Fortino Solórzano

Outbreak of Infection with Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae in a Mexican Hospital

ABSTRACT Thirty-one strains of Klebsiella pneumoniae (including 10 duplicates) from 21 septicemic pediatric patients (age, <2 months) were studied during a 4-month period (June to October 1996) in which the fatality rate was 62% (13 of 21). These isolates identified by the API 20E system yielded the same biotype. Pulsed-field gel electrophoresis experiments revealed the same clone in 31 strains. The isolates were multidrug-resistant but were still susceptible to ciprofloxacin, imipenem, and cefoxitin. A 135-kb plasmid was harbored in all of the isolates. No transconjugants were obtained that were resistant to ampicillin, cefotaxime, tetracycline, or gentamicin. Isoelectric focusing for β-lactamases was performed on all strains, and three bands with pIs of 5.4, 7.6, and 8.2 were obtained. Of these, the pI 8.2 β-lactamase had an extended-spectrum β-lactamase phenotype. PCR amplification of both TEM- and SHV-type genes was obtained. The sequence analysis of the SHV PCR product indicated a mutation corresponding to the SHV-5 β-lactamase.

Clonal and Horizontal Dissemination of Klebsiella pneumoniae Expressing SHV-5 Extended-Spectrum β-Lactamase in a Mexican Pediatric Hospital

ABSTRACT One hundred eighty-four clinical isolates of Klebsiella pneumoniae were recovered from August 1996 to October 1997 at the Pediatric Hospital of the Instituto Mexicano del Seguro Social in Mexico City, Mexico. Most of the isolates were collected from the neonatal intensive care unit and infant wards, which are located on the same floor of the hospital. Isolates were genotypically compared by pulsed-field gel electrophoresis with XbaI restriction of chromosomal DNA. Of 184 clinical isolates, 91 belonged to cluster A and comprised three subtypes (A1, A2, and A3), while 93 isolates, comprising two minor clones, B (10 isolates) and C (7 isolates), and 76 unique patterns, were considered unrelated isolates (URI). Susceptibility patterns were indistinguishable in both groups. Fifty extended-spectrum β-lactamase-producing isolates, including 34 from clone A and 16 from URI, were examined for further studies. Molecular and genetic analysis showed that 47 of 50 clinical isolates expressed the SHV-5 β-lactamase. This enzyme, in combination with TEM-1, was encoded in a ≥170-kb conjugative plasmid. Results indicate that dissemination of this resistance was due to clonal and horizontal spread.

Audiologic and vestibular findings in a sample of Human Immunodeficiency Virus type-1-infected Mexican children under Highly Active Antiretroviral Therapy

OBJECTIVE There is little information about audiologic and vestibular disorders in pediatric patients infected with the Human Immunodeficiency Virus type-1 (HIV-1). The aim of this study was to evaluate audiologic and vestibular disorders in a sample of HIV-1-infected children receiving Highly Active Antiretroviral Therapy. METHODS Patients underwent pure tone audiometry, speech discrimination testing, auditory brainstem responses, electronystagmography, and rotatory testing. HIV-1 viral load and absolute CD4+ cell counts were registered. RESULTS Twenty-three patients were included, aged 4.5 years (median, range 5 months to 16 years). Pure tone audiometry was carried out in 12 children over 4 years of age: 4 (33%) showed hearing loss, 2 were conductive. Auditory brainstem responses were measured in all 23 patients, suggesting conductive hearing loss in 6 and sensorineural hearing loss in 2. Most patients with conductive hearing loss had the antecedent of acute or chronic suppurative otitis media but with dry ears at the time of evaluation (p=0.003). Abnormal prolongations of interwave intervals in auditory brainstem responses were observed in 3 children (13%, 4 ears), an abnormal morphology in different components of auditory brainstem responses in 4 (17.4%, 7 ears), and abnormal amplitude patterns in 11 patients (48%, 17 ears). Vestibular tests were abnormal in all six patients tested, with asymmetries in caloric and rotatory tests. Although differences were not significant, in general, audiologic abnormalities were more frequent in patients with more prolonged HIV-1 infections, higher viral loads, or lower absolute CD4+ cell counts. CONCLUSIONS Conductive hearing loss associated with previous otitis media events, abnormalities in auditory brainstem responses suggesting disorders at different levels of the auditory pathways, and unilateral vestibular hyporeflexia were frequent findings in our sample of HIV-1-infected children under Highly Active Antiretroviral Therapy. These findings suggest that HIV-1-infected children should be submitted to audiologic and vestibular evaluation as early as possible in order to reduce their impact on the psychosocial development of these patients.

Serologic evidences suggesting the presence of Borrelia burgdorferi infection in Mexico.

