Kinichi Izumikawa

Clinical features, risk factors and treatment of fulminant Mycoplasma pneumoniae pneumonia: A review of the Japanese literature

Mycoplasma pneumoniae (MP) is one of the most common causes of community-acquired pneumonia in children and young adults. Although MP sometimes causes self-limiting pneumonia, severe and fulminant cases with hypoxia occur, but their clinical features have rarely been reported. This study aimed to reveal the clinical manifestations, risk factors, and treatment of fulminant MP pneumonia (MPP). Using PubMed and abstracts from the proceedings of several domestic Japanese academic societies, we reviewed the Japanese and English literature for cases of fulminant or severe MPP reported in Japan. All clinical information such as sex, age, underlying diseases, clinical symptoms, clinical course, laboratory and radiological findings, and treatment was collected and analyzed. In total, 52 fulminant MPP cases were reported between September, 1979 and February, 2010. The dominant population of fulminant MPP was young adults without severe underlying diseases. Cough (97.3%), fever (100.0%), and dyspnea (83.3%) with diffuse abnormal findings in radiological examinations were noted. Antibiotics without anti-mycoplasmal activity were used in 32 cases (61.5%) as initial treatment prior to the onset of hypoxia. Anti-mycoplasmal drugs were appropriately used in 41 cases (78.8%) after onset of respiratory failure with steroids (23 cases, 45.1%) and effective. The majority of patients improved within 3-5 days after steroid administration. There were only 2 fatal cases. Although this small retrospective study did not reveal the apparent risk factors of fulminant MPP, initial inappropriate use of antibiotics may be a risk factor, and early administration of appropriate anti-mycoplasmal drugs with steroids as a cellular immune suppressor is required.

In vitro and in vivo activities of piperacillin-tazobactam and meropenem at different inoculum sizes of ESBL-producing Klebsiella pneumoniae

The inoculum effect is a laboratory phenomenon in which the minimal inhibitory concentration (MIC) of an antibiotic is increased when a large number of organisms are exposed. Due to the emergence of extended-spectrum β-lactamase-producing Klebsiella pneumoniae (ESBL-Kpn) infections, the inoculum effect of ESBL-Kpn on β-lactams was studied in vitro and in vivo using an experimental model of pneumonia. The in vitro inoculum effect of 45 clinical ESBL-Kpn isolates on β-lactams was evaluated at standard (10(5) CFU/mL) and high (10(7) CFU/mL) organism concentrations. The MIC50 of piperacillin-tazobactam, cefotaxime and cefepime was increased eight-fold or more and that of meropenem was increased two-fold. The in vivo inoculum effect was evaluated in an ESBL-Kpn pneumonia mouse model treated with bacteriostatic effect-adjusted doses of piperacillin-tazobactam (1000 mg/kg four times daily, %T>MIC; 32.60%) or meropenem (100 mg/kg twice daily, %T>MIC; 28.65%) at low/standard (10(4) CFU/mouse) and high (10(6) CFU/mouse) inocula. In mice administered a low inoculum, no mice died after treatment with piperacillin-tazobactam or meropenem, whereas all the control mice died. In contrast, in the high inoculum model, all mice in the piperacillin-tazobactam-treated group died, whereas all meropenem-treated mice survived and had a decreased bacterial load in the lungs and no invasion into the blood. In conclusion, meropenem was more resistant to the inoculum effect of ESBL-Kpn than piperacillin-tazobactam both in vitro and in vivo. In the management of severe pneumonia caused by ESBL-Kpn, carbapenems may be the drugs of choice to achieve a successful outcome.

Different Epidermal Growth Factor Receptor Gene Mutations in a Patient with 2 Synchronous Lung Cancers

Recently, the frequency of lung adenocarcinoma has been increasing among nonsmokers, though the etiology remains unclear. Mutations of the epidermal growth factor receptor (EGFR) gene are frequently detected in the lung adenocarcinomas seen in nonsmokers. Thus, EGFR mutations can be implicated in carcinogenesis of lung adenocarcinoma. Herein, we report a case of 2 synchronous lung adenocarcinomas composed of 2 distinct pathological subtypes with different EGFR mutations: homozygous deletion in exon 19 in the papillary subtype of adenocarcinoma and a point mutation of L858R in exon 21 in the tubular adenocarcinoma. These findings suggest that specific mutations can occur randomly in the EGFR hot spot, and that these EGFR mutations can contribute to the distinct carcinogenic process of each adenocarcinoma.

Partial lung resection of supernumerary tracheal bronchus combined with pulmonary artery sling in an adult: report of a case

An adult case of pulmonary resection for repeated infections in a supernumerary tracheal bronchus combined with a pulmonary artery sling is reported. A 33-year-old woman with a pulmonary artery sling was referred for recurrent lung infections. Chest computed tomography showed the left pulmonary artery arising from the right pulmonary artery and coursing posterior to the trachea. The lung parenchyma connected to the tracheal bronchus showed dense opacity and traction bronchiectasis. Partial pulmonary resection was performed with an ultrasonically activated scalpel after the tracheal bronchus was auto-sutured. The patient’s postoperative course was uneventful, and she is now in good condition.

Effectiveness of intravenous minocycline in patients with mycoplasmal pneumonia

Seventeen patients with mycoplasmal pneumonia were administered intravenous minocycline, a tetracycline antibiotic with long-acting effects. Excellent therapeutic effects were observed both clinically and bacteriologically. The organism was eliminated in a shorter period of time compared to other antibiotics used for the treatment ofMycoplasma pneumoniae infections. Aside from 1 patient who experienced nausea and vomiting and was taken off minocycline, no other adverse effects were noted in these patients. Minocycline should be strongly considered as therapy for mycoplasmal pneumonia because it may completely eradicate the organism within 7 days.