Increased recovery of Moraxella catarrhalis and Haemophilus influenzae in association with group A beta-haemolytic streptococci in healthy children and those with pharyngo-tonsillitis

Throat Swab Culture Positivity and Antibiotic Resistance Profiles in Children 2-5 Years of Age Suspected of Bacterial Tonsillitis at Hargeisa Group of Hospitals, Somaliland: A Cross-Sectional Study

Introduction

Tonsillitis is the third most frequently diagnosed infection in the pediatric age and is associated with significant morbidity and loss of school attendance. Throat swab cultures are useful for the confirmation of children with a clinically suspected tonsillitis. However, Somaliland is one of the underdeveloped countries with a low standard of sanitation and poor health seeking culture. Treatment of tonsillitis with antibiotics is irrational and not empirical. This study determined the bacterial throat swab culture positivity and antibiotic resistance profiles of the bacterial isolates among children 2-5 years of age with suspicion of tonsillitis at Hargeisa Group of Hospital, Somaliland.

Materials and Methods

A cross-sectional study was conducted from March to July 2020. A total of 374 children from 2 to 5 years of age suspicion of tonsillitis was included using a convenient sampling method. Throat swabs were collected, and bacterial isolation and identification were done using standard bacteriological procedures. Antimicrobial susceptibility testing was done using the disk diffusion method. Data on demographic variables and clinical profiles were collected using structured questionnaires. Logistic regression analysis was computed to identify factors associated with bacterial tonsillitis.

Results

Overall, 120 (32.1%) (95% CI 27.4-36.8%) of children were positive for bacterial throat cultures. Of these, 23 (19.2%) were mixed bacterial isolates. The most frequent bacterial isolates were beta-hemolytic streptococci 78 (55%), Staphylococcus aureus 42 (29%), and Streptococcus pneumoniae 10 (7%). Isolates revealed 83.3-100% rate of resistance to ampicillin. Beta-hemolytic streptococci isolates were 94.9% resistant to ampicillin. S. aureus was resistant to clarithromycin (38%) while S. pneumoniae isolates were 100% resistant to ampicillin. History of tonsillitis (AOR = 0.12; 95% CI = 0.06-0.21), difficulty in swallowing (AOR = 6.99; 95% CI = 3.56-13.73), and attending schools (AOR = 2.98; 95% CI = 1.64-5.42) were found to be associated with positive throat culture.

Conclusions

Resistance to ampicillin and MDR among beta-hemolytic streptococci and other isolates of throat colonizers in children with clinically suspected of bacterial tonsillitis are major concerns in Hargeisa, Somaliland. Therefore, treatments of cases are recommended to be guided by regular culture and antimicrobial susceptibility testing to prevent complications of tonsillitis and associated antibiotic resistance.

Lactoferrin versus Long-Acting Penicillin in Reducing Elevated Anti-Streptolysin O Titer in Cases of Tonsillopharyngitis

Background

Beta-Hemolytic streptococci are the most frequent bacteria causing tonsillitis. Lactoferrin may play a role in the treatment of chronic tonsillitis due to its direct antimicrobial activity.

Objective

To assess the possible role of lactoferrin in reduction of raised serum Anti-Streptolysin O Titer (ASOT) in cases of chronic tonsillopharyngitis in comparison to long acting penicillin.

Methods

This study included 117 children with tonsillopharyngitis with high ASOT randomly divided into three groups; group 1 treated with lactoferrin, group 2 treated with long acting penicillin and group 3 treated with both drugs. For all patients ASOT was measured after three and six months of starting treatment.

Results

This study included 60 males and 57 females with the mean age (8.5 ± 2.4). There is statistically significant reduction in ASOT in all groups after three months of treatment. ASOT after 3 months was significantly lower in group1 (370±440) and group 3 (350±450) in comparison to group 2 (420±560) with p value 0.02, 0.004, respectively, with no significant difference in comparing group 1 to group 3 p value 0.4. Also, ASO titre after 6 months was significantly lower in group1 (350±420) and group 3 (340±440) in comparison to group 2 (420±550) with p value 0.02, 0.007, respectively, with no significant difference in comparing group 1 to group 3 p value 0.5. In comparing ASOT at three months and six months of treatment in the three studied groups; it decreased by 2% in group 1, and 1.6% in group 3 and no change in group 2.

