- Volume 61, Issue 2, 2012

Clostridium difficile-associated disease (CDAD) is caused by a spore-forming bacterium and can result in highly variable disease, ranging from mild diarrhoea to severe clinical manifestations. Infections are most commonly seen in hospital settings and are often associated with on-going antibiotic therapy. Incidences of CDAD have shown a sustained increase worldwide over the last ten years and a hypervirulent C. difficile strain, PCR ribotype 027/REA type BI/North American pulsed-field (NAP) type 1 (027/BI/NAP-1), has caused outbreaks in North America and Europe. In contrast, only a few reports of cases in Latin America have been published and the hypervirulent strain 027/BI/NAP-1 has, so far, only been reported in Costa Rica. The potential worldwide spread of this infection calls for epidemiological studies to characterize currently circulating strains and also highlights the need for increased awareness and vigilance among healthcare professionals in currently unaffected areas, such as Latin America. This review attempts to summarize reports of C. difficile infection worldwide, especially in Latin America, and aims to provide an introduction to the problems associated with this pathogen for those countries that might face outbreaks of epidemic strains of C. difficile for the first time in the near future.

Expression of protease IV by Pseudomonas aeruginosa during ocular infections contributes significantly to tissue damage. However, several P. aeruginosa strains isolated from ocular infections or inflammatory events produce very low levels of protease IV. The aim of the present study was to characterize, genetically and phenotypically, the presence and expression of the protease IV gene in a group of clinical isolates that cause adverse ocular events of varying degrees, and to elucidate the possible control mechanisms of expression associated with this virulence factor. Protease IV gene sequences from seven clinical isolates of P. aeruginosa were determined and compared to P. aeruginosa strains PAO1 and PA103-29. Production and enzyme activity of protease IV were measured in test strains and compared to that of quorum-sensing gene (lasRI) mutants and the expression of other virulence factors. Protease IV gene sequence similarities between the isolates were 97.5–99.5 %. The strains were classified into two distinct phylogenetic groups that correlated with the presence of exo-enzymes from type three secretion systems (TTSS). Protease IV concentrations produced by PAOΔlasRI mutants and the two clinical isolates with a lasRI gene deficiency were restored to levels comparable to strain PAO1 following complementation of the quorum-sensing gene deficiencies. The protease IV gene is highly conserved in P. aeruginosa clinical isolates that cause a range of adverse ocular events. Observed variations within the gene sequence appear to correlate with presence of specific TTSS genes. Protease IV expression was shown to be regulated by the Las quorum-sensing system.

Risk factors for invasive infections by heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) may involve resistance to opsonophagocytosis and bacterial killing. hVISA strains typically have a thickened cell wall with altered peptidoglycan cross-linking. To determine whether hVISA may be endowed with an increased resistance to phagocytosis, this study assessed the characteristics of uptake and killing by granulocytes of three hVISA strains. All isolates were analysed by multilocus sequence typing and staphylococcal chromosome cassette mec typing. One of the strains belonged to the Hungarian meticillin-resistant S. aureus (MRSA) clone ST239-MRSA-III and the other two to the New York/Japan MRSA clone ST5-MRSA-II. In the presence of 10 % normal serum, the extent of phagocytosis and killing by blood granulocytes was equivalent for hVISA, MRSA and meticillin-sensitive S. aureus (MSSA) strains. Using granulocytes and serum from one patient who survived hVISA infection, the rate of phagocytosis and killing was also found to be comparable to that by control cells in the presence of 10 % serum. However, phagocytosis and killing of hVISA and MRSA (ATCC 25923) strains by normal granulocytes was markedly decreased in the presence of low concentrations (1 and 2.5 %) of serum from the patient who survived hVISA infection compared with that found with normal human serum. These data suggest that hVISA and MRSA isolates may be more resistant to opsonophagocytosis and bacterial killing than MSSA isolates, at least in some cases.

