Estudio de la actividad antibacteriana en un hospital terciario. Evolución durante el período 2000-2005

Knowledge of the antibiotic resistance in a specific healthcare area is essential for suitable application of the antibiotic policy, which can be understood as the use of recommendations for the application and consumption of antimicrobial agents, as well as for education and continual surveillance to achieve the most effective, rational and least expensive antibiotic therapy possible.

We performed a study of antimicrobial susceptibility between 2000 and 2005 in the Health Area of the West of Valladolid (Spain) corresponding to the Rio Hortega University Hospital, with a catchment area of approximately 235,0000 inhabitants.

The microorganisms tested were obtained from isolates of distinct samples from patients with infectious processes. The agents were considered causal. The most frequently isolated agents were described.

The antibiotics tested were those that showed acceptable in vitro and in vivo activity against each isolated species. The criteria considered were clinical effectiveness, the prevalence of resistance, a low possibility of developing resistance, indications for clinical use and being the first treatment choice or alternative. The results were expressed in percentages of susceptibility or sensitivity to the antibiotics analyzed.

The sensitivity criteria of the National Committee on Clinical Laboratory Standards (USA) were followed. The category of SENSITIVE to a given antibiotic implies that the infection caused by the isolated bacterium can suitably be treated with the routine dosage of this antibiotic. The RESISTANT category implies that isolated bacteria are not inhibited with the routine dosage of this antibiotic.

The antibiotic types studied followed general lines and the following agents were taken as representative of their class: Ampicillin (ampicillin and amoxicillin derivatives), Amoxicillin/clavulanic acid(ampicillin/sulbactam), Cefalotin (cefazolin, cefaclor, cephradine, cefalexin, etc), Cefoxitin (cefmetazole), Cefotaxime (ceftriaxone, imipenem, meropenem), Gentamicin (netilmicin, tobramycin), Ciprofloxacin (ofloxacin), Ofloxacin (levofloxacin). In Enterococci: Gentamicin synergy (gentamicin, tobramycin, netilmicin and amikacin). Streptomycin synergy (streptomycin).

The results obtained in the study were grouped in different antibiotic activities:

• 1.

  Antibiotic activity against Gram-positive bacteria: a. Antibiotic activity against to Staphylococcus aureus. b. Antibiotic activity against S epidermidis. c. Antibiotic activity against Enterococcus faecalis d. Antibiotic activity against E. faecium. e. Antibiotic activity against Streptococcus agalactiae.

• 2.

  Antibiotic activity against Gram-negative bacteria. a. Antibiotic activity against Enterobacteriaceae. Antibiotic activity against Escherichia coli. Antibiotic activity against Klebsiella pneumoniae and K. oxytoca. Antibiotic activity against Enterobacter cloacae. Antibiotic activity against Serratia marcescens. Antibiotic activity against Proteus mirabilis. Antibiotic activity against Morganella morganii.

• 3.

  Antibiotic activity against Non-fermenting Gram-negative bacilli (NFGNB). Antibiotic activity against Pseudomonas aeruginosa. Antibiotic activity against Acinetobacter baumannii. Antibiotic activity against Stenotrophomonas maltophilia.

• 4.

  Antibiotic activity against miscellaneous microorganisms. a. Antibiotic activity against Branhamella catarrhalis. b. Antibiotic activity against Haemophilus influenzae.

Therefore, although many antibiotic-resistant bacteria exist, there are some strains that frequently cause infections and cannot be treated with common antibiotics. Consequently routinely-used therapeutic regimens should be changed. These bacteria are usually particularly virulent and cause serious infections.