Rapid diagnosis of diarrhea caused by Shigella sonnei using dipsticks; comparison of rectal swabs, direct stool and stool culture

Background

We evaluated a dipstick test for rapid detection of Shigella sonnei on bacterial colonies, directly on stools and from rectal swabs because in actual field situations, most pathologic specimens for diagnosis correspond to stool samples or rectal swabs.

Methodology/Principal Findings

The test is based on the detection of S. sonnei lipopolysaccharide (LPS) O-side chains using phase I-specific monoclonal antibodies coupled to gold particles, and displayed on a one-step immunochromatographic dipstick. A concentration as low as 5 ng/ml of LPS was detected in distilled water and in reconstituted stools in 6 minutes. This is the optimal time for lecture to avoid errors of interpretation. In distilled water and in reconstituted stools, an unequivocal positive reaction was obtained with 4 x 10⁶ CFU/ml of S. sonnei. The specificity was 100% when tested with a battery of Shigella and different unrelated strains. When tested on 342 rectal swabs in Chile, specificity (281/295) was 95.3% (95% CI: 92.9% - 97.7%) and sensitivity (47/47) was 100%. Stool cultures and the immunochromatographic test showed concordant results in 95.5 % of cases (328/342) in comparative studies. Positive and negative predictive values were 77% (95% CI: 65% - 86.5%) and 100% respectively. When tested on 219 stools in Chile, Vietnam, India and France, specificity (190/198) was 96% (95% CI 92%–98%) and sensitivity (21/21) was 100%. Stool cultures and the immunochromatographic test showed concordant results in 96.3 % of cases (211/219) in comparative studies. Positive and negative predictive values were 72.4% (95% CI 56.1%–88.6%) and 100 %, respectively.

Conclusion

This one-step dipstick test performed well for diagnosis of S. sonnei both on stools and on rectal swabs. These data confirm a preliminary study done in Chile.

Diagnostic microbiologic methods in the GEMS-1 case/control study

To understand the etiology of moderate-to-severe diarrhea among children in high mortality areas of sub-Saharan Africa and South Asia, we performed a comprehensive case/control study of children aged <5 years at 7 sites. Each site employed an identical case/control study design and each utilized a uniform comprehensive set of microbiological assays to identify the likely bacterial, viral and protozoal etiologies. The selected assays effected a balanced consideration of cost, robustness and performance, and all assays were performed at the study sites. Identification of bacterial pathogens employed streamlined conventional bacteriologic biochemical and serological algorithms. Diarrheagenic Escherichia coli were identified by application of a multiplex polymerase chain reaction assay for enterotoxigenic, enteroaggregative, and enteropathogenic E. coli. Rotavirus, adenovirus, Entamoeba histolytica, Giardia enterica, and Cryptosporidium species were detected by commercially available enzyme immunoassays on stool samples. Samples positive for adenovirus were further evaluated for adenovirus serotypes 40 and 41. We developed a novel multiplex assay to detect norovirus (types 1 and 2), astrovirus, and sapovirus. The portfolio of diagnostic assays used in the GEMS study can be broadly applied in developing countries seeking robust cost-effective methods for enteric pathogen detection.

Persistence of antibodies in adolescents 18-24 months after immunization with one, two, or three doses of 4CMenB meningococcal serogroup B vaccine

We previously demonstrated the immunogenicity and tolerability of the serogroup B meningococcal vaccine, 4CMenB (Bexsero), in 11-17 y-olds randomized to receive 1, 2, or 3 doses at 1, 2, or 6 mo intervals. Participants in this extension study provided an additional blood sample 18-24 mo after last vaccine dose, to assess persistence of serum bactericidal activity with human complement (hSBA), and to compare with age-matched 4CMenB-naïve controls. In the original study, one month after one 4CMenB dose, 93% of subjects had seroprotective hSBA titers (≥4) against indicator serogroup B strains for individual vaccine antigens (fHbp, NadA and NZOMV), increasing to ~100% after two or three doses. After 18-24 mo, 62-73% of subjects given one dose had titers ≥4 against the three antigens, significantly lower rates than after two (77-94%) or three (86-97%) doses. Only proportions with titers ≥ 4 against NZOMV were significantly different between the two (77%) and three (90%, p < 0.0001) dose groups. These results confirm that two doses of 4CMenB, administered 1 to 6 mo apart, provide good levels of bactericidal activity against serogroup B meningococci, which were sustained at least 18-24 mo in over 64% of adolescents for all three tested vaccine-related antigens.

Antimicrobial Properties of Copper in Hearing Aid Users

Objective: 1) Evaluate the antimicrobial properties of copper in hearing aid molds against the most prevalent pathogens of otitis externa in an in vitro system. 2) Determine the most suitable mold material to allow adequate diffusion of copper ions to perform its antimicrobial action.

Method: Experimental study conducted from January to December 2010, consisting of an in vitro system with hearing-aid molds made from different materials with and without copper in them, which were inoculated with external otitis pathogens at different concentrations ( S aureus, P aeruginosa, C albicans, and A niger), then determine percentage of bacterial adhesion to materials.

Results: There was a significant reduction in the percentage of microbial adherence to different mold materials with copper in them, in relation to those without copper, at different levels of microbial concentration for S aureus, P aeruginosa, C albicans, and A niger, while the percentages of adherence reduction fluctuated between 27% and 100% in those molds that contained copper. We have observed an inverse relation between the adherence reduction and the concentration of inoculated microorganisms. A greater microbial adherence reduction was shown in molds made of UV sensitive polymer with copper in their interior, compared with other materials.

Conclusion: Results show that copper exerts its antimicrobial properties through different materials, which opens an interesting challenge in the otolaryngological field and public health area to develop clinical studies focused on confirming whether the use of hearing aids with copper sheets inside reduces the risk of infectious external otitis.

Immunogenicity and tolerability of a multicomponent meningococcal serogroup B (4CMenB) vaccine in healthy adolescents in Chile: a phase 2b/3 randomised, observer-blind, placebo-controlled study

BACKGROUND

Effective glycoconjugate vaccines against Neisseria meningitidis serogroups A, C, W-135, and Y have been developed, but serogroup B remains a major cause of severe invasive disease in infants and adolescents worldwide. We assessed immunogenicity and tolerability of a four-component vaccine (4CMenB) in adolescents.

METHODS

We did a randomised, observer-blind, placebo-controlled, study at 12 sites in Santiago and Valparaíso, Chile. Adolescents aged 11-17 years received one, two, or three doses of 4CMenB at 1 month, 2 month, or 6 month intervals. Immunogenicity was assessed as serum bactericidal activity using human complement (hSBA) against three reference strains for individual vaccine antigens, and assessed by ELISA against the fourth strain. Local and systemic reactions were recorded 7 days after each vaccination, and adverse events were monitored throughout the study. Participants were initially randomised to five groups (3:3:3:3:1) during the primary phase to receive either one dose, two doses 1 or 2 months apart, or three doses of 4CMenB, or three doses of placebo, with an additional three groups generated for the booster phase. All subjects received at least one dose of 4CMenB. Geometric mean titres, proportions of participants with serum bactericidal antibody titres of 4 or more, and Clopper-Pearson 95% CIs were calculated. The study is registered with ClinicalTrials.gov, number NCT00661713.

FINDINGS

Overall, 1631 adolescents (mean age 13·8 [SD 1·9] years) received at least one dose of 4CMenB. After two or three doses, 99-100% of recipients had hSBA titres of 4 or more against test strains, compared with 92-97% after one dose (p<0·0145) and 29-50% after placebo. At 6 months 91-100% of participants still had titres of 4 or more for each strain after two or three doses, but only 73-76% after one dose; seroresponse rates reached 99-100% for each strain after second or third doses at 6 months. Local and systemic reaction rates were similar after each 4CMenB injection and did not increase with subsequent doses, but remained higher than placebo. No vaccine-related serious adverse events were reported and no significant safety signals were identified.

