Background: Pneumonia is one of the major complications of drowning, but the optimal empirical antibiotic treatment is not clearly defined. Multidrug-resistant (MDR) bacteria and fungi have been identified in a recent series of freshwater drowning-associated pneumonia. However, microbial data in seawater drowning are scarce. The objective of the study is to describe the microorganisms isolated in early respiratory specimens obtained from seawater drowning-associated pneumonia and to provide their antibiotic susceptibility pattern.

Methods: All patients admitted for seawater drowning between 2003 and 2013 to two intensive care units, from the region in France with the highest drowning rate, were retrospectively included. Demographics, antimicrobial therapy and microbiological data from respiratory samples collected within the first 48 h after admittance were analyzed.

Results: Seventy-four drowned patients were included, of which 36 (49%) were diagnosed by the clinician as having early pneumonia. Concerning the overall population, the median simplified acute physiology score (version 2) was 45 (30-65), and the mortality was 26%. Twenty-four respiratory samples from different patients were obtained within the first 48 h. Sixteen were positive. The main microorganisms found were Enterobacteriaceae (Enterobacter spp., Klebsiella spp. and Escherichia coli) and Gram-positive aerobic cocci (Streptococcus pneumonia and Staphylococcus aureus) with a low rate of antimicrobial resistance. No MDR bacteria or fungi were identified. However, among the positive respiratory samples collected, 5/16 (31%) grew bacteria with natural resistance to amoxicillin-clavulanate, the first-line antibiotic commonly used in our cohort. Resistance was only found among Gram-negative bacteria and from respiratory samples of patients with a higher drowning grade at admission (p = 0.01).

Conclusions: This 10-year descriptive study, the largest cohort to date, provides early respiratory samples from seawater drowning patients. The microorganisms retrieved were either mostly part of the human oro-pharyngeal flora or Enterobacteriaceae and displayed low rates of antimicrobial resistance. Respiratory samples should nonetheless be collected at admittance to the ICU to avoid inappropriate treatment. Empiric use of cephalosporin could be restricted to severe patients or if Gram-negative bacilli are found after direct examination.