Arturo Galindo-Fraga

Molecular epidemiology and risk factors of bloodstream infections caused by extended-spectrum β-lactamase-producing Klebsiella pneumoniae: A case–control study

OBJECTIVES To study the prevalence, risk factors, outcome, and molecular epidemiology in patients with bacteremia caused by extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae (Kp) (cases), in comparison with patients with bacteremia caused by a susceptible Kp (controls). METHODS This was a retrospective case-control study including all episodes of Kp bacteremia for the period 1993 to 2002 at a referral hospital for adults in Mexico. ESBL production was tested for by E-test. All isolates were typed by pulsed field gel electrophoresis (PFGE). A subset of isolates underwent plasmid analysis, conjugal transfer of cefotaxime resistance to Escherichia coli J53-2, isoelectric focusing bioassay, colony-blot hybridization, PCR, and sequencing. RESULTS Of the 121 patients with bacteremia due to Kp included in the study, 17 (14.0%) had an ESBL-Kp isolate (cases). Multivariate analysis identified prior use of cephalosporins (OR 7.6, 95% CI 1.1-53.5; p=0.039) and stay in the intensive care unit (ICU; OR 5.6, 95% CI 1.1-27.9; p=0.033) as significant risk factors. No differences were observed in hospital stay or mortality after the event. Multi-drug resistance was more frequent in ESBL-Kp. There was no clonal predominance. A distinct beta-lactamase profile was identified, which included a combination of TEM-1 (pI 5.4) and SHV-5 (pI 8.2) in 13/17 ESBL-Kp isolates. Cefotaxime resistance was transferred by conjugation in 14/17 isolates with a >120-kb plasmid encoding ESBL. CONCLUSIONS The prevalence of ESBL-Kp was found to be lower than that previously reported in Latin America. ESBL-Kp bacteremia was not associated with a worse clinical outcome. We were able to identify a plasmid-mediated horizontal dissemination over the 10-year period.

Factors Associated to Prevalence and Incidence of Carbapenem-Resistant Enterobacteriaceae Fecal Carriage: A Cohort Study in a Mexican Tertiary Care Hospital.

Background Carbapenem-resistant Enterobacteriaceae (CRE) infections have emerged as a serious threat to health worldwide. They are associated with increased morbidity and mortality and are capable of silently colonizing the gastrointestinal tract. Because of this, there is great interest to characterize the epidemiology of CRE carriage and acquisition in healthcare facilities. The aim of this study was to determine the prevalence and factors associated with CRE fecal carriage (CRE-fc), and risk factors for incident cases. Methods/Results A cohort study was conducted at a tertiary care hospital from January 1st to April 30th, 2014 during a CRE outbreak. Weekly rectal swabs were performed in patients considered at risk until discharge. CRE-fc prevalence was 10.9% (CI 95% 7.7–14.7) among 330 patients. Treatment with carbapenems (OR 2.54, CI 95% 1.15–5.62); transfer from an institution (OR 2.16, CI 95% 1.02–4.59); multi-drug resistant infection within the previous six months (OR 2.81, CI 95% 1.47–5.36); intensive care unit admission (OR 0.42, CI 95% 0.20–0.88); hematologic malignancy (OR 4.02, CI 95% 1.88–8.06); invasive procedures (OR 2.18, CI 95% 1.10–4.32); and sharing a room with a known CRE carrier (OR 3.0, CI 95% 1.43–6.31) were independently associated factors for CRE-fc. Risk factors associated with CRE-fc incidence were determined for 87 patients initially negative and with subsequent screening; the incidence rate was 2.5 cases, per 1000 person-years (CI 95% 1.5–3.9). Independently associated risk factors were carbapenem treatment (HR 2.68, CI 95% 1.03–6.98), hematologic malignancy (HR 5.74, 95% CI 2.46–13.4) and a mean daily colonization pressure ≥10% (HR 5.03, IC 95% 1.77–14.28). OXA-48-like (OXA-232) and CTX-M-15 were the predominantly identified mechanisms of resistance. Conclusions We found an elevated incidence and prevalence of CRE-fc in our hospital. Hematologic patients need to be considered a population at risk, and antibiotic stewardship along with infection control programs need to be improved to avoid nosocomial spread.

