Análisis de susceptibilidad antimicrobiana y hallazgos microbiológicos: perfil en cirugía abdominal de urgencia / Microbiological findings and antimicrobial susceptibility analysis: emergency general abdominal surgery profile

Resumen Introducción La resistencia a antibióticos es un problema mundial. En los pacientes que requieren cirugía de urgencia, los antibióticos son un apoyo importante concomitante al acto quirúrgico. Objetivo Analizar los cultivos de líquido peritoneal obtenidos de pacientes operados por patología quirúrgica abdominal de urgencia. Materiales y Métodos Se realiza una cohorte prospectiva de los pacientes operados de urgencia. Se tomó cultivo de líquido peritoneal y se procesó según técnica estandarizada. Resultados Se encontró un 39,4% de cultivos positivos. E. coli fue el germen más frecuente. Destacan 5 cultivos positivos para P. aeruginosa. Existe un 25% de resistencia a ampicilina/sulbactam y 19% a quinolonas para E. coli. Conclusión La resistencia encontrada fue menor a lo reportado en la literatura, pero aún destacable. El conocimiento del perfil de bacterias y sus resistencias a antimicrobianos son importantes para las políticas hospitalarias locales de uso racional de antibióticos.

Background Antimicrobial resistance is a worldwide problem. In patients requiring emergency surgery, antibiotics are an important assistance additional to surgical intervention. Objective Analize peritoneal fluid cultures obtaines from patients who underwent emergency surgery. Methods A prospective cohort of emergency abdominal surgical patients were enrolled. Peritoneal fluid cultures were taken and processed according to standarized technique. Results A 39.4% of positive cultures was found. E. coli was the most common bacteria identified. Five positive cultures for P. aeruginosa stand out. E. coli had 25% resistance to ampicillin/sulbactam and 19% for quinolones. Conclusion Resistance found was lower than international reports, but still noteworthy. Knowledge of local bacteria profile and antimicrobial resistance is important for local antibiotic hospital policy.

Spontaneous Bacterial Peritonitis with Sepsis Caused by Enterococcus hirae

Selective intestinal decontamination (SID) with norfloxacin has been widely used for the prophylaxis of spontaneous bacterial peritonitis (SBP) because of a high recurrence rate and preventive effect of SID for SBP. However, it does select resistant gut flora and may lead to SBP caused by unusual pathogens such as quinolone-resistant gram-negative bacilli or gram-positive cocci. Enterococcus hirae is known to cause infections mainly in animals, but is rarely encountered in humans. We report the first case of SBP by E. hirae in a cirrhotic patient who have previously received an oral administration of norfloxacin against SBP caused by Klebsiella pneumoniae and presented in septic shock.

Characteristics of ascitic fluid from patients with suspected spontaneous bacterial peritonitis in emergency units at a tertiary hospital / Características do líquido ascítico de pacientes com suspeita de peritonite bacteriana espontânea nas unidades de emergência de um hospital terciário

CONTEXT AND OBJECTIVE: Spontaneous bacterial peritonitis (SBP) is a complication of ascites, especially in cirrhosis. Ascitic fluid with 250 or more neutrophils/mm³ is an acceptable criterion for diagnosis, even when bacterial fluid cultures are negative. The aims here were to estimate SBP frequency among emergency room patients based on cellular criteria and evaluate the biochemical profile of these fluids. DESIGN AND SETTING: Retrospective study at a public tertiary hospital. METHODS: Laboratory records of patients with ascites attended in emergency rooms between November 2001 and November 2006, from whom ascitic fluid samples were sent to the laboratory due to suspected SBP, were evaluated. The 691 samples included were divided into group A (presumed SBP: > 250 neutrophils/mm³; n = 219; 31.7 percent) and group B (no presumed SBP: < 250 neutrophils/mm3; n = 472; 68.3 percent). Patients' sex and age; ascitic fluid characteristics (numbers of neutrophils, leukocytes and nucleated cells); bacteriological characteristics; and protein, lactate dehydrogenase, adenosine deaminase and glucose concentrations were evaluated. RESULTS: Among group A cultured samples, 63 (33.8 percent) had positive bacterial cultures with growth of pathogens commonly associated with SBP. In total, the group A samples showed higher lactate dehydrogenase levels than seen in the group B samples. The latter presented predominance of lymphocytes and macrophages. CONCLUSION: Among the ascitic fluid samples with clinically suspected SBP, 31.7 percent fulfilled the cellular diagnostic criteria. Positive bacterial isolation was found in 33.8 percent of the cultured samples from the presumed SBP group.

