Melting corneal ulcers (keratomalacia) in dogs: A 5-year clinical and microbiological study (2014-2018).

OBJECTIVES: To identify bacterial microorganisms associated with canine keratomalacia, review their antimicrobial sensitivity, and evaluate clinical outcomes compared to results of microbial culture. METHODS: Retrospective analysis of clinical records of dogs diagnosed with a melting corneal ulcer presented to a referral hospital in Hertfordshire, UK between 2014 and 2018. RESULTS: One hundred and ten melting corneal ulcers were sampled in 106 dogs. The most common pure bacterial isolate was Pseudomonas aeruginosa (n = 26) followed by ß-hemolytic Streptococcus (n = 12). Melting corneal ulcers that cultured coagulase-positive Staphylococcus, coliform bacteria, Pasteurella multocida, Enterococcus, and Streptococcus viridans presented in smaller numbers and were analyzed together (n = 16). Multiple cultures were identified in nine cases (n = 9). Forty-seven cultures yielded no bacterial growth (n = 47). The susceptibility to fluoroquinolones remained high with the exception of ß-hemolytic Streptococci. There was no significant difference in the ulcer severity at presentation in regard to the cultured bacteria. Overall, 63 eyes (57%) received surgical grafting in addition to medical treatment. In 14 cases (13%), the progression of corneal melting despite medical ± surgical treatment resulted in enucleation. Fifty-seven percent (8/14) of the enucleated eyes cultured pure Pseudomonas aeruginosa isolates. In contrast, all ß-hemolytic Streptococcus-associated ulcers healed. CONCLUSIONS: The most common bacterial species associated with canine keratomalacia were Pseudomonas aeruginosa and ß-hemolytic Streptococcus. Because of the variation in antibacterial sensitivity between these two species, bacterial culture and sensitivity testing should be performed in all dogs presenting with keratomalacia. Melting corneal ulcers associated with pure Pseudomonas infection were significantly more likely to result in globe loss than melting corneal ulcers associated with other cultures.

Metabolomics Reveals Altered Hepatic Bile Acids, Gut Microbiome Metabolites, and Cell Membrane Lipids Associated with Marginal Vitamin A Deficiency in a Mongolian Gerbil Model.

SCOPE: This study is designed to provide a broad evaluation of the impacts of vitamin A (VA) deficiency on hepatic metabolism in a gerbil model. METHODS AND RESULTS: After 28 days of VA depletion, male Mongolian gerbils (Meriones unguiculatus) are randomly assigned to experimental diets for 28 days. Groups are fed a white-maize-based diet with ≈50 µL cottonseed oil vehicle either alone (VA-, n = 10) or containing 40 µg retinyl acetate (VA+, n = 10) for 28 days. Liver retinol is measured by high-performance liquid chromatography. Primary metabolomics, aminomics, lipidomics, bile acids, oxylipins, ceramides, and endocannabinoids are analyzed in post-mortem liver samples by liquid chromatography-mass spectrometry. RESULTS: Liver retinol is lower (p < 0.001) in the VA- versus VA+ group, with concentrations indicating marginal VA deficiency. A total of 300 metabolites are identified. Marginal VA deficiency is associated with lower bile acids, trimethylamine N-oxide, and a variety of acylcarnitines, phospholipids and sphingomyelins (p < 0.05). Components of DNA, including deoxyguanosine, cytidine, and N-carbomoyl-beta-alanine (p < 0.05), are differentially altered. CONCLUSIONS: Hepatic metabolomics in a marginally VA-deficient gerbil model revealed alterations in markers of the gut microbiome, fatty acid and nucleotide metabolism, and cellular structure and signaling.

Changes in Intestinal Microbiota Are Associated with Islet Function in a Mouse Model of Dietary Vitamin A Deficiency.

