Microbiological and Molecular Characterization of Staphylococcus hominis Isolates from Blood

Background: Among Coagulase-Negative Staphylococci (CoNS), Staphylococcus hominis represents the third most common organism recoverable from the blood of immunocompromised patients. The aim of this study was to characterize biofilm formation, antibiotic resistance, define the SCCmec (Staphylococcal Chromosomal Cassette mec) type, and genetic relatedness of clinical S. hominis isolates. Methodology: S. hominis blood isolates (n = 21) were screened for biofilm formation using crystal violet staining. Methicillin resistance was evaluated using the cefoxitin disk test and the mecA gene was detected by PCR. Antibiotic resistance was determined by the broth microdilution method. Genetic relatedness was determined by pulsed-field gel electrophoresis (PFGE) and SCCmec typed by multiplex PCR using two different methodologies described for Staphylococcus aureus. Results: Of the S. hominis isolates screened, 47.6% (10/21) were categorized as strong biofilm producers and 23.8% (5/21) as weak producers. Furthermore, 81% (17/21) of the isolates were methicillin resistant and mecA gene carriers. Resistance to ampicillin, erythromycin, and trimethoprim was observed in .70% of isolates screened. Each isolate showed a different PFGE macrorestriction pattern with similarity ranging between 0–95%. Among mecA-positive isolates, 14 (82%) harbored a non-typeable SCCmec type: eight isolates were not positive for any ccr complex; four contained the mec complex A ccrAB1 and ccrC, one isolate contained mec complex A, ccrAB4 and ccrC, and one isolate contained the mec complex A, ccrAB1, ccrAB4, and ccrC. Two isolates harbored the association: mec complex A and ccrAB1. Only one strain was typeable as SCCmec III. Conclusions: The S. hominis isolates analyzed were variable biofilm producers had a high prevalence of methicillin resistance and resistance to other antibiotics, and high genetic diversity. The results of this study strongly suggested that S. hominis isolates harbor new SCCmec structural elements and might be reservoirs of ccrC1 in addition to ccrAB1 and mec complex A

Molecular and microbiological report of a hospital outbreak of NDM-1-carrying Enterobacteriaceae in Mexico

Abstract Objectives To characterize the microbiological, molecular and epidemiological data of an outbreak of carbapenem-resistant Enterobacteriaceae (CRE) in a tertiary-care hospital in Mexico. Methods From September 2014 to July 2015, all CRE clinical isolates recovered during an outbreak in the Hospital Civil "Fray Antonio Alcalde" in Jalisco, Mexico were screened for antimicrobial susceptibility, carbapenemase production, carbapenemase-encoding genes, and plasmid profiles. Horizontal transfer of imipenem resistance; and clonal diversity by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST); as well as biofilm production and the presence of 14 virulence genes were analyzed in selected isolates. Results Fifty-two carbapenem-resistant isolates corresponding to 5 species were detected, i.e., Klebsiella pneumoniae (n = 46), Enterobacter cloacae (n = 3), Escherichia coli (n = 1), Providencia rettgeri (n = 1) and Citrobacter freundii (n = 1) with carbapenemase encoding genes blaNDM-1 (n = 48), blaVIM (n = 3), blaIMP (n = 1) and blaKPC (n = 1) detected in these isolates. The blaNDM-1 gene was detected in plasmids from 130- to 170-kb in K. pneumoniae (n = 46); E. cloacae (n = 3), E. coli (n = 1) and P. rettgeri (n = 1). The transfer of plasmids harboring the blaNDM-1 gene was obtained in eight transconjugants. One plasmid restriction pattern was detected, with the blaNDM-1 identified in different restriction fragments. Predominant clone A of K. pneumoniae isolates archived 28/46 (60%) isolates and belongs to ST392. Besides, ST307, ST309, ST846, ST2399, and ST2400 were detected for K. pneumoniae; as well as E. cloacae ST182 and E. coli ST10. The fimA and uge genes were more likely to be identified in K. pneumoniae carbapenemsusceptible isolates (p =<0.001) and biofilm production was more liable to be observed in carbapenem-resistant isolates (p =<0.05). Conclusions Four Enterobacteriaceae species harboring the blaNDM-1 gene were detected in a nosocomial outbreak in Mexico; horizontal transfer and strain transmission were demonstrated for the blaNDM-1 gene. Given the variation in the size of the plasmid harboring blaNDM-1, complex rearrangements must also be occurring