INTERPRETATION

On the basis of immunogenicity responses this study provides evidence for an adolescent 4CMenB vaccine schedule of two doses, 1-6 months apart, to provide protection against meningococcal B infection. The extent of this protection against meningococcus B variants circulating worldwide will be determined by national surveys.

FUNDING

Novartis Vaccines and Diagnostics.

Novel recombinant norovirus causing outbreaks of gastroenteritis in Santiago, Chile

Capsid and polymerase (RdRp) genes of 13 norovirus outbreak strains from Chile were compared. The genes sequences were discordant for five strains, and recombination was confirmed for two of them by amplification of a 1,360-bp gene segment containing a fragment of both genes. These strains belonged to a novel genogroup by RdRp sequence and to genogroup GII/3 by capsid sequence. Determining the clinical and epidemiological impact of human calicivirus recombination will require future studies.

Single multiplex PCR assay to identify simultaneously the six categories of diarrheagenic Escherichia coli associated with enteric infections

We designed a multiplex PCR for the detection of all categories of diarrheagenic Escherichia coli. This method proved to be specific and rapid in detecting virulence genes from Shiga toxin-producing (stx(1), stx(2), and eae), enteropathogenic (eae and bfp), enterotoxigenic (st II and lt), enteroinvasive (vir F and ipa H), entero-aggregative (aaf II), and diffuse adherent (daa E) Escherichia coli in stool samples.

Caliciviruses and foodborne gastroenteritis, Chile

Human caliciviruses caused 45% of 55 gastroenteritis outbreaks occurring in Santiago, Chile, during 2000–2003. Outbreaks affected ≤99 persons, occurred most commonly in the home, and were associated with seafood consumption. Thirteen outbreak strains sequenced were noroviruses, including 8 GII, 2 GI, and 3 belonging to a novel genogroup.

[Activity of cefpodoxime against pathogens causing respiratory, urinary or soft tissue infections]

BACKGROUND

Cefpodoxime is a new antimicrobial in the Chilean market, recommended for treatment of respiratory and urinary tract infections.

AIM

To study the susceptibility of common pathogens isolated from Chilean patients to cefpodoxime and other antimicrobials.

MATERIAL AND METHODS

The in vitro activity of cefpodoxime, expressed as Minimal Inhibitory Concentration, was studied in 331 S pneumoniae, H influenzae, M catarrhalis, E coli, S aureus and S pyogenes strains, isolated between 2000 and 2004 from respiratory, urinary and soft tissue infections, respectively.

RESULTS

Eleven percent of S pneumoniae isolates were resistant to penicillin, 11% were resistant to cefuroxime and 10% to cefpodoxime. All H influenzae isolates were susceptible to cefpodoxime. No H influenzae isolates were resistant to second or third generation cephalosporines. Four percent of H influenzae isolates were resistant to ampicillin by ss-lactamase production. In contrast 81% of M catarrhalis strains were resistant to ampicillin. Six percent of E coli isolates were resistant to cefpodoxime, 9% to cefuroxime, 11% to cefadroxile and 50% to ampicillin or trimethoprim/sulphamethoxazole. Cefpodoxime was the most active antimicrobial against S pyogenes.

CONCLUSIONS

Cefpodoxime, recently introduced in Chile, is a good alternative for the treatment of common respiratory and urinary tract infections.

Surveillance for antimicrobial resistance profiles among Shigella species isolated from a semirural community in the northern administrative area of santiago, chile

Variations in antibiotic resistance patterns were studied among 178 Shigella strains isolated from 1997 to 2001 in children less than five years of age with acute diarrhea from Colina, a semi-rural community in Santiago, Chile. The minimal inhibitory concentration of several commonly used antibiotics was determined by the agar dilution method. Shigella strains showed high rates of resistance to ampicillin (82%), cotrimoxazole (65%), tetracycline (53%), and chloramphenicol (49%). Furthermore, 51% of the strains showed resistance patterns to multiple antibiotics. Only 9% of the strains were resistant to amoxicillin-clavulanic acid and no resistance was observed to ciprofloxacin, nalidixic acid, or cefotaxime. Continuous monitoring of resistance patterns in Shigella is essential for establishing and updating guidelines for antibiotic treatment in shigellosis.

Genetic analysis of antibiotic-resistance determinants in multidrug-resistant Shigella strains isolated from Chilean children

A total of 162 clinical isolates of Shigella collected from children in a semi-rural community of Chile were examined for the presence of genetic determinants of resistance to ampicillin, chloramphenicol, tetracycline, and trimethoprim. Ampicillin resistance was most frequently associated with the presence of bla(OXA) in S. flexneri and with bla(TEM) in S. sonnei. The bla(OXA) gene but not bla(TEM) was located in class 1 integrons. The dhfrIa gene encoding for resistance to trimethoprim was associated to class 2 integrons and detected exclusively in S. flexneri, whereas dhfrIIIc was found in all S. sonnei strains and in 10% of the S. flexneri isolates. Cat, coding for choramphenicol resistance, and bla(OXA) genes were located in the chromosome in all cases, whereas tetA gene, coding for tetracycline resistance, and bla(TEM), dhfrIa and dhfrIIIc genes were found either in the chromosome or in conjugative plasmids. Our results show a heterogenous distribution of antibiotic-resistance determinants between S. flexneri and S. sonnei.

[Assessment of two DNA extraction methods to amplify the pneumolysin gene (PLY) from blood culture samples of Streptococcus pneumoniae]

BACKGROUND

Streptococcus pneumoniae is a common etiologic agent of invasive respiratory infections among children under 5 years of age and older adults. Isolation rates of S. pneumoniae by traditional culture techniques are low.

AIM

To study the sensitivity and specificity of two different DNA extraction methods to amplify the ply gene, applied to three different types of blood culture broths, experimentally inoculated with S. pneumoniae.

MATERIAL AND METHODS

DNA was extracted from the cultures using an organic method or a technique that consists in dilution, washing with NaOH and concentration of the sample. This was followed by PCR amplification of a 355 pb fragment of the pneumolysin gene (ply).

RESULTS

The organic DNA extraction method inhibited the PCR reaction at all concentrations studied (0.6 to 10(6) colony forming units/mL). Using the NaOH extraction, ply gene amplification was positive in all three blood culture broths, but only at concentrations of 10(3) colony forming units/mL, or higher. Using the same DNA extraction method, PCR was negative when the broths were inoculated with seven other related bacterial species, which results in a 100% specificity.

CONCLUSIONS

Detection of S. pneumoniae by amplification of ply gene from blood cultures using the protocol of NaOH for DNA extraction is specific and provides results in a short lapse. However, the diagnostic sensitivity is not optimal, which limits its clinical use.

Multiplex PCR for diagnosis of enteric infections associated with diarrheagenic Escherichia coli

A multiplex PCR for detection of three categories of diarrheagenic Escherichia coli was developed. With this method, enterohemorrhagic E. coli, enteropathogenic E. coli, and enterotoxigenic E. coli were identified in fecal samples from patients with hemorrhagic colitis, watery diarrhea, or hemolytic-uremic syndrome and from food-borne outbreaks.

