Tracking of Pseudomonas aeruginosa Infections and Correlation of Lipase-Phospholipase C activity with Neutrophil Functions in Nigeria Burn Patients.

Iwalokun, B.A¹; Fadeyibi, I²; Iwalokun, S.O²; Ogunledun A³

¹Department of  Biochemistry; ²Burn and Plastic surgery Unit, Department of Surgery, Lagos State University; ³Department of Medical Microbiology and Parasitology, Olabisi Onabanjo University, Nigeria.

E-mail: bawmwal@yahoo.com

Phone: 234-1-8504327

ABSTRACT

Background: Burns are the most common form of trauma in Nigeria, a malaria endemic country with patients eliciting high risk of systemic and pulmonary complications due to virulence bacterial infections and altered neutrophil-mediated innate immunity. This study investigated the dynamics of Pseudomonas aeruginosa infections and expression of virulence factors (lipase and phopholipase C, PLC) from the clinical samples of Nigerian patients with burn injuries in relation to their neutrophil functions in vitro.

Methodology: A cohort of 43 patients (Male, 27; Female; 16) aged 14 – 36 years (mean age, 25.8 yr) with burn injuries seen at Accident and emergency /Burns Units of Lagos State University and district hospitals in Lagos, Nigeria were consecutively enrolled with consent and ethical approval. Extent of burns as total body surface area burned (TBSA) and etiologies were determined and clinical samples (Blood, sputum, wound swab) were collected into appropriate containers under sterile conditions. The samples were submitted to bacteriological identification P. aeruginosa and other pathogens using standard methods. Pseudomonas lipase and PLC activity in trypticase soy broth culture supernatant was determined spectrophotometrically, while neutrophils recovered from whole blood by Ficol partition were subjected to in vitro phagocytosis of P. aeruginosa ATCC 22853 and myeloperoxidases assays. Finger pricked blood samples were thick filmed for P. falciparum detection. Genetic relatedness of the recovered P. aeruginosa isolates was investigated by plasmid profiling. Fifteen age and sex matched apparently healthy subjects were used as control. Data was subjected to chi-square, correlation and univariate analyses.

Results: Of the 125 isolates recovered, 39 (31.2% ) were P. eruginosa from sputum (6.4%), wound (21.6%) and blood (3.2%) respectively with significant (P<0.05) disparity in isolation rate (66.7 vs. 33.3%), lipase (27.3+2.8 vs. 19.1+1.9 U/mL) and PLC (20.4+3.6 vs. 13.7+2.1 U/mL) activity between > 30% TBSA and < 30% TBSA patients. Univariate analyses revealed P. falciparum parasitaemia (Odd ratio, OR = 3.4), TBSA > 30% (OR = 2.8), K pneumoniae or S. aureus co-infection (OR = 1.9), inhalation injury (OR = 1.8), PLC >15 U/mL and Lipase >24 U/mL as risk factors of pseudomonas bacteremia in the patients.  Neutrophil phagocytosis (39.6 – 73.5% of control) was observed to correlate negatively with PLC activity (r = -0.71, P < 0.05). Whereas myeoloperoxidase activity showed significant (P < 0.05) elevation in > 30% TBSA (605.3+37.2 vs.372.9+64.1 U/mL), its relationship with pseudomonas lipase or PLC activity was not significant (P > 0.05), Neutropenia was associated with plasmodium-polymicrobial infection and plasmid analysis showed genetic relatedness in 79.6% of the P. aeruginosa isolates.

Conclusion: Our results indicate reduced neutrophil phagocytosis and susceptibility of PLC expressing P. aeruginosa infection in Nigerian >30% TBSA patients with malaria.