Lázaro A. Vélez

CC8 MRSA Strains Harboring SCCmec Type IVc are Predominant in Colombian Hospitals

Background Recent reports highlight the incursion of community-associated MRSA within healthcare settings. However, knowledge of this phenomenon remains limited in Latin America. The aim of this study was to evaluate the molecular epidemiology of MRSA in three tertiary-care hospitals in Medellín, Colombia. Methods An observational cross-sectional study was conducted from 2008–2010. MRSA infections were classified as either community-associated (CA-MRSA) or healthcare-associated (HA-MRSA), with HA-MRSA further classified as hospital-onset (HAHO-MRSA) or community-onset (HACO-MRSA) according to standard epidemiological definitions established by the U.S. Centers for Disease Control and Prevention (CDC). Genotypic analysis included SCCmec typing, spa typing, PFGE and MLST. Results Out of 538 total MRSA isolates, 68 (12.6%) were defined as CA-MRSA, 243 (45.2%) as HACO-MRSA and 227 (42.2%) as HAHO-MRSA. The majority harbored SCCmec type IVc (306, 58.7%), followed by SCCmec type I (174, 33.4%). The prevalence of type IVc among CA-, HACO- and HAHO-MRSA isolates was 92.4%, 65.1% and 43.6%, respectively. From 2008 to 2010, the prevalence of type IVc-bearing strains increased significantly, from 50.0% to 68.2% (p = 0.004). Strains harboring SCCmec IVc were mainly associated with spa types t1610, t008 and t024 (MLST clonal complex 8), while PFGE confirmed that the t008 and t1610 strains were closely related to the USA300-0114 CA-MRSA clone. Notably, strains belonging to these three spa types exhibited high levels of tetracycline resistance (45.9%). Conclusion CC8 MRSA strains harboring SCCmec type IVc are becoming predominant in Medellín hospitals, displacing previously reported CC5 HA-MRSA clones. Based on shared characteristics including SCCmec IVc, absence of the ACME element and tetracycline resistance, the USA300-related isolates in this study are most likely related to USA300-LV, the recently-described ‘Latin American variant’ of USA300.

A comparison of methicillin-resistant and methicillin-susceptible Staphylococcus aureus reveals no clinical and epidemiological but molecular differences

Most studies on Staphylococcus aureus have focused on the molecular epidemiology of methicillin-resistant S. aureus (MRSA) infections. In contrast, little information is available regarding the molecular epidemiology of currently circulating methicillin-susceptible S. aureus (MSSA) isolates in hospital settings, an epoch when the epidemiology of S. aureus has undergone significant changes. We conducted a cross-sectional study to compare the clinical, epidemiological, and genetic characteristics of MSSA and MRSA isolates at 3 tertiary-care hospitals in Medellín, Colombia, from February 2008 to June 2010. The infections were classified according to the Centers for Disease Control and Prevention (CDC) definitions. Genotypic analysis included spa typing, multilocus sequence typing (MLST) and staphylococcal cassette chromosome (mec) (SCCmec) typing. A total of 810 patients was enrolled. One hundred infections (12.3%) were classified as community-associated (31 CA-MSSA, 69 CA-MRSA), 379 (46.8%) as healthcare-associated community-onset (136 HACO-MSSA, 243 HACO-MRSA), and 331 (40.9%) as healthcare-associated hospital-onset (104 HAHO-MSSA, 227 HAHO-MRSA). Genotype analyses showed a higher diversity and a more varied spa type repertoire in MSSA than in MRSA strains. Most of the clinical-epidemiological characteristics and risk factors evaluated did not allow for discriminating MRSA- from MSSA-infected patients. The lack of equivalence among the genetic backgrounds of the major MSSA and MRSA clones would suggest that the MRSA clones are imported instead of arising from successful MSSA clones. This study emphasizes the importance of local surveillance to create public awareness on the changing S. aureus epidemiology.