AIMS: The underlying mechanisms involved in Vitamin A- (VA-) related changes in glucose metabolic disorders remain unclear. Recent evidence suggests that intestinal microbiota is closely linked to the metabolic syndrome. Here, we explored whether and how intestinal microbiota affects glucose homeostasis in VA-deficient diet-fed mice. METHODS: Six-week-old male C57BL/6 mice were randomly placed on either a VA-sufficient (VAS) or VA-deficient (VAD) diet for 10 weeks. Subsequently, a subclass of the VAD diet-fed mice was switched to a VA-deficient rescued (VADR) diet for an additional 8 weeks. The glucose metabolic phenotypes of the mice were assessed using glucose tolerance tests and immunohistochemistry staining. Changes in intestinal microbiota were assessed using 16S gene sequencing. The intestinal morphology, intestinal permeability, and inflammatory response activation signaling pathway were assessed using histological staining, western blots, quantitative-PCR, and enzyme-linked immunosorbent assays. RESULTS: VAD diet-fed mice displayed reduction of tissue VA levels, increased area under the curve (AUC) of glucose challenge, reduced glucose-stimulated insulin secretion, and loss of ß cell mass. Redundancy analysis showed intestinal microbiota diversity was significantly associated with AUC of glucose challenge and ß cell mass. Redundancy analysis showed intestinal microbiota diversity was significantly associated with AUC of glucose challenge and κB signaling pathway activation. Reintroduction of dietary VA to VAD diet-fed mice restored tissue VA levels, endocrine hormone profiles, and inflammatory response, which are similar to those observed following VAS-controlled changes in intestinal microbiota. CONCLUSIONS: We found intestinal microbiota effect islet function via controlling intestinal inflammatory phenotype in VAD diet-fed mice. Intestinal microbiota influences could be considered as an additional mechanism for the effect of endocrine function in a VAD diet-driven mouse model.

Vitamin A deficiency in mice alters host and gut microbial metabolism leading to altered energy homeostasis.

Vitamin A deficiency (A-) is a worldwide public health problem. To better understand how vitamin A status influences gut microbiota and host metabolism, we systematically analyzed urine, cecum, serum and liver samples from vitamin A sufficient (A+) and deficient (A-) mice using 1H NMR-based metabolomics, quantitative (q)PCR and 16S rRNA gene sequencing coupled with multivariate data analysis. The microbiota in the cecum of A- mice showed compositional as well as functional shifts compared to the microbiota from A+ mice. Targeted 1H NMR analyses revealed significant changes in microbial metabolite concentrations including higher butyrate and hippurate and decreased acetate and 4-hydroxyphenylacetate in A+ relative to A- mice. Bacterial butyrate-producing genes including butyryl-CoA:acetate CoA-transferase and butyrate kinase were significantly higher in bacteria from A+ versus bacteria from A- mice. A- mice had disturbances in multiple metabolic pathways including alterations in energy (hyperglycemia, glycogenesis, TCA cycle and lipoprotein biosynthesis), amino acid and nucleic acid metabolism. A- mice had hyperglycemia, liver dysfunction, changes in bacterial metabolism and altered gut microbial communities. Moreover, integrative analyses indicated a strong correlation between gut microbiota and host energy metabolism pathways in the liver. Vitamin A regulates host and bacterial metabolism, and the result includes alterations in energy homeostasis.

Modulation of urinary siderophores by the diet, gut microbiota and inflammation in mice.

Mammalian siderophores are believed to play a critical role in maintaining iron homeostasis. However, the properties and functions of mammalian siderophores have not been fully clarified. In this study, we have employed Chrome Azurol S (CAS) assay which is a well-established method for bacterial siderophores study, to detect and quantify mammalian siderophores in urine samples. Our study demonstrates that siderophores in urine can be altered by diet, gut microbiota and inflammation. C57BL/6 mice, fed on plant-based chow diets which contain numerous phytochemicals, have more siderophores in the urine compared to those fed on purified diets. Urinary siderophores were up-regulated in iron overload conditions, but not altered by other tested nutrients status. Further, germ-free mice displayed 50% reduced urinary siderophores, in comparison to conventional mice, indicating microbiota biotransformation is critical in generating or stimulating host metabolism to create more siderophores. Altered urinary siderophores levels during inflammation suggest that host health conditions influence systemic siderophores level. This is the first report to measure urinary siderophores as a whole, describing how siderophores levels are modulated under different physiological conditions. We believe that our study opens up a new field in mammalian siderophores research and the technique we used in a novel manner has the potential to be applied to clinical purpose.