Conclusion

Lactoferrin alone or in combination with long acting penicillin is safe and more effective than long acting penicillin alone in reducing ASOT. Treatment for six months with lactoferrin alone or in combination with long acting penicillin could offer a better response.

In Vivo Secretion of β-Lactamase-Carrying Outer Membrane Vesicles as a Mechanism of β-Lactam Therapy Failure

Outer membrane vesicles carrying β-lactamase (βLOMVs) protect bacteria against β-lactam antibiotics under experimental conditions, but their protective role during a patient’s treatment leading to the therapy failure is unknown. We investigated the role of βLOMVs in amoxicillin therapy failure in a patient with group A Streptococcus pyogenes (GAS) pharyngotonsillitis. The patient’s throat culture was examined by standard microbiological procedures. Bacterial vesicles were analyzed for β-lactamase by immunoblot and the nitrocefin assay, and in vivo secretion of βLOMVs was detected by electron microscopy. These analyses demonstrated that the patient’s throat culture grew, besides amoxicillin-susceptible GAS, an amoxicillin-resistant nontypeable Haemophilus influenzae (NTHi), which secreted βLOMVs. Secretion and β-lactamase activity of NTHi βLOMVs were induced by amoxicillin concentrations reached in the tonsils during therapy. The presence of NTHi βLOMVs significantly increased the minimal inhibitory concentration of amoxicillin for GAS and thereby protected GAS against bactericidal concentrations of amoxicillin. NTHi βLOMVs were identified in the patient’s pharyngotonsillar swabs and saliva, demonstrating their secretion in vivo at the site of infection. We conclude that the pathogen protection via βLOMVs secreted by the flora colonizing the infection site represents a yet underestimated mechanism of β-lactam therapy failure that warrants attention in clinical studies.

Treatment Challenges of Group A Beta-hemolytic Streptococcal Pharyngo-Tonsillitis

Introduction  Despite its in vitro efficacy, penicillin often fails to eradicate Group A β-hemolytic streptococci (GABHS) from patients with acute and relapsing pharyngo-tonsillitis (PT). Objective  This review of the literature details the causes of penicillin failure to eradicate GABHS PT and the therapeutic modalities to reduce and overcome antimicrobial failure. Data Synthesis  The causes of penicillin failure in eradicating GABHS PT include the presence of β lactamase producing bacteria (BLPB) that "protect" GABHS from any penicillin; the absence of bacteria that interfere with the growth of GABHS; co-aggregation between GABHS and Moraxella catarrhalis; and the poor penetration of penicillin into the tonsillar tissues and the tonsillo-pharyngeal cells, which allows intracellular GABHS and Staphylococcus aureus to survive. The inadequate intracellular penetration of penicillin can allow intracellular GABHS and S. aureus to persist. In the treatment of acute tonsillitis, the use of cephalosporin can overcome these interactions by eradicating aerobic BLPB (including M. catarrhalis), while preserving the potentially interfering organisms and eliminating GABHS. Conclusion  In treatment of recurrent and chronic PT, the administration of clindamycin, or amoxicillin-clavulanic acid, can eradicate both aerobic and anaerobic BLPB, as well as GABHS. The superior intracellular penetration of cephalosporin and clindamycin also enhances their efficacy against intracellular GABHS and S. aureus.