CONTEXTO E OBJETIVO: Peritonite bacteriana espontânea (PBE) é uma complicação da ascite, especialmente na cirrose. Líquido ascítico com 250 ou mais neutrófilos/mm³ é um critério aceitável para o diagnóstico, mesmo com cultura bacteriana negativa. Os objetivos foram estimar a frequência de PBE em pacientes atendidos na sala de emergência, baseando-se no critério celular e avaliar o perfil bioquímico desses líquidos peritoneais. TIPO DE ESTUDO E LOCAL: Estudo retrospectivo em hospital público terciário. MÉTODOS: Foram avaliados registros laboratoriais de pacientes com ascite atendidos no setor de emergência entre novembro de 2001 e novembro de 2006, cujas amostras de líquido ascítico foram encaminhadas ao laboratório por suspeita de PBE. As 691 amostras incluídas foram divididas em grupo A (PBE presumida: > 250 neutrófilos/mm³; n = 219; 31.7 por cento) e grupo B (Ausência de PBE presumida: < 250 neutrófilos/mm3; n = 472; 68.3 por cento). Também foram avaliados sexo e idade dos pacientes além de características dos líquidos ascíticos: número de neutrófilos, leucócitos e células nucleadas; bacteriologia; e concentrações de proteínas, desidrogenase láctica, adenosina deaminase e glicose. RESULTADOS: Das amostras cultivadas do grupo A, 63 (33,8 por cento) tiveram cultura bacteriana positiva com crescimento de patógenos comumente associados à PBE. O total de amostras do grupo A exibiu maiores níveis de desidrogenase lática que as do grupo B. Este último demonstrou predomínio de linfócitos e macrófagos. CONCLUSÃO: Dos líquidos ascíticos com suspeita clínica de PBE, 31.7 por cento preencheram o critério diagnóstico celular. O isolamento bacteriano foi positivo em 33.8 por cento das amostras cultivadas no grupo PBE presumida.

Cirrosis hepática: medidas preventivas de algunas de sus complicaciones / Liver cirrhosis: some complications preventive measures

Cirrosis hepática es una enfermedad prevalente en el mundo. Su diagnóstico y tratamiento debe ser dominio de todo médico general e internista. En los últimos años han ocurrido notables avances en el diagnóstico, fisiopatología, tratamiento y en la identificación de factores pronósticos de cirrosis y de sus complicaciones mayores. Particular atención ha existido en desarrollar medidas preventivas de sus complicaciones como por ejemplo: hemorragia por várices esofágicas, peritonitis bacteriana espontánea, síndrome hepatorrenal. Estas medidas preventivas han influido de forma muy favorable en el pronóstico de los pacientes cirróticos. En este artículo se discuten las diversas estrategias preventivas que han demostrado su efectividad en cirrosis hepática

Liver cirrhosis is a prevalent disease around the world. Its diagnosis and treatment must be in the knowledge of every general physicians and internist.Over the last years, there have been notorious advances in the diagnosis, pathophysiology, treatment and the identification of prognosis factors for cirrhosis major complications.There has been particular attention to the development of preventive measures for its complications, such as variceal bleeding, spontaneous bacterial peritonitis, hepatorenal syndrome. These preventive measures have had a favorable influence on the prognosis of cirrhotic patients. This article discusses several preventive strategies that have proven its effectiveness in hepatic cirrhosis

Fisiopatología de la peritonitis bacteriana espontánea / Physiopathology of spontaneous bacterial peritonitis

La peritonitis bacteriana espontánea es la infección más característica del cirrótico, asociándose a un mal pronóstico a corto y mediano plazo. El presente artículo pretende revisar los mecanismos fisiopatológicos más importantes en su génesis, con especial énfasis en aquellos que favorecen la translocación bacteriana (sobrecrecimiento bacteriano y pérdida de barrera intestinal). Igualmente se analizan los eventos involucrados en el agravamiento del paciente con peritonitis bacteriana en curso, y las medidas profilácticas y terapéuticas que se derivan del conocimiento de los mecanismos fisiopatológicos.

The spontaneous bacterial peritonitis is the most typical infection in cirrhotic patients being associated with a bad short and long-term prognosis. The present article tries to review the most important pathophysiological mechanisms in their genesis, with special emphasis on those that favor bacterial translocation (intestinal bacterial overgrowth and loss of intestinal barrier). Equally, this article analyzes events that are involved in the worsening of the patient with bacterial peritonitis in course, and the prophylactic and therapeutic measures resulting from the knowledge of the pathophysiological mechanisms.