Isolation of lactobacillus reuteri from Peyer's patches and their effects on sIgA production and gut microbiota diversity.

SCOPE: We previously reported that specific Lactobacillus reuteri colonized within mouse Peyer's patches (PP) effectively prevented high fat diet induced obesity and low-grade chronic inflammation. We further investigated the role of PP Lactobacillus reuteri on sIgA production in rats in this study. METHODS AND RESULTS: Lactobacilli were isolated from rat PP. All isolates were L. reuteri and belonged to three phenotypes according to amplified fragment length polymorphism analysis. Typical strains of two main clusters, PP1 and PP2, were used to treat control and vitamin A deficient (VAD) rats, respectively. The feeding of PP1 and PP2 affected sIgA and Lactobacillus diversity by strain-specific manner. Free sIgA was significantly increased by PP1 (p = 0.069) and PP2 (p < 0.05) in the control rats but not in the VAD rats. Only PP1 significantly changed PP Lactobacillus diversity in the control rats (p < 0.05). However, PP2 specifically changed ileal Lactobacillus diversity in both control and VAD rats. Fecal sIgA was correlated with PP Lactobacillus diversity (R(2) = 0.7958, p = 0.011). CONCLUSION: Modulation of sIgA production by PP L. reuteri of rat is dependent on vitamin A and change of Lactobacillus diversity in PP.

The pleiotropic role of vitamin A in regulating mucosal immunity.

The effect of vitamin A on mucosal immunity has never been subjected to extensive studies until recently. We started to work in this area in the early 1970s when we observed that children with protein-calorie malnutrition (PCM) often had defective mucosal immunity, judging from the incidence of respiratory tract infections and diarrhea. We reported that these children had depressed secretory IgA (sIgA) levels in their nasal wash fluids. The IgA level in specimens collected from those superimposed with some degrees of vitamin A deficiency state appeared to be more severely affected. In order to better understand the underlying mechanism associated with this condition, we started to study more detail the deficiency state using experimental vitamin A-deficient rats. From a series of experiments using this animal model, we proposed that vitamin A was needed for transport and/or secretion of sIgA across the mucosa. This conclusion was based on the observation that the secretory component of sIgA synthesized by the epithelial cells of these vitamin A deficient animals was adversely affected as compared to the control animals. From that time onward, much progress has been made by several other groups showing that other mechanisms could also influence the integrity and immune function of the mucosa. For instance, recent studies demonstrated that retinoic acid which is a biologically active form of vitamin A has an essential role in mucosal homeostasis, controlling tolerance and immunity in these non-lymphoid tissues. Such a conclusion was made possible by the availability of sophisticated new molecular biology and genetic engineering techniques together with advances in the field of immunoregulation, e.g., the discovery of dendritic cells (DCs) and T helper cell subsets in 1980s, and the role of Toll-like receptors (TLRs) together with other innate immune regulators in controlling adaptive immune response in the early 1990s. These advances provided considerable new insights into the pleiotropic roles of vitamin A including educating mucosal DCs, differentiation of lymphocyte lineages and imprinting them with mucosal-homing properties as well as in regulating tolerance and immunity. The identification of a novel lymphocyte subpopulation, innate lymphoid cells (ILCs), at the beginning of this century has provided us with an additional insight into a new role of vitamin A in regulating homeostasis at the mucosal surface through influencing ILCs. Another new player that regulates intestinal homeostasis and mucosal immune response is microbiota whose composition is known to vary with vitamin A status. So it appears now that the role of vitamin A on mucosal immunity is far beyond regulating the adaptive Th1-Th2 cell response, but is highly pleiotropic and more complicating, e.g., polarizing the phenotype of mucosal DCs and macrophages, directing gut-homing migration of T and B cells, inducing differentiation of effector T cells and Treg subpopulation, balancing mucosal ILCs subpopulation and influencing the composition of microbiota. In this review, I will attempt to bring together these important advances to provide a comprehensive and contemporary perspective on the role of vitamin A in regulating mucosal immunity.

