**3. aPDT of respiratory tract diseases**

#### **3.1 Pharyngotonsillitis**

Sore throat is a frequent complaint in outpatient medical consultations and emergencies. Acute pharyngotonsillitis represents a significant source of social disorders in the child population, such as missed classes repeated use of antimicrobials, and can cause complications such as peritonsillar or retropharyngeal abscess, otitis, sinusitis, pneumonia, rheumatic fever, and post-streptococcal glomerulonephritis [20]. Bacterial infections of the respiratory system can be located in the pharynx (pharyngotonsillitis). Viruses cause around 90% of pharyngitis, and 10% are caused by bacteria that have the vast majority associated with *Streptococcus pyogenes* or Beta-hemolytics of Lancefield group A (EBHGA) [21] however, other bacteria can cause pharyngotonsillitis such as *Streptococcus mutans and Streptococcus pyogenes, Staphylococcus aureus, Moraxella catarrhalis, Haemophilus influenzae, Prevotella* sp.*, Bacteroids fragilis, and Fusobacterium* sp.

The diagnosis of EBHGA infection should preferably be confirmed microbiologically by rapid antigens detection tests and through oropharyngeal secretion culture. The gold standard for diagnosing oropharyngeal infections by EBHGA is culture [22], which should be done before starting treatment with antibiotics [23]. Clinical samples should be seeded on blood agar plates, which allows a preliminary screening of β-hemolytic colonies. Subsequent confirmation of suspected colonies such as EBHGA can be obtained by several laboratory tests, which are easily and quickly performed and which are still widely applied in clinical microbiology, despite the increasing use of automatic identification systems. EBHGA can be an oropharyngeal colonizing agent and thus, the microbiological investigation must be guided by clinical and epidemiological factors: patient's age, clinical signs and symptoms, season, and personal exposure to EBHGA [24].

#### *Antimicrobial Photodynamic Therapy of the Respiratory Tract: From the Proof of Principles… DOI: http://dx.doi.org/10.5772/intechopen.95602*

According to the World Health Organization (WHO), approximately 600 million new pharyngotonsillitis cases due to EBHGA occur annually, and of these, 500 thousand may progress with rheumatic fever and about 300 thousand with rheumatic carditis [25]. In developing countries, the occurrence is three times higher than in developed countries. The preliminary diagnosis and treatment of tonsillitis and pharyngitis is a common cause of inappropriate use of antibiotics.

Penicillin is the drug of choice for *S. pyogenes* infections' empirical treatment, despite more than 60 years of use. S. pyogenes remains sensitive to penicillin, and resistance tests for penicillins or other beta-lactams approved for its treatment are unnecessary. However, more than 10% of patients report an allergy to penicillin, which leads to the use of cephalosporins, clindamycin, or macrolides as alternative treatments [26]. As rates of resistance to macrolides among isolated *S. pyogenes* have been increasing in North America and Europe, resistance tests for these substances may be indicated. Sore throat is a symptom that leading people to seek medical attention, and although it spontaneously remits, primary care doctors usually prescribe antibiotics for it. In a systematic review, Spinks and collaborators concluded that antibiotics confer relative benefits in the treatment of sore throat. However, the absolute benefits are modest [27].

The research carried out at Santa Casa Hospital of São Carlos city (São Paulo, Brazil) by the CEPOF - Optics and Photonics Research Center" from University of São Paulo - São Carlos is composed of a clinical trial - "Turmeric and LED in the treatment of sore throat" with objectives as assessing the therapeutic efficacy of PDT with curcumin as an adjunct in the treatment of acute pharyngotonsillitis in adults in the municipality of São Carlos [28]. The photosensitizer used in this study was curcumin (0.75 mg/ml), using two minutes of illumination with a blue light (LED) at 450 nm. The clinical trial is randomized and controlled with adults aged 18 to 45 years diagnosed with acute pharyngotonsillitis. Participants are undergoing a rapid test for the detection of group A beta-hemolytic streptococcus (EBHGA). Participants with streptococcal pharyngotonsillitis are divided into Antibiotic therapy comparison groups in conjunction with photodynamic therapy; and Antibiotic Therapy Group in conjunction with a photodynamic therapy placebo, and the therapeutic response will be evaluated in terms of clinical symptoms (sore throat and fever) and microbiological response, mainly considering the presence of EBHGA in the clinical response.