Infección del líquido pleural y ascítico por Listeria monocytogenes: caso clínico / Pleural and ascitic fluid infection by Listeria monocytogenes: report of one case

Ascitic and pleural fluids infection by Listeria monocytogenes is uncommon. The association of spontaneous bacterial peritonitis and empyema caused by this microorganism has been seldom reported. A 61 year-old male with an alcoholic cirrhosis and an upper right ¡obectomy for a lung cáncer, consulted because of an exacerbation of dyspnea, abdominal pain and fever. Listeria monocytogenes was isolated from ascitic and pleural fluids and from blood cultures. He was successfully treated with ampicillin and a chest tube for drainage.

Successful management of chylous ascites using omental patch

To assess possible factors that may play a role in the etiology of chylous ascites formation, to determine the management of each type according to its causation, and to compare between the results of conservative and operative management. This is a prospective study conducted from 1990 to 2004 in the surgical department of Erbil, Iraq. A group of 46 patients with chylous ascites were subdivided into five subgroups according to the etiological factors. The initial assessment included: age, sex, history of trauma and previous surgery, time between the trauma, if it was present, and the appearance of chylous ascites, and aspiration of ascetic fluid for chemical and bacteriological analysis. Further assessment included the use of ultrasonography, computerized axial tomography, and Magnetic resonance imaging [MRI]. There were 12 female and 34 male patients. Their ages ranged form one year to 63 years [mean age 37 years]. There was abdominal distention resulting from the accumulation of chyle in the peritoneal cavity in all five subgroups of patients. A definitive diagnosis was made by paracentesis and laparotomy. Thirty-eight patients [82.6%] underwent explorative laparotomy. The surgical success rate for trauma patients was about 93.7%, while it was very poor for malignant cases. The surgical technique in this study with the best results was overswing with omental patch. The results indicate that patients with chylous ascites caused by trauma to the abdomen who undergo surgery may have a success rate up to about 93.7% using omental patches, especially if preoperative resuscitation is done. The outcome of patients with malignant chylous ascites, however, was very poor. Conservative treatment was not satisfactory in any of these cases

Spontaneous empyema in cases with cirrhosis

Spontaneous bacterial empyema is an infection of a preexisting hydrothorax in a cirrhotic patient that cannot be attributed to chest condition. It is associated with a bad prognosis and mortality rate may reach over 20%. Infection is usually by enteric bacteria which reach pleural cavity by hematogenous spread; though transfer through bowel wall can occur. The aim of the present work is to study spontaneous bacterial empyema in cirrhotic patients with hepatic hydrothorax and its relation to ascetic fluid. The present study was performed on 40 patients with hepatic hydrothorax from Tropical Medicine Dept. Tanta University. All patients were subjected to full history taking, thorough clinical examination, routine laboratory investigations, abdominal US. Tuberculin testing and ZN examination of sputum were done to exclude TB. Examination of pleural fluid of all cases was done including Adenosine Deaminase [ADA] and LDH. Pleural fluid was examined bacteriologically for Gram stain and Ziehl Neelsen staining. Cultures were done using the conventional method and modified method. According to these data, cases were further divided into two groups: group I: thirteen patients [13] with cirrhosis, hepatic hydrothorax with Spontaneous bacterial empyema. Group II: Twenty seven patients [27] with cirrhosis and hepatic hydrothorax. Ascitic fluid analysis macroscopically, biochemically and bacteriologically was done for all cases. There were no significant differences as regards child score, hemoglobin, white cell count, Serum bilirubin and transaminases, but there was a significant deterioration of renal function in group I compared to group II. Comparison of pleural and ascitic fluid in the two groups proved significant differences as regards total leucocytes, PMN, LDH and pH in group I compared to group II. Main bacterial pathogen in pleural fluid was E. coli followed by Pseudomonas aeroginosa. Culture was negative in 46.2% of ascitic fluid and 30.7% in pleural fluid. Spontaneous bacterial empyema is a relatively common complication of cirrhotic patients with hydrothorax. Diagnostic thoracocentesis is mandatory in cases with hepatic hydrothorax regardless the presence or absence of ascites. E. coli is the most common pathogen, and hematogenous spread may play a main role. Modified method of culture is the method of choice to increase sensitivity