Anaplasma phagocytophilum is an emerging tick-borne pathogen that infects humans, domestic animals and wildlife throughout the Holarctic. In the far-western United States, multiple rodent species have been implicated as natural reservoirs for A. phagocytophilum. However, the presence of multiple A. phagocytophilum strains has made it difficult to determine which reservoir hosts pose the greatest risk to humans and domestic animals. Here we characterized three genetic markers (23S–5S rRNA intergenic spacer, ank and groESL) from 73 real-time TaqMan PCR-positive A. phagocytophilum strains infecting multiple rodent and reptile species, as well as a dog and a horse, from California. Bayesian and maximum-likelihood phylogenetic analyses of all three genetic markers consistently identified two major clades, one of which consisted of A. phagocytophilum strains infecting woodrats and the other consisting of strains infecting sciurids (chipmunks and squirrels) as well as the dog and horse strains. In addition, analysis of the 23S–5S rRNA spacer region identified two unique and highly dissimilar clades of A. phagocytophilum strains infecting several lizard species. Our findings indicate that multiple unique strains of A. phagocytophilum with distinct host tropisms exist in California. Future epidemiological studies evaluating human and domestic animal risk should incorporate these distinctions.

Data correlating β-lactamases found in commensal Escherichia coli of human and animal origin are limited. In this study, 447 commensal E. coli isolates from the faeces of humans and swine (280 human isolates from four hospitals and 167 swine isolates from seven farms) were collected between September 2006 and January 2009 in western China. For extended-spectrum β-lactamase (ESBL)-producing and other cephalosporin-resistant isolates, the relevant β-lactamase genes (bla TEM, bla SHV, bla CTX-M-1/2/9 group, bla CMY-2 and bla KPC) were detected by PCR analysis. Of the 447 isolates tested, 120 (26.8 %) were confirmed as producing ESBL. Among these, 70 and 40 human isolates carried a member of the bla CTX-M-1 group (13 bla CTX-M-3, 21 bla CTX-M-15, four bla CTX-M-22, eight bla CTX-M-28, four bla CTX-M-36, 15 bla CTX-M-55 and five bla CTX-M-69) or bla SHV (14 bla SHV-2, seven bla SHV-5, ten bla SHV-12, five bla SHV-57 and four bla SHV-97),respectively, whilst six and four swine isolates carried a member of the bla CTX-M-1 group (one bla CTX-M-15 and five bla CTX-M-22) or bla SHV (three bla SHV-2 and one bla SHV-12), respectively. Furthermore, 59 human and swine isolates and seven human isolates carried bla CMY-2 and bla KPC, respectively. These findings indicate that the bla CTX-M-1 group, including the novel variant bla CTX-M-69, and bla SHV are the predominant ESBL genes in both humans and swine in western China, and bla CMY-2 is also common in both groups. The carriage rates of broad-spectrum β-lactamases among commensal E. coli was much lower in swine than in humans, suggesting that β-lactamase genes have not established themselves in animal ecosystems in western China.

Feral pigeons (Columba livia) are commonly infected with Chlamydia psittaci, the agent of psittacosis in humans. To assess the risk of zoonosis posed by feral pigeons in the urban environment, we determined the prevalence of Chlamydia psittaci by detection of the outer-membrane protein A (ompA) gene of this pathogen in pharyngeal and cloacal samples of 202 feral pigeons present in a loft in Basel, Switzerland. Additionally, we examined 620 fresh faecal droppings of feral pigeons at six public sites in Basel. The ompA gene of C. psittaci could be detected in only 17 (8.4 %) of the 202 feral pigeons in the loft. C. psittaci DNA was present in nine (2.0 %) of 447 of the pharyngeal swabs and 11 (3.2 %) of the 348 cloacal swabs. Genotyping of the ompA gene revealed genotype B in seven of the birds. In one bird, a mixed infection was detected with the genotypes A, B and E/B, which, to our knowledge is the first time such an infection has been reported. Some of these birds immigrated into the loft as adults. To our knowledge, this is the first study to document how the interconnectedness between feral pigeon subpopulations favours the spread of C. psittaci. C. psittaci DNA was not detected in any of the faecal droppings collected at the six public areas. In spite of the low levels of C. psittaci shedding by feral pigeons in Basel, close contact to feral pigeons bears the risk of zoonotic transmission of C. psittaci. Feral pigeon management programmes and public education should be implemented to reduce the risk of a pigeon-to-human transmission of such pathogenic agents.

