BACKGROUND: Klebsiella pneumoniae invasion syndrome (KPIS) is a severe multi-site infection that is usually caused by hypervirulent Klebsiella pneumoniae. The bacteria are relatively common in Asian diabetics and can cause organ abscesses or sepsis. When patients develop intracranial infection, the prognosis is poor. After anti-infective treatment, the Klebsiella pneumoniae-induced liver and lung abscesses and pulmonary fungal infection were relieved, but the brain abscesses worsened. Such complex and severe infection cases are rarely reported. Early identification of intracranial infection, selection of antibiotics with high concentrations in cerebrospinal fluid, and active treatment of complications such as diabetes and fungal infection are of great significance for the prognosis of patients.
METHODS: A 71-year-old patient diagnosed with liver abscess in another hospital was transferred to our hospital due to a worsening condition. On day 1 (day of admission), the patient was given invasive mechanical ventilation, continuous renal replacement therapy combined with endotoxin adsorption, antimicrobial treatment with imipenem-cilastatin, and percutaneous catheter drainage for liver abscess. Metagenomic next-generation sequencing in bronchoalveolar lavage fluid indicated Klebsiella pneumoniae (K. pneumoniae), Candida albicans, and Aspergillus flavus complex, and no viruses were detected. Blood and pus cultures revealed K. pneumoniae that was sensitive to piperacillin/tazobactam. The anti-infection therapy was adjusted to piperacillin/tazobactam combined with voriconazole. On day 14, a head computed tomography (CT) scan showed no significant changes, and a chest CT scan showed absorption of multiple abscesses in both lungs. The patient was still unconscious. After the endotracheal tube was removed, cranial magnetic resonance imaging (MRI) showed multiple brain abscesses. Finally, his family gave up, and the patient was discharged and died in a local hospital.
CONCLUSIONS: In cases of K. pneumoniae infection, the possibility of intracranial, liver, lung, or other site infections should be considered, and physicians should be vigilant for the occurrence of KPIS. For patients suspected of developing an intracranial infection, cerebrospinal fluid should be tested and cultured as soon as possible, a head MRI should be performed, and antibiotics with high distribution in cerebrospinal fluid should be used early. When patients are complicated with diabetes, in addition to glycemic control, vigilance for concurrent fungal infections is also needed.

BACKGROUND: Legionnaires\' Disease (LD) rarely evolves into pulmonary abscesses. The current systematic review has been designed to explore therapeutical strategies in pulmonary cavitary LD.
METHODS: A research strategy was developed and applied to the databases Embase, Pubmed, and Web of Science from the 1st of January 2000 to the 1st of November 2022. Original articles, case series, case reports, and guidelines written in English, French, German, Italian, and Dutch were considered. Furthermore, medical records of patients treated at the University Hospital UZ Brussel for LD cavitary pneumonia, between the 1st of January 2016 to the 1st of January 2022, were reviewed.
RESULTS: Two patients were found by the UZ Brussel\'s medical records investigation. Through the literature review, 23 reports describing 29 patients, and seven guidelines were identified. The overall evidence level was low.
UNASSIGNED: The median age was 48 years and 65% were male. A polymicrobial infection was detected in 11 patients (44%) with other aerobic bacteria being the most commonly found. At diagnosis, 52% of patients received combination therapy, and fluoroquinolones were the preferred antimicrobial class. Anaerobic coverage was neglected in 33% of patients.
UNASSIGNED: Three guidelines favor monotherapy with fluoroquinolones or macrolides, while one suggested an antimicrobial combination in case of severe LD. Four guidelines recommended anaerobic coverage in case of lung abscesses.
CONCLUSIONS: To date, the evidence supporting cavitary LD treatment is low. Monotherapy lowers toxicity and might be as effective as combination therapy. Finally, anaerobes should not be neglected.