Clinical characteristics and outcomes of influenza and other influenza-like illnesses in Mexico City

Summary Background Influenza-like illnesses (ILI) are estimated to cause millions of deaths annually. Despite this disease burden, the etiologic causes of ILI are poorly described for many geographical regions. Methods Beginning in April 2010, we conducted an observational cohort study at five hospitals in Mexico City, enrolling subjects who met the criteria for ILI. Evaluations were conducted at enrollment and on day 28, with the collection of clinical data and a nasopharyngeal swab (or nasal aspirate in children). Swabs were tested by multiplex PCR for 15 viral pathogens and real-time PCR for influenza. Results During the first year, 1065 subjects were enrolled in this study, 55% of whom were hospitalized; 24% of all subjects were children. One or more pathogens were detected by PCR in 64% of subjects, most commonly rhinovirus (25% of all isolates) and influenza (24% of isolates). Six percent of subjects died, and of those, 54% had no pathogen identified. Rhinovirus was the most common pathogen among those who died, although it did not have the highest case fatality rate. Conclusions Multiple respiratory viruses beyond influenza are associated with significant morbidity and mortality among adults and children in Mexico City. Detection of these agents could be useful for the adjustment of antibiotic treatment in severe cases.

Effectiveness of Highly Active Antiretroviral Therapy (HAART) Among HIV-Infected Patients in Mexico

The National Government HAART Program (NGP) for the provision of HAART to uninsured HIV-infected persons in Mexico began in 2001. The objective was to describe the virologic outcome of patients enrolled in the NGP in a large HIV treatment center in Mexico City. HIV-infected persons, naive or < or =6 months on HAART, who entered the NGP from 2001 to 2005 were included. Patients with virological suppression were compared to those with virologic failure (VF) during follow-up. Of 377 patients enrolled, 191 where eligible for analysis. The median age was 35.9 (18-75 years) and 85% were male. The median baseline CD4(+) T cell count was 183 cells/mm(3); 63.9% had <200 cells/mm(3) and/or an AIDS-defining event. During follow-up (median: 17.77 months), 55 patients (28.7%) changed their first regimen: 8.3% because of VF and the remaining due to toxicity. The probability of VF at 48 months was 20%. VF was associated with age <30 years (p = 0.003, RR 4.7, IC 95% 1.5-14.4). The use of NNRTI was associated with lower risk of VF (p = 0.042, RR 0.3, IC 95% 0.12-0.99). Nadir CD4(+) and AIDS-defining at baseline were not associated with VF. Implementation of NGP for HAART access in a specialized care setting in Mexico resulted in an excellent virologic response. Younger age was a significant risk factor for VF.

Impact of the immune reconstitution inflammatory syndrome (IRIS) on mortality and morbidity in HIV-infected patients in Mexico

OBJECTIVES To estimate the impact of immune reconstitution inflammatory syndrome (IRIS) on morbidity and mortality in patients starting highly-active antiretroviral therapy (HAART). METHODS A retrospective cohort study of HIV-positive patients starting HAART was conducted at a tertiary care referral center in Mexico City. We estimated the incidence of IRIS, hospitalizations and death rates during the first 2 years of HAART. The relative risk of death (RR) and hospitalization for patients with IRIS were adjusted for relevant covariates using regression methods. RESULTS During the 2-year follow-up period, 27% of patients developed IRIS (14 IRIS cases per 100 person-years). The relative risk of death among patients who developed IRIS was 3 times higher (95% confidence interval (CI) 1.19-7.65, p = 0.03). After adjusting for previous opportunistic infections we still observed a higher death rate among patients with IRIS (RR 2.3, 95% CI 0.9-5.9, p=0.09). An effect modification of IRIS over mortality was observed by previous opportunistic infection. CONCLUSIONS IRIS-associated mortality is strongly confounded by previous opportunistic infection. Patients with AIDS who eventually developed IRIS had the highest risk of death at the 2-year follow-up.

Vancomycin-resistant enterococci, Mexico City.