High Incidence of Tuberculosis, Low Sensitivity of Current Diagnostic Scheme and Prolonged Culture Positivity in Four Colombian Prisons. A Cohort Study

Objective To determine the incidence of pulmonary tuberculosis (TB) in inmates, factors associated with TB, and the time to sputum smear and culture conversion during TB treatment. Methods Prospective cohort study. All prisoners with respiratory symptoms (RS) of any duration were evaluated. After participants signed consent forms, we collected three spontaneous sputum samples on consecutive days. We performed auramine-rhodamine staining, culturing with the thin-layer agar method, Löwestein-Jensen medium and MGIT, susceptibility testing for first-line drugs; and HIV testing. TB cases were followed, and the times to smear and culture conversion to negative were evaluated. Results Of 9,507 prisoners held in four prisons between April/30/2010 and April/30/2012, among them 4,463 were screened, 1,305 were evaluated for TB because of the lower RS of any duration, and 72 were diagnosed with TB. The annual incidence was 505 cases/100,000 prisoners. Among TB cases, the median age was 30 years, 25% had <15 days of cough, 12.5% had a history of prior TB, and 40.3% had prior contact with a TB case. TB-HIV coinfection was diagnosed in three cases. History of prior TB, contact with a TB case, and being underweight were risk factors associated with TB. Overweight was a protective factor. Almost a quarter of TB cases were detected only by culture; three cases were isoniazid resistant, and two resistant to streptomycin. The median times to culture conversion was 59 days, and smear conversion was 33. Conclusions The TB incidence in prisons is 20 times higher than in the general Colombian population. TB should be considered in inmates with lower RS of any duration. Our data demonstrate that patients receiving adequate anti-TB treatment remain infectious for prolonged periods. These findings suggest that current recommendations regarding isolation of prisoners with TB should be reconsidered, and suggest the need for mycobacterial cultures during follow-up.

Livestock-associated methicillin-susceptible Staphylococcus aureus ST398 infection in woman, Colombia.

To the Editor: Staphylococcus aureus causes health care– and community-associated infections worldwide in humans and animals. It also asymptomatically colonizes a large proportion (20%–60%) of otherwise healthy individuals. In recent years, various countries have reported an increasing number of humans infected with livestock-associated S. aureus multilocus sequence type (ST) 398, which suggests that this strain is emerging in community and health care settings (1). Methicillin-resistant S. aureus (MRSA) ST398 has received particular attention as a causative agent of infection in pigs, dogs, horses, cattle, and poultry. Colonization and infection in humans have also been described in Europe (2), Asia (3), Canada (4), and the United States (5), particularly among persons with frequent exposure to animals, such as farmers, veterinarians, and their household members. However, infections with MRSA ST398 and methicillin-susceptible S. aureus (MSSA) ST398 have recently been described in persons with no history of contact with livestock (6–10). We report infection of a woman with MSSA ST398 in Colombia, South America. On November 3, 2009, this 82-year-old woman was admitted to the emergency unit of the Hospital Universitario San Vicente Fundacion in Medellin, reporting a 15-day history of fever, dyspnea, and pain in her left leg. She lived in a rural area and reported previous contact with dogs and chickens. Her medical history included diabetes mellitus, hypertension, valvular heart disease, and chronic arterial occlusive disease. Four months earlier she had received a femoro–popliteal vascular prosthetic graft in her left leg. At the time of admission, blood culture was requested, and intravenous vancomycin (1 g every 12 hours) and piperacillin/tazobactam (4.5 g every 8 hours) were empirically administered. S. aureus was subsequently isolated from blood culture, and antimicrobial drug susceptibility was assessed in accordance with Clinical Laboratory Standards Institute guidelines by using a Vitek 2 instrument (bioMerieux, Marcy l’Etoile, France). The isolate was susceptible to methicillin, rifampin, and vancomycin but resistant to clindamycin, erythromycin, gentamicin, levofloxacin, minocycline, moxifloxacin, tetracycline, and trimethoprim/sulfamethoxazole. Additional laboratory results showed an elevated leukocyte count with predominant polynuclear neutrophils and increased C-reactive protein levels (21.2 mg/L). Angiography of the left femoro–popliteal segment showed a collection surrounding the entire vascular prosthetic graft, which was presumed to be the bacteremic focus. Accordingly, rifampin (600 mg every 12 hours) was added to the regimen, the femoro-popliteal graft was surgically removed, the collection was drained, and the limb was amputated. After the surgery, cephradine was administered for 14 days, after which clinical signs and symptoms of bacteremia resolved completely, and the patient was discharged from the hospital. The blood culture isolate was subsequently confirmed as S. aureus by PCR with primers directed to the nuc gene. Genes encoding the following virulence factors were also evaluated by PCR, but none were detected: Panton-Valentine leukocidin, arginine catabolic mobile element, staphylococcal enterotoxins A–E, exfoliating toxins A and B, and toxic shock syndrome toxin 1. Genotypic analysis indicated that the isolate belonged to multilocus ST398 (allelic profile 3-35-19-2-20-26-39) and spa type t571 (eGenomics spa type 109); pulsed-field gel electrophoresis with SmaI digestion yielded no results, as described previously for ST398 (1). This report documents the emergence of human infection caused by MSSA spa type t571 ST398 in South America. Despite being about only 1 case, this report nevertheless highlights the changing epidemiology of S. aureus within the region. The study was limited by the inability to sample animals from a surrounding farm to determine the potential for zoonotic spread of S. aureus in domestic environments. Notably, spa type t571 ST398 has been found recently in MSSA carriage isolates from New York City (6), the Dominican Republic (6), and the Amazonian region of French Guiana (9) and in clinical MSSA isolates from the Netherlands (7), People’s Republic of China (8), and France (10). Given the patients’ absence of contact with livestock in most of these reports, transmission of MSSA ST398 spa type t571 may not be limited to animal exposure, suggesting the possibility of person-to-person spread. Accordingly, our finding reinforces the need to heighten awareness of the transmission and virulence potential of MSSA ST398, particularly in developing countries where understanding of S. aureus colonization and transmission dynamics is probably limited. Such information has implications for the design of appropriate control measures to reduce human and animal infections from this emerging pathogen.

