The interaction of mycoplasmas and influenza viruses in tracheal organ cultures

Influenza A in Bovine Species: A Narrative Literature Review

It is quite intriguing that bovines were largely unaffected by influenza A, even though most of the domesticated and wild animals/birds at the human-animal interface succumbed to infection over the past few decades. Influenza A occurs on a very infrequent basis in bovine species and hence bovines were not considered to be susceptible hosts for influenza until the emergence of influenza D. This review describes a multifaceted chronological review of literature on influenza in cattle which comprises mainly of the natural infections/outbreaks, experimental studies, and pathological and seroepidemiological aspects of influenza A that have occurred in the past. The review also sheds light on the bovine models used in vitro and in vivo for influenza-related studies over recent years. Despite a few natural cases in the mid-twentieth century and seroprevalence of human, swine, and avian influenza viruses in bovines, the evolution and host adaptation of influenza A virus (IAV) in this species suffered a serious hindrance until the novel influenza D virus (IDV) emerged recently in cattle across the world. Supposedly, certain bovine host factors, particularly some serum components and secretory proteins, were reported to have anti-influenza properties, which could be an attributing factor for the resilient nature of bovines to IAV. Further studies are needed to identify the host-specific factors contributing to the differential pathogenetic mechanisms and disease progression of IAV in bovines compared to other susceptible mammalian hosts.

A review of the role of antibiotic policies in the control of antibiotic resistance

The optimal antibiotic control measures remain to be described and probably vary between institutions. Nevertheless, various control measures have been shown to be useful in reducing costs of therapy and total amounts of prescribing, while maintaining quality of care. More recently, interest has turned to whether antibiotic policies can reduce the spread of resistance and even reverse current high levels. Early studies indicated this was feasible, but mathematical models and the recent discovery of the role of transposons and integrons in multi-drug resistance have both cast doubt on likely future success in this area. Nevertheless, there have been some major successes in recent studies, both in the community and hospital. While cross-infection is a major impediment to control of resistance, there is little doubt that careful antibiotic prescribing can curtail the emergence and reduce the prevalence of resistance.

Clinical observations of children with pleuropneumonia due to Mycoplasma pneumoniae

A comparative study on the clinical presentation of Mycoplasma pneumoniae infection was performed in 56 patients with pleuropneumonia and those who had pneumonia without pleural effusion. The latter consisted of 773 cases; their age distribution reached a peak at 3-5 years of age in males and at 4-6 years in females. The 56 cases with pleuropneumonia were distributed among children of all ages. Pneumococcal infection was demonstrated by blood culture in one of 56 cases. Serological tests revealed a higher prevalence of mixed viral infections among children with pleuropneumonia (18/44) than with pneumonia but no effusion (69/419). There was a tendency toward a severe and prolonged course of illness with strong indications of infection among pleuropneumonia cases. Complications such as exanthema or liver dysfunction were observed more frequently among pleuropneumonia cases than among simple pneumonia cases. These results suggest that other pathogenic agents or unknown host reactions to these agents may modify the clinical picture of pleuropneumonia caused by M. pneumoniae.

The effects of Mycoplasma mobile 163 K on the ciliary epithelium of tracheal organ cultures

Mycoplasma (M.) mobile 163 K, isolated from the gills of a tench (Tinca tinca L.), was examined for cytotoxic capacities using tracheal organ cultures from gnotobiotic rats and gnotobiotic piglets in pH-controlled experiments (pH 7.2-7.6). The mycoplasmas caused an inhibition of the ciliary activity at incubation temperatures of 20, 25 and 30 degrees C. The strongest cilia stopping effect was observed at an incubation temperature of 25 degrees C, the optimal growth temperature of the mycoplasmas. No ciliostasis occurred at 37 degrees C. The number of the organisms did clearly affect the severity of ciliostasis in the range from 4.0 x 10(4) to 7.7 x 10(8) c.f.u. in rat as well as in porcine tracheal organ cultures. Toxic substances, secreted by the mycoplasmas into the culture medium, could not be detected. In histological investigations cytopathological changes were observed in the epithelial cells, apparent in the destruction and loss of cilia, cytoplasmatic vacuolization, swelling of mitochondria, peripheral orientation of the nuclear chromatin and detachment of epithelial cells from each other and the basal membrane. The final stage of the infection was characterized by complete exfoliation of the epithelial cells and the complete destruction of the multi-layer epithelium. The localization of the mycoplasmas attached to the ciliary epithelium was shown by scanning and transmission electron microscopy.

Antimycoplasmal activity of dimethylphenols in a tracheal explant culture system

Mycoplasma pneumoniae induces pneumonia-like symptoms in hamsters and causes ciliostasis and cytonecrosis in hamster tracheal explants. 2,4-Dimethylphenol and, to a lesser extent, its 2,3-, 2,5-, and 2,6-dimethylphenol isomers protected tracheal explants from these changes after exposure to virulent M. pneumoniae strain PI 1428. The effect was concentration, time, and isomer dependent. At concentrations of 10(-9) M or greater, 2,4-dimethylphenol completely prevented the morphological (loss of ciliated cells) and biochemical (decreased dehydrogenase activity) changes normally observed after exposure to M. pneumoniae. Apparently, 2,4-dimethylphenol interfered with an early event in the infection process. Complete protection required that it be present during the first 2 h of exposure of the explants to the infecting mycoplasmas. These xylenols may prove to be useful tools for helping to define the mechanisms of pathogenesis in certain respiratory infections.