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 role of the local microbial ecosystem in respiratory health and disease

Respiratory tract infections are a major global health concern, accounting for high morbidity and mortality, especially in young children and elderly individuals. Traditionally, highly common bacterial respiratory tract infections, including otitis media and pneumonia, were thought to be caused by a limited number of pathogens including Streptococcus pneumoniae and Haemophilus influenzae. However, these pathogens are also frequently observed commensal residents of the upper respiratory tract (URT) and form-together with harmless commensal bacteria, viruses and fungi-intricate ecological networks, collectively known as the 'microbiome'. Analogous to the gut microbiome, the respiratory microbiome at equilibrium is thought to be beneficial to the host by priming the immune system and providing colonization resistance, while an imbalanced ecosystem might predispose to bacterial overgrowth and development of respiratory infections. We postulate that specific ecological perturbations of the bacterial communities in the URT can occur in response to various lifestyle or environmental effectors, leading to diminished colonization resistance, loss of containment of newly acquired or resident pathogens, preluding bacterial overgrowth, ultimately resulting in local or systemic bacterial infections. Here, we review the current body of literature regarding niche-specific upper respiratory microbiota profiles within human hosts and the changes occurring within these profiles that are associated with respiratory infections.

The role of the local microbial ecosystem in respiratory health and disease

Respiratory tract infections are a major global health concern, accounting for high morbidity and mortality, especially in young children and elderly individuals. Traditionally, highly common bacterial respiratory tract infections, including otitis media and pneumonia, were thought to be caused by a limited number of pathogens including Streptococcus pneumoniae and Haemophilus influenzae. However, these pathogens are also frequently observed commensal residents of the upper respiratory tract (URT) and form-together with harmless commensal bacteria, viruses and fungi-intricate ecological networks, collectively known as the 'microbiome'. Analogous to the gut microbiome, the respiratory microbiome at equilibrium is thought to be beneficial to the host by priming the immune system and providing colonization resistance, while an imbalanced ecosystem might predispose to bacterial overgrowth and development of respiratory infections. We postulate that specific ecological perturbations of the bacterial communities in the URT can occur in response to various lifestyle or environmental effectors, leading to diminished colonization resistance, loss of containment of newly acquired or resident pathogens, preluding bacterial overgrowth, ultimately resulting in local or systemic bacterial infections. Here, we review the current body of literature regarding niche-specific upper respiratory microbiota profiles within human hosts and the changes occurring within these profiles that are associated with respiratory infections.

Haemophilus influenzae: recent advances in the understanding of molecular pathogenesis and polymicrobial infections

PURPOSE OF REVIEW

Non-typeable Haemophilus influenzae (NTHi) is a human-specific mucosal pathogen and one of the most common causes of bacterial infections in children and patients with chronic obstructive pulmonary disease. It is also frequently found in polymicrobial superinfections. Great strides have recently been made in the understanding of the molecular mechanisms underlying NTHi pathogenesis.

RECENT FINDINGS

By using new methodology, such as experimental human colonization models and whole-genome approaches, investigators have shed light upon the various strategies of NTHi that are involved in pathogenesis. These include the escape of the mucociliary elevator, evasion of host immunity, survival in environments with scarce nutrients, and finally participation in polymicrobial infections. Lipooligosaccharide branching, proteinous adhesins, metabolic adaption to nutrient availability and many scavenging systems are implicated in these processes. Interestingly, genome-based studies comparing virulent and commensal strains have identified many hypothetical proteins as virulence determinants, suggesting that much regarding the molecular pathogenesis of NTHi remains to be solved.

SUMMARY

NTHi is an opportunistic pathogen and highly specialized colonizer of the human respiratory tract that has developed intricate mechanisms to establish growth and survival in the human host. Continued research is needed to further elucidate NTHi host-pathogen and pathogen-pathogen interactions.

Bacterial prevalence and antimicrobial prescribing trends for acute respiratory tract infections

BACKGROUND AND OBJECTIVES

Antimicrobials are frequently prescribed for acute respiratory tract infections (ARTI), although many are viral. We aimed to determine bacterial prevalence rates for 5 common childhood ARTI - acute otitis media (AOM), sinusitis, bronchitis, upper respiratory tract infection, and pharyngitis- and to compare these rates to nationally representative antimicrobial prescription rates for these ARTI.