Inflammatory mediators in plasma and peritoneal fluid in cirrhotic patients with spontaneous bacterial peritonitis

Spontaneous bacterial peritonitis [SBP] in cirrhotic patients is associated with an increased production and decreased metabolism of inflammatory mediators [cytokines] such as tumour necrosis factor a [TNF-alpha], interleukin 6 [IL-6] and interleukin 1-beta [IL-l beta]. The present study was designed to investigate the relationship between the development of SBP and the degree of inflammatory response in patients with liver cirrhosis and to assess the diagnostic value of the inflammatory mediators in cirrhotic patients with SBP. This study was carried out on 46 cirrhotic patients with SBP, 22 cirrhotic patients with ascites but without evidence of SBP, and 12 healthy subjects as a control group. All patients were subjected for history taking, clinical examination and abdominal ultrasound. Blood samples were collected for complete blood count [CBC], liver function tests and measurement of TNF-alpha, IL- l beta, and IL-6 levels [in patients and control]. Ascitic fluid samples were collected for measurement of TNF-alpha, IL- l beta, and IL-6 and for aerobic and anaerobic cultures [only in patients with SBP]. Cirrhotic patients with SBP showed significantly higher plasma and ascitic fluid levels of TNF-alpha, IL- l beta and IL-6 than cirrhotic patients without SBP [despite that severity of liver disease was similar in the two groups] and normal control subjects [p<0.001]. Ascitic fluid TNF-alpha, IL- l beta and IL-6 were also higher in the cirrhotic patients with SBP than in plasma, [p<0.001 for each]. Also the plasma levels of TNF-alpha, IL- l beta and IL-6 in cirrhotic patients with SBP were significantly higher than in healthy control subjects [p<0.001]. There was a strong direct correlation between plasma and ascitic fluid levels of TNF-alpha, [r=0.9624, p<0.001] IL-l beta [r=0.4024, p<0.01], and IL-6 [r=0.2890, p<0.05] at the time of diagnosis of SBP. A significant correlation was also observed between TNF-alpha, IL- l beta, and IL-6 in ascitic fluid [r=1.0000, p<0.001] and in plasma [r=0.8500, p<0.001]. PMN cell count in ascites correlated significantly with the ascitic fluid level of IL- l beta [r=0.3156, p<0.05], but did not correlate with both TNF-alpha [r-0.0953, p>0.05] and IL-6 [r=0.0702, p>0.05]. Patients with culture-positive SBP showed significantly higher plasma and ascitic fluid levels of TNF-alpha, IL- l beta, and IL-6 than patients with culture-negative SBP. The PMN cell count in the ascitic fluid was also significantly higher in the culture-positive vs culture-negative SBP patients [6.813 +/- 0.24 vs 1.36110.07, p<0.001]. Cirrhotic patients with SBP display a marked increase of TNF-alpha, IL- l beta, and IL-6 levels in ascitic fluid and plasma. Specificity and sensitivity of these cytokines detection of SBP in cirrhotic patients strongly favor its measurement during acute phase of the disease

Sepsis and Meningitis due to Listeria Monocytogenes

PURPOSE: This study focused on the effect of immuno-compromising conditions on the clinical presentation of severe listerial infection. PATIENTS AND METHODS: Nine human listeriosis cases seen from 1991-2002 were reviewed. All adult patients, from whose blood, peritoneal fluid or cerebrospinal fluid (CSF) the L. monocytogenes was isolated, were included in this retrospective study. RESULTS: Listeriosis presented as primary sepsis with positive blood cultures in 5 cases and meningitis with positive CSF cultures in 4 cases. All of these patients had at least one underlying disease, most commonly, hematologic malignancy, diabetes mellitus, amyloidosis and hepatic cirrhosis; 55.6% had received immunosuppressive or corticosteroid therapy within a week before the onset of listeriosis. The patients were adults with a mean age of 60 years. Fever, night sweats, chills and lethargy were the most common symptoms; high temperature (> 38 degrees C), tachycardia, meningeal signs and poor conditions in general were the most common findings on admission. The mortality rate was 33.3% and was strictly associated with the severity of the underlying disease. Mortality differences were significant between sepsis (20%) and meningitis (50%) patients. CONCLUSION: Listeriosis as an uncommon infection in our region and that immuno- suppressive therapy is an important pre-disposing factor of listeriosis. Sepsis and meningitis were more common in this group of patients and had the highest case-fatality rate for food-borne illnesses.