Detection of Shiga toxin-producing Escherichia coli in food

Shiga toxin-producing Escherichia coli are emerging as a significant source of food-borne infectious disease all over the world. Illness caused by Shiga toxin-producing E. coli can range from self limited, watery diarrhea to life-threatening manifestations such as hemorrhagic colitis, hemolytic uremic syndrome or thrombotic thrombocytopenic purpura and death. Shiga toxin-producing E. coli can potentially enter the human food chain from a number of animal sources, most commonly by contamination of meat with feces or intestinal contents after slaughter or cross-contamination of unpasteurized milk products. Because of the low infectious dose of the O157:H7 Shiga toxin-producing E. coli strain, laboratory diagnosis of Shiga toxin-producing E. coli in food samples has developed a great importance. This review will focus on the microorganism, giving priority to illness prevention and Shiga toxin-producing E. coli detection in food.

[Evaluation of molecular and immunoenzymatic assays for detecting Enterohemorrhagic E coli in food borne outbreaks]

BACKGROUND

Enterohemorrhagic Escherichia coli (EHEC), is an emergent pathogen that causes sporadic infections and outbreaks of gastroenteritis associated with consumption of contaminated food products. Because detection of EHEC in diarrhea patients is not routinely performed, infection is most probably underestimated.

AIM

To compare three techniques to detect EHEC: Colony hybridization with DNA probes, polymerase chain reaction (PCR) for the detection of stx1 and stx2 genes and immunoenzymatic detection by ELISA (Premier EHEC) of Stx1 and Stx2 toxins.

MATERIAL AND METHODS

Four outbreaks of food-borne gastroenteritis were studied including 16 patients and 78 strains of E coli. Twenty-one (26.9%) strains, hybridized with the stx1 probe, 1 (1.3%) hybridized only with the stx2 probe and 36 (46.1%) with both probes. PCR amplification for cytotoxin genes was observed in 6 strains (7.7%) from the second outbreak studied. The immunoenzymatic assay detected the cytotoxins in 18 (23.0%), of the 78 studied strains. Agreement between probes and ELISA was 44.8%, between PCR and probes 34.7% and 82.4% between ELISA and PCR.

CONCLUSIONS

These results indicate a variable yield among different EHEC detection techniques. Considering PCR as the gold standard, ELISA technique showed a better sensitivity and specificity than probes.

Management of the female stimulus during semen collection and its association with libido re-establishment and semen characteristics of goats

The effect of management of the female stimulus during semen collection and its association with libido re-establishment and the semen characteristics of sexually mature goats was evaluated. Eight 2-yr-old bucks were individually subjected to 12 weekly trials in which one of the following three treatments was applied alternately. In treatment one, each male performed two ejaculations on an estrus-induced, restrained doe and semen was collected with an artificial vagina (AV). In treatment two, males were collected as in the former treatment, but a different doe served as the stimulus female for the second ejaculation. In treatment three, two restrained does were present while collecting each buck, allowing males to choose which female to mount and serve in each of the two collections. Number of mounts before first ejaculation and reaction times (period from introduction of the ram to the test arena to his first ejaculation) were similar among treatments (P > 0.05). A significant (P < 0.05) decrease was found for number of mounts performed before achieving the second ejaculation and for latency between ejaculations in the third treatment. No differences (P > 0.05) were found for semen volume (0.8+/-0.03, 1.0+/-0.03, and 0.9+/-0.02 mL) or sperm concentration (4.4+/-0.15, 4.6+/-0.13, and 4.4+/-0.86 spermatozoa/mL) among the three treatments or between the first and second collection. However, a trend to decrease volume and concentration was observed. It was concluded that the simultaneous presence of two females while bucks are collected reduced the number of mounts performed before the second ejaculation and the latency between ejaculations.

Immunogenicity and reactogenicity of a combined hepatitis A and B vaccine in healthy Chilean subjects

OBJECTIVES

A combination vaccine against hepatitis A and B provides the opportunity for simultaneous protection against both diseases with a single vaccine. This clinical study investigated the reactogenicity and immunogenicity of a combined hepatitis A and B vaccine (Twinrix, GlaxoSmithKline Biologicals, Rixensart, Belgium) in healthy Chilean adults between 18 and 40 years of age.

METHODS

In total, 345 healthy, seronegative health care workers were enrolled and randomized to three groups who received one of three lots of Twinrix on a 0-, 1- and 6-month schedules. Blood samples were screened 1 month after each dose for anti-HAV and anti-HBs antibodies. Reactogenicity after each dose was assessed using diary cards.

RESULTS

The nature and incidence of symptoms were similar to those reported for other Twinrix studies. Very few symptoms were scored as severe. Upon completion of the vaccination, all subjects had anti-HAV antibodies with titers $6000 mIU/mL, and all but one were protected against hepatitis B, with titers $4000 mIU/mL.

CONCLUSIONS

We have demonstrated the high immunogenicity and tolerance of the combined hepatitis A and B vaccine. Combined vaccination has the advantage of offering dual protection with a reduction in the number of injections needed, lower associated costs, and a positive impact on compliance.

[Epidemiological situation of foodborne diseases in Santiago, Chile in 1999-2000]

BACKGROUND

Foodborne diseases are becoming an important cause of morbidity in Chile. In the Metropolitan Region of Chile, the Environmental Health Service started a surveillance program for foodborne diseases in 1994. In 2000, this program was complemented with an etiologic study of individuals involved in outbreaks.

AIM

To report the incidence of foodborne outbreaks in the Metropolitan Region of Chile and its causative agents.

RESULTS

One hundred ninety outbreaks of foodborne diseases were reported in 1999 and 260 in 2000. The Southern Metropolitan health service had the higher incidence rates (7.5 in 1999 and 8.2 in 2000). The mean attack rates were 25% in both periods, affecting 1248 individuals in 1999 and 1774 in 2000. In 18% of outbreaks, a pathogen was identified; the most frequent agents were Salmonella Spp, Staphylococcus aureus and Shigella. In 15% of subjects, the cause was histamine or chemical agents. In the rest of the cases, the cause was not identified. The foods with higher risk of causing foodborne diseases were hot prepared dishes, home made goat cheese and meats.

CONCLUSIONS

The incidence rates of foodborne disease in Metropolitan Area of Chile are high and maybe underestimate, only in a low rate of outbreaks was possible to have samples for etiologic studies. For a better understanding of this problem, timely notification of foodborne diseases must be encouraged and educational campaigns about the proper manipulation of food items must be implemented.

[Molecular characterization of resistance mechanisms to chloramphenicol in Shigella flexneri strains isolated from Chilean children with acute diarrhea]

BACKGROUND

Chloramphenicol is one of the therapeutic options for shigellosis, but resistance to this antimicrobial is increasing.

AIM

To characterize molecular mechanisms conferring resistance to chloramphenicol (Cm) in Shigella flexneri strains isolated from Chilean children with acute diarrhea.

MATERIAL AND METHODS

Thirty one Shigella filexneri strains, including 22 with the Cm phenotype were analyzed. Strains were tested for antimicrobial susceptibility by plate dilution and for the presence of an internal fragment of the cat gene encoding for chloramphenicol o-acetyl-transferase, by polymerase chain reaction and Southern blot analysis.

RESULTS

All Cm strains had a minimal inhibitory concentration over 64 micrograms/ml and amplified the internal fragment of the cat gene. Southern blot analyses indicated that this gene was located in the bacterial chromosome.

CONCLUSIONS

Resistance to chloramphenicol in this group of Shigella flexneri strains was mediated by a chromosomally located cat gene.

[Profile of antimicrobial resistance of agents causing urinary tract infections in Chilean children. PRONARES surveillance program]

BACKGROUND

PRONARES (Programa Nacional de Vigilancia de Resistencia) is a national surveillance program for antimicrobial susceptibility, focused in different syndromes and among these, urinary tract infections. The work is done in a laboratory net that uses common protocols and whose data are centrally analyzed using the WHONET program.

