Agence de la Biomédecine/Agence Régionale de Santé de la Guadeloupe/Inserm-REACTing.

The sequences of the ftsI gene, encoding the transpeptidase domain of penicillin binding protein (PBP) 3A and/or PBP 3B, which are involved in septal peptidoglycan synthesis, were determined for 108 clinical strains of Haemophilus influenzae with reduced susceptibility to ␤-lactam antibiotics with or without ␤-lactamase production and were compared to those of the ampicillin-susceptible Rd strain and ampicillin-susceptible clinical isolates. The sequences have 18 different mutation patterns and were classified into two groups on the basis of amino acid substitutions deduced from the nucleotide sequences located between bp 960 and 1618 of the ftsI gene. In group I strains (n ‫؍‬ 7), His-517 was substituted for Arg-517. In group II strains (n ‫؍‬ 101), Lys-526 was substituted for Asn-526. In subgroup IIa (n ‫؍‬ 5; H. influenzae ATCC 49247), the only observed substitution was Lys-526 for Asn-526; in subgroup IIb (n ‫؍‬ 56), Val-502 was substituted for Ala-502 (n ‫؍‬ In spite of the widespread use of the anti-Haemophilus b vaccine in the industrialized countries and the decreased incidence of invasive diseases (18), Haemophilus influenzae remains a key species in bronchopulmonary and ear, nose, and throat (ENT) infections in both adults and children. These diseases are most often caused by noncapsulated strains (10,14). Treatment of such infections can be severely affected by antibiotic resistance. In H. influenzae resistance to antibiotics, especially to ␤-lactams, has, for a number of years, become a serious problem (6,15,30).Two main mechanisms are at the origin of resistance to aminopenicillins: enzymatic hydrolysis of the antibiotic and a change in penicillin-binding proteins (PBPs). By far the more frequent is the production of ␤-lactamase, usually of the TEM-1 type but sometimes of the ROB-1 type (15,32). In certain countries, the incidence of strains producing ␤-lactamase is particularly high, reaching 50% in type b strains, which are responsible for invasive manifestations (before anti-Haemophilus b vaccination), and 20 to 30% in noncapsulated strains that lead to bronchopulmonary and ENT infections (5, 12, 32).Resistance by mechanisms other than ␤-lactamase production is based on decreased affinity of the PBPs involved in septal peptidoglycan synthesis (4). The first observations of ampicillin-resistant non-␤-lactamase producing (BLNAR) strains were reported in the early 1980s and concerned type b capsulated (20, 27) and noncapsulated strains (2, 25). In contrast to the incidence of ␤-lactamase-producing strains, the incidence of BLNAR strains remains low in various countries (4,5,8,32), but in Japan the proportion of BLNAR clinical isolates is more than 25% and seems to be increasing (33,36).In H. influenzae, ampicillin resistance unrelated to ␤-lactamase production was shown to be chromosomally mediated and was correlated with alterations in PBPs 3A and 3B (4,22,29,34). Recently, Ubukata et al. (36) demonstrated that mutations in the ftsI gene, which is involved in septal peptidoglycan synthesis, are th...

Depletion of CD4 + T cells from the gut occurs rapidly during acute HIV-1 infection. This has been linked to systemic inflammation and disease progression as a result of translocation of microbial products from the gut lumen into the bloodstream. Combined antiretroviral therapy (cART) substantially restores CD4 + T cell numbers in peripheral blood, but the gut compartment remains largely depleted of such cells for poorly understood reasons. Here, we show that a lack of recruitment of CD4 + T cells to the gut could be involved in the incomplete mucosal immune reconstitution of cART-treated HIV-infected individuals. We investigated the trafficking of CD4 + T cells expressing the gut-homing receptors CCR9 and integrin α4β7 and found that many of these T cells remained in the circulation rather than repopulating the mucosa of the small intestine. This is likely because expression of the CCR9 ligand CCL25 was lower in the small intestine of HIV-infected individuals. The defective gut homing of CCR9 + β7 + CD4 + T cells -a population that we found included most gut-homing Th17 cells, which have a critical role in mucosal immune defense -correlated with high plasma concentrations of markers of mucosal damage, microbial translocation, and systemic T cell activation. Our results thus describe alterations in CD4 + T cell homing to the gut that could prevent efficient mucosal immune reconstitution in HIV-infected individuals despite effective cART.

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