Rare Shewanella spp. associated with pulmonary and bloodstream infections of cancer patients, China: a case report

Case 1

A esophageal cancer patient who was diagnosed as S. haliotis pulmonary inflammation.

A 68-year-old male patient was admitted to people’s hospital of Liaocheng city, China, on July 24, 2016, because of “hematemesis for 4 hours”. He had been diagnosed with the operation of esophageal cancer for more than 2 years. His admitted physical examinations were body temperature of 36.3 °C, pulse rate 92 beats/min, breathing of 22 times/min and blood pressure 135/80 mmHg. Nonpalpable enlargement of bilateral neck and supraclavicular lymph nodes, trachea in the middle, pectoral symmetry, visible scars at right chest, clear percussion sound at double lung, auscultation of coarse breath sound, no dry and wet rales, regular rhythm, percussion no pain of the kidney area, negative for shifting dullness and bowel sounds of 3 times/min. His admission diagnosis was esophageal cancer after operation and hypertension. On admission, the auxiliary examinations were performed to determine the source of hematemesis. The painless gastroscopy was carried out, but no obvious abnormalities was observed. The painless bronchoscopic examination revealed posterior basal segment of left lower lobe hemorrhage. Brushing pathology indicated no obvious tumor cells. Thoracic and abdominal enhanced computed tomography scan showed that he had esophageal surgery, bronchitis and emphysema, middle lobe of right lung nodules, right upper lobe and left lower lobe interstitial lesions and the lower lobe of the left lung inflammation. He was given medicine (3 g of cefoperazone/sulbactam was administrated twice a day for 6 days) and therapy of anticancer, anti-inflammatory, rehydration and hemostasis. After six days’ treatment, his symptoms improved and the patient was discharged from the hospital.

The bronchoalveolar lavage fluid (BALF) was collected when he received painless bronchoscopic examination and the cell number was over 10⁴ cfu/ml. Sample was streak-inoculated on blood agar medium for bacterial culture. Strains of different phenotypic features at blood plates were isolated and identified as S. algae, Escherichia coli and Klebsiella pneumoniae by VITEK 2 system using the ID-GN card (boiMérieux). Since only two Shewanella species, S. putrefaciens and S. algae, were registered in the database of VITEK 2 system, the 16S rRNA gene sequence was amplified by a PCR described previously [4]. The PCR product was sequenced and the nucleotide sequence had been deposited at GenBank, under the accession number of MF589233. BLAST analysis of 16S rRNA gene sequence at GenBank showed a similarity of 99.0% with type strain of S. haliotis DW01 (accession numbers NR_117770.1). Further phylogenetic analysis with all type sequences of Shewanella species available in the GenBank database, confirmed the strain was identified as species of S. haliotis (LC2016–1 in Fig. 1).

To further confirm the bacterial community composition and richness of the BALF, sample was subjected to the 16S rRNA amplicon sequencing [5, 6]. The result indicated the bacterial community composition included genera of Shewanella (88.34%), Escherichia (11.11%) and Streptococcus (0.38%), et al., whereas the majority of genus was Shewanella.

Antibiotic susceptibility testing was performed by microdilution method on Mueller-Hinton broth. The strain was susceptible to piperacillin/tazobactam (minimal inhibitory concentration, MIC: 8 μg/ml), ceftazidime (1 μg/ml), cefepime (1 μg/ml), amikacin (2 μg/ml), gentamicin (1 μg/ml), imipenem (4 μg/ml), meropenem (4 μg/ml), but was resistant to ciprofloxacin (8 μg/ml) and levofloxacin (8 μg/ml).

Case 2

A gastric cancer patient who was diagnosed as S. algae bacteremia.

A 56-year-old man was admitted to people’s hospital of Liaocheng city, China, on 6, Oct. 2016, because of “discomfort of upper abdominal pain for 1 month”. His admitted physical examination included body temperature of 36.1 degrees, pulse rate of 72 beats/min, breathing 18 times/min and blood pressure 140/90 mmHg. Detection of nonpalpable enlargement of bilateral neck and supraclavicular lymph nodes, flat abdomen, no gastrointestinal or peristaltic waves were observed. Soft abdominal muscles, mild tenderness in the upper abdomen and no obvious rebound pain were reported. His liver and spleen did not touch under the rib and no palpable mass was discovered. Negative for shifting dullness, normal bowel sounds and no abnormal of rectal examination were detected. The gastroscope suggested visible ulcer lesions at the cardiac involving gastric fundus and gastric body. The pathological results indicated adenocarcinoma. His admission diagnoses were gastric cancer and hypertension.

On admission, the auxiliary examination were carried out on Oct. 9, 2016. Laparoscopy indicated he was in the late stage tumors without radical resection. He then received intravenous and intraperitoneal chemotherapy, followed by severe bone marrow suppression with blood cells and platelets significantly lower than normal. He was given further treatment of anti infection, nutritional support, rehydration, stimulating granulopoiesis and symptomatic treatment. On Oct. 26, 2016, patients had shortness of breath, heart rate and other symptoms with lung breath sounds rough, and no rales, limbs cold. He was considered the existence of septic shock. He was given non-invasive mechanical ventilation and fluid expansion, colloid, blood transfusion products, anti infection (1 g of imipenem was administrated every 8 h for 7 days), maintain circulation, acid suppression, liver protection, nutritional support, maintenance of water and electrolyte acid-base balance, monitoring blood pressure, heart rate, respiratory function, hour urine volume and bleeding. Patient had severe infection, and the presence of multiple organ dysfunction syndrome (breathing, circulation, gastrointestinal, blood and kidney). Patient and his family members required automatic discharge for hospice care. His discharge diagnoses were multiple organ dysfunction syndrome (respiratory, circulatory, gastrointestinal, blood and kidney), gastric cancer and hypertension.

After appearing septic shock, his blood culture was sampled to separate the bacteria. The microbial growth was detected in both anaerobic and aerobic bottles and the positive reported time were 8.1 and 11.9 h, respectively. Both bottles yielded an uniform Gram-negative bacillus. After 24 h incubation, haemolytic, oxidase-positive yellow colonies grew on blood agar. The strain was identified as S. putrefaciens by VITEK 2 system using the ID-GN card (boiMérieux). The 16S rRNA gene sequence of the strain had been deposited at GenBank (accession number: MF589234). BLAST analysis at GenBank showed a similarity of 100.0% with S. upenei strain VITVAGJ (accession numbers KP090164.1). Further phylogenetic analysis with all type sequences of Shewanella species available in the GenBank database, confirmed the strain belonged to species of S. upenei (LC2016–5 in Fig. 1). On the day of blood sampling, his peritoneal drainage fluid was also collected and cultured using the same identification methods, and the results of bacterial identification and drug sensitivity were consistent with that of blood.

Antibiotic susceptibility testing was performed by microdilution method on Mueller-Hinton broth. The strain was susceptible to aztreonam (1 μg/ml), ceftazidime (1 μg/ml), cefepime (1 μg/ml), amikacin (2 μg/ml), gentamicin (1 μg/ml) and levofloxacin (1 μg/ml), but was intermediate to imipenem (8 μg/ml), piperacillin/tazobactam (64 μg/ml) and ciprofloxacin (2 μg/ml).