Expression of virulence factors in non-typhoidal Salmonella enterica depends on a wide variety of general and specific transcriptional factors that act in response to multiple environmental signals. Expression of genes for cellular invasion located in the Salmonella pathogenicity island 1 (SPI-1) is tightly regulated by several transcriptional regulators arrayed in a cascade, while repression of this system is exerted mainly by H-NS. In SPI-1, H-NS represses the expression mainly by binding to the regulatory region of hilA and derepression is exercised mainly by HilD. However, the possible regulatory role of H-NS in genes downstream from HilD and HilA, such as those regulated by InvF, has not been fully explored. Here the role of H-NS on the expression of sopB, an InvF dependent gene encoded in SPI-5, was evaluated. Our data show that InvF is required for the expression of sopB even in the absence of H-NS. Furthermore, in agreement with previous results on other InvF-regulated genes, we found that the expression of sopB requires the InvF/SicA complex. Our results support that SicA is not required for DNA binding nor for increasing affinity of InvF to DNA in vitro. Moreover, by using a bacterial two-hybrid system we were able to identify interactions between SicA and InvF. Lastly, protein-protein interaction assays suggest that InvF functions as a monomer. Derived from these results we postulate that the InvF/SicA complex does not act on sopB as an anti-H-NS factor; instead, it seems to induce the expression of sopB by acting as a classical transcriptional regulator.

On January 27, 2012, a 45-year-old woman was admitted for hospitalization. She was from the Bacame Nuevo community, Etchojoa, Sonora, Mexico (Fig 1), a community with a desert climate, dedicated to agriculture and livestock. The patient had a history of outdoor activities and contact with cattle, rodents, dogs, and ticks. She presented with fever, arthralgias, diaphoresis, asthenia, adynamia, fatigue, headache, eye pain, tachycardia, abdominal pain, dyspnea, generalized diffuse rash, insomnia, nocturnal diaphoresis, daytime drowsiness, and character changes that included irritability. During January, she exhibited approximately five febrile episodes of greater than 39˚C and was symptomatically treated. She was diagnosed with a fever of unknown origin because she was serologically negative for other common diseases including leptospirosis, syphilis, and Lyme disease. The patient received treatment with beta-lactam antibiotics (amoxicillin for 15 days) without improvement in the symptoms. At her last evaluation, a blood sample was obtained, and spirochetes were observed by dark-field microscopy. She remained serologically negative to leptospirosis, syphilis, and Lyme-disease-causing spirochetes using commercially available diagnostic tests (Leptospira immunoglobulin G [IgG] immunoglobulin M [IgM] ELISA test [Diagnostic Automation, Woodland Hills, CA, USA], Bioelisa Syphilis 3.0 test [Biokit, Llic ¸à d'Amunt, Spain], and Lyme Disease IgG/IgM ELISA kit [Diagnostic Automation]). The patient was not hospitalized, but she was treated with doxycycline for 14 days and recovered. A retrospective evaluation of this patient's history and her clinical summary resulted with the suspicion of a tick-borne relapsing fever (TBRF). Borrelia sp. was suspected as the causative agent because of the proximity to the U.S. border and that cases of borreliosis have been identified in regions neighboring the Mexican state of Sonora, specifically Arizona and Texas [1, 2, 3, 4]. Also, during her examination, the patient reported that she found an insect bite on her leg. She had no history of traveling outside of the state of Sonora before the symptoms presented. The tick vectors of Borrelia turicatae and B. mazzottii have been collected along the Texas-Mexico border and into northern Mexico [5, 6];

Magnusiomyces capitatus (also denominated “Geotrichum capitatum” and “the teleomorph stage of Saprochaete capitata”) mainly affects immunocompromised patients with hematological malignancies in rare cases of invasive fungal infections (IFIs). Few cases have been reported for pediatric patients with acute lymphoblastic leukemia (ALL), in part because conventional diagnostic methods do not consistently detect M. capitatus in infections. The current contribution describes a systemic infection in a 15-year-old female diagnosed with ALL. She arrived at the Children’s Hospital of Mexico City with a fever and neutropenia and developed symptoms of septic shock 4 days later. M. capitatus ENCB-HI-834, the causal agent, was isolated from the patient’s blood, urine, bile, and peritoneal fluid samples. It was identified with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and a phylogenetic reconstruction using internal transcribed spacer (ITS) and 28S ribosomal sequences. The phylogenetic sequence of M. capitatus ENCB-HI-834 clustered with other M. capitatus-type strains with a 100% identity. In vitro antifungal testing, conducted with the Sensititre YeastOne susceptibility system, found the following minimum inhibitory concentration (MIC) values (μg/mL): posaconazole 0.25, amphotericin B 1.0, fluconazole > 8.0, itraconazole 0.25, ketoconazole 0.5, 5-flucytosine ≤ 0.06, voriconazole 0.25, and caspofungin > 16.0. No clinical breakpoints have been defined for M. capitatus. This is the first clinical case reported in Mexico of an IFI caused by M. capitatus in a pediatric patient with ALL. It emphasizes the importance of close monitoring for a timely and accurate diagnosis of neutropenia-related IFIs to determine the proper treatment with antibiotics, antifungals, and chemotherapy for instance including children with ALL.

The isolation of tick-borne relapsing fever (TBRF) spirochetes has proven to be a useful tool to understand their distribution in geographic areas where the tick vectors inhabit. However, their isolation and culture are not easy and in general an animal model is needed to achieve this task. Here, argasid ticks were collected from a neighborhood in Ciudad Caucel, and they were identified as Ornithodoros (Alectorobius) puertoricensis. To determine whether these were infected with TBRF bacteria they were fed with healthy mice but only a low burden of spirochetes was observed. An immunosuppressed mouse model was used to feed the ticks suspected to be infected with spirochetes. After tick feeding, a higher number of bacteria was observed in blood samples, and spirochetes were successfully cultivated in Barbour-Stoenner-Kelly (BSK)-IIB media. Molecular analyses indicated that the isolate was Borrelia puertoricensis, while whole genome sequencing confirmed the finding. In summary, the present report shows that A. puertoricensis is present in Ciudad Caucel, an urban neighborhood in the outskirts of Merida city, and these ticks are infected with B. puertoricensis. Despite the fact that this species has not been directly associated with TBRF it represents a potential medical and veterinary health risk.