Paolo Guglielmetti

Patterns of antimicrobial use and antimicrobial resistance among healthy children in Bolivia

Summary

Distribution of cphA or related carbapenemase-encoding genes and production of carbapenemase activity in members of the genus Aeromonas.

The prevalence of the cphA gene or related carbapenemase-encoding genes was investigated in 114 Aeromonas strains belonging to the six species of major clinical interest. A species-related distribution of cphA-related sequences was observed. Similar sequences were found in A. hydrophila, A. veronii bv. sobria, A. veronii bv. veronii, and A. jandaei, but not in A. caviae, A. trota, or A. schubertii. However, a single A. caviae strain (of 62 tested) was found carrying cphA-related sequences, suggesting the possibility of the horizontal transfer of this gene to species which normally do not carry it. Production of carbapenemase activity was detectable in 83% of the hybridization-positive strains but in none of the hybridization-negative ones. When it was present, carbapenemase activity was always inhibitable by EDTA. Either carbapenemase-producing or not, Aeromonas strains appeared to be susceptible to imipenem when in vitro susceptibility testing was performed with inocula of conventional size (10(5) CFU), for which MICs were always < or = 1 microgram/ml. With a larger inoculum (10(8) CFU), the MICs for carbapenemase-negative strains always remained < or = 1 microgram/ml, while those for carbapenemase-producing strains were always > or = 4 micrograms/ml, being usually higher than the breakpoint for susceptibility. The present results indicate that the production of metallocarbapenemase activity, apparently encoded by cphA homologs, is widespread among some of the Aeromonas species of clinical interest (A. hydrophila, A. veronii bv. sobria, A. veronii bv. veronii, and A. jandaei) and that imipenem MICs for carbapenemase-producing strains are subjected to a relevant inoculum size effect.

Acute Diarrhea Associated with Heat-stable Enteroxin Producing Strains of Vibrio cholerae Non-O1: First Report from Cuba

A five month old male infant was referred withwatery diarrhea, vomiting and fever, to the paedi-atric ward of the provincial Pediatric Hospital ofLas Tunas, Cuba. Abdominal examination revealedtenderness; liver and spleen were normal.Chest, cardiovascular and other systems werenormal. The patient was rehydratated with oralrehydratation with solution according to the WorldHealth Organization formula and breast-feedingwas continued. The clinical picture improvedgradually and the patient was discharged after sixdays without diarrhea and in good condition. Onadmission stool sample was taken and cultured onSalmonella-Shigella and MacConkey agar for iso-lation of Salmonella, Shigella spp., enterotoxigenicand enteropathogenic Escherichia coli, Vibrio spp .,Aeromonas spp ., and Plesiomonas shigelloides (JFMcFaddin 1980, p. 19-34. Biochemical Test forIdentification of Medical Bacteria, 2nd ed., TheWilliams and Wilkins Co, Baltimore).Blood agar suplemented with Butzler’s antimi-crobials was employed for the isolation ofCampylobacter spp. The presence of Rotavirus wasruled out by latex agglutination assay. Three dif-ferent samples of feaces were analyzed by conven-tional microscopic examination for the presenceof ova, cyst or vegetative forms of parasites(Organizacion Mundial de la Salud 1992, p. 10-20, Metodos Basicos de Laboratorio enParasitologia Medica, OMS, Geneva).The stool specimen plated on MacConkey agaryielded a pure culture of lactose non-fermentingGram-negative rods, moved by polar flagella, iden-tified at genus level as Vibrio. The national strat-egy for cholera control in Cuba shows that thecountry is still free from cholera. A slide aggluti-nation with polyvalent O1 group antiserum for pre-sumptive identification of V. cholerae O1 strain wasperformed; the test was negative.The coproparasitological examination wasnegative and no Rotavirus or other bacterialenterophatogen were found or isolated from stoolsamples. The Vibrio strain isolated was sent to theNational Reference Laboratory for Diarrhoeal Dis-eases and Cholera Control at the “Pedro Kouri”Institute of Tropical Medicine, Havana City, andconfirmed to be a non-O1 and non-O139 V.cholerae by standard methods (JJ Farmer & FWHickman Brenner 1992, p. 2552-3011. In ABallows, HG Truper, M Dworkin, W Harder, KHSchleifer (eds), The Prokaryotes: a Handbook onthe Biology of Bacteria, Vol. 3, Springer, Verlag,New York). The strain was susceptible to 10- and150 µg disks of the vibriostatic agent O/129; theantimicrobial susceptibility test, performed with theKirby-Bauer method, showed that the strain wassusceptible to tetracycline, ampicillin, cloram-phenicol, trimethoprim, sulphametoxazol, nalid-ixic acid, ciprofloxacin, streptomycin, erytromycin,gentamicin, cefuroxime and furazolidone (CWStratton & RC Cooksey 1991, p. 1153-1165. In ABalows, WJ Hausler Jr, KL Herrmann, HDIsenberg, HJ Shadomy (eds), Manual of ClinicalMicrobiology, 5th ed., ASM, Washington, DC). Thestrain was analyzed for the presence of genomicsequences related to the V. cholerae O1 ctx ge-netic element, that includes the cep, orFU, ace, zot,and ctxAB genes, by using a colony-blot hybrid-ization procedure (T Karasawa et al. 1993 FEMSMicrobiol Letters 106: 143-146). The hybridiza-tion probe used was a 4.4 kbp cloned DNA frag-ment containing the entire ctx element of V.cholerae, and was labeled with (a 32P) dCTP bythe random priming technique.The presence of aheat-stable enterotoxin gene was investigated byPCR amplification as previously described (PGuglielmetti et al. 1994 Mol Cell Probes 8: 39-44). The biological activity of the strain was testedby the conventional suckling mouse assay (YTakeda et al. 1979 Infec Immun 25 : 978-985). Theresults of the molecular characterization of the

Malaria parasitological indices in the Cordillera Province (Santa Cruz Department, Bolivia).

In 1988-1989, as part of a co-operative programme with the local Unidad Sanitaria, two cross-sectional surveys were carried out to study the prevalence of malaria in eight villages in the rural areas near Camiri, Boyuibe and Gutierrez (Cordillera Province, Santa Cruz Department, Bolivia). Thick and thin blood films were collected from all available two- to nine-year-old children at the end of the dry season, in the first survey (252 samples), and after the rainy season, in the second survey (346 samples). The parasite and gametocyte indices increased between surveys from 1.59-25.72 and from 0.40-1.73, respectively. All infections were due to Plasmodium vivax. Both prevalence and parasite load were lower in children aged two to four years than in older children. Prevalences, parasite loads, and parasite densities were highest in rural areas near Camiri and Gutierrez.