ß-carotene-producing bacteria residing in the intestine provide vitamin A to mouse tissues in vivo.

Vitamin A deficiency (VAD) is an overwhelming public health problem that affects hundreds of millions of people worldwide. A definitive solution to VAD has yet to be identified. Because it is an essential nutrient, vitamin A or its carotenoid precursor ß-carotene can only be obtained from food or supplements. In this study, we wanted to establish whether ß-carotene produced in the mouse intestine by bacteria synthesizing the provitamin A carotenoid could be delivered to various tissues within the body. To achieve this, we took advantage of the Escherichia coli MG1655*, an intestine-adapted spontaneous mutant of E. coli MG1655, and the plasmid pAC-BETA, containing the genes coding for the 4 key enzymes of the ß-carotene biosynthetic pathway (geranylgeranyl pyrophosphate synthase, phytoene synthase, phytoene desaturase, and lycopene cyclase) from Erwinia herbicola. We engineered the E. coli MG1655* to produce ß-carotene during transformation with pAC-BETA (MG1655*-ßC) and gavaged wild-type and knockout mice for the enzyme ß-carotene 15,15'-oxygenase with this recombinant strain. Various regimens of bacteria administration were tested (single vs. multiple and low vs. high doses). ß-Carotene concentration was measured by HPLC in mouse serum, liver, intestine, and feces. Enumeration of MG1655*-ßC cells in the feces was performed to assess efficiency of intestinal colonization. We demonstrated in vivo that probiotic bacteria could be used to deliver vitamin A to the tissues of a mammalian host. These results have the potential to pave the road for future investigations aimed at identifying alternative, novel approaches to treat VAD.

Vitamin A deficiency is associated with gastrointestinal and respiratory morbidity in school-age children.

Infection is an important cause of morbidity throughout childhood. Poor micronutrient status is a risk factor for infection-related morbidity in young children, but it is not clear whether these associations persist during school-age years. We examined the relation between blood concentrations of micronutrient status biomarkers and risk of gastrointestinal and respiratory morbidity in a prospective study of 2774 children aged 5-12 y from public schools in Bogotá, Colombia. Retinol, zinc, ferritin, mean corpuscular volume, hemoglobin, erythrocyte folate, and vitamin B-12 concentrations were measured in blood at enrollment into the cohort. Children were followed for 1 academic year for incidence of morbidity, including diarrhea with vomiting, cough with fever, earache or ear discharge with fever, and doctor visits. Compared with adequate vitamin A status (≥30.0 µg/dL), vitamin A deficiency (<10.0 µg/dL) was associated with increased risk of diarrhea with vomiting [unadjusted incidence rate ratio (IRR): 2.17; 95% CI: 0.95, 4.96; P-trend = 0.03] and cough with fever (unadjusted IRR: 2.36; 95% CI: 1.30, 4.31; P-trend = 0.05). After adjustment for several sociodemographic characteristics and hemoglobin concentrations, every 10 µg/dL plasma retinol was associated with 18% fewer days of diarrhea with vomiting (P < 0.001), 10% fewer days of cough with fever (P < 0.001), and 6% fewer doctor visits (P = 0.01). Every 1 g/dL of hemoglobin was related to 17% fewer days with ear infection symptoms (P < 0.001) and 5% fewer doctor visits (P = 0.009) after controlling for sociodemographic factors and retinol concentrations. Zinc, ferritin, mean corpuscular volume, erythrocyte folate, and vitamin B-12 status were not associated with morbidity or doctor visits. Vitamin A and hemoglobin concentrations were inversely related to rates of morbidity in school-age children. Whether vitamin A supplementation reduces the risk or severity of infection in children over 5 y of age needs to be determined.