Antibiotic Susceptibility of Biofilm Cells and Molecular Characterisation of Staphylococcus hominis Isolates from Blood

Objectives We aimed to characterise the staphylococcal cassette chromosome mec (SCCmec) type, genetic relatedness, biofilm formation and composition, icaADBC genes detection, icaD expression, and antibiotic susceptibility of planktonic and biofilm cells of Staphylococcus hominis isolates from blood. Methods The study included 67 S. hominis blood isolates. Methicillin resistance was evaluated with the cefoxitin disk test. mecA gene and SCCmec were detected by multiplex PCR. Genetic relatedness was determined by pulsed-field gel electrophoresis. Biofilm formation and composition were evaluated by staining with crystal violet and by detachment assay, respectively; and the biofilm index (BI) was determined. Detection and expression of icaADB Cgenes were performed by multiplex PCR and real-time PCR, respectively. Antibiotic susceptibilities of planktonic cells (minimum inhibitory concentration, MIC) and biofilm cells (minimum biofilm eradication concentration, MBEC) were determined by the broth dilution method. Results Eighty-five percent (57/67) of isolates were methicillin resistant and mecA positive. Of the mecA-positive isolates, 66.7% (38/57) carried a new putative SCCmec type. Four clones were detected, with two to five isolates each. Among all isolates, 91% (61/67) were categorised as strong biofilm producers. Biofilm biomass composition was heterogeneous (polysaccharides, proteins and DNA). All isolates presented the icaD gene, and 6.66% (1/15) isolates expressed icaD. This isolate presented the five genes of ica operon. Higher BI and MBEC values than the MIC values were observed for amikacin, vancomycin, linezolid, oxacillin, ciprofloxacin, and chloramphenicol. Conclusions S. hominis isolates were highly resistant to methicillin and other antimicrobials. Most of the detected SCCmec types were different than those described for S. aureus. Isolates indicated low clonality. The results indicate that S. hominis is a strong biofilm producer with an extracellular matrix with similar composition of proteins, DNA and N-acetylglucosamine; and presents high frequency and low expression of icaD gene. Biofilm production is associated with increased antibiotic resistance

Diarrea asociada a Clostridioides difficile en pacientes de servicios quirúrgicos en México

Introducción: Clostridioides difficile (CD) es la primera causa de diarrea asociada al cuidadode salud en los países desarrollados. En los últimos a˜nos, la incidencia de la infección asociadaa CD (ICD) ha aumentado en el ámbito mundial. En México, la información al respecto es escasay se conoce poco sobre los factores de riesgo para esta enfermedad en pacientes hospitalizadosen servicios quirúrgicosMaterial y métodos: Estudio de casos y controles. Se compararon hallazgos epidemiológicos yfactores de riesgo entre pacientes quirúrgicos con ICD confirmada por PCR contra pacientes qui-rúrgicos con diarrea PCR negativa y contra pacientes quirúrgicos sin diarrea. Se realizó análisisestadístico mediante el paquete estadístico SPSS versión 22.0.Resultados: La mayoría de los pacientes quirúrgicos con ICD correspondían a las áreas de neu-rocirugía, cardiocirugía, ortopedia y cirugía general. El 53% de los casos de ICD se asociaron a lacepa hipervirulenta de CD NAP1/027. La presencia de moco en heces (RM 1.5, p = 0.001), fiebre(RM 1.4, p = 0.011), leucocitos en heces (RM 3.2, p = < 0.001), hospitalización en las últimas12 semanas (RM 2.0, p = < 0.001), uso de antibióticos (RM 1.3, p = 0.023) y uso de ceftriaxona(RM 1.4, p = 0.01) constituyeron factores de riesgo independientes para el desarrollo de ICD. Conclusiones: La diarrea por CD en servicios quirúrgicos es frecuente en nuestra institución(Hospital Civil de Guadalajara Fray Antonio Alcalde)

Risk factors and outcome associated with the acquisition of linezolid-resistant Enterococcus faecalis