AIM

To analyze the pattern of antimicrobial susceptibility of agents causing urinary infections in children in the period 1997-1999.

MATERIAL AND METHODS

In the study period, 5,525 strains were analyzed. Of these, 2,307 came from pediatric patients (1,495 hospitalized and 803 ambulatory).

RESULTS

The most common causative agent was E. coli in 74.2% of cases, followed by Klebsiella spp in 8.2% and other agents in a lower frequency. Of E. coli strains, 74% were resistant to ampicillin, 52% to clotrimoxazole and 30% to first generation cephalosporins. These strains were sensitive to second and third generation cephalosporins, aminoglycosides, ciprofloxacin and nitrofurantoin. Strains from nosocomial or community infections had similar antimicrobial susceptibility. Klebsiella spp had a high rate of antimicrobial resistance (over 40%), that was even higher among nosocomial strains. It was 90% susceptible to ciprofloxacin and 100% to imipenem. All centers from which strains came had a similar pattern of susceptibility, with the exception of a pediatric center that had significantly higher resistance levels.

CONCLUSIONS

The current therapeutic recommendations for urinary tract infections in children caused by E coli, are still pertinent, but the use of first generation cephalosporins must be cautious. The treatment of Klebsiella spp requires an individual antibiogram.

[Trends of etiology of acute bacterial meningitis in Chilean children from 1989 to 1998. Impact of the anti-H influenzae type b vaccine]

BACKGROUND

Acute bacterial meningitis still has a high mortality and rate of complications.

AIM

To assess the impact of anti H influenzae vaccination on the epidemiology of acute bacterial meningitis in Chilean children.

MATERIAL AND METHODS

A retrospective study of hospital discharge records of patients with acute bacterial meningitis. Causative agents were studied globally, by hospital and by age group. The changes in etiology from 1989 to 1995 were also assessed. Between 1996 and 1998, only those patients with acute bacterial meningitis caused by H influenzae were recollected.

RESULTS

In the period prior to vaccination (1989-1995), 1000 cases were registered. The main causative agents were N meningitidis in 33.8%, H influenzae type b in 21.9% and S pneumoniae in 15.4%. The incidence of H influenzae decreased in the period from 36.4 to 9.9% (p < 0.001) and the incidence of N meningitidis increased from 22.9 to 52.1% (p < 0.001). The incidence of S pneumoniae did not change significantly. H influenzae predominated in children between 4 and 24 months of age and N meningitidis predominated in children over 25 months of age. In the period after the introduction of vaccination (1995-1998), there was a further decrease in the incidence of H influenzae from 10 to 2% (p < 0.001). Until 1997, there was a considerable increase in the incidence of N meningitidis, specially in children over 25 months of age. It declined in 1998 to 38%.

CONCLUSIONS

There was a reduction in the incidence of acute bacterial meningitis caused by H influenzae prior to the introduction of the vaccine against H influenzae type b. The decrease was more pronounced after the introduction of the vaccine.

Detection of enterohemorrhagic Escherichia coli in meat foods using DNA probes, enzyme-linked immunosorbent assay and polymerase chain reaction

Enterohemorrhagic Escherichia coli (EHEC) is an important cause of diarrhoea with blood and haemolytic uremic syndrome (HUS) in children and elderly people. Infections with EHEC are a world-wide public health problem, related to consumption of contaminated ground beef. The aim of this study was to establish whether different meat foods sold in Santiago, Chile pose an infection risk by EHEC and to evaluate three different diagnostic techniques in foods, to determine which is most applicable for use in Chile. A parallel analysis was performed on 64 samples of meat foods (23 refrigerated ground meat, 23 refrigerated long pork sausages and 18 frozen hamburgers) sold in Santiago, Chile using DNA probes, enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). Twenty-four samples (24 of 64 = 37.5%) were positive by DNA probes, ELISA or PCR. The positive and negative predictive values, sensitivity and specificity of ELISA were 26.7, 81.6, 30.8 and 78.4%, respectively. The positive and negative predictive values, sensitivity and specificity of PCR were 91.7, 96.2, 84.6 and 98%, respectively. The EHEC serogroups most frequently isolated were O158, O157, O119, O125 and O114. These results show that, although molecular techniques such as enzyme immunoassays are useful for EHEC detection in meat foods, PCR has advantages in terms of sensitivity, specificity, cost and ease of implementation in Chile.

[In vitro comparative activity of moxifloxacin and other antimicrobials against respiratory pathogens]

BACKGROUND

Respiratory pathogens are becoming increasingly resistant to antimicrobials. A new group of drugs, called respiratory quinolones have been synthesized to overcome this problem.

AIM

To study the in vitro susceptibility of respiratory pathogens to old and new antimicrobials.

MATERIALS AND METHODS

Forty five strains of S pneumoniae, 44 strains of H influenzae, 21 strains of M catarrhalis, 10 strains of methicillin susceptible S aureus and 20 strains of methicillin resistant S aureus were studied. All were isolated from community acquired respiratory infections during 1999. Minimal inhibitory concentrations of moxifloxacin, amoxicillin, amoxicillin/clavulanic acid, clarithromycin, azithromycin, ciprofloxacin and levofloxacin were determined using the Etest method. Beta-lactamase production by H influenzae and M catarrhalis was also studied.

RESULTS

S pneumoniae strains were 100% susceptible to quinolones and cotrimoxazole, 2% were resistant to macrolides, 11% were resistant to amoxicillin/clavulanic acid and 47% were resistant to cefuroxime. H influenzae was 100% susceptible to quinolones, azithromycin and amoxicillin/clavulanic acid. There was a 53% resistance to cotrimoxazole, 21% to amoxicillin, 9% to clarithromycin and 7% to cefuroxime. M catarrahalis was 100% susceptible to quinolones and 100% resistant to amoxicillin, 5% resistant to macrolides, 14% resistant to amoxicillin/clavulanic acid, 20% to cefuroxime and 30% to cotrimoxazole. Methicillin susceptible S aureus was susceptible to all antimicrobials and methicillin resistant S aureus was resistant to all.

CONCLUSIONS

Maxifloxacin and the new respiratory quinolones can be useful in the treatment of respiratory infections.

[Prevalence of enterohemorrhagic Escherichia coli in a cattle area of Argentina. Genotypic characterization of the strains of animal origin]

BACKGROUND

There is a high prevalence of infection by Enterohemorrhagic Escherichia coli (EHEC) and patients with hemolytic uremic syndrome (HUS) in Argentina.

AIM

To study cattle and pigs as a possible reservoir of EHEC in Argentina.

MATERIAL AND METHODS

One hundred two healthy animals (68 cattles and 31 pigs) from a livestock in Argentina, were studied. Stool samples were obtained with a rectal swab. The strains were identified by DNA hybridization with specific gene probes detecting Shiga-like toxin 1 and 2 (Stx1, Stx2), and hly gen related to fimbrial adhesin-associated plasmid. EHEC strains were serogrouped using commercial antisera.

RESULTS

EHEC was isolated from 30 out of 68 bovines cultures (44.1%) and from 25 out of 31 pigs (58.1%). Isolates carrying genes codifying both Stx1 and Sxt2, were observed in 50% of cattle and 63.9% of pigs. The gene which codifies for hemolysin (associated to fimbrial adhesin) was observed in about 41% of EHEC isolates. Strains belonging to serogroups O26, O111, and O157 were isolated from cattle, and O111, and O157 from pigs.

