromycin group, 9% in the 10 mg/kg azithromycin group, and 5% in the penicillin V group. Azithromycin in a dosage of 10 or 20 mg/kg/day one daily for three days was as safe and effective as penicillin V administered four times daily in the treatment of paediatric patients with acute pharyngitis/tonsillitis.