To the Editor: Vancomycin-resistant Enterococcus (VRE) has become an important nosocomial pathogen because of its rapid spread, limited therapy options, mortality, and the possibility of transfer of vancomycin resistance to other pathogens such as Staphylococcus aureus. Vancomycin-resistant E. faecium (VREF) and E. faecalis were first described in 1988 (1,2).They have become major nosocomial pathogens, but their prevalence in Latin America has remained <2% (3). In Mexico, VRE has rarely been reported (4,5). In a recent study in Mexico City, 100% (n = 60) of the isolates of E. faecium and E. faecalis were susceptible to vancomycin (6). From May 2004 to April 2005, the rate of vancomycin resistance among all Enterococcus isolates was 0.27%. However, in May 2005 the first fully VREF was isolated at our hospital, and the rate of vancomycin resistance was 6.23% (a 23-fold increase) during the following 12-month period. We performed a retrospective study to describe the isolates and the characteristics of patients with VREF. All VREF isolates from May 2005 through April 2006 were included. We collected demographic and clinical data. For the final identification of the isolates, the VITEK system (bioMerieux, Lyon, France) with VITEK GPI cards (bioMerieux, Inc., Durham NC, USA) were used. Antimicrobial drug susceptibility was tested by using the VITEK GPS-111 card and confirmed by MIC determination that used broth microdilution. Resistance to vancomycin and teicoplanin was confirmed by E-test (AB Biodisk, Solna, Sweden). An isolate was considered vancomycin resistant when the MIC was ≥32 μg/mL and was considered to have high-level resistance when the MIC was ≥256 μg/mL. A PCR for detection of the vanA or vanB genotype was used (7). Isolates were characterized by pulsed-field gel electrophoresis (PFGE) (8,9); a dendrogram was constructed with the GelCompare II 4.0 software (Applied Maths, Kortrijk, Belgium), and the similarity was compared with the Dice coefficient. In the study period, VREF was isolated from 27 patients. The median age was 40 years (range 22–84 years). VREF was isolated from the abdomen in 14 patients (51.9%); 11 isolates were from an abscess, 2 from infected surgical sites, and 1 from ascites. An additional 8 isolates were from the urinary tract (29.6%), 2 from the bloodstream (7.4%), 2 from soft-tissue (7.4%), and 1 (3.7%) from bone. Residence in the general medical wards during the isolation of VREF was most common, 17 (63%) cases, followed by 6 (22.2%) in the intensive care unit. The remaining 4 (14.8%) were distributed in other areas. Median time of hospitalization before the isolation was 21 days (range 1–84 days). Twenty-five patients (92.6%) had a central line, 12 (44.4%) had mechanical ventilation, and 20 (74.1%) previous surgery. Of the last group, 17 (85%) of 20 had abdominal surgery. Twenty-four patients (88.8%) received an antimicrobial drug before the isolation of VREF: third- or fourth-generation cephalosporins (89%), metronidazole (70.4%), aminoglycosides (70.4%), vancomycin (66.7%), carbapenems (66.7%), amoxicillin or ampicillin (48.1%), antifungal agents (48.1%); and <20% received quinolones, trimethoprim-sulfamethoxazole, colistin, macrolides, and antimycobacterial or antiviral agents. The median time of antimicrobial drug use was 11 days (range 1–84 days). During hospitalization, 7 patients died (crude death rate, 25.9%), 5 of them from sepsis with at least another microorganism isolated; the remaining 2 died of gastrointestinal hemorrhage. All isolates of E. faecium had a vancomycin MIC ≥256 μg/mL and a vanA phenotype (teicoplanin resistance); 26 (96.3%) had vanA genotype. Only 1 isolate of E. faecium was classified as non–vanA, non vanB, even though it demonstrated high-level resistance to vancomycin and teicoplanin. Resistance to other antimicrobial agents was as follows: ampicillin and ciprofloxacin, 100%; high-level gentamicin, 48.2%; quinupristin/dalfopristin, 7.4%; and linezolid, 0%. PFGE analysis showed several genotypes of E. faecium; however, 18 of 26 of the isolates had <3 band differences from the predominant strain classified as type A. One isolate of E. faecium could not be typed (Figure). Figure Pulsed-field gel electrophoresis (PFGE) banding patterns of chromosomal DNA of 26 isolates of vancomycin-resistant enterococci. There is a clear predominant type, classified as type A (≥80% similarity), composed of 18 isolates of Enterococcus ... As in most tertiary-care centers, our PFGE data suggest that a heterogenous population of VREF exists, but a particular clone established itself as the dominant strain. Although infection control measures are well established in our hospital, in disseminated outbreaks caused by several different clones, infection control measures and control of vancomycin use have shown only limited efficacy. This suggests selection pressure by antimicrobial drugs other than vancomycin (10). Early detection of VREF is of extreme importance because of the possibility that the vanA gene may be transferred to a variety of gram-positive microorganisms, including S. aureus. The rate of isolation of VREF at our hospital increased considerably during the last year. Even though the number of patients is small, we consider this finding to be of utmost importance, since VREF seems to be emerging in Mexico. To our knowledge, this is the first well-documented outbreak of high-level resistance to vancomycin in enterococci in Mexico. Further research is needed to determine if the problem is limited to our hospital or if it is a nationwide trend.