CONCLUSIONS

The high percentage of EHEC in both cattle and pigs and the presence of human infection-associated serogroups, suggests that these animals are a reservoir of EHEC associated with disease in humans.

[Prevalence of the Chlamydia trachomatis in neonatal conjunctivitis determination by indirect fluorescence and gene amplification]

BACKGROUND

Chlamydia trachomatis is one of the most common identifiable infectious agents in neonatal conjunctivitis. It also causes pneumonitis, that is preceded by conjunctivitis in one third of cases.

AIM

To asses the prevalence of Chlamydia trachomatis in newborns with conjunctivitis.

PATIENTS AND METHODS

In 162 newborns, coming from 14 Primary Health Centers from Santiago de Chile, C. trachomatis was detected by indirect fluorescence and two polymerase chain reaction (PCR 1 and 2), which amplified different sequences from the common endogenous plasmid. Those patients with positive indirect fluorescence and PCR 2 were defined as infected:

RESULTS

The prevalence of C. trachomatis was 8%, and the distribution of the positive cases was similar in the different Health Centers. Other isolates were: S. aureus (9.8%), S. pneumoniae (8%), S. viridans (6.2%) y H. influenzae (5.5%).

CONCLUSIONS

The prevalence of C. trachomatis in neonatal conjunctivitis in Chile is similar to that of developed countries. Therefore, C. trachomatis should be considered in the election of antimicrobials for the treatment of neonatal conjunctivitis, to avoid ocular and respiratory complications.

[Emergence of resistance to macrolides in Streptococcus pyogenes]

BACKGROUND

Diseases produced by Streptoccocus pyogenes are still a problem in Chile, as in the rest of the world. It exhibits in vitro susceptibility to different antimicrobials, but penicillin continues to be the treatment of choice. Alternative drugs have been developed for allergic patients, such as erythromycin, new macrolides and cephalosporins. Nevertheless, resistant strains are appearing due to the indiscriminate use of macrolides.

AIM

To assess present antimicrobial susceptibility of S Pyogenes strains isolated from chilean patients.

MATERIAL AND METHODS

The susceptibility to penicillin, macrolides, clindamycin, cephalotin and vancomycin of 153 S Pyogenes strains, obtained from different health centers of the Metropolitan Region and isolated between 1996 and 1998, was assessed using the Kirby-Bauer method. Agar dilution minimal inhibitory concentration was then determined to macrolide resistant strains.

RESULTS

All strains were susceptible to penicillin. There was a 7.2% cross-resistance to macrolides.

CONCLUSIONS

These results confirm that S Pyogenes resistance to macrolides has increased considerably in the Metropolitan Region of Chile during the last years.

Effect of small bowel bacterial overgrowth on the immunogenicity of single-dose live oral cholera vaccine CVD 103-HgR

Several live oral vaccines (polio, bovine rotavirus, CVD 103-HgR cholera) are less immunogenic in developing than in industrialized countries. It was hypothesized that proximal small bowel bacterial overgrowth (common in children in less developed countries but rare in industrialized settings) diminishes the vibriocidal antibody response to CVD 103-HgR. In total, 202 fasting Santiago schoolchildren aged 5-9 years had lactulose breath H2 tests to detect proximal small bowel bacteria 1 day before ingesting CVD 103-HgR. Florid small bowel overgrowth was observed in 10 (5.6%) of 178 analyzable children. In children with florid overgrowth, vibriocidal seroconversion differed little from other children (60% vs. 67%), but the geometric mean titer was lower (160 vs. 368; P=.25). By logistic regression, increased peak breath H2 at small bowel time points was associated with diminished seroconversion (P=.04), as was the interaction of H2 value and weight (children >25 kg had lower seroconversion rates among subjects with heaviest overgrowth).

Genotypic survey of recent beta-lactam-resistant pneumococcal nasopharyngeal isolates from asymptomatic children in Chile

To assess pneumococcal strain variability among young asymptomatic carriers in Chile, we used serotyping, antibiotic susceptibility testing, and genotyping to analyze 68 multidrug-resistant pneumococcal isolates recovered from 54 asymptomatic children 6 to 48 months of age. The isolates represented capsular serotypes 19F (43 isolates), 14 (14 isolates), 23F (7 isolates), 6B (3 isolates), and 6A (1 isolate). Genotypic analysis, which included pulsed-field gel electrophoresis (PFGE) of chromosomal digests, penicillin binding protein (PBP) gene fingerprinting, and dhf gene fingerprinting, revealed that the isolates represented six different genetic lineages. Clear circumstantial evidence of capsular switching was seen within each of four of the genetically related sets. The majority of the isolates, consisting of the 43 19F isolates and 2 type 6B isolates, appeared to represent a genetically highly related set distinct from previously characterized pneumococcal strains. Each of three other genetically defined lineages was closely related to one of the previously characterized clones Spain(6B)-2, France(9V)-3, or Spain(23F)-1. A fifth lineage was comprised of four type 23F isolates that, by the techniques used for this study, were genetically indistinguishable from three recent type 19F sterile-site isolates from the United States. Finally, a sixth lineage was represented by a single type 23F isolate which had a unique PFGE type and unique PBP and dhf gene fingerprints.

[Current status of immunity to hepatitis A virus in various adult groups]

BACKGROUND

As sanitary and economic conditions improve, the prevalence of antibodies to hepatitis A is now significantly lower.

AIM

To evaluate the prevalence of hepatitis A virus antibodies in healthy Chilean adults.

MATERIAL AND METHODS

Antibodies to hepatitis A virus were measured, using a commercial ELISA assay, in 215 voluntary blood donors (163 male, aged 19 to 30 years old) and 295 medical students and health personnel (156 male, aged 19 to 39 years old), residing in Valdivia, Chile.

RESULTS

Antibodies against hepatitis A virus were found in 68.2% of the total sample (351/510). Ninety percent of flood donors and 54% of health personnel and students were positive (p < 0.01). Age specific prevalence in blood donors 19 to 22, 23 to 29 and 27 to 30 years old was 81.0%, 95.2% and 95.6% respectively. Among the same age groups in medical students, the prevalence was 47.9%, 53.2% and 61.9% respectively (p < 0.01).

CONCLUSIONS

This study indicates a reduction in the prevalence of hepatitis A virus antibodies among adults in Valdivia (Chile). Differences detected between individuals are probably related to different socioeconomic levels. Medical students have an increased risk for hepatitis A infections than the general population.

[Antimicrobial resistance of agents causing urinary tract infections in 11 Chilean hospitals. PRONARES project]

BACKGROUND

The computer program WHONET generates a common database to analyze local or general antimicrobial resistance of bacteria. A surveillance of agents causing urinary tract infections in Chile has been performed using this program.

AIM

To report the results after 12 months of urinary tract infection agent surveillance.

MATERIAL AND METHODS

Since November, 1997, a surveillance of in vitro antimicrobial resistance, using agar diffusion techniques, has been performed in 20 to 40 bacterial strains per month, isolated from 11 hospitals in the country. Results have been analyzed using WHONET program.

RESULTS

In first 12 months, 3144 strains, 1625 coming from outpatients, have been studied. Seventy four percent of isolated strains were E coli, 19% were other enterobacteria, 4.1% were non fermenting bacilli and 2.1% were Gram (+) cocci. Sixty five percent of E coli strains were resistant to ampicillin, 11% to cefazolin, 2.5% to cefuroxime, 19% to ceftriaxone, 9% to ceftazidime, 4.2% to gentamicin 1.3% to amikacin, 5.6% to ciprofloxacin, 8.4% to grepafloxacin, 4.3% to nitrofurantoin and 43% to trimeproprim/sulphamethoxazole. Eighty two percent of other enterobacteria strains were resistant to ampicillin, 45.5% to cefazolin, 33.5% to cefuroxime, 26.6% to ceftriaxone, 21.5% to ceftazidime, 30.3% to gentamicin 17.2% to amikacin, 21% to ciprofloxacin, 16.3% to grepafloxacin, 48.2% to nitrofurantoin and 44.6% to trimeproprim/sulphamethoxazole. There were differences in betalactamic resistance among hospitals.