Streptococcus pneumoniae-induced pneumonia and Citrobacter rodentium-induced gut infection differentially alter vitamin A concentrations in the lung and liver of mice.

In the developing world, vitamin A (VA) deficiency is endemic in populations that are also at great risk of morbidity and mortality because of pneumococcal pneumonia and enteric infections. To better understand how lung and gastrointestinal pathogens affect VA status, we assessed VA concentrations in serum, lung, and liver during an invasive pneumonia infection induced by Streptococcus pneumoniae serotype 3, and a noninvasive gut infection induced by Citrobacter rodentium, in vitamin A-adequate (VAA) and vitamin A-deficient (VAD) mice. For pneumonia infection, mice were immunized with pneumococcal polysaccharide serotype 3 (PPS3), or not (infected-control), 5 d prior to intranasal inoculation with S. pneumoniae. Two days post-inoculation, immunization was protective against systemic infection regardless of VA status as PPS3 immunization decreased bacteremia compared with infected-control mice (P < 0.05). Retinol concentrations in the lung were higher in infected-control VAA mice (15.7 nmol/g: P < 0.05) compared with PPS3-immunized mice (8.23 nmol/g), but this was not associated with increased lung bacterial burden. VAA mice had reduced severity of C. rodentium-induced gut infection as measured by fecal bacterial shedding compared with VAD mice (P < 0.05). Liver retinol and retinyl ester concentrations in VAA mice decreased at the peak of infection (retinol, 8.1 nmol/g; retinyl esters, 985 nmol/g; P < 0.05, compared with uninfected mice; retinol, 29.5 nmol/g; retinyl esters, 1730 nmol/g), whereas tissue VA concentrations were low in VAD mice during both infections. Colonic mucin gene expression was also depressed at peak infection compared with uninfected mice (P < 0.05). Overall, pneumonia had less effect on VA status than gastrointestinal infection, predominantly owing to reduced hepatic VA storage at the peak of gut infection.

Impact of Giardia intestinalis on vitamin a status in schoolchildren from northwest Mexico.

We conducted a cross-sectional study in northwest Mexico in order to investigate the association between giardiasis and serum vitamin A in 40 Giardia-infected and 70 Giardia-free schoolchildren who were covered by a regional school breakfast program. There were no significant differences in age, Z-scores for nutritional indices of height for age, weight for age, or weight for height, socioeconomic conditions (employment and education of the parents, household conditions, sanitation facilities, type of drinking water, and family income), and mean daily intakes of vitamin A in the Giardia-free (899 +/- 887 microg) and the Giardia-infected (711 +/- 433 microg) groups. A higher concentration of serum retinol was found in the Giardia-free group than in the Giardia-infected group (0.75 micromol/L versus 0.61 micromol/L, respectively; p < 0.0001). Giardia-infected children were more likely to be vitamin A-deficient than the Giardia-free children (OR = 3.2; 95% CI = 1.2-8.5). Although 95% of the children met the daily-recommended intakes of vitamin A, half of them showed subclinical vitamin A deficiency. It is recognized that vitamin A deficiency is multifactorial and giardiasis was a factor significantly associated with this deficiency in this study. Mexican program developers and policymakers should be aware about the distinction between dietary deficiencies and deficiency diseases when current national program strategies for parasitic control and vitamin A supplementation are redesigned.

Vitamin A deficiency leads to severe functional disturbance of the intestinal epithelium enzymes associated with diarrhoea and increased bacterial translocation in gnotobiotic rats.