Porphyromonas endodontalis is an oral anaerobic bacterium associated with periodontitis but seldomly been detected in other diseases. Only one case of respiratory disease caused by Porphyromonas endodontalis, pyopneumothorax, has been reported so far. A 53-year-old man with refractory periodontitis was admitted due to an indeterminate lung space-occupying lesion. Following mNGS analysis of the liquefaction necrotic area and solid component of the lesion through biopsy, Porphyromonas endodontalis and Parvimonas micra were detected. Therefore, the patient was diagnosed with an aspiration lung abscess and discharged after receiving effective antibacterial treatment. The Chest computed tomography (CT) scan revealed a remarkable improvement during outpatient follow-up. In this study, we applied mNGS to diagnose a case of lung abscess attributed to an uncommon bacterium successfully, suggesting that when patients complicated with periodontal diseases and clinical respiratory symptoms, the possibility of inhalation disease caused by oral pathogens should be considered.

Streptococcus intermedius is frequently associated with brain and liver abscesses, while pleuropulmonary infections are considered rarer. Even less frequent is the association of lung and brain abscesses due to this agent with infective endocarditis. We describe the case of a 40-year-old man complaining of cough, fever, and headache who was diagnosed with a brain abscess due to S. intermedius, a concomitant lung abscess, and aortic native valve endocarditis. He was treated with surgical drainage of the brain abscess and a 4-week course of intravenous ceftriaxone, followed by oral amoxicillin/clavulanate, obtaining healing of the lesions without relapse of the infection.

BACKGROUND: Fusobacterium necrophorum is an anaerobic, gram-negative, non-motile, filamentous, non-spore forming bacillus found in the oral cavity, gastrointestinal tract, and female genital tract, responsible of a rare disease named Lemierre Syndrome, characterized by septic thrombophlebitis of the internal jugular vein, which mainly affects previously healthy adolescents and young adults; some risk factors are reported, as smoking or primary viral or bacterial infection leading to the disruption of mucosa. The syndrome originates commonly from an upper respiratory infection such as pharyngotonsillitis, acute otitis media, cervical lymphadenitis, sinusitis, or odontogenic abscess, and may result in multiorgan metastasis, more frequently leading to pulmonary complications, especially lung abscesses.
METHODS: We describe two cases of adolescents with atypical Lemierre Syndrome evaluated in a tertiary care center, one with a confirmed infection by Fusobacterium necrophorum and one with a presumptive diagnosis based on clinical features, who developed lung abscesses needing a prolonged antibiotic course and hospitalization. Of interest, both were user of electronic cigarette, configuring a possible new risk factor. The proper diagnosis of Lemierre Syndrome is often difficult to establish, so a high degree of suspicion is needed, especially in the case of lung abscesses in otherwise healthy adolescents.
CONCLUSIONS: The current study will contribute to providing insight into Lemierre Syndrome clinical presentation and management in adolescents, promoting awareness for a rare but potentially fatal disease. Moreover, it suggests a possible relationship between Lemierre syndrome and the use of electronic cigarette, that should be investigated by future studies.

A nocardial abscess is a relatively rare opportunistic infection that typically occurs after immunosuppressive treatment and is a clinical challenge. In the present study, the case of a 69-year-old patient with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, and lung and kidney involvement, was reported. The patient received systemic glucocorticoid and cyclophosphamide treatment for 6 months, after which a large encapsulated abscess appeared on magnetic resonance imaging and CT in the subcutaneous tissue of the left hip and lung, respectively, and the pus culture showed Nocardia. Orthopedic abscess incision and ultrasound-guided thoracic puncture drainage were performed, and the lesion was completely absorbed after 1 month of treatment with linezolid and compound sulfamethoxazole. Tests for ANCA were negative, and renal function and urine tests were completely normal after 1 year of follow-up. Furthermore, a literature review performed for the present study retrieved a few reports of successful treatment of multiple nocardial abscesses secondary to ANCA-associated vasculitis in elderly patients in a short period of time. Therefore, the present case report and literature review have been reported to improve awareness of this rare disease, so as to facilitate its early diagnosis and treatment.