BACKGROUND Lyme disease is the most common vector-borne human disease in Europe and the United States. In Mexico, clinical cases suggestive of Lyme borreliosis have been reported; however, infection was not confirmed by serologic or microbiologic tests. METHODS To study the prevalence of IgG antibodies against Borrelia burgdorferi among Mexican persons, a community-based sero-survey including all states of Mexico was done. A sample of 2,890 sera representing individuals of all ages and all socioeconomic levels was studied. Antibodies anti-B. burgdorferi were determined by enzyme-linked immunosorbent assay (ELISA) using a whole-cell sonicated extract of B. burgdorferi strain B31. Serum specimens positive for ELISA were further studied by Western blot (WB). A serum sample was considered positive by WB if at least three of the following protein bands were recognized: 18, 24, 28, 29, 31, 34, 39, 41, 45, 58, 62, 66, and 93 kDa. Some WB positive specimens were further confirmed with an immunodot-blot (IDB) test using recombinant and purified B. burgdorferi proteins. RESULTS Of the 2,890 specimens, 34 were positive for ELISA; nine of these 34 were confirmed as positive by WB. Four of the nine WB positive sera were tested by IDB and all four were positive. The prevalence of WB confirmed cases in the sample studied was 0.3%. Positive specimens were from residents of the northeastern and central areas of Mexico. CONCLUSIONS The serological evidences of this study suggest that Borrelia burgdorferi infection is present in the Mexican population. This finding should be confirmed by documenting the infection in clinical cases and in tick vectors.

Antimicrobial Resistance from Enterococci in a Pediatric Hospital. Plasmids in Enterococcus faecalis Isolates with High-Level Gentamicin and Streptomycin Resistance

BACKGROUND Enterococcus spp. is an important nosocomial and community-acquired pathogen. Recent studies have documented the increasing importance of this pathogen in children, particularly in the hospital setting. Our objective in this study was to report the frequency of antimicrobial resistance in enterococci and to determine the characteristics of high-level gentamicin resistance (HLGR) plasmids in Enterococcus faecalis clinical isolates. METHODS Two hundred eighty-nine enterococcal isolates were collected during an 18-month period from a tertiary-care pediatric hospital in Mexico City. Isolates were screened for antibiotic resistance, including HLGR. High-level, gentamicin-resistant E. faecalis strains were selected for pulsed-field electrophoresis (PFGE) typing and plasmid analysis. Transferability of resistance markers was carried out using filter matings. RESULTS Seventy-six percent of isolates were E. faecalis, 10% were E. avium, 5.2% E. faecium, 5.2% E. raffinossus, 1.38% E. malodoratus, 0.6% E. hirae, and 0.6% E. casseliflavus. Antimicrobial resistance was ampicillin and penicillin 29%, imipenem 17%, and vancomycin 3%, HLGR 5%. The following 15 high-level, gentamicin-resistant isolates were identified: six E. faecalis; four E. avium; three E. faecium, and two E. casseliflavus. Five of the six E. faecalis isolates were different by PFGE and transferred gentamicin and streptomycin resistance on filter membranes. Transfer frequencies ranged from 8.2 x 10(-4) to 6.92 x 10(-5) transconjugants/recipient cell. The plasmid content of donors and transconjugants were homogeneous (one plasmid of 47 kb). CONCLUSIONS In this pediatric hospital, antimicrobial resistance in Enterococcus spp. is common. Frequency of high-level, gentamicin-resistant strains is low. Mechanism of HLGR appears to be due to a single plasmid dissemination.

Gram-negative infections in pediatric and neonatal intensive care units of Latin America

In order to review the epidemiology of Gram-negative infections in the pediatric and neonatal intensive care units (PICUs and NICUs) of Latin America a systematic search of PubMed and targeted search of SciELO was performed to identify relevant articles published since 2005. Independent cohort data indicated that overall infection rates were higher in Latin American PICUs and NICUs versus developed countries (range, 5%-37% vs 6%-15%, respectively). Approximately one third of Latin American patients with an acquired PICU or NICU infection died, and crude mortality was higher among extremely low-birth-weight infants and those with an infection caused by Gram-negative bacteria. In studies reporting > 100 isolates, the frequency of Gram-negative pathogens varied from 31% (Colombia) to 63% (Mexico), with Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli the predominant pathogens in almost all countries, and Acinetobacter spp. and Serratia spp. isolated sporadically. The activity of quinolones and third-generation cephalosporins against P. aeruginosa, Acinetobacter spp., and Enterobacteria was seriously compromised, coincident with a high prevalence of circulating extended-spectrum β-lactamases. Furthermore, we identified two observational studies conducted in Chile and Brazil reporting infections by P. aeruginosa and Acinetobacter baumannii in PICUs, demonstrating resistance to carbapenems, and two outbreaks of carbapenem-resistant K. pneumoniae in Colombia and Brazil. The endemicity of multidrug-resistant Gram-negative infections in Latin American PICUs and NICUs is punctuated by intermittent clonal outbreaks. The problem may be alleviated by ensuring ICUs are less crowded, increasing staffing levels of better-trained health care personnel, and implementing antimicrobial stewardship and surveillance programs.