Ureaplasma urealyticum and Mycoplasma hominis in chlamydial and non-chlamydial nongonococcal urethritis

Urethral specimens from 726 patients with nongonococcal urethritis (NGU) were examined for Chlamydia trachomatis, Ureaplasma urealyticum, and Mycoplasma hominis. Chlamydiae were isolated from 35.9% of ureaplasma-positive patients and from 36.5% of ureaplasma-negative patients. Ureaplasmas were isolated from 52.5% of chlamydia-positive patients and from 53.1% of chlamydia-negative patients, an observation which contrasts with that of some workers who have suggested that ureaplasmas are significantly associated with chlamydia-negative NGU. Furthermore, the numbers of ureaplasmas isolated from patients who did or did not harbour chlamydiae were not significantly different nor was there a particular association of ureaplasmas with chlamydia-negative NGU in patients experiencing their first episode of disease. In addition, M. hominis was not isolated more frequently from those from whom chlamydiae were or were not isolated. The only significant associations were the isolation of M. hominis from patients who were ureaplasma-positive and of ureaplasmas from those who were M. hominis-positive. These findings do not necessarily mitigate against ureaplasmas being responsible for some cases of chlamydia-negative NGU.

Alterations in the metabolism of hamster tracheas in organ culture after infection by virulent Mycoplasma pneumoniae

Exposure of hamster tracheal rings in organ culture to virulent Mycoplasma pneumoniae organisms leads to alterations in macromolecular biosynthesis and metabolic activity of the respiratory epithelial cells. Avirulent organisms derived from the same parent strain do not produce these effects. During the course of infection by virulent mycoplasmas, tracheal rings show an initial increase in [14C]galactose uptake followed by a significant decline as infection progresses which is also accompanied by abnormal processing of galactose as evidenced by amounts of 14CO2 released. Parallel decreases in the rate of [3H]orotic acid and [3H]amino acid uptake are observed. Within 24 h after infection of tracheal rings by virulent mycoplasmas, inhibition of host cell ribonucleic acid and protien synthesis is evident. Ribonucleic acid synthesis in infected cells, analyzed by gel electrophoresis, is reduced by 80% at 48 h and is negligible by 96 h. The course of mycoplasma infection can be interrupted or reversed by erythromycin after the initial mycoplasma-host cell interaction since addition of erythromycin 24 h or earlier after infection prevents the onset of abnormal orotic acid uptake. However, 48 h after infection, rescue of host cells by erythromycin cannot occur and cytopathology becomes evident. These data suggest that mediation of host cell injury requires continued protein synthesis by attached mycoplasmas, and the primary effect of mycoplasma infection on tracheal organ culture may be at a transcriptional or translational level.

Comparative activity of tobramycin, amikacin, and gentamicin alone and with carbenicillin against Pseudomonas aeruginosa

The effect of gentamicin against 130 clinical isolates of Pseudomonas aeruginosa was compared with that of two investigational aminoglycoside antibiotics, tobramycin and amikacin. Minimal inhibitory concentration data indicated that, on a weight basis, tobramycin was two to four times as active as gentamicin against most isolates. However, 14 of 18 organisms highly resistant to gentamicin (>/=80 mug/ml) were also highly resistant to tobramycin. Amikacin was the least active aminoglycoside on a weight basis, but none of the isolates were highly resistant to this antibiotic. When therapeutically achievable concentrations were used, adding carbenicillin to gentamicin or to tobramycin enhanced inhibitory activity against those isolates susceptible (</=5 mug/ml) or moderately resistant (10 to 40 mug/ml) to the aminoglycoside. Such synergy was seldom demonstrated for isolates highly resistant to gentamicin or tobramycin. The combination of carbenicillin and amikacin enhanced inhibition against all but two of the isolates. Both tobramycin and amikacin offer in vitro advantages over gentamicin against P. aeruginosa.

Mycoplasma-virus interrelationships in mouse tracheal organ cultures

The effects produced by single and mixed infections with Mycoplasma pulmonis and influenza A/PR-8 virus were studied in mouse tracheal organ cultures. M. pulmonis multiplied in the tracheal organ cultures, producing inhibition of ciliary activity and histologic tissue damage. The organism grew in close association with the cell membranes but did not appear to attach directly to the membranes or the cilia. Influenza A virus also replicated in tracheal organ cultures, producing ciliary inhibition and more extensive cytopathologic changes. Virus particles were seen by electron microscopy to attach to and cause clumping of the cilia. Simultaneous infection of the organ cultures with mycoplasma and virus resulted in more rapid inactivation of ciliary activity and greater tissue damage than occurred when the cultures were infected with only mycoplasma or virus. Presence of the virus appeared to have no effect on the growth of the mycoplasma; however, the mycoplasma partially interfered with virus replication.