CONCLUSIONS

Noteworthy is the high resistance rates to third generation cephalosporins, evidenced when the new cutoff values for E coli and Klebsiella spp are used. This national surveillance provides updated information on antimicrobial resistance of agents causing urinary tract infections.

Palatability, reactogenicity and immunogenicity of engineered live oral cholera vaccine CVD 103-HgR in Chilean infants and toddlers

BACKGROUND

Live oral cholera vaccine CVD 103-HgR is well-tolerated and immunogenic when administered to adults, school age children and preschool children in a single 5 x 10(9) colony-forming unit dose. Because elicitation of immune responses after administration of a single dose is exceptional for any oral vaccine in any age group, CVD 103-HgR was used as a probe to investigate the clinical acceptability, practicality and immunogenicity of this vaccine in infants and toddlers 3 to 17 months of age.

METHODS

The study was undertaken successively in 12- to 17-month-olds (n = 104), 7- to 11-month-olds (n = 106) and 3- to 5-month-olds (n = 102). One-half of the subjects were randomly allocated to receive vaccine and the other one-half to receive placebo, in double blind fashion. After 2 weeks of double blind follow-up, all subjects received a dose of vaccine. Vibriocidal antibody titers were measured on coded sera collected at baseline and 2 weeks after each dosing. The buffered vaccine "cocktail" had a volume of 100 ml; subjects who ingested > or =70 ml were considered fully vaccinated.

FINDINGS

Only 37% of subjects overall (25% of 3- to 5-month-olds) ingested > or =70 ml of the cocktail. The vaccine was well-tolerated with no significant differences in the rate or severity of adverse reactions after ingestion of vaccine vs. placebo. Seroconversion after ingestion of a single dose of CVD 103-HgR was similar in fully vaccinated subjects (66%) and in those who ingested a smaller fraction of the vaccine cocktail (63%). Of subjects who ingested two doses, 5 of 118 excreted vaccine organisms on Day 7 after the first dose vs. 0 of 118 after the second dose.

INTERPRETATION

Single dose oral CVD 103-HgR is well-tolerated and immunogenic in infants even when a partial dose is ingested. The buffered vaccine cocktail that is readily imbibed by older children is not appealing to young infants, and improved vaccine formulations and delivery vehicles for immunizing infants must be sought.

Population-based study of the incidence of Shigella diarrhea and causative serotypes in Santiago, Chile

BACKGROUND

Shigella is an important cause of diarrheal disease in children in developing countries. The increasing prevalence of antibiotic-resistant strains has stimulated interest in the use of multivalent Shigella vaccines. Because Shigella vaccines under development are based on eliciting immunity to O antigens, monitoring the distribution of serotypes in defined target populations is critical. We initiated health center-based surveillance in a poor semirural community in Colina, Santiago (7489 children <60 months of age) to determine the age-specific incidence of Shigella disease and the responsible serotypes.

FINDINGS

Surveillance was maintained at the 2 health centers during warm seasons (November 1 through April 30) for 4 successive years (1994 to 1998). Shigella was recovered from 54 of 243 cases of dysentery (22%) and from 215 of 3966 cases of nondysenteric diarrhea (5.4%) (P < 0.001). The peak mean annual incidence of shigellosis occurred among children 12 to 47 months of age (9.0 to 12.6 cases/10(3) children), although the incidence in infants (5.2/10(3)) and children 48 to 59 months of age (6.2/10(3)) was also substantial. During the 1995 through 1996 season, an age-matched healthy control was cultured for every child <60 months of age with diarrhea. Shigella isolation from cases (34 of 576, 5.9%) was >8-fold higher than controls (4 of 576, 0.7%) (P < 0.01). Four serotypes, Shigella sonnei (45%), Shigella flexneri 2b (19%), S. flexneri 2a (14%) and S. flexneri 6 (11%), accounted for 89% of all cases.

INTERPRETATION

Shigella remains an important pediatric pathogen in Santiago. The serotype distribution from Colina, which closely resembles data from a population-based surveillance study in Santiago in the mid-1980s, demonstrates a remarkable degree of serotype stability in Santiago during a 15-year period.

Clonal diversity of Chilean isolates of enterohemorrhagic Escherichia coli from patients with hemolytic-uremic syndrome, asymptomatic subjects, animal reservoirs, and food products

To determine clonal relationship among Chilean enterohemorrhagic Escherichia coli (EHEC) strains from different sources (clinical infections, animal reservoirs, and food), 54 EHEC isolates (44 of E. coli O157, 5 of E. coli O111, and 5 of E. coli O26) were characterized for virulence genes by colony blot hybridization and by pulsed-field gel electrophoresis (PFGE). By colony blotting, 12 different genotypes were identified among the 44 E. coli O157 isolates analyzed, of which the genetic profile stx1+ stx2+ hly+ eae+ was the most prevalent. All human O157 strains that were associated with sporadic cases of hemolytic-uremic syndrome (HUS) carried both the stx1 and stx2 toxin-encoding genes and were eaeA positive. Only 9 of 13 isolates from human controls were stx1+ stx2+, and 8 carried the eaeA gene. Comparison of profiles obtained by PFGE of XbaI-digested genomic DNA showed a great diversity among the E. coli O157 isolates, with 37 different profiles among 39 isolates analyzed. Cluster analysis of PFGE profiles showed a wide distribution of clinical isolates obtained from HUS cases and asymptomatic individuals and a clonal relationship among O157 isolates obtained from HUS cases and pigs. Analysis of virulence genes showed that a correlation exists among strains with the genotype stx1+ stx2+ eae+ and pathogenic potential. A larger difference in the PFGE restriction patterns was observed among the EHEC strains of serogroups O26 and O111. These results indicate that several different EHEC clones circulate in Chile and suggest that pigs are an important animal reservoir for human infections by EHEC. Guidelines have been proposed for better practices in the slaughter of animals in Chile.

[Antimicrobial multiresistance of Shigella sp strains in a semi rural community of northern Santiago]

Appropriate antimicrobial therapy shortens the duration of Shigellosis and significantly reduces the risk of transmission. Shigella strains resistant to common antimicrobials have increased during the past years, determining the need for a periodic surveillance, to guide effective therapy.

AIM

To report the results of a surveillance program in a rural community near Santiago (Colina), for Shigella infections.

MATERIAL AND METHODS

Between 1995 and 1997, stool samples from 3,534 episodes of diarrhoea, that occurred in Colina, were obtained. Two hundred twenty six Shigella strains were isolated and studied for susceptibility to ampicilin (AM), amoxicillin/clavulanic acid (AMC), cotrimoxazole (STX), chloramphenicol (CAF), tetracycline (TET), furazolidine (FU), ciprofloxacine (CIPR), nalidixic acid (AC NAL), gentamycin (GENT) and cefotaxime (CFTX).