METHODS

We performed (1) a meta-analysis of English language pediatric studies published between 2000 and 2011 in Medline, Embase, and the Cochrane library to determine ARTI bacterial prevalence rates; and (2) a retrospective cohort analysis of children age <18 years evaluated in ambulatory clinics sampled by the 2000-2010 National Ambulatory Medical Care Survey (NAMCS) to determine estimated US ARTI antimicrobial prescribing rates.

RESULTS

From the meta-analysis, the AOM bacterial prevalence was 64.7% (95% confidence interval [CI], 50.5%-77.7%); Streptococcus pyogenes prevalence during pharyngitis was 20.2% (95% CI, 15.9%-25.2%). No URI or bronchitis studies met inclusion criteria, and 1 sinusitis study met inclusion criteria, identifying bacteria in 78% of subjects. Based on these condition-specific bacterial prevalence rates, the expected antimicrobial rescribing rate for ARTI overall was 27.4% (95% CI, 26.5%-28.3%). However, antimicrobial agents were prescribed in NAMCS during 56.9% (95% CI, 50.8%-63.1%) of ARTI encounters, representing an estimated 11.4 million potentially preventable antimicrobial prescriptions annually.

CONCLUSIONS

An estimated 27.4% of US children who have ARTI have bacterial illness in the post-pneumococcal conjugate vaccine era. Antimicrobials are prescribed almost twice as often as expected during outpatient ARTI visits, representing an important target for ongoing antimicrobial stewardship interventions.

Group A streptococci are protected from amoxicillin-mediated killing by vesicles containing β-lactamase derived from Haemophilus influenzae

OBJECTIVES

Group A streptococci (GAS) cause, among other infections, pharyngotonsillitis in children. The species is frequently localized with the Gram-negative respiratory pathogens non-typeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis, which both produce outer membrane vesicles (OMVs). The aim of this study was to investigate whether OMVs isolated from NTHi contain functional β-lactamase and whether the OMVs hydrolyse amoxicillin and thus protect GAS from killing by the antibiotic.

METHODS

The antibiotic susceptibility of isolates was determined using the Etest. The resistance genes blaTEM-1 (encoding NTHi β-lactamase), bro-1 (encoding M. catarrhalis β-lactamase) and ftsI (encoding NTHi penicillin-binding protein 3) were searched for by PCR, followed by sequencing. OMVs were isolated by ultracentrifugation and the presence of β-lactamase was detected by western blots including specific rabbit polyclonal antibodies. The chromogenic substrate nitrocefin was used to quantify and compare the β-lactamase enzyme activity in the OMVs. The hydrolysis of amoxicillin by β-lactamase was estimated by an agar diffusion method.

RESULTS

We showed that OMVs released from β-lactam-resistant M. catarrhalis and NTHi contain functional β-lactamase that hydrolyses amoxicillin and protects GAS from killing by amoxicillin.

CONCLUSIONS

This is the first report of the presence of β-lactamase in NTHi OMVs. We suggest that OMV-derived β-lactamase from coinfecting pathogens such as NTHi and M. catarrhalis may contribute to the occasional treatment failures seen in GAS tonsillitis.

Viral and bacterial interactions in the upper respiratory tract

Respiratory infectious diseases are mainly caused by viruses or bacteria that often interact with one another. Although their presence is a prerequisite for subsequent infections, viruses and bacteria may be present in the nasopharynx without causing any respiratory symptoms. The upper respiratory tract hosts a vast range of commensals and potential pathogenic bacteria, which form a complex microbial community. This community is assumed to be constantly subject to synergistic and competitive interspecies interactions. Disturbances in the equilibrium, for instance due to the acquisition of new bacteria or viruses, may lead to overgrowth and invasion. A better understanding of the dynamics between commensals and pathogens in the upper respiratory tract may provide better insight into the pathogenesis of respiratory diseases. Here we review the current knowledge regarding specific bacterial–bacterial and viral–bacterial interactions that occur in the upper respiratory niche, and discuss mechanisms by which these interactions might be mediated. Finally, we propose a theoretical model to summarize and illustrate these mechanisms.