Reading and interpretation of chest X-ray in adults with community-acquired pneumonia

INTRODUCTION Traditional reading of chest X-rays usually has a low prognostic value and poor agreement. OBJECTIVE This study aimed to determine the interobserver and intraobserver agreement using two reading formats in patients with community-acquired pneumonia, and to explore their association with etiology and clinical outcomes. METHODS A pulmonologist and a radiologist, who were blind to clinical data, interpreted 211 radiographs using a traditional analysis format (type and location of pulmonary infiltrates and pleural findings), and a quantitative analysis (pulmonary damage categorized from 0 to 10). For both, the interobserver and intraobserver agreement was estimated (Kappa statistic and intraclass correlation coefficient). The latter was assessed in a subsample of 25 radiographs three months after the initial reading. Finally, the observers made a joint reading to explore its prognostic usefulness via multivariate analysis. RESULTS Seventy-four chest radiographs were discarded due to poor quality. With the traditional reading, the mean interobserver agreement was moderate (0.43). It was considered good when the presence of pleural effusion, and the location of the infiltrates in the right upper lobe and both lower lobes, were evaluated; moderate for multilobar pneumonia; and poor for the type of infiltrates. The mean intraobserver agreement for each reviewer was 0.71 and 0.5 respectively. The quantitative reading had an agreement between good and excellent (interobserver 0.72, intraobserver 0.85 and 0.61). Radiological findings were neither associated to a specific pathogen nor to mortality. CONCLUSION In patients with pneumonia, the interpretation of the chest X-ray, especially the smallest of details, depends solely on the reader.

