No evidence of nosocomial Pneumocystis carinii infection via health care personnel

Healthcare related transmission of Pneumocystis pneumonia: From key insights toward comprehensive prevention

In at risk populations, Pneumocystis pneumonia (PCP) may occur as a solitary event as well as in a cluster- or outbreak setting due to interpatient transmission of Pneumocystis jirovecii. Despite the data and insights obtained from studies of outbreaks of PCP, the development and implementation of comprehensive recommendations for the prevention of healthcare related transmission of P. jirovecii have been delayed. Both optimization of chemoprophylaxis strategies as well as combination with prudent use of isolation precautions are warranted to achieve this goal. The rationale of the available measures for the prevention of PCP should be viewed in the context of what is currently known about the complex biology and epidemiology of P. jirovecii. From there, phased but practical prevention strategies can be deducted to balance the efforts, costs and negative consequences of chemoprophylaxis and isolation precautions with the beneficial effect of preventing healthcare related transmission of P. jirovecii and development of PCP.

Infections in the immunosuppressed host

The interaction between host immunity and infections in the context of a suppressed immune system presents an opportunity to study the interaction of colonization and infection with the development of acute and chronic pulmonary morbidity and mortality. This article summarizes presentations at the Pittsburgh International Lung Conference about comorbid consequences in two categories of immunosuppressed hosts: HIV-infected individuals and lung transplant recipients. Specifically, chronic obstructive pulmonary disease, pulmonary hypertension, and chronic lung rejection after transplant are three diseases that may be consequences of colonization or infection by viruses or fungi, whether HIV itself or the opportunistic infections Pneumocystis and cytomegalovirus. In the fourth section, we discuss unique aspects of infections after lung transplant as well as the battle against multidrug-resistant organisms in this population and theorize that the immunosuppressed population may provide a unique group of patients in which to study ways to overcome nosocomial pathogenic challenges. These host-pathogen interactions serve as models for developing new strategies to reduce acute and chronic morbidity due to colonization and subclinical infection, and potential therapeutic avenues, which are often overlooked in the clinical arena.

Healthcare worker occupation and immune response to Pneumocystis jirovecii

Humans may be a reservoir for this pathogen and transmit it from person to person.

The reservoir and mode of transmission of Pneumocystis jirovecii remain uncertain. We conducted a cross-sectional study of 126 San Francisco General Hospital staff in clinical (n = 103) and nonclinical (n = 23) occupations to assess whether occupational exposure was associated with immune responses to P. jirovecii. We examined antibody levels by ELISA for 3 overlapping fragments that span the P. jirovecii major surface glycoprotein (Msg): MsgA, MsgB, and MsgC1. Clinical occupation participants had higher geometric mean antibody levels to MsgC1 than did nonclinical occupation participants (21.1 vs. 8.2, p = 0.004); clinical occupation was an independent predictor of higher MsgC1 antibody levels (parameter estimate = 0.89, 95% confidence interval 0.29–1.48, p = 0.003). In contrast, occupation was not significantly associated with antibody responses to either MsgA or MsgB. Healthcare workers may have occupational exposure to P. jirovecii. Humans may be a reservoir for P. jirovecii and may transmit it from person to person.

Pneumocystis pneumonia – a retrospective study 1991–2001 in Gothenburg, Sweden

OBJECTIVES

Pneumocystis pneumonia (PCP) is a severe opportunistic infection in immunosuppressed patients, caused by Pneumocystis jiroveci. The incidence among HIV negative patients is considered to have increased during the last decade.

METHODS

We collected data retrospectively from the cases with PCP diagnosed at Sahlgrenska University Hospital between January 1991 and December 2001.

RESULTS

118 episodes of PCP were registered in 108 patients. The most common underlying immunosuppressions were HIV and solid organ transplantation with 29 and 26 cases, respectively. The number of PCP cases did not increase during the study period. Out of the 118 episodes of PCP 89 (75%) were in patients not infected with HIV. No clusters were found among HIV positive patients. We found 5 smaller clusters among non-HIV patients. Among the cases with proven PCP, 17% were on prophylaxis: 30% of the HIV infected patients and 13% of the non-HIV patients.