Protective mechanisms of respiratory tract Streptococci against Streptococcus pyogenes biofilm formation and epithelial cell infection

Streptococcus pyogenes (group A streptococci [GAS]) encounter many streptococcal species of the physiological microbial biome when entering the upper respiratory tract of humans, leading to the question how GAS interact with these bacteria in order to establish themselves at this anatomic site and initiate infection. Here we show that S. oralis and S. salivarius in direct contact assays inhibit growth of GAS in a strain-specific manner and that S. salivarius, most likely via bacteriocin secretion, also exerts this effect in transwell experiments. Utilizing scanning electron microscopy documentation, we identified the tested strains as potent biofilm producers except for GAS M49. In mixed-species biofilms, S. salivarius dominated the GAS strains, while S. oralis acted as initial colonizer, building the bottom layer in mixed biofilms and thereby allowing even GAS M49 to form substantial biofilms on top. With the exception of S. oralis, artificial saliva reduced single-species biofilms and allowed GAS to dominate in mixed biofilms, although the overall two-layer structure was unchanged. When covered by S. oralis and S. salivarius biofilms, epithelial cells were protected from GAS adherence, internalization, and cytotoxic effects. Apparently, these species can have probiotic effects. The use of Affymetrix array technology to assess HEp-2 cell transcription levels revealed modest changes after exposure to S. oralis and S. salivarius biofilms which could explain some of the protective effects against GAS attack. In summary, our study revealed a protection effect of respiratory tract bacteria against an important airway pathogen and allowed a first in vitro insight into local environmental processes after GAS enter the respiratory tract.

Anaerobic bacteria in upper respiratory tract and head and neck infections: microbiology and treatment

Anaerobes are the predominant components of oropharyngeal mucous membranes bacterial flora, and are therefore a common cause of bacterial infections of endogenous origin of upper respiratory tract and head and neck. This review summarizes the aerobic and anaerobic microbiology and antimicrobials therapy of these infections. These include acute and chronic otitis media, mastoiditis and sinusitis, pharyngo-tonsillitis, peritonsillar, retropharyngeal and parapharyngeal abscesses, suppurative thyroiditis, cervical lymphadenitis, parotitis, siliadenitis, and deep neck infections including Lemierre Syndrome. The recovery from these infections depends on prompt and proper medical and when indicated also surgical management.

Biofilm formation by bacteria isolated from upper respiratory tract before and after adenotonsillectomy

Failure of antibiotics to eradicate the microbial pathogens primarily responsible for otorhinolaryngological diseases has led to the hypothesis that these microorganisms may be structured in a biolfilm. Aim of the study was to evaluate the ability to produce biofilm among bacteria isolated from tonsils and/or adenoids and nasopharynx. Biopsies and swabs were collected during surgery and after 3 and 6 months in 32 children undergoing adenoidectomy and/or tonsillectomy. Production of biofilm by Staphylococcus aureus, Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae was evaluated in vitro by means of spectrophotometry after growth in microplates and staining with crystalviolet. Of the isolates from intraoperative samples, 44.7% were either moderate or strong biofilm producers compared with 27% of isolates at 6 months after surgery. A decrease in biofilm production was observed for H. influenzae and S. aureus. In conclusion, the rate of isolation and ability to form biofilm decreased in bacteria isolated subsequent to adenoidectomy and/or tonsillectomy. This suggests a role for biofilm in pathogenesis of recurrent and chronic pharyngeal diseases and rhinopharingitis.

Atypical bacteria in adenoids and tonsils of children requiring adenotonsillectomy

CONCLUSIONS

The results of this study suggest that atypical bacteria may be involved not only in acute upper airway diseases but also in recurrent infections requiring adenoidectomy and/or tonsillectomy. Therefore, their identification, followed by an appropriate treatment, should be considered.