RESULTS

Shigella flexnerii represented 134 of 226 Shigella strains isolated. All strains were susceptible to CIPR, AC NAL, GENT and CFTX. Yearly variation of resistance patterns to other antimicrobials were observed for these strains. Resistance to AM varied from 56 to 76%, to AMC from 25 to 56%, to STX from 21 to 47%, to CAF from 36 to 69%, to TET from 44 to 78% and to FU from 9 to 18%. Overall resistance was higher during 1997. All 85 strains of S sonnei were susceptible to CIPR, AC NAL and CFTX. Resistance throughout the years varied from 56 to 88% for AM, from 0 to 28% for AMC, from 44 to 53% for STX, from 11 to 40% for CAF, from 11 to 42% for TET and from 5 to 11% for FU. Overall resistance was also higher during 1997, except for AM and STX. Seven S hoydii strains were isolated, only during 1995. All seven were resistant to AM and TET and none were resistant to FU, CIPR, AC NAL and CFTX. Two strain was resistant to AMC, STX and CAF.

CONCLUSIONS

Antimicrobial resistance patterns of Shigella sp isolated in Colina have increased from 1995 to 1997, specially for commonly used antimicrobials. Resistance remains low for furazolidine and all strains remain susceptible to quinolones.

Prevalence of astrovirus infection among Chilean children with acute gastroenteritis

The frequency of astrovirus infection in 456 Chilean children with diarrhea was determined by enzyme-linked immunosorbent assay, reverse transcriptase PCR, and cell culture. Astrovirus was detected in 16.5% of rotavirus-negative and 7% of rotavirus-positive samples obtained from emergency rooms or hospitals and in 11% of samples from day care centers. HAst-1 was the predominant serotype identified.

Capsular serotype and antibiotic resistance of Streptococcus pneumoniae isolates in two Chilean cities

We compared the incidence of nasopharyngeal colonization by Streptococcus pneumoniae, the serotypes causing mucosal and invasive diseases, and the antibiotic resistance of these strains in patients admitted to three large hospitals and children attending day care centers in two Chilean cities (Santiago and Temuco). The populations in both cities were similar in ethnic background, socioeconomic status, family size, and access to medical care. Significant differences in nasopharyngeal colonization rates, in serotypes causing infections, and in antibiotic resistance were found between the two cities. In children 0 to 2 years of age, 42% were colonized with S. pneumoniae in Santiago compared to 14% in Temuco. A total of 41 serotypes were identified in both Chilean cities studied. Six serotypes were found only in Santiago; 14 serotypes were found only in Temuco. Antibiotic-resistant serotypes 6A, 6B, 14, 19F, and 23F were detected only in Santiago. We show that important differences in the incidence of nasopharyngeal carriage, infection, and S. pneumoniae serotypes can exist in similar populations in different areas of the same country. Our findings are relevant for prevention strategies, antibiotic usage, and vaccine design.

[Efficacy and tolerance of a five day course of ciprofloxacin in the treatment of urinary tract infection in women. Multicenter study]

BACKGROUND

There is no consensus about the ideal antimicrobial agent and duration of treatment for urinary tract infection in women.

AIM

To assess the efficacy of a five days course of ciprofloxacin for the treatment of urinary tract infection in women.

PATIENTS AND METHODS

Women with urinary tract infection were treated with ciprofloxacin (Baycip, Bayer) 250 mg bid during 5 days. Patients were evaluated three to four days after treatment start, two to seven days and one month after treatment end.

RESULTS

Of 101 eligible women, 96 aged 18 to 65 years old, coming from three major Chilean cities, participated in the study and 80 completed the follow up period. There was a 95% clinical success, 2.5% partial improvement and 2.5% treatment failure. The causal microorganism was erradicated in 90% of cases, in 1.2% treatment failed and in 8.7% a re-infection occurred. Adverse effects attributable to the drug were observed in 12 patients (headache in 3, gastrointestinal disturbances in 8, somnolence in 1 and irritability in 1).

CONCLUSIONS

Ciprofloxacin is an useful antimicrobial for the treatment of lower urinary tract infection in women.

[Chlamydia trachomatis infection in asymptomatic Chilean men and with urethritis. Usefulness of first catch urine samples]

BACKGROUND

Chlamydia trachomatis is responsible for 30 to 50% of genital tract infections and is present, without symptoms, in 20% of men and 60% of women. We have little information in Chile about the prevalence of this infection.

AIM

To assess the prevalence of Chlamydia trachomatis in men, using first catch urine samples.

SUBJECTS AND METHODS

Three hundred and fifty one first catch urine samples of asymptomatic men and 50 samples coming from men with a primary urethritis, were analyzed. Urethral discharge samples from the latter were simultaneously studied. Analysis was performed using an enzyme immuno analysis (MicroTrak Chlamydia EIA, Syva Co.) and a nested polymerase chain reaction towards the gene that codifies MOMP (PCR/OMP).

RESULTS

Among asymptomatic men, two of 154 teenagers aged 18 to 19 years old (1.3%), 10 of 100 university students (10%) and eight of 97 adults over 30 years old (8.2%), were infected. The global prevalence of infection in these men was 5.7%. The prevalence of infection in men with urethritis was 12%. Urine EIA had a higher detection frequency than PCR/OMP, but according to another PCR assay, these results were false positives. EIA in first catch urine, had a sensitivity, specificity, positive and negative predictive value of 83.3, 75, 31.3 and 97% respectively, for the detection of Chlamydia trachomatis. The figures for PCR/OMP were 100% for all these parameters.

CONCLUSIONS

The prevalence of Chlamydia trachomatis infection in Chilean men is similar to that reported in developed countries. Enzyme immuno assay in first catch urine had a good diagnostic accuracy and could be used in epidemiological studies in asymptomatic men.

[Isolation and characterization of Yersinia enterocolitica from pigs and bovines in Chile]

The occurrence of Yersinia enterocolitica in tonsils and rectal swabs from 100 healthy pigs and the rectal swabs of 100 healthy cattle slaughtered at Santiago-Chile were analysed. Yersinia enterocolitica was isolated from 48 (48%) pigs but not from cattle. 98.2% of strains were of 4/O3 bioserogroup, considered to be pathogenic for humans. All of the strains were resistant to penicillin producing beta-lactamase. Most of them were resistant to neomicin and tetracycline. The pYV marker was used to demonstrate pathogenicity in all strains by four different assays: 65.5% of the strains were pYV positive by their plasmid profile; 73.3% by crystal violet binding; 84.5% by calcium dependency and 87.9% by hybridization with probe associated with cytotoxicity to Hep-2 cells in vitro. All of the Yersinia enterocolitica strains were pYV positive with at least one of the four tests analysed, 46/58 strains were positive by three tests simultaneously. The similarities between associated cytotoxic genes of porcine and human strains is discussed. The phenotypic and genotypic characteristics demonstrated by the isolates strains suggest that the pigs in Chile are reservoir of potential pathogenic Yersinia enterocolitica for humans.

Detection and characterization of enterohaemorrhagic Escherichia coli in slaughtered cattle

Fecal samples from slaughtered cattle were studied for enterohaemorrhagic Escherichia coli (EHEC) by DNA hybridization with biotin-labelled DNA probes specific for the EHEC virulence plasmid, Shiga-like toxin I (SLT I), Shiga-like toxin II (SLT II) and eae gene. Among 136 animals analysed, 47 (34.5%) were found to carry EHEC. The cytotoxic genotypes observed for EHEC strains were: 60.4% SLT I, 12.5% SLT II and 10.4% SLT I + SLT II; 16.7% resulted SLT I and SLT II negative. A total of 14 out of 48EHEC strains (29.2%) hybridized with a fimbrial probe and 14 of 48 strains with an sas probe. An important number of strains (18 out of 48) belonged to serogroups O157, O26 and O111, serogroups also commonly isolated from haemolytic uremic syndrome cases in Chile. While EHEC isolates from the same animal were usually of the same serogroup, one animal was found to carry two EHEC strains of different serogroups. A total of 50% of EHEC strains were sorbitol negative, irrespective of the O serogroup or EHEC genotypic profile. Results obtained in this study strongly suggest that cattle in Chile are a reservoir of EHEC associated with disease in humans.