Diphtheria-like human illness caused by Corynebacterium ulcerans is an emerging threat in developed countries, with incidence sometimes higher than that of diphtheria caused by Corynebacterium diphtheriae. Companion animals are considered a potential source of human infections. In order to determine the prevalence of C. ulcerans among dogs, we performed a screening for the bacterium in 583 dogs in the custody of the Osaka Prefectural government. Forty-four dogs (7.5 %) were positive for the bacterium, although they did not show any clinical symptoms. All bacterial isolates showed resistance or decreased sensitivity to clindamycin, and some showed decreased sensitivity to levofloxacin. Comparative analysis of isolates using PFGE, toxin gene typing and antibiotic sensitivities suggests that transmission between asymptomatic dogs might have occurred.

The aim of this study was evaluate changes in the cholinesterase activity in blood, lymphocytes and serum of rats infected with Leptospira interrogans serovar Icterohaemorrhagiae (‘L. icterohaemorrhagiae’). Sixty adult Wistar rats were divided into six groups of 10 animals: three control groups and three test groups. The animals from the test groups were intraperitoneally inoculated with 1 ml medium containing 1×108 leptospires. The activity of acetylcholinesterase in blood and butyrylcholinesterase in serum increased on days 5 (P<0.05) and 30 (P<0.021) post-infection, respectively. A decrease in lymphocyte count was observed on days 15 (P<0.01) and 30 post-infection (P<0.05). On day 15 post-infection, acetylcholinesterase activity (P<0.001) in lymphocytes decreased in infected rats. However, on day 30 post-infection there was an increase in acetylcholinesterase activity in lymphocytes. In conclusion, our results showed that the activity of enzymes of the cholinergic system in the total blood, lymphocytes and serum is altered as a result of inflammation caused by infection with L. icterohaemorrhagiae. The possible causes of these alterations will be discussed in this paper.

Oral candidiasis caused by Candida albicans is recognized as one of the most frequent opportunistic infections in human immunodeficiency virus (HIV)-infected individuals. The overall severity and chronicity of oral candidiasis has been attributed exclusively to the HIV-induced immune deficiency of the affected individuals but not to the virulence factors of the pathogen, i.e. C. albicans. However, genotypic and phenotypic studies have suggested that HIV infection might be associated with preferential selection of C. albicans strains with altered virulence determinants, leading to colonization with Candida populations that are better able to cause disease in these immunologically compromised hosts. If this process of selection is indeed related to pathogenicity, it may be possible to measure alterations in different virulence factors produced by C. albicans in HIV-infected patients. To evaluate this hypothesis, the present work was undertaken to determine simultaneously the expression of five virulence factors in oral C. albicans isolates colonizing and infecting HIV-positive and -negative individuals. The significance of genotypes in the pathogenesis of oral candidiasis was also elucidated. Oral swabs were collected from 335 consecutive individuals (210 HIV-positive and 125 HIV-negative). Virulence factors and genotypes were determined for all the C. albicans strains isolated. The results showed significantly increased expression of proteinase, phospholipase and haemolytic activities, as well as a greater ability to adhere, in isolates from HIV-positive compared with HIV-negative individuals (P<0.05). However, no significant differences in virulence factor expression in isolates colonizing or infecting HIV-positive individuals were seen. Genotype A was the predominant type (71.3 %); however, a relationship could not be established between the genotypes and the virulence factors, or with clinical infection. These data support the concept of preferential C. albicans strain selection with altered virulence determinants in HIV-infected individuals and emphasize the need for further molecular genetic linkage studies that could be helpful in dissecting the molecular causes of preferential strain selection, which may lead to new approaches for therapeutic intervention.

We present an unusual case of a patient with scrub typhus who developed acalculous cholecystitis, aseptic meningitis and mononeuritis multiplex. The patient was successfully treated with oral minocycline. To our knowledge, this is the first report of mononeuritis multiplex caused by scrub typhus.