OBJECTIVE

Although viruses and group A beta-haemolytic streptococci (GABHS) represent the most frequent bacterial aetiological agents of paediatric upper respiratory tract infections (URTIs), chlamydia and Mycoplasma pneumoniae have also been found in acute tonsillopharyngitis. Nevertheless their relevance in chronic or recurrent URTI has never been evaluated. This study aimed to further address the role of atypical bacteria in recurrent URTIs requiring adenoidectomy and tonsillectomy.

METHODS

Samples from 55 consecutive children who underwent adenoidectomy and/or tonsillectomy for recurrent or chronic URTI were cut transversely into smaller sections of 5 mm. Each section was pooled and assayed by specific PCR for viruses and bacteria.

RESULTS

Adenovirus was detected in 10 patients (18.2%), influenza A virus in one patient and influenza B virus in another. None of the other tested viruses was found. GABHS was found in 37 patients (67.3%). Moraxella catarrhalis and Haemophilus influenzae were detected in 30 patients (54.5%). M. pneumoniae was detected in 6 patients (10.9%) and C. pneumoniae was found in 10 patients (18.2%).

Haemophilus influenzae and Haemophilus haemolyticus in tonsillar cultures of adults with acute pharyngotonsillitis

OBJECTIVE

The aim of this study was to evaluate the clinical implication of Haemophilus haemolyticus, one of the closest relative of Haemophilus influenzae, on acute pharyngotonsillitis.

METHODS

We applied polymerase chain reaction (PCR) for 16S ribosomal DNA (rDNA) and IgA protease gene (iga) to distinguish H. haemolyticus and H. influenzae.

RESULTS

Among the 199 Haemophilus spp. isolated from 214 patients with acute pharyngotonsillitis, 52 (24.3%) H. influenzae strains and 23 (10.7%) H. haemolyticus strains were identified by polymerase chain reaction (PCR) for 16S rDNA and IgA protease gene (iga). All H. haemolyticus strains showed hemolysis on horse blood agar and there were no other Haemophilus spp., nonhemolytic H. haemolyticus and H. influenzae variant strains that had absent iga gene. H. hemolyticus showed close genetic relationship with H. influenzae evaluated by pulsed field gel electrophoresis (PFGE). The cases of acute pharyngotonsillitis showing WBC=7000/mm(3) or CRP=8 mg/dl were frequently found among cases with H. influenzae rather than cases with H. haemolyticus.

CONCLUSION

H. haemolyticus is a pharyngeal commensal that is isolated frequently from adults with acute pharyngotonsillitis.

Beta-lactam effects on mixed cultures of common respiratory isolates as an approach to treatment effects on nasopharyngeal bacterial population dynamics

Background

Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae are bacteria present in the nasopharynx as part of normal flora. The ecological equilibrium in the nasopharynx can be disrupted by the presence of antibiotics.

Methodology/Principal Findings

A computerized two-compartment pharmacodynamic model was used to explore β-lactam effects on the evolution over time of a bacterial load containing common pharyngeal isolates by simulating free serum concentrations obtained with amoxicillin (AMX) 875 mg tid, amoxicillin/clavulanic acid (AMC) 875/125 mg tid and cefditoren (CDN) 400 mg bid regimens over 24 h. Strains and MICs (µg/ml) of AMX, AMC and CDN were: S. pyogenes (0.03, 0.03 and 0.015), S. pneumoniae (2, 2 and 0.25), a β-lactamase positive H. influenzae (BL⁺; >16, 2 and 0.06) and a β-lactamase positive AMC-resistant H. influenzae (BLPACR, >16, 8 and 0.06). Mixture of identical 1∶1∶1∶1 volumes of each bacterial suspension were prepared yielding an inocula of ≈4×10⁶ cfu/ml. Antibiotic concentrations were measured both in bacterial and in bacteria-free antibiotic simulations. β-lactamase production decreased AMX concentrations and fT_>MIC against S. pneumoniae (from 43.2% to 17.7%) or S. pyogenes (from 99.9% to 24.9%), and eradication was precluded. The presence of clavulanic acid countered this effect of co-pathogenicity, and S. pyogenes (but not BL⁺ and S. pneumoniae) was eradicated. Resistance of CDN to TEM β-lactamase avoided this co-pathogenicity effect, and CDN eradicated S. pyogenes and H. influenzae strains (fT_>MIC >58%), and reduced in 94% S. pneumoniae counts (fT_>MIC ≈25%).

