No abstract

As part of the basic characterization of Ornithobacterium rhinotracheale, the minimal inhibitory concentrations of 10 antimicrobial drugs were determined for reference strains and Mexican isolates by a broth microdilution method. For optimal growth of the organisms, a supplemented brain-heart infusion broth was used. The susceptibility of O. rhinotracheale to amoxicillin, enrofloxacin, and oxytetracycline was variable. However, consistent higher minimal inhibitory concentrations values were obtained for gentamicin, fosfomycin, trimethoprim, sulfamethazine, sulfamerazine, sulfaquinoxaline, and sulfachloropyridazine. Obtained results among Mexican isolates indicate a marked antimicrobial drug resistance trend.

Ten gram-negative, pleomorphic, rod-shaped isolates from coryza-like, respiratory diseased laying and broiler chickens were identified as Ornithobacterium rhinotracheale. All O. rhinotracheale isolates showed typical biochemical and enzymatic characteristics. Also, all isolates showed hemagglutinating activity with glutaraldehyde-fixed erythrocytes. On the basis of this property, a rabbit-raised antiserum was produced for an isolate. All isolates were identified by antiserum by hemagglutination-inhibition tests. No cross-reactions were observed when O. rhinotracheale isolates were tested with Haemophilus paragallinarum antisera, and vice versa. Mild respiratory signs, including mild nasal discharge, slight rales, and sneezing, were observed in challenged chickens. At postmortem examination, multifocal pneumonia, airsacculitis, and foamy exudate in abdominal cavity were observed. Furthermore, because bacterial adherence is regarded as an essential step in the infection process, in vitro adherence of O. rhinotracheale isolates to chicken tracheal epithelial cells was tested. All isolates showed positive adherence. Obtained results indicate that O. rhinotracheale is a pathogenic agent present in the Mexican poultry.

The enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) technique was used for fingerprinting of reference strains and Mexican isolates of Haemophilus paragallinarum. A total of nine ERIC patterns were given by the nine serovar reference strains of this bacteria. Two Modesto (C-2) reference strains from different sources showed the same ERIC pattern. Seventeen ERIC patterns were obtained among 29 Mexican isolates included in the study, belonging to serovars prevalent in Mexico (A-1, A-2, B-1, and C-2). Obtained results indicate that the ERIC-PCR technique could be used as a molecular laboratory tool for subtyping of H. paragallinarum.

A total of 42 isolates of Haemophilus paragallinarum from Mexico were serotyped by the Kume hemagglutinin scheme. Serovars A-1, A-2, B-1, and C-2 were recognized among 11 (26.2%), 7 (16.6%), 4 (9.5%), and 14 (33.3%) isolates, respectively. A further six isolates (14.3%) showed hemagglutinating activity but could not be classified into any serovar. Commercial vaccines containing Kume serovars A-1, A-2, B-1, and C-2 may provide better protection than those bi- or trivalent infectious coryza vaccines currently used in Mexico.

The virulence of the reference strains of the nine currently recognized Kume serovars of Haemophilus paragallinarum was investigated. The capacity of the H. paragallinarum strains to cause the typical clinical signs of upper respiratory tract disease associated with infectious coryza in unvaccinated, nasal-challenged chickens was assessed. Differences in virulence were assessed by means of a standardized scoring system for clinical signs. All nine strains were pathogenic to chickens, producing typical clinical signs of infectious coryza. The highest clinical signs score was obtained for serovar C-1 (1.72), while the lowest clinical signs score was obtained for serovar C-4 (0.32). Our results indicate that virulence differences exist among the serovars of H. paragallinarum.

The carbohydrate fermentation, antimicrobial drug resistance and serological properties of 40 isolates of Haemophilus paragallinaru m from outbreaks of infectious coryza in Mexico are described. Four biochemical biovariants and five antimicrobial drug resistance patterns were recognized. All isolates were serotyped by the Page scheme, with 21 isolates being assigned to serogroup A, five isolates to serogroup B and 14 isolates to serogroup C.

, an outbreak of bloody diarrhea occurred in the neonatal nursery ward of the Policlínico Neuquén, in Neuquén, a city in the southwestern region of Argentina. Seven patients of the intermediate care unit were affected. Isolates of Escherichia coli O18ac:H31 that were non-lactose and -sorbitol fermenting were recovered from outbreak cases. Although the strains were negative for a number of virulence factors typically found in diarrheagenic groups of E. coli, all isolates from the present neonatal outbreak possessed the enterohemolysin gene, ehl1. All isolates showed resistance to the antibiotics ampicillin and chloramphenicol. These isolates showed a low adherence property in HeLa cells without any recognizable pattern. In order to evaluate the outbreak dissemination in the neonatology ward, a prevalence study was conducted on 13 November. Stool specimens were obtained from 16 neonates hospitalized in the sector and from 33 medical staff members. E. coli isolates with identical biochemical characteristics of the outbreak strain were recovered from 11 of 16 inpatients and from 4 of 33 staff members during the prevalence study. A total of 15 E. coli strains recovered both from the outbreak and the prevalence study were processed by random amplified polymorphic DNA (RAPD)-PCR and pulsed-field gel electrophoresis (PFGE). By RAPD-PCR 14 of 15 strains showed patterns with 85 to 100% similarity, and by PFGE these strains were identical, each showing a unique pattern with 15 bands between 40 and 400 kb. One strain isolated from a nurse during the prevalence study presented a pattern not related to the others, and this was characterized as E. coli O81:HNM resistant to ampicillin only and negative for all the virulence factors studied. This outbreak occurred despite strict regulations in place to prevent cross-infection in the hospital. Postoutbreak prevalence studies were performed weekly thereafter without detecting new cases.