A 16-year-old male was admitted with persistent fever, diarrhea, and anorexia 8 days after the diagnosis of coronavirus disease-2019 (COVID-19). Radiological examination of the lungs showed a cavitary lesion with an air-fluid level, but no apparent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia. The lesion was diagnosed as a lung abscess after COVID-19. Treatment with antimicrobials was initiated, which attenuated symptoms and the lung lesion. Specific pathogens were not detected despite repeated sputum cultures, which suggested that lung abscess was caused by oral bacteria as a secondary infection of COVID-19. To date, several cases of lung abscess as a complication of COVID-19 have been reported. However, the majority of cases occurred after intubation to treat COVID-19, and there have been no cases involving young adults. This healthy young patient may have developed lung abscess due to COVID-19.

Odontogenic brain and pulmonary abscesses are extremely rare infectious diseases. It is mainly caused by the upward or downward transmission of local infection or blood-borne spread. In recent years, with the wide application of some novel testing methods in clinical practice, the diagnosis of unexplained infections such as odontogenic abscesses in different organs has gradually become clear. We report a case of a 21-year-old male who was healthy and had not received any oral treatment before onset. He started with acute gastroenteritis-related symptoms, then developed meningitis-related symptoms seven days later with septic shock. No obvious abscess lesions were found on head computed tomography (CT) at admission, and the etiology was not clear by routine examination, which was very easy to misdiagnose as a serious infection caused by intestinal pathogens. But odontogenic pathogens were found both in his blood and cerebrospinal fluid through metagenomic next-generation sequencing (mNGS) analysis. Subsequently, rechecked imaging examination displayed multiple brain and pulmonary abscesses. Finally, it was diagnosed as an odontogenic brain and pulmonary abscess. After an extremely lengthy anti-infection course (13 weeks of intravenous antibiotics plus 2 weeks of oral antibiotics) and surgery, the patient was improved and discharged from the hospital. From this case, we could see that the development of new diagnostic technologies such as mNGS plays an important role in the early and confirmed diagnosis of diseases previously difficult to diagnose such as odontogenic polymicrobial infections and ultimately helps to improve the prognosis of these patients.

(1) Background: Lung abscess is a lung infection that leads to the destruction of the lung parenchyma, resulting in a cavity formation and central necrosis filled with purulent fluids. It is an uncommon pediatric problem, and there is a paucity of literature reviews on this subject, especially for the pediatric age group. Lung abscess is commonly divided into those considered primary in previously well children or secondary in those with predisposing co-morbidities. The predominant pathogens isolated from primary lung abscesses are the aerobic organisms, including streptococcal species, Staphylococcus aureus, and Klebsiella pneumoniae, while anaerobic bacteria such as Bacteroides species are predominant in secondary groups. Children usually present with fever, cough, shortness of breath, chest pain, and sputum. While physical examination may reveal diffuse crackles on auscultation, the diagnosis is usually confirmed by chest X-ray. (2) Methods: We report four different cases with lung abscesses from both primary and secondary group with similar presentations and radiological findings, but the approach was different in each according to the underlining cause. (3) Conclusions: Conservative therapies with a prolonged course of antibiotics remain the cornerstone of therapy for both primary and secondary lung abscesses. The underlying cause should be considered when there is a suboptimal response. However, invasive intervention is becoming more popular with better yield, shorter duration of antibiotics and admission, and excellent prognosis.

Mycoplasma hominis is a rarely identified cause of respiratory infection that can cause significant morbidity and mortality in immunocompromised patients. It is often missed due to the difficult detection of the organism with routine laboratory methods. We present the case of a 63-year-old male with a history of lymphoma who was transferred to our hospital with recurrent right-sided empyema and lung abscess in the right lower lobe. Advanced microbiological analysis finally revealed infection with M hominis. Despite appropriate antibiotic treatment, prolonged drainage as well as repeated surgery, which eventually resulted in right lower bilobectomy, were necessary for clinical improvement of our patient. Infection with M hominis may be more prevalent than previously indicated and can cause severe morbidity and mortality in thoracic surgery patients. Due to the diagnostic challenge, the appropriate antimicrobial treatment is often delayed. Inherent resistance to macrolides and inactivity of cell wall-active agents potentially complicate empiric antibiotic therapy. A review of the currently available literature enables a better understanding of the diagnostic difficulties and importance of this infection.