Histoplasmosis en pacientes con sida. Un estudio de cohorte en Medellín, Colombia

Introduction: histoplasmosis is an endemic mycosis in Colombia and a relatively common complication in HIV patients. The aim of this study was to identify clinical and epidemiological characteristics and mortality risk factors in patients infected with histoplasmosis and HIV. Materials and methods: a retrospective cohort study was carried out at Hospital Universitario San Vicente de Paul in Medellin with 1177 HIVpositive patients. Patients with histoplasmosis were confirmed by isolation of Histoplasma capsulatum from culture or by identification of intracellular yeasts through microscopy. Data collected from patients included demographic and clinical variables, laboratory values, treatment, and survival. Results: histoplasmosis affected 44/709 patients with AIDS (6.2%). Out of those, 95.4% had fever, 54.5% disseminated illness, and 61.3% pulmonary disease. Culture was positive in 89.3%, and histopathology in 93.3%. Concomitant tuberculosis and Pneumocystis jirovecii infection were diagnosed in 15.9% and 11.4%, respectively. General mortality was 22.7%. Mortality was higher in patients with disseminated forms (all 10 deaths occurred in this fashion), dyspnea (RR 13; 95% CI 1.8-93.8), hypotension (RR 4.5; 95% CI 1.6-13.1), lactate dehydrogenase >2 times the upper limit of the normal range (RR 5.2; 95% CI 1.2-22.5), and it was lower among patients treated with amphotericine B (RR 0.3; 95% CI 0.1-0.8). Discusion: histoplasmosis is frequent in AIDS patients in the region. As the diagnosis yield of routine techniques to identify H. capsulatum is high, they must be required in any compatible setting. Many patients with AIDS-histoplasmosis co-infection acquire other opportunistic infections. Patients with disseminated forms, dyspnea, hypotension, and high levels of DHL have a higher mortality risk. Exposure to amphotericine B is associated with longer survival.

Microscopic diagnosis of Pneumocystis jirovecii pneumonia in bronchoalveolar lavage and oropharyngeal wash samples of immunocompromised patients with pneumonia

INTRODUCTION The diagnosis of Pneumocystis jirovecii pneumonia is based on observation of the microorganism using several staining techniques in respiratory samples, especially bronchoalveolar lavage and induced sputum. Recently, the fungus also has been detected in oropharyngeal wash samples, but only using molecular tests. OBJECTIVE The diagnostic yield of two microscopic stains, toluidine blue O and direct fluorescent antibody, was compared in bronchoalveolar lavage and oropharyngeal wash samples for the detection of P. jirovecii in immunocompromised patients with pneumonia. MATERIALS AND METHODS Cross-sectional evaluation diagnostic tests were used in 166 immunosuppressed patients with suspected P. jirovecii. By protocol, bronchoscopic bronchoalveolar lavage and oropharyngeal wash samples were prepared by cytocentrifugation, and slides were stained with toluidine blue and fluorescent antibody. The proportion of positive results from each stain and concordance between them were determined. RESULTS Twenty-four cases (14.5%) of P. jirovecii were detected in bronchoalveolar lavage samples. Of them, 21 were positive by both toluidine blue and fluorescent antibody stains, whereas 3 cases were detected by fluorescent antibody alone. None of the 166 oropharyngeal wash samples were positive by either of these techniques. No significant differences were found between proportions from positive results (p=0.63). Concordance (kappa coefficient) between both stains was 0.92 (95% CI: 0.84-1.00). CONCLUSIONS Both techniques were useful to diagnose P. jirovecii in bronchoalveolar lavage samples. However, toluidine blue stain did not detect 12% of fluorescent antibody positive cases. Oropharyngeal wash samples do not provide sufficient material for the microscopic identification of this fungus.

