Parvimonas micra: A Rare Cause of Pleural Empyema With COVID-19 Co-infection

Parvimonas micra, an oral anaerobe and a known gastrointestinal microbiota, has also been found to be enriched in mucosal tissues of the colon. Our patient presented with chest pain, productive cough, and hypoxia. He was diagnosed with COVID-19 pneumonia with a suspected superimposed bacterial infection. After the initiation of treatment, the patient developed a right hydropneumothorax/loculated pleural effusion on X-ray. Bedside drainage was done, and cross-sectional imaging showed findings of pleural empyema. Cultures obtained after bedside drainage grew P. micra. The patient underwent right posterolateral open thoracotomy, total lung decortication, wedge resection, pneumonolysis, and mechanical pleurodesis. Antimicrobial therapy was adjusted based on culture sensitivities and infectious disease evaluation. Adequate drainage and source control were achieved, COVID-19 infection was resolved, and the patient was discharged on oral antibiotics. This case report highlights a rare and interesting case of pleural empyema caused by a superimposed bacterial infection with P. micra in a patient with COVID-19 pneumonia.


Introduction
Parvimonas micra, is a Gram-positive coccus, an obligate anaerobe that resides dominantly in the human oral cavity, which rarely causes pneumonia or empyema, and is often challenging to identify in laboratory testing [1,2].To the best of our knowledge, no cases of pneumonia with empyema caused by coinfection with the COVID-19 virus have been reported in the literature.This case report highlights the pathogenicity of P. micra and its potential association with COVID-19 co-infection.The study emphasizes the importance of early diagnosis and appropriate management of this rare condition to improve patient outcomes and reduce morbidity and mortality.

Case Presentation
A 50-year-old Hispanic male who resided in a shelter had a past medical history of active cigarette smoking (17.5 pack year), polysubstance use disorder (cocaine and heroin), and hyperlipidemia and presented to the emergency room with chest pain and productive cough for 2 weeks before presentation.There were no recent sick contacts, only a recent trip to Florida.In the emergency room, the patient reported having worsened chest pain with cough and occasional hypoxia.Physical exam was notable for mild tachypnea, aeration decrease on the right, rhonchi and rales present bilaterally.
He was hemodynamically stable with SpO2 >95%.WBC elevated, neutrophil % elevated, lactate within normal range, Elevated Pro-inflammatory markers: procalcitonin, ferritin, C-reactive protein, LDH, and Ddimer; with elevated Pro-BNP (Table 1).Chest x-ray showed hazy opacification of the right lower lung field; areas of lucency in the medial margin of the consolidation may correspond to the aerated lung; however, necrosis can have a similar appearance (Figure 1).ECG showed normal sinus rhythm.

FIGURE 1: AP Chest x-ray showing hazy opacification of the right lower lung field; areas of lucency in the medial margin of the consolidation
The patient was found to have COVID-19 pneumonia with a suspected superimposed bacterial infection.The patient was admitted to the medical floor in isolation.He was initiated on COVID-19/community-acquired pneumonia treatment with Remdesivir, Ceftriaxone, and Azithromycin.Critical care was consulted on hospital day (HD) 2 due to the having right-sided chest pain tachypnea/respiratory distress.The patient was started on non-invasive positive pressure ventilation.Thoracic surgery was consulted on HD 5 due to the development of a right moderate-size pneumothorax and a loculated pleural effusion seen on the chest x-ray (Figure 2).He remained hemodynamically stable, afebrile, and had an uptrending (Table 1), also on steroids.Intraoperatively, he was found to have multiple loculated abscesses, dense adhesions, and fibrosis.Pleural fluid was neutrophilic exudate, cultures grew P. micra.Post-operative chest x-ray showed improvement in the right-sided opacities and blunting of the right costophrenic angle (Figure 3).He required vasopressor support for septic shock with highest leukocytosis of 67, and received 2 days of albumin.He was extubated on POD 2, and his septic Shock and pressure requirement improved.One of the right chest tubes was removed on POD 4, and the remaining on POD 5 without complications.He remained stable and was downgraded to the medical/surgical unit on 8/31/2022 and accepted for transfer to Medicine.His repeat testing for COVID-19 returned negative.He received an approximate total of 14 days of the new antibiotic regimen.Discharged on POD 13 on oral augmentin.He was seen in the clinic for 3 visits, showing significant improvement clinically and radiologically (Figure 4).