Conclusions/Significance

Co-pathogenicity seems to be gradual since clavulanic acid countered this effect for strains very susceptible to AMX as S. pyogenes but not for strains with AMX MIC values in the limit of susceptibility as S. pneumoniae. There is a potential therapeutic advantage for β-lactamase resistant cephalosporins with high activity against streptococci.

Overcoming penicillin failures in the treatment of Group A streptococcal pharyngo-tonsillitis

The causes of penicillin failure in eradicating Group A beta-hemolytic streptococcal pharyngo-tonsillitis (GABHS PT) are described. These include the presence of beta-lactamase producing bacteria that "protect" Group A beta-hemolytic streptococci (GABHS) from penicillins; the absence of bacteria that interfere with the growth of GABHS; co-aggregation between GABHS and Moraxella catarrhalis; and the poor penetration of penicillin into the tonsillar tissues and the tonsillo-pharyngeal cells. The use of antimicrobials that can overcome and modulate these phenomena and achieve better cure of the infection is described.

Characterization of the IgD binding site of encapsulated Haemophilus influenzae serotype b

Encapsulated Haemophilus influenzae is a causative agent of invasive disease, such as meningitis and septicemia. Several interactions exist between H. influenzae and the human host. H. influenzae has been reported to bind IgD in a nonimmune manner, but the responsible protein has not yet been identified. To define the binding site on IgD for H. influenzae, full-length IgD and four chimeric IgDs with interspersed IgG sequences and Ag specificity for dansyl chloride were expressed in stably transfected Chinese hamster ovary cells. The binding of recombinant IgD to a panel of encapsulated H. influenzae serotype b (Hib) and nontypeable strains were investigated using a whole cell ELISA and flow cytometry. IgD binding was detected in 50% of the encapsulated Hib strains examined, whereas nontypeable H. influenzae did not interact with IgD. Finally, mapping experiments using the chimeric IgD/IgG indicated that IgD CH1 aa 198-224 were involved in the interaction between IgD and H. influenzae. Thus, by using recombinant IgD and chimeras with defined Ag specificity, we have confirmed that Hib specifically binds IgD, and that this binding involves the IgD CH1 region.

Microbiology and Principles of Antimicrobial Therapy for Head and Neck Infections

The principles of antimicrobial management for head and neck infections include establishing an accurate clinical and microbiologic diagnosis and treating the patient initially with an empiric antimicrobial regimen based on predicted likelihood of success and reduced potential for resistance. Subsequent adjustments may be required based on clinical response and available culture results. This article summarizes the aerobic and anaerobic microbiology of selected acute and chronic infections of the head and neck and the approaches to antimicrobial therapy.

The evidence base for cephalosporin superiority over penicillin in streptococcal pharyngitis

Current treatment guidelines from the Infectious Diseases Society of America, the American Heart Association, and the American Academy of Pediatrics recommend only oral penicillin V or intramuscular benzathine penicillin G as the drugs of choice for treatment of group A beta-hemolytic streptococcal (GABHS) pharyngitis. Ten-day treatment courses with 1st-generation oral cephalosporins or erythromycin are recommended as suitable alternatives in patients who are allergic to penicillin. Despite these recommendations, oral cephalosporins are used as drugs of choice for many patients with GABHS pharyngitis. Simpler and/or short-course regimens of cephalosporins that have been approved by the Food and Drug Administration offer alternatives with the potential for unchanged patient compliance. Increasing cephalosporin use in patients with GABHS pharyngitis has followed from numerous reports and metaanalyses of cephalosporin superiority over penicillin for bacteriologic eradication and clinical response. This review examines the evidence supporting the use of cephalosporins as a first choice of treatment for many patients with GABHS pharyngitis.