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Extended spectrum β lactamase-producing Klebsiella pneumoniae (ESBL-KP) is being reported with high morbidity and mortality rates and is considered as the highest priority for new antimicrobial strategies. To develop an alternative antimicrobial agent, phage KP1801 with broad lytic activity was isolated. The genome of phage KP1801 was double stranded DNA of 49,835 base pairs, with a GC content of 50.26%. There were 75 putative open reading frames. Phage KP1801 was classified as being in the order Caudovirales , belonging to the Siphoviridae family. About 323 proteins were detected by shotgun proteome analysis. The phage inhibited biofilm formation and reduced pre-formed biofilm in a dose dependent manner. Scanning electron microscopic studies demonstrated a membrane damage of bacterial cells treated with phage, resulting in cell death. Prophylactic and therapeutic efficacies of the phage were evaluated in Galleria mellonella . Administration of ESBL-KP infection with phage significantly improved the survival of G. mellonella . The number of intracellular bacteria in larvae showed a significant decrease compared with untreated control while the number of phage increased. These studies suggested that phage KP1801 has the potential for development as an alternative for antibiotics and biocontrol agents against ESBL-KP infection.

The virulence factors of Vibrio harveyi, the causative agent of luminous vibriosis, are not completely understood. We investigated the correlations between shrimp mortality, hemolysis, the presence of a hemolysin gene (vhh), and a gene involved in the type III secretion system (the Vibrio calcium response gene vcrD). V. harveyi HY01 was isolated from a shrimp that died from vibriosis, and 36 other V. harveyi isolates were obtained from fish and shellfish in Hat Yai city, Thailand. An ocean isolate of V. harveyi BAA-1116 was also included. Thirteen isolates including V. harveyi HY01 caused shrimp death 12 h after injection. Most V. harveyi isolates in this group (designated as Group A) caused hemolysis on prawn blood agar. None of the shrimp died after injection with V. harveyi BAA-1116. Molecular analysis of all V. harveyi isolates revealed the presence of vcrD in both pathogenic and non-pathogenic strains. Although vhh was detected in all V. harveyi isolates, some isolates did not cause hemolysis, indicating that vhh gene expression might be regulated. Analysis of the V. harveyi HY01 genome revealed a V. cholerae like-hemolysin gene, hlyA (designated as hhl). Specific primers designed for hhl detected this gene in 3 additional V. harveyi isolates but the presence of this gene was not correlated with pathogenicity. Random amplified polymorphic DNA (RAPD) analysis revealed a high degree of genetic diversity in all V. harveyi isolates, and there were no correlations among the hhl-positive isolates or the pathogenic strains.KEY WORDS: Vibrio harveyi · Type III secretion system · TTSS · vcrD · vhh · hhl · Random amplified polymorphic DNA analysis · RAPD Resale or republication not permitted without written consent of the publisherDis Aquat Org 86: [113][114][115][116][117][118][119][120][121][122] 2009 against sheep and fish erythrocytes compared with non-virulent isolates from sea water or diseased Talorchestia sp. (Liu et al. 1996). Investigations of the pathogenicity of V. harveyi isolates in fish (Atlantic salmon and rainbow trout) have demonstrated that both pathogenic and non-pathogenic V. harveyi isolates induced hemolysis against erythrocytes from sheep, rabbit, donkey, and horse, and the presence of the hemolysin gene vhh has been demonstrated in V. harveyi (Zhang & Austin 2000, Zhang et al. 2001). An investigation of the mortality of Artemia franciscana nauplii after inoculation with V. harveyi isolates from healthy and diseased penaeid shrimp from Asia and the Americas indicated that particular exoenzymes were associated with virulent strains (Soto-Rodriguez et al. 2003). No correlation between the hemolytic activity against sheep erythrocytes and the death of infected shrimps was detected (Soto-Rodriguez et al. 2003). Further research is needed to resolve these controversies between the pathogenicity of V. harveyi and its ability to cause hemolysis.Recent studies have shown that many bacteria use a cell-cell communication process known as quorum sensing to control cell population density and...

Infection by the pandemic clone of Vibrio parahaemolyticus is prevalent in southern Thailand. This study actively surveyed the incidence of V. parahaemolyticus infection in this area. A total of 865 isolates of V. parahaemolyticus was obtained from patients at Hat Yai Hospital, the main public hospital in Songkhla Province, Thailand, from 2000 to 2005. The isolates were examined by group-specific PCR (GS-PCR) specific for the pandemic clone, and for the presence of two major virulence genes, tdh and trh, and the O : K serotype. Representative isolates were also examined by antibiogram pattern and DNA fingerprinting using an arbitrarily primed PCR method to determine the clonal relationships between isolates. The total number of isolates was less in 2000 and more in 2004 and 2005 than in the years 2001–2003. The increase in the numbers of infections in 2004 and 2005 was not due to the emergence of a particular clone having unique characteristics, but was probably due to climate change. From 2000 to 2003, the percentages of pandemic strains of V. parahaemolyticus, defined as GS-PCR-positive tdh + trh −, was stable at 64.1, 67.5, 69.7 and 67.7 % of the total isolates each year, respectively. However, in 2004 and 2005, the percentages decreased to 56.1 and 55.5 %, respectively. The O : K serotypes of the pandemic isolates remained unchanged. The proportional decrease in infections caused by the pandemic strains are probably due to the population in this area gradually developing immunity to the pandemic clone whilst continuing to be susceptible to other strains.

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