Detection of M. tuberculosis in clinical samples of diversified nature by IS6110 based PCR.

Performance of the polymerase chain reaction technique based on IS6110 sequence was evaluated in clinical samples obtained from pulmonary and extrapulmonary cases of tuberculosis. One hundred and seventy two samples were processed for detection of M. tuberculosis by ZN stained smear examination, LJ medium culture, BACTEC radiometric culture and PCR tests amplifying 123bp region of IS6110 sequence. A significant difference was seen in the sensitivities of different tests, the figures being 83% for PCR test, 35.2% for smear examination, 47.16% for LJ culture and 53.45% for BACTEC culture (p < 0.05). However, no significant difference was found as far as specificity was concerned. PCR test sensitivity in. pulmonary and extrapulmonary clinical samples were 90.14% and 77.27% respectively and found to be significantly higher (p < 0.05) when compared with those of other tests. The mean detection time for M. tuberculosis was 24.03 days by LJ medium culture, 12.89 days by BACTEC culture and less than one day by PCR test. PCR based on IS6100 sequence is highly sensitive method for the early diagnosis of pulmonary and extrapulmonary tuberculosis.

Listeria monocytogenes peritonitis in cirrhotic patients: first description in Brazil / Peritonite bacteriana espontânea causada por Listeria monocytogenes em pacientes com cirrose: primeiro relato de caso no Brasil

Two cases of spontaneous bacterial peritonitis (SBP) caused by Listeria monocytogenes in cirrhotic patients are reported. In one of the cases, the microorganism was isolated from pleural effusion and ascites. SBP is a serious and common complication of patients with ascites caused by hepatic cirrhosis and the culture of the ascitic fluid is an important tool for the diagnosis and for the more appropriate treatment. Although a third generation cephalosporin has usually been employed for empiric treatment of SBP, it does not provide adequate coverage against Listeria spp. In such cases the use of ampicillin (with or without sulbactam) or sulfamethoxazole-trimethoprim is recommended. The last one is used for secondary prophylaxis, instead of norfloxacin. To summarize, Listeria monocytogenes infection is a rare cause of SBP, whose treatment should be specific for the bacteria.

Foram relatados dois casos de peritonite bacteriana espontânea (PBE) por Listeria monocytogenes em pacientes com cirrose. Em um dos casos isolamos também o agente no líquido pleural. A PBE é uma complicação comum e grave de pacientes com ascite por cirrose e a cultura do líquido ascítico é de grande importância para o diagnóstico e para o tratamento mais adequado. Embora uma cefalosporina de terceira geração seja geralmente utilizada para o tratamento empírico da PBE, ela não oferece cobertura adequada contra a Listeria spp. Nesses casos, recomenda-se o uso de ampicilina (com ou sem sulbactam) ou sulfametoxazol-trimetoprim. Para a profilaxia secundária indica-se o uso deste último, ao invés da norfloxacina. Em resumo, a infecção por Listeria monocytogenes é uma causa rara de PBE e o tratamento específico deve ser administrado.

Peritonitis bacteriana espontánea por Listeria monocytogenes, en un paciente con cirrosis hepática: Caso clínico / Spontaneous bacterial peritonitis caused by Listeria in a patient with cirrhosis: Case report

Infections caused by Listeria monocytogenes are usually found in cattle and occasionally appear in humans, particularly pregnant women and immunocompromised individuals. Peritonitis by Listeria monocytogenes is a rare but dangerous condition that must be recognized early, since it requires a specific treatment. We report a 31 year-old male with alcoholic cirrhosis that developed ascites with abdominal pain and fever. The peritoneal fluid culture yielded Listeria monocytogenes. The patients was initially treated with cefotaxim and later with ampicillin and levofloxacin. The patient voluntarily abandoned treatment and died at home two weeks later.

Spontaneous bacterial peritonitis in isolated splenic vein thrombosis with portal hypertension.

Spontaneous bacterial peritonitis (SBP) is a known complication of ascites due to cirrhosis; it has also been reported in some non-cirrhotic conditions with ascites. We report a 50-year-old lady with isolated splenic vein thrombosis who developed SBP due to E. coli .

Bacterial isolation with on-site inoculation of ascites fluid into hemoculture bottle in spontaneous bacterial peritonitis.