Atypical bacterial pneumonia in the HIV-infected population

Human immunodeficiency virus (HIV)-infected individuals are more susceptible to respiratory tract infections by other infectious agents (viruses, bacteria, parasites, and fungi) as their disease progresses to acquired immunodeficiency syndrome. Despite effective antiretroviral therapy, bacterial pneumonia (the most frequently occurring HIV-associated pulmonary illness) remains a common cause of morbidity and mortality in the HIV-infected population. Over the last few decades, studies have looked at the role of atypical bacterial pneumonia (i.e. pneumonia that causes an atypical clinical presentation or responds differently to typical therapeutics) in association with HIV infection. Due to the lack of available diagnostic strategies, the lack of consideration, and the declining immunity of the patient, HIV co-infections with atypical bacteria are currently believed to be underreported. Thus, following an extensive database search, this review aimed to highlight the current knowledge and gaps regarding atypical bacterial pneumonia in HIV. The authors discuss the prevalence of Chlamydophila pneumoniae, Mycoplasma pneumoniae, Coxiella burnetii, Legionella species and others in the HIV-infected population as well as their clinical presentation, methods of detection, and treatment. Further studies looking at the role of these microbes in association with HIV are required. Increased knowledge of these atypical bacteria will lead to a more rapid diagnosis of these infections, resulting in an improved quality of life for the HIV-infected population.

Diagnosis and treatment of latent tuberculosis in patients with multiple sclerosis, expert consensus. On behalf of the Colombian Association of Neurology, Committee of Multiple Sclerosis:

Background Multiple sclerosis is an inflammatory and neurodegenerative demyelinating disease. Current treatment of multiple sclerosis focuses on the use of immunomodulatory, immunosuppressant, and selective immunosuppressant agents. Some of these medications may result in high risk of opportunistic infections including tuberculosis. Objective The purpose of this study was to obtain consensus from a panel of neurologists, pulmonologists, infectious disease specialists, and epidemiology experts regarding the diagnosis, treatment, and monitoring of latent tuberculosis in patients with multiple sclerosis. Methods A panel of experts in multiple sclerosis and tuberculosis was established. The methodological process was performed in three phases: definition of questions, answer using Delphi methodology, and the discussion of questions not agreed. Results Tuberculosis screening is suggested when multiple sclerosis drugs are prescribed. The recommended tests for latent tuberculosis are tuberculin and interferon gamma release test. When an anti-tuberculosis treatment is indicated, monitoring should be performed to determine liver enzyme values with consideration of age as well as comorbid conditions such as a history of alcoholism, age, obesity, concomitant hepatotoxic drugs, and history of liver disease. Conclusion Latent tuberculosis should be considered in patients with multiple sclerosis who are going to be treated with immunomodulatory and immunosuppressant medications. Transaminase level monitoring is required on a periodic basis depending on clinical and laboratory characteristics. In addition to the liver impairment, other side effects should be considered when Isoniazid is prescribed.

Usefulness of FTA® cards as a Pneumocystis-DNA extraction method in bronchoalveolar lavage samples

ABSTRACT Background FTA® cards (Fast Technology for Analysis of Nucleic Acids) are an alternative DNA extraction method in bronchoalveolar lavage (BAL) samples for Pneumocystis jirovecii molecular analyses. The goal was to evaluate the usefulness of FTA® cards to detect P. jirovecii-DNA by PCR in BAL samples compared to silica adsorption chromatography (SAC). Methods This study used 134 BAL samples from immunocompromised patients previously studied to establish microbiological aetiology of pneumonia, among them 15 cases of Pneumocystis pneumonia (PCP) documented by staining and 119 with other alternative diagnoses. The FTA® system and SAC were used for DNA extraction and then amplified by nested PCR to detect P. jirovecii. Performance and concordance of the two DNA extraction methods compared to P. jirovecii microscopy were calculated. The influence of the macroscopic characteristics, transportation of samples and the duration of the FTA® card storage (1, 7, 10 or 12 months) were also evaluated. Results Among 134 BAL samples, 56% were positive for P. jirovecii-DNA by SAC and 27% by FTA®. All 15 diagnosed by microscopy were detected by FTA® and SAC. Specificity of the FTA® system and SAC were 82.4% and 49.6%, respectively. Compared to SAC, positivity by FTA® decreased with the presence of blood in BAL (62% vs 13.5%). The agreement between samples at 7, 10 and 12 months was 92.5% for FTA®. Positive cases by FTA® remained the same after shipment by mail. Conclusions Results suggest that FTA® is a practical, safe and economical method to preserve P. jirovecii-DNA in BAL samples for molecular studies.