A disturbance of the integrity of the intestinal epithelium with an increased risk for bacterial translocation is one of the suggested factors underlying the increased incidence of infections and septicaemia during vitamin A deficiency. In the present study the effects of vitamin A deficiency on the enzymic activity of enterocytes in response to bacterial colonization with a non-pathogenic Escherichia coli strain were studied in monocolonized and conventional Wistar rats. The monocolonized, but not the conventional, vitamin A-deficient rats had markedly reduced weight compared to their pair-fed controls and presented neurological symptoms, such as hind leg weakness, tremor and slow gait. Moreover, only in the monocolonized vitamin A-deficient rats were severe diarrhoea and bacterial translocation to extraintestinal sites-mainly kidneys-detected. Measurements of enterocyte brush-border enzyme activities revealed that lactase, sucrase, gamma-glutamyltranspeptidase (GGT) and dipeptidyl peptidase IV (DPP IV) were significantly reduced in the monocolonized vitamin A-deficient rats compared to the pair-fed controls, indicating a severe functional disturbance of the enterocytes. In conventional vitamin A-deficient rats only sucrase activity was markedly lower than in the respective controls. Our observation, that the deficient vitamin A status led to a strong reduction of enterocyte enzymic activities, associated with diarrhoea and increased bacterial translocation, mainly in the gnotobiotic rats, suggests that the composition of the bacterial flora, i.e. the colonization state, has a strong influence on triggering the severity of the functional disturbances of the intestinal epithelium, and adds to the clinical manifestations of vitamin A deficiency.

Micronutrient malnutrition, infection, and immunity: an overview.

Micronutrient deficiencies and infectious diseases often coexist and exhibit complex interactions leading to the vicious cycle of malnutrition and infections among underprivileged populations of the developing countries, particularly in preschool children. Several micronutrients such as vitamin A, beta-carotene, folic acid, vitamin B12 vitamin C, riboflavin, iron, zinc, and selenium, have immunomodulating functions and thus influence the susceptibility of a host to infectious diseases and the course and outcome of such diseases. Certain of these micronutrients also possess antioxidant functions that not only regulate immune homeostasis of the host, but also alter the genome of the microbes, particularly in viruses, resulting in grave consequences like resurgence of old infectious diseases or the emergence of new infections. These micronutrient infection and immune function interactions and their clinical and public health relevance in developing countries are briefly reviewed in this article.

Conjunctival impression cytology for vitamin A deficiency in the presence of infectious trachoma.

BACKGROUND/AIMS: Increased morbidity and mortality from a number of infectious diseases have been associated with vitamin A deficiency. Trachoma and vitamin A deficiency are both important causes of blindness in Nepal. The purpose of this study was to determine the association between the diagnosis of vitamin A deficiency by conjunctival impression cytology and the diagnosis of infectious trachoma by the polymerase chain reaction (PCR) in the Lumbini zone of Nepal. METHODS: 70 children under the age of 11 in a rural village in the Lumbini zone were examined for clinical evidence of active trachoma. The conjunctiva of each child was tested for ocular Chlamydia trachomatis infection using PCR, and for loss of goblet cells (a sign of subclinical vitamin A deficiency) using conjunctival impression cytology. RESULTS: The presence of infectious trachoma was associated with the loss of goblet cells on conjunctival impression cytology (p = 0.02). This relation was present and significant even when adjusted for age (p = 0.05) and degree of inflammation (p = 0.02). In fact, even subclinical infection with chlamydia was associated with an abnormal conjunctival impression cytology (p = 0.02). CONCLUSIONS: Children with infectious trachoma are significantly more likely to have an abnormal conjunctival impression cytology, even if the infection is subclinical. Thus, the diagnosis of vitamin A deficiency from conjunctival impression cytology alone should be made with some caution in areas with endemic trachoma. Further studies will be needed to determine the cause of this association.

Increased translocation of Escherichia coli and development of arthritis in vitamin A-deficient rats.