Discussion
Parvimonas micra (P.micra) was first identified and classified as Peptostreptococcus micros.The species was then reclassified as Micromonas micros in 1999 and again as P. micra in 2006.It is the sole species in the Parvimonas genus [1,2].
It is a Gram-positive coccus, an obligate anaerobe that resides dominantly in the human oral cavity as a commensal pathogen, where it is most abundant in the subgingival dental plaque.[1,2] Pulmonary infections by P. micra, although rare, include pulmonary abscess, pleural effusion, and empyema.
Poor dental hygiene is a determinant that favors an increased flora of P. micra.The main risk factors for infection may include dental procedures such as periodontitis, tooth extraction, apical abscesses or dental caries.In oral infections, the pathogenicity of P. Micra has been attributed to their adhesion to gingival epithelial cells, cell morphotype, and/or proteolytic activity, as well as other factors such as the response of human macrophages.However, in isolated infections, these factors are not clear [3].
The diagnosis of P. micra infection is mainly based on the culture of an adequate sample obtained from the site of infection.The culture of drainage or aspiration fluid, tissue samples, or blood cultures are adequate for the diagnosis of P. micra.Infections caused by P. micra are rare and require a high index of suspicion because of their non-specific symptoms and insidious evolution [3].
In a study by Hatta et al. demonstrated increased tumorigenesis properties caused by P. micra infection in the colon [1].Previous studies discovered that P. micra is often sensitive to metronidazole, penicillin, amoxicillin-clavulanate, and clindamycin [4,5].
The evidence available for P. micra is limited to case reports, literature, and systematic reviews.Through our literature review, there were no cases reported with co-infection of COVID-19 virus and P. micra causing lung abscess/empyema.Our patient was treated with Cephalosporin and Azithromycin initially.AATS recommends empiric treatment of community-acquired acute empyema with third-generation Cephalosporins and Metronidazole or IV Penicillin with Beta-lactamase The duration of therapy for empyema has not been studied in comparative trials.The final duration should be determined by the organism's sensitivities, the adequacy of source control, and the response to therapy [6].
Tube thoracostomy is the most common type of drainage; Large bore tubes versus smaller tubes have not shown any difference regarding mortality and prognosis.
The main goal of surgical intervention in empyema is the evacuation of the pus from the pleural cavity and achieving adequate lung expansion.In patients requiring surgical intervention in acute empyema, videoassisted thoracoscopy (VATS) is the standard of care provided there are no contraindications.Contraindications include the inability to tolerate single lung ventilation, inadequate evacuation of pus/lung expansion via thoracoscopy, and uncontrolled bleeding [7].

Conclusions
This case report highlights a rare and interesting case of pleural empyema caused by a superimposed bacterial infection with P. micra in a patient with COVID-19 pneumonia, that was successful managed after appropriate surgical intervention.Timely and accurate diagnosis, identification of causative pathogens and appropriate management are critical in effectively treating pneumonia with empyema, thereby improving patient outcomes.

FIGURE 2 :VIDEO 1 :
FIGURE 2: AP Chest x-ray showing right moderate-size pneumothorax and a loculated pleural effusion

FIGURE 3 :
FIGURE 3: Post-operative AP Chest x-ray showing improvement in the right-sided opacities and blunting of the right costophrenic angle.

FIGURE 4 :
FIGURE 4: Chest x-ray showing significant interval improvement in aeration in the right lower lung parenchyma, mild right-sided pleural effusion present tracking along the lateral wall.