Molecular Analysis of Mycobacterium tuberculosis Strains with an Intact pks15/1 Gene in a Rural Community of Mexico

BACKGROUND Mycobacterium tuberculosis (MTB) is one of the leading causes of morbidity and mortality worldwide and infects approximately 1/3 of the human population, but only 10% of all infected individuals will ever develop the disease and half of these may result in a rapid progression to disease during the first 2 years after being infected. On the other hand, some phenotypic differences among mycobacterial strains contribute to variations in the outcome of the infection, e.g., the hypervirulent phenotype described in the Beijing family has been associated with the production of a phenolic glycolipid, which reduces the production of Th1 cytokines in the experimental model and requires the activity of a polyketide synthase enzyme encoded by the pks15/1 gene. METHODS We analyzed clinical isolates characterized by recent transmission and rapid progression to disease to identify factors that may influence such behavior from a rural and semi-urban community in eastern Mexico. RESULTS Using various typing tools, we were able to identify intrafamilial clusters which belonged to the East Asian lineage of MTB isolates (Beijing family) and another that belonged to the Indo-Oceanic lineage (Manila family). All isolates within these two clusters showed an intact pks15/1 gene sequence. Additionally, we identified three more family clusters that belonged to the Euro-American lineage and showed the typical 7-bp deletion of the pks15/1 gene. This 7-bp deletion was also found in the remaining 23 cases from non-family clusters. CONCLUSIONS This is the first report of cases caused by strains with an intact pks15/1 gene in Mexico. Interestingly, we identified the three main mycobacterial lineages described so far: East-Asian, Indo-Oceanic, and Euro-American in a human population with almost no present-day migration.

Elevation of plasmatic endothelin in patients with heart failure

BACKGROUND Endothelin 1 is an autocrine and paracrine factor with vasoconstrictive, mitogenic, and inotropic activities in vascular and cardiac muscles. Its elevation has been reported in patients with chronic heart failure and its production may be conditioned by activation of other neurohumoral factors that are stimulated by the disease. METHODS The objective of this study was to correlate level of endothelin (ET) with echocardiographic, clinical, and biochemical markers and to determine its role as an independent marker of severity. We included patients with congestive heart failure in whom echocardiographic evaluation had been done and serum markers measured. Serum endothelin 1 levels were determined by radioimmunoassay (RIA). Correlation between endothelin concentration, echocardiographic parameters, potentially confounding factors, and severity of heart failure was made. RESULTS Patients with symptomatic heart failure and longer time of evolution had higher levels of endothelin unrelated to levels of troponin T, tumor necrosis factor, and atrial natriuretic peptide. There were no differences in levels of endothelin, independently of the etiology of cardiac failure. CONCLUSIONS These results support the idea that endothelin plays an important independent role in the physiopathology of heart failure. It may be a severity marker and an attractive therapeutic target.

Concordance Between Two Enzyme Immunoassays for the Detection of Clostridium difficile Toxins

BACKGROUND AND AIMS The diagnosis of Clostridium difficile-associated disease (CDAD) is based on the detection of toxins from stool samples. There are several immunoassays for this purpose. The aim of this study was to determine the concordance between the two immunoassays and their performance in comparison to the toxigenic culture as part of the initial evaluation of a suspected case of CDAD. METHODS All fecal samples submitted for detection of C. difficile toxins during a 5-month period to our laboratory were analyzed by two immunoassays, VIDAS Toxin CDA/B assay (BioMerieux) and ImmunoCard Toxins A/B (Meridian Bioscience). We cultured on cycloserine-cefoxitin-fructose agar and PCR was used for detection of toxigenic genes. Real-time PCR was performed directly from samples to detect the tcdC gene. RESULTS At the end of the study we processed 230 samples, 13 were positive using VIDAS CDA/B (5.6%), and 14 using ImmunoCard A/B (6.0%); kappa coefficient was 0.857. With ImmunoCard A/B we obtained a sensitivity of 80%, a specificity of 99%, positive predictive value (PPV) 86% and negative predictive value (NPV) 98%, as compared to toxigenic culture. For VIDAS CDA/B we obtained a sensitivity of 90%, a specificity of 98%, PPV 69% and NPV 99%, compared to the same standard. There were seven undetermined results (3.0%) by VIDAS CDA/B. Five of these had a positive culture and all the patients had symptoms of CDAD. Considering these undetermined results as positive, we calculated a sensitivity of 93%, specificity of 97%, PPV 71% and NPV of 99% for this test, and a kappa of 0.856. Both immunoassays showed similar results and are suitable for the initial evaluation of patients with suspected CDAD. CONCLUSIONS Our data suggest that an undetermined result of VIDAS CDA/B should be considered as positive if CDAD is suspected. Additionally, both immunoassays showed similar results and are suitable for the initial evaluation of patients with suspected CDAD.

Epidemiology and clinical characteristics of respiratory syncytial virus infections among children and adults in Mexico

Respiratory syncytial virus (RSV) is a leading etiological agent of acute respiratory tract infections and hospitalizations in children. However, little information is available regarding RSV infections in Latin American countries, particularly among adult patients.