CONCLUSIONS

The number of PCP cases is not increasing, 75% of the patients are HIV negative, Only 17% of the patients were on prophylaxis before the episode of PCP, indicating that not all patients at risk are identified.

Enzyme-linked immunosorbent assay and serologic responses to Pneumocystis jiroveci

Seroepidemiologic studies of Pneumocystis pneumonia (PCP) in humans have been limited by inadequate reagents. We have developed an enzyme-linked immunosorbent assay (ELISA) using three overlapping recombinant fragments of the human Pneumocystis major surface glycoprotein (MsgA, MsgB, and MsgC) for analysis of antibody responses in HIV-positive patients and healthy blood donors. HIV-positive patients had significantly higher antibody levels to all Msg fragments. Furthermore, HIV-positive patients who experienced a previous episode of PCP (PCP-positive) had higher levels of antibodies to MsgC than patients who never had PCP. A significant association was found between ELISA antibody level and reactivity by Western blot in HIV-positive patients, especially those who were PCP-positive. Thus, this ELISA will be useful in studying serum antibody responses to Pneumocystis in different human populations.

Pneumocystis carinii BCK1 functions in a mitogen-activated protein kinase cascade regulating fungal cell-wall assembly

Pneumocystis pneumonia remains the most common AIDS-defining opportunistic infection in people with HIV. The process by which Pneumocystis carinii constructs its cell wall is not well known, although recent studies reveal that molecules such as beta-1-3-glucan synthetase (GSC1) and environmental pH-responsive genes such as PHR1 are important for cell-wall integrity. In closely related fungi, a specific mitogen-activated protein kinase (MAPK) cascade regulates cell-wall assembly in response to elevated temperature. The upstream mitogen-activated protein kinase kinase kinase (MAPKKK, or MEKK), BCK1, is an essential component in this pathway for maintaining cell-wall integrity and preventing fungal cell lysis. We have identified a P. carinii MEKK gene and have expressed it in Saccharomyces cerevisiae to gain insights into its function. The P. carinii MEKK, PCBCK1, corrects the temperature-sensitive cell lysis defect of bck1Delta yeast. Further, at elevated temperature PCBCK1 restored the signaling defect in bck1Delta yeast to maintain expression of the temperature-inducible beta-1-3-glucan synthetase gene, FKS2. PCBCK1, as a functional kinase, is capable of autophosphorylation and substrate phosphorylation. Since glucan machinery is not present in mammals, a better understanding of this pathway in P. carinii might aid in the development of novel medications which interfere with the integrity of the Pneumocystis cell wall.

Transmission of Pneumocystis carinii DNA from a patient with P. carinii pneumonia to immunocompetent contact health care workers

The transmission of Pneumocystis carinii from person to person was studied by detecting P. carinii-specific DNA in prospectively obtained noninvasive deep-nasal-swab samples from a child with a documented P. carinii pneumonia (PCP), his mother, two contact health care workers, and 30 hospital staff members who did not enter the patient's room (controls). Nested-DNA amplification was done by using oligonucleotide primers designed for the gene encoding the mitochondrial large subunit rRNA of rat P. carinii (P. carinii f. sp. carinii) that amplifies all forms of P. carinii and internal primers specific for human P. carinii (f. sp. hominis). P. carinii f. sp. hominis DNA was detected in samples from the patient and all of his contacts versus none of the 30 hospital staff members. The results, as previously shown in murine models of P. carinii pneumonia, document that person-to-person transmission of P. carinii is possible. This observation suggests that immunocompromised patients not on PCP prophylaxis should not enter the room of a patient with PCP, and it also raises the question as to whether healthy contacts can transmit the disease to immunocompromised patients at risk.