[Temporal variation of genotypes and serotypes of enterohemorrhagic E Coli isolated from Chilean children with intestinal infections or hemolytic uremic syndrome]

BACKGROUND

Infections by enterohemorrhagic E. Coli may be asymptomatic, may cause diarrhea, sometimes bloody or a hemolytic uremic syndrome in 2 to 7% of children. These diseases appear sporadically or as outbreaks. Host and agent factors influence the appearance of hemolytic uremic syndrome.

AIM

To study the distributions and prevalence of virulence genes and enterohemorrhagic E. Coli serogroups isolated from Chilean children.

MATERIALS AND METHODS

Thirty six strains isolated from children with hemolytic uremic syndrome (8 obtained in 1988-1989, 15 obtained in 1990-1993 and 13 obtained in 1995-1996), 33 strains from asymptomatic children, obtained in similar periods and 30 strains from children with bloody diarrhea, obtained in 1995-1996 were studied. Virulence factors were investigated with a colony hybridization technique using probes that identify virulence genes. Serotypes were identified with commercial antisera.

RESULTS

Both SLTI and SLTII genes predominated in strains obtained from children with hemolytic uremic syndrome in 1988-1989 and 1995-1996 and SLTI gene predominated in strains obtained in 1990-1993. Similar temporal variations in virulence genes of strains obtained from asymptomatic children were observed. SLTI/SLTII pattern predominated in strains obtained from children with bloody diarrhea and the frequency of O157 serogroup was lower, compared to strains obtained from children with hemolytic uremic syndrome.

CONCLUSIONS

There was a temporal variation in toxigenic genotypes of enterohemorrhagic E. Coli strains, but no association between these genotypes and the risk for hemolytic uremic syndrome was observed.

[Phenotypic and molecular features of Vibrio cholerae isolated in Chile, Peru and Bolivia. Comparison with environmental reservoirs]

BACKGROUND

Since 1991, a massive cholera epidemic started in Peru and involved most Central and South American Countries. In Chile, 147 cases were registered, the last one in 1995.

AIM

To study the phenotypic and molecular features of Vibrio cholerae strains isolated from patients in Perú, Bolivia and Chile and from environmental reservoirs in Santiago, Chile.

MATERIALS AND METHODS

The phenotype, biotype and susceptibility to nine antimicrobials was determined for each isolated strain. Also, the genes of cholera and termolabile toxins were determined using DNA probes and a chromosomal restriction profile was done using HindIII, EcoRI and NotI enzymes.

RESULTS

Features studied were similar in the 53 strains isolated from patients. Those isolated from environmental reservoirs had different antimicrobial susceptibility, showing ampicillin resistance, and the GT gene was detected in one of 20 strains, compared to clinical samples were it was present in all. Strains isolated from patients and environment had similar chromosomal restriction profiles.

CONCLUSIONS

The chromosomal restriction profile gives an image of bacterial genome and it is a useful and reliable tool for the epidemiological surveillance of cholera.

[Emergent infectious diseases: a new problem?]

Are the emergent pathogenic microbes, persistent bacteria that have changed their virulence or new diagnostic techniques now allow their recognition? Or, have they found a new possibility of transmission due to ecological, social or cultural changes? The present Editorial analyses the geographical distribution, features and host factors that favor infections by Helicobacter pylorii, Enterohemorrhagic E. Coli, invasive Streptococcus pyogenes and Borrelia Burgdorferi. The surveillance and care of infections caused by emergent germs requires laboratory learning programs as those established in the United States.

[In vitro comparative activity (E test) of sparfloxacin and other 8 antimicrobial agents against bacteria isolated from patients with respiratory infections acquired in the community]

Sparfloxacin is a new antimicrobial that, while maintaining a good activity against gram negative bacilli, has a better in vitro activity against gram positive bacteria such as S pneumoniae, intracellular pathogens and anaerobic bacteria. The aim of this work was to study the in vitro activity of sparfloxacin against bacteria isolated from patients with community acquired respiratory infections between October 1994 and January 1995. Using the E-test technique, we studied the susceptibility to sparfloxacin, ciprofloxacin, ampicillin, amoxicillin/clavulanic acid, cefuroxime, cefotaxime, erythromycin, methicillin and nalidixic acid of 50 strains of S pneumoniae, 50 strains of H. influenzae, 50 strains of S aureus and 50 strains of S pyogenes. Sparfloxacin was active against 100% of S pneumoniae, H influenzae and S pyogenes strains. Twenty two percent of S aureus strains were resistant and the MIC 90 was 12 micrograms/ml. Sparfloxacin showed the best in vitro activity against H influenzae and S aureus, a similar activity with ampicillin and cefotaxime against S pneumoniae and a similar activity with ampicillin but superior to all other studied antimicrobial against S pyogenes. It is concluded that sparfloxacin is a good antimicrobial for bacteria isolated from patients with respiratory infections.

[In vitro susceptibility of enterohemorrhagic Escherichia coli to 11 antimicrobials. Relationship between antibiotic resistance and toxigenic genotype]

Enterohemorrhagic E coli (EHEC) has been recognized as the main etiologic agent of hemorrhagic colitis and hemolytic uremic syndrome (HUS). The usefulness of antibiotic treatment in patients with EHEC infections is a matter of current debate. Knowledge on EHEC antimicrobial susceptibility patterns in different geographic areas is important for both treatment considerations and for strain characterization. We studied by diffusion disk agar technique the antibiotic susceptibility of 83 EHEC strains obtained from stools of patients with HUS or diarrhea. Eleven antimicrobials were tested (ampicillin, cotrimoxazole, tetracycline, chloramphenicol, furazolidone, gentamycin, amikacin, ciprofloxacin, erythromycin, vancomycin, and metronidazol). Resistant strains by disk diffusion were tested for MIC (mg/ml) by agar dilution. SLT-I and SLT-II were detected with specific biotinylated gene probes. All 83 strains were susceptible to furazolidone, ciprofloxacin, gentamycin and amikacin. Resistance was detected to tetracycline 4%, chloramphenicol 5%, cotrimoxazole 24% and ampicillin 25%. As expected for EHEC strains all were resistant to erythromycin, vancomycin, and metronidazol. Resistant strains were significantly more common in non toxigenic and SLT-I producing strains (p = 0.01). Resistant strains were similarly distributed among patients who had diarrhea only and those who developed HUS (p = 0.3). In Chile, resistant EHEC strains seem to be more common and of different genotypes than those reported in more developed countries. Regional differences of EHEC antibiotic susceptibility patterns indicate a need for continuous monitoring, specially if antibiotics prove to be useful in disease prevention.

Sorbitol-negative phenotype among enterohemorrhagic Escherichia coli strains of different serotypes and from different sources

Enterohemorrhagic Escherichia coli (EHEC) strains detected with DNA probes (for virulence plasmid and Shiga-like toxins) from subjects with hemolytic-uremic syndrome (n = 19) or diarrhea (n = 41) or asymptomatic carriers (n = 29) were examined for sorbitol fermentability, as were enterotoxigenic (n = 40), enteropathogenic (n = 40), and enteroinvasive (n = 40) E. coli and urinary tract infection (n = 40) strains and normal flora E. coli strains (n = 40). Sorbitol negativity was common only in EHEC, particularly among strains from severe clinical infections. All 19 EHEC strains from patients with hemolytic-uremic syndrome, irrespective of O:H serotype or Shiga-like toxin genotype, were sorbitol negative.