We studied the immune response and the colonization pattern in vitamin A-deficient rats that were colonized with the Escherichia coli O6 K13 pOmp 21 strain, which is genetically manipulated to produce ovalbumin and to be resistant to ampicillin. In the vitamin A-deficient rats, the number of bacteria per gram of feces was about five times higher than in the paired fed control rats 4 weeks after colonization. In the control rats, the colon and the lower part of the ileum were colonized, while in the vitamin A-deficient rats all parts of the small intestine, as well as the colon, were heavily inhabited by bacteria. Furthermore, in 75% of the vitamin A-deficient rats, the E. coli bacteria were found in the mesenteric lymph nodes, and in 50% of the rats E. coli were found in the kidneys. These animals also developed severe arthritis. The levels of serum immunoglobulin G (IgG), IgM, IgE, and biliary IgA antibodies against the bacterial antigens were significantly higher in the vitamin A-deficient rats than in the control rats. The number of IgA-producing cells in the lamina propria of the small intestine was significantly lower in the vitamin A-deficient rats than in the control rats; however, there was an increase in the number of CD8+ cells and transforming growth factor beta-producing cells in the lamina propria of the vitamin A-deficient rats. Disturbances in T-cell function were demonstrated, since spleen cells from the vitamin A-deficient rats produced more gamma interferon and interleukin-2 in vitro than control spleen cells. In summary, vitamin A deficiency led to a decrease in the ability to control the localization of intestinal bacteria and an increase in translocation, which was followed by development of arthritis regardless of substantial levels of antibacterial antibodies. The bacterial invasion made the animals hyperresponsive to the bacterial antigens, despite the fact that vitamin A deficiency is normally associated with suppressed antibody production, as previously shown by us and others.

Effects of viral and mycoplasmal infections, ammonia exposure, vitamin A deficiency, host age, and organism strain on adherence of Mycoplasma pulmonis in cultured rat tracheas.

Adherence to host cells is thought to be a pathogenetic mechanism in mycoplasmal diseases, thus, factors affecting adherence could affect disease expression. To determine whether factors that affect expression of Mycoplasma pulmonis respiratory disease in rats alter adherence of the organism to respiratory epithelium, we studied adherence of radiolabelled M. pulmonis in perfused whole rat tracheas. Adherence was significantly increased in tracheas from rats with sialodacryoadenitis virus infection or vitamin A deficiency (103 +/- 16% and 112 +/- 29% of control means, respectively), but Sendai virus infection, ammonia exposure, and host age (40 versus 8 weeks) were not associated with increased adherence. We also assessed the relationship between adherence and virulence of M. pulmonis strains. The virulent strain 5782C was more adherent (51 +/- 7%) than the type strain, PG34(Ash), and a polystyrene-adherent, hemadsorbing UAB CT subclone was more adherent (229 +/- 40%) than a UAB CT subclone that does not adhere to polystyrene or erythrocytes. PG34(Ash) and the UAB CT subclones caused rhinitis only; however, the adherent UAB CT subclone caused significantly more severe rhinitis than either the nonadherent subclone or PG34(Ash) as determined by scoring of histologic sections. To determine whether M. pulmonis itself induces changes in respiratory epithelium resulting in enhanced adherence, we studied adherence in tracheas from rats inoculated with M. pulmonis 3 weeks earlier. Adherence was increased 64 +/- 22%, compared with that in tracheas from control rats. Adherence in infected tracheas treated with tetracycline for 2 days was not increased, indicating that M. pulmonis-induced changes in epithelial adherence are rapidly resolved after elimination of infection.

Secondary ocular bacterial infection in hypovitaminosis a xerophthalmia.

Extraocular bacterial culture was performed in 100 patients with hypovitaminosis A xerophthalmia. There was corneal ulceration in 29 cases and corneal perforation in 22 cases. Eighty-six percent of the patients harbored frankly pathogenic bacteria (46 patients) and potentially pathogenic bacteria (40 patients). All but two patients with either cornal ulceration or perforation harbored potentially pathogenic or frankly pathogenic bacteria. Pseudomonas aeruginosa, Diplococcus pneumoniae, and Moraxella species were isolated in 37% (19 patients) of cases with corneal ulceration and perforation. I cultured P. aeruginosa from 36% (eight patients) of cases with corneal perforation. The many ocular secondary bacterial infections in the early stages of xerophthalmia seem to suggest that bacterial action plays a major role in causing the corneal ulceration and perforation in hypovitaminosis A xerophthalmia.