Table 1

HIV associated pulmonary infections

Bacteria	Mycobacteria	Fungi	Parasites	Viruses
*The common causes of bacterial pneumonia are shown.^5,⁶ One third of the pneumonias are bacteraemic. Bacteraemia is more common in pneumococcal pneumonia. Pseudomonal pneumonia is associated with a lower CD4 count than with pneumococcal pneumonia.⁶
**Multidrug-resistant (MDR) tuberculosis (resistant to isoniazid and rifampicin) is becoming an increasing problem among HIV positive individuals in North America. Antituberculous treatment requires careful monitoring for drug interactions and toxicity, especially if the patient is on HAART. Interactions such as those between the rifamycins and protease inhibitors or non-nucleoside reverse transcriptase inhibitors can lead to lower efficacy or increased toxicity of the anti-retroviral regimen.⁴
***Cryptococcal infection presents either as a primary lung infection or as part of a disseminated infection with cryptococcaemia, pneumonia, meningitis, and cutaneous disease.⁸
Streptococcus pneumoniae*	M tuberculosis**	Pneumocystis carinii	Toxoplasma gondii,	Influenza
Haemophilus influenzae*	M avium intracellulare	Cryptococcus neoformans***	Cryptosporidium spp	Parainfluenza
Staphylococcus aureus*	M kansasii	Candida albicans	Microsporidium spp	Respiratory syncytial virus
Klebsiella pneumoniae*		Aspergillus spp	Leishmania spp	Rhinovirus
Pseudomons aeruginosa*		Penicillium marneffei	Strongyloides stercoralis	Adenovirus
Nocardia asteroides		Histoplasma capsulatum		Cytomegalovirus
Rochalimaea henselae		Coccidiodes immitis		Herpes simplex virus
		Blastomyces dermatitidis		Herpes varicella-zoster virus
Bacterial pneumonia occurs more frequently in HIV positive patients at all CD4 counts than HIV negative controls. The risk increases as the CD4 count falls below 200 cells/mm³and in intravenous drug users⁵	HIV positive individuals are at increased risk of infection with M tuberculosis, whatever the CD4 count, and should be offered an HIV test.⁷ Extrapulmonary tuberculosis tends to occur at CD4 counts <150 cells/mm³. M avium intracellulare and M kansasii both occur late in the course of HIV infection when the CD4 count falls below 50–100 cells/mm³	Pulmonary infections with Candida and Aspergillus are relatively rare. Endemic mycoses caused by Histoplasma capsulatum, Coccidiodes immitis and Blastomyces dermatitidis occur in patients who live in North America		Common respiratory viral infections occur comparably in HIV infected and non-infected people. CMV is frequently isolated in BAL, but its role in causing disease is not clear. The presence of CMV in BAL is associated with a worse prognosis in PCP⁹