Aetiology and Significance of Hospital-Acquired Infections in Mexico

Hospital-acquired infections (HAIs) are infections that develop in the hospital environment and can be acquired by a patient or hospital staff. They are complications that combine diverse risk factors that make an individual susceptible and are frequently caused by endogenous and exogenous bacterial agents. The most commonly studied etiological agents are bacteria and fungi, with the former representing the most common etiological agents reported to the Hospital Epidemiological Surveillance Network (RHOVE) between 2007 and 2012. Among these agents were Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, coagulase-negative Staphylococci (CNS), Enterococcus spp., and Streptococcus pneumoniae. Although obligate anaerobic bacteria are also etiological agents of HAIs, clinical laboratories do not usually perform bacteriological tests to isolate and identify these bacteria. As a result, patients are at a greater risk of not surviving an infection and the epidemiology of this bacterial group is unknown. An important problem associated with HAIs is bacterial multiple drug resistance, which not only increases morbidity and mortality but also the cost of inpatient care. The aim of this review is to provide current information to healthcare professionals on the status of HAIs in Mexico with an emphasis on the etiology, diagnosis, and antimicrobial resistance.

Markers of pathogenicity islands in strains of Aeromonas species of clinical and environmental origin

The aim of this study was to investigate the presence of markers of pathogenicity islands that may be informative to detect the virulent PAI carriers of clinical and environmental strains of Aeromonas spp. isolated in Mexico. virB2, virB9 and virB11 genes were found in Aeromonas strains isolated from environmental and clinical sources while cagE and tfc16 genes were only in strains of environmental origin. Having performed the wide screening presented in this study, we now have a set of strains to map and confirm the presence of a pathogenicity island in Aeromonas strains isolated in Mexico.

Usefulness of Chromogenic CromoCen® AGN agar medium for the identification of the genus Aeromonas: Assessment of faecal samples

Selective screening media for the detection and identification of Aeromonas strains are needed to guide primary isolation procedures in the clinical laboratory. This study compared the selective CromoCen® AGN chromogenic agar medium for the detection and identification of Aeromonas strains that were isolated from various samples against the conventional selective agar media that are commonly used for the isolation of this organism in food, environmental and clinical samples. The Miles and Misra and ecometric methods were used to evaluate the microbiological performance of CromoCen® AGN chromogenic agar medium, which was shown to be satisfactory. A total of 14 reference Aeromonas strains, 44 wild strains and 106 clinical stool specimens were examined using both non-chromogenic selective agars that are commonly used for Aeromonas isolation and CromoCen® AGN agar. The latter exhibited 94.73% sensitivity and 100% specificity for the various samples. On CromoCen® AGN agar medium, Aeromonas formed colonies with light green, greenish and salmon pigments with or without a surrounding wide transparent zone (halo) of 2-3mm in diameter around the entire border. This medium is recommended for the isolation and potential identification of the Aeromonas genus.

Phylogenetic analysis of the genus Aeromonas based on two housekeeping genes

The phylogenetic relationships of all known species of the genus Aeromonas, and especially Aeromonas bestiarum and Aeromonas salmonicida, were investigated on 70 strains using the rpoD sequence, which encodes the sigma70 factor. This analysis was complemented with the sequence of gyrB, which has already proven useful for determining the phylogenetic relationships in the genus. Nucleotide sequences of rpoD and gyrB showed that both genes had similar substitution rates (< 2 %) and a similar number of variable positions (34 % for rpoD versus 32 % for gyrB). Strain groupings by analysis of rpoD, gyrB and a combination of both genes were consistent with the taxonomic organization of all Aeromonas species described to date. However, the simultaneous analysis of both clocks improved the reliability and the power to differentiate, in particular, closely related taxa. At the inter-species level, gyrB showed a better resolution for differentiating Aeromonas sp. HG11/Aeromonas encheleia and Aeromonas veronii/Aeromonas culicicola/Aeromonas allosaccharophila, while rpoD more clearly differentiated A. salmonicida from A. bestiarum. The analysis of rpoD provided initial evidence for clear phylogenetic divergence between the latter two species.