Molecular Epidemiology of a Multiresistant Pseudomonas aeruginosa Outbreak in a Paediatric Intensive Care Unit

After isolation of multiresistant (MR) Pseudomonas aeruginosa from 3 hospitalized patients in a paediatric intensive care unit (PICU), a prospective surveillance programme was established to detect infected and/or colonized patients in the hospital. Isolates were examined by means of outer membrane protein (OMP) profiles, serotyping and DNA genomic analysis using pulsed-field gel electrophoresis (PFGE). Fifty-five P. aeruginosa strains were isolated from 23 hospitalized patients during September and October 1997. The median hospital stay before isolation of P. aeruginosa was 8 d. PFGE demonstrated that the same clone infected 14 patients, 4 of whom were not hospitalized in the PICU. Susceptibility patterns and OMP profiles correlated with PFGE results in 37.8% and 36.4% of cases, respectively. Serotype O11 correlated with pattern A in 77% of cases and serotype O4 correlated with unrelated strains in 75% of cases but did not discriminate between outbreak and unrelated isolates. Extensive investigation of cultures failed to identify a reservoir of P. aeruginosa. PFGE was superior to OMP analysis and serotyping for discriminating between strains. The possible mode of acquisition for most of the patients infected with the same clone was cross-contamination.

Response to Two Consecutive Protease Inhibitor Combination Therapy Regimens in a Cohort of HIV-1-infected Children

The response to 2 consecutive protease inhibitor (PI) combination regimens was evaluated in a cohort of HIV-1-infected children. Twelve children, most of whom had been heavily treated, received a 3-drug treatment: saquinavir in hard gelatin capsules (SQVhgc) + zidovudine (ZDV) + didanosine. When this treatment failed it was replaced by a 4-drug regimen: ritonavir + SQVhgc + ZDV + lamivudine. A mild and temporary decrease in viral load (VL) was observed with the initial regimen (p=0.22). Therapy failure occurred in 7 patients (58%) within 9 months and in another 3 (25%) within 9-18 months. The 7 children who failed within 9 months received the subsequent boosted regimen, leading to a significant and lasting reduction in VL ( p = 0.001). None of the patients failed on the boosted regimen: 5/7 achieved a VL of < 400 copies/ml and 3/7 achieved a VL of < 50 copies/ml. Our results suggest that a 4-drug regimen including 2 PIs produces a better and more sustained response than a 3-drug regimen including only 1 PI, and that a good, sustained response is possible with subsequent boosted regimens even in heavily treated children.

Identification of the High-Virulence Clone of Group B Streptococci in Mexican Isolates by Growth Characteristics at 40°C

Abstract. Group B streptococci (GBS) colonizing the vagina and rectum of pregnant women cause invasive disease of the offspring in a small number of cases. The immune status of the host and differences in virulence among strains appear to be the main determinants for neonatal infection. A high-virulence clone (HVC) was proposed to cause much of the morbidity and mortality when a collection of GBS isolates was examined by multilocus enzyme electrophoresis. HVC isolates could be further distinguished by their inability to grow at 40°C. This characteristic was used in the present study to examine a collection of 57 GBS isolates from Mexico City for the HVC. Three serotype III invasive strains were classified in the HVC. The other eleven invasive strains and all carrier isolates had growth curves unaffected at 40°C. These results demonstrate the presence of the HVC in Mexico. Such a low prevalence could explain in part the low rate of GBS invasive neonatal disease in Mexico.

High-Virulence Clone of Group B Streptococci Unable to Grow at High Temperatures Is Present in Serotypes Other Than Type III

Highly virulent clonotypes of serotype III seem to cause much of the perinatal morbidity and mortality attributed to Streptococcus agalactiae (group B streptococci, GBS), One of these clonal types, designated the “high-virulence clone” (HVC), was identified by its inability to grow at 40°C in a chemically defined medium. In the present study, this inability to grow at high temperatures was used as a marker to identify HVC in a sample of 286 Mexican GBS isolates. Forty-three isolates (15%) were identified as belonging to this clone: 15 were invasive isolates, 33 were serotype III (77%), and 10 were of serotypes other than type III (23%). These results demonstrate that HVC is more prevalent in Mexico than previously reported and that this clone is not restricted to serotype III isolates.