Objectives: Linezolid is a synthetic oxazolidinone antibiotic frequently used to treat vancomycin-resistant enterococcal infections. Vancomycin-susceptible Enterococcus faecalis can develop resistance to linezolid in environments with excessive linezolid use. The aim of this study was to define risk factors and outcome associated with the acquisition of linezolid-resistant E. faecalis (LREfs). Methods: A retrospective case–control study was designed including patients hospitalised from January 2014 to October 2017 at Hospital Civil de Guadalajara ‘Fray Antonio Alcalde’ in Guadalajara, Mexico. A total of 50 patients culture-positive for LREfs and 100 control patients hospitalised in the same room and time as the cases were included. Clinical and demographic data were collected and analysed. Results: Risk factors for the presence of LREfs included prior linezolid use [odds ratio (OR) = 6.74], prior clindamycin use (OR = 6.72) and previous surgery (OR = 5.79). The mortality rate was 18% for LREfs cases versus 9% for controls. Conclusion: LREfs has emerged and spread in our hospital, an environment in which linezolid use is considerable. Risk factors for LREfs are prior antibiotic use, including linezolid, and previous surgery

Clostridioides difficile-associated diarrhea in surgical service patients in Mexico

Introduction: Clostridium difficile is the first cause of healthcare-associated diarrhea in developed countries. In recent years the incidence of C. difficile infection (CDI) has increased worldwide. There is not much information on the topic in Mexico, and little is known about the risk factors for the infection in patients that are hospitalized in surgical services. Materials and methods: A case-control study was conducted that compared the epidemiologic findings and risk factors between surgical patients with PCR-confirmed CDI, surgical patients with diarrhea and a negative PCR test, and surgical patients with no diarrhea. The statistical analysis was carried out using the SPSS version 22.0 program. Results: The majority of the surgical patients with CDI belonged to the areas of neurosurgery, cardiac surgery, orthopedics, and general surgery. A total of 53% of the CDI cases were associated with the hypervirulent CD NAP1/027 strain. The presence of mucus in stools (OR: 1.5, p = 0.001), fever (OR: 1.4, p = 0.011), leukocytes in stools (OR: 3.2, p < 0.001), hospitalization within the past twelve weeks (OR: 2.0, p < 0.001), antibiotic use (OR: 1.3, p = 0.023), and ceftriaxone use (OR: 1.4, p = 0.01) were independent risk factors for the development of CDI

Genetic Diversity of Mycobacterium tuberculosis from Guadalajara, Mexico and Identification of a Rare Multidrug Resistant Beijing Genotype

Determining the genetic diversity of M. tuberculosis strains allows identification of the distinct Mycobacterium tuberculosis genotypes responsible for tuberculosis in different regions. Several studies have reported the genetic diversity of M. tuberculosis strains in Mexico, but little information is available from the state of Jalisco. Therefore, the aim of this study was to determine the genetic diversity of Mycobacterium tuberculosis clinical isolates from Western Mexico. Sixty-eight M. tuberculosis isolates were tested for susceptibility to first-line drugs using manual Mycobacteria Growth Indicator Tube method and genotyped using spoligotyping and IS6110-restriction fragment length polymorphism (RFLP) pattern analyses. Forty-seven (69.1%) isolates were grouped into 10 clusters and 21 isolates displayed single patterns by spoligotyping. Three of the 21 single patterns corresponded to orphan patterns in the SITVITWEB database, and 1 new type that contained 2 isolates was created. The most prevalent lineages were T (38.2%), Haarlem (17.7%), LAM (17.7%), X (7.4%), S (5.9%), EAI (1.5%) and Beijing (1.5%). Six (12.8%) of the clustered isolates were MDR, and type 406 of the Beijing family was among the MDR isolates. Seventeen (26.2%) isolates were grouped into 8 clusters and 48 isolates displayed single patterns by IS6110-RFLP. Combination of IS6110-RFLP and spoligotyping reduced the clustering rate to 20.0%. The results show that T, Haarlem, and LAM are predominant lineages among clinical isolates of M. tuberculosis in Guadalajara, Mexico. Clustering rates indicated low transmission of MDR strains. We detected a rare Beijing genotype, SIT406, which was a highly resistant strain. This is the first report of this Beijing genotype in Latin America

Molecular epidemiology of coagulase-negative bloodstream isolates: detection of Staphylococcus epidermidis ST2, ST7 and linezolid-resistant ST23