OBJECTIVE: To compare the on-site bacterial inoculation of ascites fluid into hemoculture bottle with routine method in the patients who were preliminary diagnosed of SBP. MATERIAL AND METHOD: A retrospective analysis of case records during January-December 2001. RESULTS: A total of 673 specimens from 325 patients were retrieved from the data records at the Department of Microbiology, Siriraj Hospital in 2001. The neutrocytic ascites were found in 163 specimens (94 patients). The routine method and on-site inoculation into the hemoculture bottle were employed in 107 and 56 specimens respectively. Culture-positive neutrocytic ascites was found in the routine method 16 (14.9%) specimens and in the on-site inoculation 26 (46.4%) specimens (p < 0.0001). Among these samples, the two methods were simultaneously performed in 42 specimens of which 18 paired specimens were eligible for analysis. Positive culture was found in 2 samples in which the routine method and in an additional 5 samples in which on-site inoculation into hemoculture bottle method. Using Kappa analysis (e score = 0.328, 95% CI = -0.172 to 0.829) that can be interpreted the on-site inoculation method had a higher yield than the routine technique. Moreover, 21 cases also had their blood and ascites samples simultaneously collected and cultured. 4 of ten (19%) and 5 of eleven (23.8%) cases were found in the routine and on-site and direct inoculation groups respectively. These finding suggested that the severity of infection in among two groups were similar and unlikely to be the cause of the difference of the positive isolation rate in both groups. CONCLUSION: The on-site and direct inoculation of ascites into hemoculture bottle method had a significantly higher isolation rate than routine method (i.e. 46.4% versus 14.9% p < 0.0001) either with separated or paired samples of ascites.

Coloración de Gram de muestras tomadas por punción: ¿sigue siendo útil? / Gram's stain in needle aspiration specimens. is it yet useful?

Para contribuir a aclarar la frecuente discusión con respecto a la utilidad de la coloración de Gram en el diagnóstico preliminar de un proceso infeccioso, se determinó su utilidad, estudiando 455 muestras tomadas por punción. Se efectuó coloración de Gram, examen microscópico en fresco y cultivo semicuantitativo de 287 muestras provenientes de piel y partes blandas: (celulitis y pie diabético, líquidos abdominales, líquidos sinoviales, heridas quirúrgicas y bilis) y de 168 sitios estériles (LCR, líquido pleural, líquidos ascíticos). La sensibilidad (S), especificidad (E), valor predictivo positivo (VPP) y valor predictivo negativo (VPN) fueron: 43,1 por ciento, 97,2 por ciento, 90,4 por ciento y 73,6 por ciento respectivamente para el primer grupo y de 45,5 por ciento, 99,4 por ciento, 83,3 por ciento y 96,3 por ciento respectivamente para el segundo. En las muestras en las que no se observaron microorganismos en la coloración de Gram, en su mayoría se obtuvo desarrollo sólo en medio líquido. Al considerar estos aislamientos como no significativos, la sensibilidad de la coloración de Gram aumentó a 51,7 por ciento para el primer grupo y 66,7 por ciento para el segundo. El grado de concordancia entre la observación de microorganismos en la coloración de Gram y el cultivo fue del 92,2 por ciento. A pesar de su baja S, por su aceptable E, VPP y VPN, bajo costo y rapidez, la coloración de Gram de muestras tomadas por punción constituye un importante aporte para predecir infección y orientar a un adecuado y temprano tratamiento antimicrobiano

Virulence of Malaysian isolates of Orientia tsutsugamushi in mice.

The pathogenicity of Malaysian isolates of Orientia tsutsugamushi was investigated by a mouse virulence assay. The isolates could be differentiated as low (4 isolates), moderately (3 isolates) and highly virulent (2 isolates) based on the different responses in infected mice. No direct correlation between severity of human scrub typhus infections and virulence of the O. tsutsugamushi in mice was observed. Mice infected with virulent strains of O. tsutsugamushi showed splenomegaly, ascitis accumulation and enlargement of kidneys and livers whereas avirulent O. tsutsugamushi strains were asymptomatic and exhibited ruffled fur for a short period after infection. There was low antibody response in mice infected with isolates of low pathogenicity as compared with those of highly virulent isolates. Upon dissection of the infected mice, enlargement of mouse organs such as spleen, kidney and liver was noted. Presence of rickettsemia in mice was confirmed by the growth of O. tsutsugamushi in the L929 cells when inoculated with blood from infected mice. O. tsutsugamushi was also cultured from the peritoneal exudates of the infected mice. However, DNA of O. tsutsugamushi was only detected in the peritoneal exudates (by PCR) and blood (by cell culture) and not from other tissue samples.