Nosocomial infections in patients with HIV disease

Throughout the AIDS epidemic, nosocomial infection in the patient with HIV disease has presented a constant problem--not only for the hospitalized patient but also for the clinic attender. The nosocomial spread of multidrug-resistant tuberculosis has emphasized the need for effective control of infection measures in dealing with the immunodeficient. Increased recognition of nosocomial bacterial pneumonias has raised questions about the place, if any, of antimicrobial prophylaxis in preventing Gram-negative and Legionella infection. The use of long-term indwelling venous catheters for the administration of parenteral therapy is associated with an increased risk of nosocomial bloodstream infection--particularly from staphylococci and Pseudomonas spp. Evidence now exists for the nosocomial spread of opportunistic infections, including Cryptosporidium parvum, Mycobacterium avium complex and Pneumocystis carinii. The delay between exposure and diagnosis, the atypical presentation of infections such as tuberculosis and repeated hospital admissions of AIDS patients can combine to confuse the issue with the result that a nosocomial infection may be mis-classified as community-acquired. It seems likely that the burden of nosocomial infection in HIV disease is continually underestimated.

Biomolecular techniques to detect Pneumocystis carinii f. sp. hominis pneumonia in patients with acquired immunodeficiency syndrome

OBJECTIVES

To verify the clinical value of two different polymerase chain reactions (PCRs) for noninvasive diagnosis and follow-up during Pneumocystis carinii f. sp. hominis pneumonia (PCP) and to analyze the P. carinii f. sp. hominis genotypes involved.

METHODS

Internal transcribed spacers (ITSs) nested PCR was applied to 630 samples (bronchoalveolar lavage, sera, peripheral blood mononuclear cells, and oropharyngeal samples) from 122 patients with acquired immunodeficiency syndrome and pneumonia and 40 control samples from 20 subjects seronegative for human immunodeficiency virus. One hundred and eighty samples also were examined by mt-rRNA PCR. Bronchoalveolar lavage samples and 33 sera were analyzed by type-specific oligonucleotide hybridization.

RESULTS

On bronchoalveolar lavage samples, the two PCRs consistently confirmed the morphologic diagnosis of PCP. The sensitivity of ITSs nested PCR versus mt-rRNA PCR was 57.3% versus 14.3% on sera, 32.3% versus 22. 8% on peripheral blood mononuclear cells, and 69.1% versus 48.6% on oropharyngeal samples (garglings). Both PCRs had 100% specificity. Type-specific oligonucleotide hybridization revealed in 72.2% of bronchoalveolar lavage samples a single P. carinii f. sp. hominis genotype, whereas in 27.8% co-infection with more than one strain was detected.

CONCLUSION

On noninvasive samples, ITSs nested PCR was more sensitive than mt-rRNA PCR, and it confirmed the diagnosis in all patients with PCP. For each patient with PCP at least one noninvasive sample was positive for P. carinii f. sp. hominis DNA.

Combined use of blood and oropharyngeal samples for noninvasive diagnosis of Pneumocystis carinii pneumonia using the polymerase chain reaction

To evaluate the clinical use of a polymerase chain reaction (PCR) assay for diagnosis of Pneumocystis carinii pneumonia (PCP) using samples collected noninvasively, the Internal Transcribed Spacers (ITSs) nested PCR was performed on 148 samples from 40 subjects. Bronchoalveolar lavage (BAL) fluid sera, gargled oropharyngeal washes, and peripheral blood mononuclear cells (PBMC) from 14 AIDS patients (mean age, 35.6 years; mean CD4+ cell count, 49.2 cells/mm3) with proven PCP and from 13 HIV-seropositive controls (mean age, 34.6 years; mean CD4+ cell count, 107.3 cells/mm3) with other AIDS-related opportunistic infections were evaluated. Sera and oropharyngeal samples were also collected from 13 HIV-seronegative health care personnel working in an infectious disease ward for use as negative controls. The ITSs nested PCR confirmed the morphological diagnosis of PCP in all patients when BAL fluid was tested (100% sensitivity). This technique also detected Pneumocystis carinii DNA in oropharyngeal samples from 78.6% of patients, in sera from 71.4% of patients, in PBMC from 35.7% of patients. When all results obtained after ITSs nested PCR were considered together for the same patient, the sensitivity for PCP diagnosis was 100% for blood and oropharyngeal samples (gargled saline), as confirmed by subsequent BAL. All samples collected noninvasively from 26 of 26 controls were negative using ITSs nested PCR (100% specificity).