Update on Pan-American Research on Anaerobes: The Situation in Argentina

UC: CID The study of anaerobic bacteria became important in Argentina when the first outbreak of botulism was reported in Mendoza in 1922. In the 1970s, the emphasis was on the development of methods to obtain suitable samples for isolation and identification of anaerobic bacteria. In 1985, a working group belonging to the Argentine Association of Microbiology was organized to study anaerobic bacteria and infections. Last year, I became involved with the immunologic, microbiological, and epidemiological features of periodontitis. Other investigators in our country are studying Clostridium difficile, Campylobacter species, and Helicobacter species as well as lactobacilli, Propionibacterium species (as probiotics to protect the gastrointestinal tracts of children), anaerobic veterinary infections, food contamination by anaerobes, and biotechnological applications of anaerobes. Botulism As mentioned above, the first outbreak of botulism was repoted in Mendoza in 1922. Gimenez and Cicarelli, from the Medical School of Mendoza University, subsequently described novel Clostridium botulinum subtypes, as well as their association with specific outbreaks [2]. C. botulinum subtype Af [2] and C. botulinum type G (currently called C. argentinense) were first described by these authors. In 1982, two cases of botulism in infants were simultaneously reported in Mendoza and Buenos Aires [3]. Later, several other cases with associated mortality rates ranging from 0 to 30.6% (R. Fernandez, personal communication) were reported from different areas of our country. It is of interest that the first case of botulism in an infant in Chile, just across the Andean range, was only recently reported [4]. In 1992, Cicarelli and Fernandez [5] isolated a strain of C. botulinum from a leg wound; this infection was fatal [5]. Endogenous Infection To promote the study of anaerobic bacteria and anaerobic infections, the Anaerobic Bacteria Study Group (ABSG) was founded in 1985 by the Argentine Association of Microbiology (AAM). In 1991, the ABSG conducted the first multicenter study on antimicrobial susceptibility of anaerobic bacteria. The in vitro activities of penicillin, piperacillin, ampicillin/sulbactam, imipenem, cefoxitin, chloramphenicol, clindamycin, and metronizadole against gram-negative and gram-positive organisms isolated from diverse clinical sources were assessed. No resistance to metronidazole, chloramphenicol, imipenem, or ampicillin/sulbactam was detected. However, resistance to clindamycin and cefoxitin was found among Bacteroides fragilis group species; resistance rates varied from 2.5% to 14% for clindamycin and 6% to 7% for cefoxitin [6]. In 1994, the ABSG performed a study to assess the disk elution broth method because it was still being used in severe clinical situations in our country neither microdilution systems nor the Etest (AB BIODISK, Solna, Sweden) had yet been marketed in Argentina. The ABSG found that the disk elution broth method correlated satisfactorily with the reference agar dilution method (1.5% discrepancy) for determing susceptibilities (table 1). In addition, good interlaboratory and intralaboratory reproducibility was observed (unpublished data). In 1995, the ABSG published Anaerobic Bacteria: A Practical Guide to Processing Clinical Specimens, which was drawn up according to the facilities at our laboratories to promote more reliable etiologic diagnoses of anaerobic infections [7]. At present, the ABSG is conducting a national survey on clinical laboratory diagnosis of anaerobic infections. Accordingly, questionnaires were sent to medical and biochemical colleges throughout the 22 provinces of Argentina; the results were published in the AAM Bulletin. The ABSG is currently analyzing the 48 replies from different hospitals with bed capacities ranging from 50 to 400. Some degree of anaerobic microbiological study was performed at 77% of these facilities, but identification of organisms to the species level was done at only 50% of these facilities. Not all hospital laboratories performed susceptibility tests, and when they did, the disk elution broth method was frequently used. Few laboratories achieved complete diagnosis of anaerobic infections, probably because of lack of interest on the part of physicians or because of lack of facilities (no financial support), as well as the shortage of qualified bacteriologists devoted to the study of anaerobes. The AAM has strongly encouraged ABSG activities, thereby increasing the knowledge regarding anaerobic infections on the basis of the findings obtained from our own clinical experience. I have been studying anaerobic infections since 1976. My interest is in diagnosis and emerging resistance, especially among gram-negative pigmented and nonpigmented rods [6, 9]. There has been a worrisome increase in cefoxitin resistance among isolates of the B. fragilis group over the last 15 years in our hospital; the rate soared from 0 to 22%. Likewise, MICs50 and MICs90 increased from 1 mg/mL to 16 mg/mL and from 2 mg/mL to 64 mg/mL, respectively (figure 1). In addition, the first two strains (B. fragilis and Bacteroides vulgatus) displaying decreased susceptibility to ampicillin/sulbactam (MIC, 16 mg/mL) appeared in our hospital in 1995 [9]. These strains represent 3.9% of all Bacteroides species studied during this period. At the same time, Valenzuela [10], in Chile, reported resistance rates of 1.5% and 2% to amoxicillin/clavulanic acid and ampicillin/sulbactam, respectively [10]. At present, our laboratory is focusing on the immunologic, microbiological, and epidemiological features of periodontitis [11]. We began to work on this subject jointly with the Maimonides Odontology School (Buenos Aires) and the Buenos Aires Odontology School. Other groups in Argentina and neighboring countries such as Chile, Uruguay, and Brazil are studying lactobacilli and Propionibacterium species as probiotics to protect the gastrointestinal tracts of children; diseases due to species of Campylobacter, Helicobacter, and Clostridium difficile; oral and odontogenic infections; veterinary infections; food contamination; and biotechnological applications of anaerobes. (...truncated)