Bacteraemia caused by Rahnella aquatilis: report of two cases and review

Rahnella aquatilis Sepsis in a Premature Newborn

Rahnella aquatilis is an infrequently isolated Gram-negative rod within the Enterobacteriaceae family. The organism's natural habitat is water. The organism is rarely isolated from clinical specimens and it seldom causes infection in immunocompetent individuals. Here we present a one-month-old boy who was born prematurely at 27th week of gestation by cesarean section with a birth weight of 730 g. He developed sepsis caused by Rahnella aquatilis during the treatment for ventilator associated pneumonia due to Stenotrophomonas maltophilia with ciprofloxacin. He was successfully treated with a combination of amikacin plus meropenem. Although R. aquatilis is one of the saprophyticus organisms, it may cause life-threatening infection in newborn.

Biological Warfare of the Spiny Plant Introducing Pathogenic Microorganisms into Herbivore's Tissues

Recently, it has been proposed that plants which have spines, thorns, and prickles use pathogenic aerobic and anaerobic bacteria, as well as pathogenic fungi, for defense against herbivores, especially vertebrates. Their sharp defensive appendages may inject various pathogenic agents into the body of the herbivores by piercing the outer defensive layer of the skin in a type of biological warfare. Here, we review data regarding the various bacterial taxa found on spines, as well as the medical literature regarding infections by bacteria and fungi related to spine injuries. We also present new evidence that, concerning the microbial flora, spines belonging to the palm tree Washingtonia filifera are probably a different habitat than the nondefensive green photosynthetic leaf surfaces. In addition, many plant species have microscopic internal and external spines (raphids and silica needles) which can also wound large herbivores as well as insects and other small invertebrate herbivores that usually attack in between large spines, prickles, and thorns. The large spines and sharp microscopic structures may inject not only the microorganisms that inhabit them into the herbivore's tissues, but also those preexisting on the skin surface or inside the digestive system of the herbivores and on the surface of nonspiny plant parts. A majority of the spiny plants visually advertise their spiny nature, a characteristic known as aposematism (warning coloration). The pathogenic microorganisms may sometimes be much more dangerous than the physical wounds inflicted by the spines. In accordance, we suggest that the possible cooperation or even just the random association of spines with pathogenic microorganisms contributed to the evolution of aposematism in spiny plants and animals. The role of these sharp defensive structures in inserting pathogenic viruses into the tissues of herbivores was never studied systematically and deserves special attention.

Infection caused by Rahnella aquatilis

The authors report a case of a 27-year-old African American woman with sickle cell disease who developed septic shock caused by a Rahnella aquatilis infection associated with a peripherally inserted central venous catheter. The infection was treated successfully with ciprofloxacin. R aquatilis is a Gram-negative rod, first isolated from freshwater in 1976, which has been linked to human disease in rare instances, most commonly in immunosuppressed individuals. In addition to this case report, the authors also review the literature.

Plant biological warfare: thorns inject pathogenic bacteria into herbivores

Thorns, spines and prickles are among the rich arsenal of antiherbivore defence mechanisms that plants have evolved. Many of these thorns are aposematic, that is, marked by various types of warning coloration. This coloration was recently proposed to deter large herbivores. Yet, the mechanical defence provided by thorns against large herbivores might be only the tip of the iceberg in a much more complicated story. Here we present evidence that thorns harbour an array of pathogenic bacteria that are much more dangerous to herbivores than the painful mechanical wounding by the thorns. Pathogenic bacteria like Clostridium perfringens, the causative agent of the life-threatening gas gangrene, and others, were isolated and identified from date palm (with green-yellow-black aposematic spines) and common hawthorn (with red aposematic thorns). These thorn-inhabiting bacteria have a considerable potential role in antiherbivory, and may have uniquely contributed to the common evolution of aposematism (warning coloration) in thorny plants.

Rahnella aquatilis bacteremia in a patient with relapsed acute lymphoblastic leukemia

Rahnella aquatilis infections are rare. We report the case of a 46-y-old African-American male with relapsed acute lymphoblastic leukemia who had R. aquatilis bacteremia after beginning reinduction chemotherapy. He was treated for 4 weeks with piperacillin-tazobactam and gentamicin. He recovered from the infection and had an allogenic bone marrow transplant a month later.

Rahnella aquatilis sepsis in an immunocompetent adult

Rahnella aquatilis, a rare enteric gram-negative rod which is infrequently isolated in immunocompromised patients, was isolated as a causative organism of sepsis in a 26-year-old immunocompetent male patient. The contaminated intravenous fluid was confirmed to be the source of the organism.

Two epidemiologically related cases of Rahnella aquatilis bacteremia

Rahnella aquatilis was isolated from the blood cultures of two patients who were in different units of the same hospital. Both isolates were susceptible to aminoglycosides, fluoroquinolones, cotrimoxazole, piperacillin, third generation cephalosporins and amoxicillin-clavulanate, but resistant to amoxicillin, ticarcillin, and first generation cephalosporins. The synergistic activity of amoxicillin and clavulanic acid suggested the presence of a beta-lactamase, confirmed by a positive nitrocefin test and by analytical isoelectric focusing. Pulsed-field gel electrophoresis and ribotyping with the pKK3535 probe showed that the isolates shared the same banding pattern. The results of an epidemiological study suggested that an in-house total parenteral nutrition solution might be the source of this unusual gram-negative rod.

Enterobacteriaceae found in high numbers in fish, minced meat and pasteurised milk or cream and the presence of toxin encoding genes

Enterobacteriaceae were found in high numbers after storage at 7 degrees C in 6% of consumers packs of pasteurised milk or cream, in 31% of retailed fish and in 100% of retail packs of minced meat. Seventy two fresh-water fishes, 40 packs of minced meat and 430 milk packs were sampled. One hundred and eighty four isolates were randomly picked from Tryptone glucose extract (TGE) agar (30 degrees C for 3d) or Violet red bile glucose (VRBG) agar (37 degrees C for 1d). In minced meat, Serratia liquefaciens, Hafnia alvei, Rahnella aquatilis were frequently encountered. On fish, the most frequently found species were R. aquatilis, and in milk, the dominating species were S. liquefaciens, H. alvei and R. aquatilis. One to three isolates of Citrobacter freundii were found in all three food categories. Using a polymerase chain reaction (PCR) technique, the gene of Escherichia coli heat-labile toxin (lt) was indicated in one fish isolate of R. aquatilis whereas heat-stable toxin genes (s.t.) were indicated in four H. alvei isolates, two originating from fish and two from minced meat. Positive PCR-reaction for vero cytotoxin genes were found in one H. alvei strain originating from fish (vt1), in two S. liquefaciens strains from minced meat (vt2), and in a C. freundii reference strain. One of the st-positive H. alvei strains from meat harboured the eaeA gene involved in the attaching phenotype of enteropathogenic E. coli.