The mechanisms contributing to persistence of coagulase-negative staphylococci are diverse; to better understanding of their dynamics, the characterization of nosocomial isolates is needed. Our aim was to characterize phenotypic and molecular characteristics of Staphylococcus epidermidis and Staphylococcus haemolyticus human blood isolates from two tertiary care hospitals in Mexico, the Hospital Universitario in Monterrey and the Hospital Civil in Guadalajara. Antimicrobial susceptibility was determined. Biofilm formation was assessed by crystal violet staining. Detection of the ica operon and Staphylococcal Cassette Chromosome mec typing were performed by PCR. Clonal relatedness was determined by Pulsed-fiel gel electrophoresis and Multi locus sequence typing. Methicillin-resistance was 85.5% and 93.2% for S. epidermidis and S. haemolyticus, respectively. Both species showed resistance >70% to norfloxacin, clindamycin, levofloxacin, trimethoprim/sulfamethoxazole, and erythromycin. Three S. epidermidis and two S. haemolyticus isolates were linezolid-resistant (one isolate of each species was cfr+). Most isolates of both species were strong biofilm producers (92.8% of S. epidermidis and 72.9% of S. haemolyticus). The ica operon was amplified in 36 (43.4%) S. epidermidis isolates. SCCmec type IV was found in 47.2% of the S. epidermidis isolates and SCCmec type V in 14.5% of S. haemolyticus isolates. No clonal relatedness was found in either species. Resistance to clindamycin, levofloxacin, erythromycin, oxacillin, and cefoxitin was associated with biofilm production for both species (p < 0.05). A G2576T mutation in 23S rRNA gene was detected in an S. haemolyticus linezolid-resistant isolate. All linezolid-resistant S. epidermidis isolates belonged to ST23; isolate with SCCmec type IV belonged to ST7, and isolate with SCCmec type III belonged to ST2. This is the first report of ST7 in Mexico. There was a high genetic diversity in both species, though both species shared characteristics that may contibute to virulence

Staphylococcal Cassette Chromosome mec (SCCmec) in coagulase negative staphylococci

Coagulase-negative staphylococci (CoNS) are among the main causative agents of bacteremia. Staphylococcus epidermidis and Staphylococcus haemolyticus are the CoNS species most frequently isolated. These species are often associated with infections in immunocompromised patients who have a medical device implant. Methicillin resistance was first described in Staphylococcus aureus; it has also been reported in CoNS species. Methicillin resistance is conferred by expression of the mecA gene, contained within the staphylococcal cassette chromosome (SCCmec). mecA gene codes for the PBP2a protein which shows poor binding to beta-lactam antibiotics, so methicillin-resistant strains are resistant to beta-lactams. The presence of SCCmec in CoNS species complicates infections caused by these organisms, since it confers resistance to a variety of antibiotics, making treatment difficult. This review analyzes the clinical relevance of SCCmec as well as the diversity and structure of elements present in CoNS species

Risk factors and molecular mechanisms associated with trimethoprim–sulfamethoxazole resistance in Stenotrophomonas maltophilia in Mexico

Abstract Purpose. Stenotrophomonas maltophilia is a multidrug-resistant opportunistic pathogen causing an increasing number of nosocomial infections. Our aim was to evaluate the risk factors and mechanisms associated with trimethoprim– sulfamethoxazole (SXT) resistance in S. maltophilia infections in Mexico. Methodology. Clinical isolates and patients’ demographic and clinical data were collected from February 2007 to August 2015 in two tertiary-care hospitals in Mexico. Antimicrobial susceptibility and analysis of sul and SmeABC and SmeDEF efflux pump overexpression were performed in all isolates. Results/Key findings. In the 9-year period, 196 patients infected with S. maltophilia were identified. Most patients were male, and the mean age was 46.2years. The mean Charlson score was 1.42, and the most frequent comorbidities were arterial hypertension (26.7%), type 2 diabetes (21.2%) and cerebral infarction (11.6%). High drug resistance to meropenem (93.4%), gentamicin (55.1%), ceftazidime (52.3%), cefotaxime (51.5%), amikacin (42.3%) and cefepime (32.1%), and lower resistance to ciprofloxacin (26.0%), SXT (25.0%), chloramphenicol (14.3%) and levofloxacin (2.6%) were detected. SXT resistance was not associated with the sul genes. SmeABC overexpression was associated with gentamicin (P=0.001) and levofloxacin resistance (P=0.041), whereas SmeDEF overexpression was associated with ceftazidime resistance (P=0.003). Prolonged hospitalization (�15days) was an independent risk factor for SXT-resistant S. maltophilia infections (OR=3.05; 95%CI=1.12– 8.86; P=0.029). Conclusion. Given the high SXT resistance rate, SXT is not an effective first-line therapy for our patients; instead, levofloxacin could be used as an appropriate therapeutic option against S. maltophilia infections